ACI 237R 07 Self Consolidating Concrete (1)

ACI 237R-07

Self-Consolidating Concrete

Reported by ACI Committee 237

Emerging Technology Series

American Concrete Institute®

Advancing concrete knowledge

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First PrintingApril 2007

ISBN 0-87031-244-8ISBN-13: 978-0-87031-244-1

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237R-1

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Self-Consolidating ConcreteReported by ACI Committee 237

Self-consolidating concrete (SCC) has been successfully used in manyprojects around the world and has made a major impact on concrete place-ment and construction economics. This report contains the current state ofknowledge with respect to SCC. The information in this document isexpected to inform concrete producers, users, and specifiers of SCC of knownpractices and processes. Because SCC is a viable solution to various concreteplacement problems, ASTM has established Subcommittee C09.47, Self-Consolidating Concrete, to develop standard test methods for SCC.

Keywords: admixture; aggregate; air entrainment; bleeding; cement;consolidation; curing; placing; self-consolidating concrete; specification;viscosity, workability.

CONTENTSChapter 1—Introduction, p. 237R-2

1.1—Definition of self-consolidating concrete (SCC)1.2—Advantages1.3—Development history of SCC1.4—Selected case studies

Chapter 2—Fresh properties, p. 237R-92.1—Terminology relative to SCC2.2—Performance requirements of SCC2.3—General2.4—Characteristics2.5—Target guidelines for fresh properties2.6—Quality control

Chapter 3—Hardened properties, p. 237R-123.1—General3.2—Mechanical properties3.3—Long-term durability3.4—Aesthetics

Chapter 4—Guide for selecting proportions for SCC, p. 237R-14

4.1—General4.2—Performance requirements4.3—Materials4.4—Mixture proportioning procedure4.5—Examples of SCC mixture proportions

Chapter 5—Production, p. 237R-185.1—General5.2—Production issues that influence fresh SCC properties5.3—Performance targets

Claude Bedard Chiara F. Ferraris Beatrix Kerkhoff Mohammed Sonebi

Van K. Bui Sidney Freedman Gary F. Knight Richard Szecsy

John F. Cook John V. Gruber Frank A. Nadeau Jody R. Wall

Charles R. Cornman Venkatesh S. Iyer H. Celik Ozyildirim James A. Wamelink

Kirk K. Deadrick Philippe Jost Qizhong Sheng

*Associate member Mark Bury contributed to this report.

Joseph A. DaczkoChair

Kamal H. KhayatSecretary

ACI 237R-07Emerging Technology Series

ACI encourages the development and appropriate use of new and emerging technologies through the publication of the Emerging TechnologySeries. This series presents information and recommendations based on available test data, technical reports, limited experience with fieldapplications, and the opinions of committee members. The presented information and recommendations, and their basis, may be less fullydeveloped and tested than those for more mature technologies. This report identifies areas in which information is believed to be less fullydeveloped, and describes research needs. The professional using this document should understand the limitations of this document and exercisejudgment as to the appropriate application of this emerging technology.

237R-2 ACI COMMITTEE REPORT

5.4—Mock-up5.5—Employee training

Chapter 6—Transport, placement, and finishing,p. 237R-20

6.1—General6.2—Transport6.3—Discharge of SCC for slabs or open-top molds for

factory-type precast elements6.4—Forms, element characteristics, and reinforcement6.5—Placement techniques6.6—Finishing6.7—Curing

Chapter 7—SCC specification guidelines, p. 237R-247.1—Concrete materials7.2—Execution

Chapter 8—Test methods, p. 237R-248.1—Measuring SCC characteristics8.2—Slump flow8.3—Visual stability index8.4—T508.5—J-ring8.6—L-box8.7—Column segregation8.8—Other tests

Chapter 9—References, p. 237R-279.1—Referenced standards and reports9.2—Cited references

CHAPTER 1—INTRODUCTION1.1—Definition of self-consolidating concrete (SCC)

Self-consolidating concrete (SCC) is highly flowable,nonsegregating concrete that can spread into place, fill theformwork, and encapsulate the reinforcement without anymechanical consolidation. In general, SCC is concrete madewith conventional concrete materials and, in some cases,with a viscosity-modifying admixture (VMA). SCC has alsobeen described as self-compacting concrete, self-placingconcrete, and self-leveling concrete, which all are subsets ofSCC. The nomenclature of this technology has been previouslydiscussed (Szecsy 2002). In this report, conventional concrete isreferred to as concrete that does not meet the definition of SCC.

1.2—AdvantagesProperly proportioned and placed SCC can result in both

economic and technological benefits for the end user. The in-place cost savings, performance enhancements, or both, arethe driving forces behind the use of SCC. Specifically, SCCcan provide the following benefits:• Reduce labor and equipment.

º No need for vibration to ensure proper consolidation.This also results in savings in equipment purchasingand equipment maintenance and operation; and

º Less need for screeding operations to ensure flatsurfaces (self-leveling characteristic).

• Enable the casting of concrete that develops the desired

mechanical properties independent of the skill of thevibrating crew;

• Accelerate construction through higher rate of castingor placing and shorter construction duration;

• Facilitate and expedite the filling of highly reinforcedsections and complex formwork while ensuring goodconstruction quality. This can ensure better produc-tivity, reduce the labor requirement and cost, or both;

• Enable more flexibility in spreading placing pointsduring casting. This can reduce the need for frequentmovement of transit trucks and the need to move thepump lines to place concrete (possible reduction in thenumber of pumps, pump operators, and so on). Thisgreater flexibility in scheduling construction activitiesand procuring the required resources results in bothtime and resource savings;

• Reduce noise on the job site (especially critical inurban areas and for sections requiring heavy vibrationconsolidation):º Reduce the need of vibration for construction typi-

cally requiring the use of heavy consolidation(such as fiber-reinforced concrete and precastoperations). In some cases, the use of noise-free orsilent concrete can potentially extend constructionhours in urban areas, enabling the scheduling ofsome construction activities during otherwisecurfew periods to alleviate difficulties related totraffic conditions in urban areas; and

º Reduce insurance premiums. Precasting facilitiesgenerating considerable noise pollution aresometimes required to pay premiums to nationalinsurance agencies responsible for eventual treatmentof hearing-impaired workers. Insurance premiumreductions can partially offset the additionalmaterial cost of SCC, making it attractive forprecast operations.

• Decrease employee injuries by facilitating a saferworking environment where strenuous and labor-intensiveoperations can reduce tripping hazards through theremoval of some electrical cords or air lines(Walraven 2003);

• Permit more flexibility for detailing reinforcing bars.Avoid the need to bundle reinforcement to facilitateplacement and consolidation, and in some cases, enablethe use of small and closely spaced reinforcing steel tocontrol cracking;

• Create smooth surfaces free of honeycombing and signsof bleeding and discoloration, obtained when using awell-proportioned SCC mixture, high-quality formworkwith an adequate release agent, and sound placementpractices (Chapter 6). Superior surface quality is critical inarchitectural concrete and cast-in-place and precastconcrete for residential construction (walls); and

• Eliminate the need for materials, such as underlay-ments, that are used to level and prepare substrates forfinal flooring materials, such as carpeting and tile,whenever allowed by building regulations.

SELF-CONSOLIDATING CONCRETE 237R-3

1.3—Development history of SCCThe use of SCC has gained wide acceptance in Japan since

the late 1980s. Initially, it was developed to ensure properconsolidation in applications where concrete durability andservice life were of concern. SCC was later used to facilitateconstruction operations and reduce construction time andcost. For example, it has been used to cast sections withhighly congested reinforcement and areas that presentrestricted access to placement and consolidation, includingthe construction of tunnel lining sections and the casting ofhybrid concrete-filled steel tubular columns. The followingreferences provide various examples of the early use of SCCin civil engineering applications: Tanaka et al. (1993);Hayakawa et al. (1993, 1995); Miura et al. (1993); Okamuraand Ozawa (1994); Takeuchi et al. (1994); Izumi et al.(1995); Fukute et al. (1995); Kitamura et al. (1996); andUshijima et al. (1995).

SCC has recently been used in concrete repair applicationsin Canada and Switzerland, including the repair of bridgeabutments and pier caps, tunnel sections, parking garages,and retaining walls, where it ensured adequate filling ofrestricted areas and provided high surface quality (Jacobsand Hunkeler 2001; Khayat and Morin 2002).

Since the early development of SCC in Japan, this newclass of high-performance concrete has been employed inseveral countries in cast-in-place and precast applications(RILEM 2000; Khayat and Aïtcin 1998; Skarendahl 2001;Walraven 2001; Ouchi 2001).

The use of SCC in North America has grown dramatically,especially in the precast industry, where it has been used inregular production at precast plants in the United States since2000. The majority of such concrete has been used toproduce precast elements for parking garage structures andarchitectural panels. The estimated volume of SCC in theprecast market in the United States was 177,000 yd3

(135,000 m3) in 2000; it increased to 2.3 million yd3 (1.8million m3) in 2003.* In 2002, 40% of precast manufacturersin the United States had used SCC, and in some cases, newplants are currently being built around the idea of using SCCtechnology.* On the other hand, the use of SCC in the readymixed concrete industry is still in its infancy in the UnitedStates, with estimated production in 2002 limited to130,000 yd3 (100,000 m3) (Vachon and Daczko 2002).

1.4 — Selected case studiesTable 1.1 includes video clips of several SCC applications.

For comparison purposes, there are clips showing a precastwall panel being produced with both conventional 8 in.(200 mm) slump concrete and SCC. Following Table 1.1 arefive case studies that describe projects where SCC has beensuccessfully used in North America. The mixture propor-tions included in these case studies are for example purposesonly. For development of SCC mixture proportions, guide-lines are provided in Chapter 4.

*Daczko, J., 2003, “Use of SCC in the Precast Industry in the United States.”(private communication)

Table 1.1—SCC project video clips*Project

typeResidential footings*

Precast jail cell*

Prestress double-tee* Wall panel* Wall panel*

Slump flow, in. (mm)

26 (650) 28 (700) 23 (575) 26 (650) N/A

Slump, in. (mm)

N/A N/A N/A N/A 8 (200)

*Click blue link of a table column heading to view related video.


Pedestrian Overpass (I-4), Seminole Country, Orlando, Fla.

Challenge: The required mixture was to be placed within an anchor blockstructure as part of the pedestrian overpass. The 3 in. (75 mm) maximumslump for the Class IV FL DOT concrete mixture, combined with twochannel sections that ran the length of the sides toward the top of the block,made it virtually impossible to use an immersion vibrator for proper consol-idation of the concrete.

Solution: The contractor proposed using SCC to properly fill and consolidatethe concrete for this reinforced concrete structure. The only change to thespecification was the elimination of the slump requirement to allow the useof SCC.

To view related video, click here.

Mixture proportions:Cement:

GGBFS/fly ash:

Coarse aggregate (No. 57):

(No. 89):

Fine aggregate: w/cm:

Admixtures:HRWRA:WRA:VMA:

530 lb/yd3 (309 kg/m3)120 lb/yd3 (77 kg/m3)1152 lb/yd3 (684 kg/m3)542 lb/yd3 (322 kg/m3)1277 lb/yd3 (758 kg/m3)0.43

15 fl oz/cwt (9.8 mL/kg)1.5 fl oz/cwt (1.0 mL/kg)3.0 fl oz/cwt (1.95 mL/kg)

Fresh concrete properties:Slump flow: 28 in. (710 mm)

Compressive strength:24 hours: 1800 psi (12.4 MPa)30 hours: 2500 psi (17.2 MPa)28 days: 7460 psi (51.5 MPa)

Engineer/Architect/Specifier: Harding ESE (a Mactec Company)Concrete producer: RMC EwellContractor: Martin K. Eby Construction Co., Inc.

Comments:~ Haul time was approximately 30 to 45 minutes.~ 22 ft (6.7 m) high walls, 58 ft (17.7 m) long.~ Engineered cold joint at 11 ft (3.4 m).~ SCC allowed to free fall 15 ft (4.6 m).~ No mechanical vibration.~ During one delay in placement, the mixture maintained its workability for 2.5 hours at 90 °F (32 °C).~ Excellent aesthetics.


National Museum of the American Indian, Washington, D.C.

The National Museum of the American Indian (NMAI) was built on the Washington Mall and is intended to resemble a solid piece of rock carved over timeby wind and water. Everything is highly symbolic and nonrepetitive. The five-story building has an area of approximately 260,000 ft2 (24,000 m2). Theentire structure has no right angle, and the forms were all customer built.

The main reason to use an SCC mixture was the overcrowded reinforcementand the complicated shapes of the structure. There was little to no room leftfor vibrators. Vibration caused forms to fail in certain instances. A signifi-cant amount of the concrete was exposed. SCC enabled the placing ofcertain elements in one lift and significantly improved the aesthetics. Thestress on the formwork was also reduced due to the use of SCC, as thevibration could be eliminated. The use of SCC also enabled turnaroundtimes to be reduced from 5 days to 2 days.

The total quantity of SCC used was greater than 30,000 yd3 (23,000 m3).

Mixture proportions:Cement (Type 1):

GGBFS:

Coarse aggregate:

w/cm:

Admixtures:HRWRA:

390 lb/yd3 (230 kg/m3)260 lb/yd3 (155 kg/m3)Gravel (No. 67)

0.47

8 fl oz/cwt (5.2 mL/kg)

Fresh concrete properties:Air content: 6.0%Slump flow: 24 in. (610 mm)Unit weight: 148 lb/ft3 (2370 kg/m3)

Compressive strength:28 days: 6000 psi (41.4 MPa)

Owner: Smithsonian InstitutionConcrete producer: Aggregate Industries, MarylandGeneral contractor: Joint venture between Clark Construction Group Inc. and Table Mountain Rancheria Enterprises (TMR) of Fraint, Calif., an American Indian firm.


Double-Tee Production, Nitterhouse Concrete Products Inc., Chambersburg, Pa.Nitterhouse is a producer of double tees for precast parking garages, and it is involved throughout the construction process from specifications to erection. Nitterhouse places one 500 ft (150 m) bed and one 380 ft (115) bed of double tees on a daily basis. The particular project is the parking garage at Harrisburg International Airport, Harrisburg, Pa. All-white cement was used in this project to increase the reflectivity of the structure without the need for paint.

The main reason for the use of SCC was cost savings, arising from the reduction in labor costs. Other benefits for the use of SCC included improved appearance of the concrete and reduction in noise levels.

Mixture proportions:Cement (Type I):

GGBFS:

Coarse aggregate:

w/cm:

Admixtures:HRWRA:Set accelerator:VMA:

639 lb/yd3 (385 kg/m3)113 lb/yd3 (68 kg/m3)Gravel (No. 57)

0.40

9 fl oz/cwt (5.9 mL/kg)12 fl oz/cwt (7.85 mL/kg)4 gal./yd3 (20 L/m3)

Fresh concrete properties:Air content: 5.5%Slump flow: 22 ± 2 in. (560 ± 50 mm)Unit weight: 148 lb/ft3 (2370 kg/m3)

Compressive strength:13 hours: 4000 psi (27.6 MPa)28 days: >7200 psi (>49.7 MPa)

Concrete producer: Nitterhouse Concrete Products Inc., Chambersburg, Pa.


Rosenthal Center for Contemporary Arts, Cincinnati, Ohio

Challenge:1. One component of the design of this building was a roll-up that resembleda 96 ft (29.3 m) 3/4 circular section that connected the wall to the floor.The form for this curved roll-up provided very little access for internalvibration; and

2. Formwork for structural diamond-shaped columns consisted of squarecolumn forms with plywood inserts to create their diamond shape. The formdetail resulted in “dead areas” on two sides that restricted access for propervibration of the concrete.

Solution:To ensure proper consolidation and to minimize surface blemishes, SCCusing a a blend of aggregates was selected for both the roll-up section andthe diamond-shaped columns.

Mixture proportions:Cement (Type I):

Coarse aggregate (No. 57):

(No. 8):

Fine aggregate:Water:

w/cm:

Admixtures:HRWRA:VMA:

750 lb/yd3 (445 kg/m3)1000 lb/yd3 (593 kg/m3)500 lb/yd3 (297 kg/m3)1500 lb/yd3 (890 kg/m3)300 lb/yd3 (178 kg/m3)0.40

12.0 fl oz/cwt (7.8 mL/kg)1.5 fl oz/cwt (1.0 mL/kg)

Fresh concrete properties:Slump flow: 26 in. (660 mm)

Compressive strength:Requirement

3000 psi (21 MPa) at 3 days6000 psi (42 MPa) at 28 days

Actual6600 psi (45.5 MPa) at 3 days9000 psi (62.1 MPa) at 28 days

Engineer/Architect/Specifier: Zaha HadidConcrete producer: Hilltop Basic ResourcesContractor: Baker Concrete Construction

Comments:~ The surface appearance of both the roll-up and column significantly enhanced over that of a conventional concrete mixture.~ For the first two columns, an increase of approximately 20% in concrete volume placed per man-hour was achieved compared with the placement rate for a

conventional 8 in. (200 mm) slump concrete. As construction progressed, the placement efficiency increased in excess of 350% of the conventional mixture.~ There was increased job-site safety because vibration was eliminated; there was decreased tripping over power cords and decreased electrocution potential.


Reaction Wall in Structural Laboratory, Université de Sherbrooke, Sherbrooke, Quebec, Canada

A strong reaction wall design to enable dynamic testing of large structuralsections was constructed at the structural engineering laboratory at theUniversité de Sherbrooke using high-performance SCC. This projectstarted in late 1997 and targeted demonstrating the use of SCC in structuralapplications.

The wall measures 30.5 ft (9.3 m) wide, 23 ft (7 m) high, and 13 ft (4 m)thick, and has three hollow sections in the middle. The wall is supported ona 9.8 ft (3 m) deep foundation system made of a series of highly reinforcedbeams anchored to rock bed. The wall is moderately reinforced with reinforce-ment steel and post-tensioning rods. The total volume of the SCC used tobuild the wall was 315 yd3 (240 m3), with 105 yd3 (80 m3) used for theunderground section and 78 yd3 (60 m3) for each of the two 10.5 ft (3.5 m)high lifts above ground level.

Concrete was produced in a local concrete plant and was delivered inbatches of 7.8 yd3 (6 m3). In total, 40 concrete deliveries were tested uponarrival at the job site.

The SCC was pumped into place and spread readily among the reinforce-ment. SCC enabled the placing of the concrete from two points along thewall. The use of SCC reduced the noise in the laboratory and facilitatedconstruction activities in a working environment. High quality was secured.

Mixture proportions:Cements:Mass of fine aggregates:w/cm:

Admixtures:HRWRA:Liquid-based VMA:WRA:

880 lb/yd3 (520 kg/m3)Crushed aggregate (5 to 10 mm)0.42

4.4 fl oz/cwt (2.9 mL/kg)9.2 fl oz/cwt (6.0 mL/kg)2 fl oz/cwt (1.3 mL/kg)

Fresh concrete properties:Air content: 1.0%Slump flow: 25 in. (640 mm); COV* = 3%V-funnel flow time: 3.8 seconds; COV = 24%Caisson filling capacity: 83%; COV = 5%

Compressive strength:24 hours: 870 psi (6 MPa); COV = 22%7 days: 3700 psi (25.5 MPa); COV = 12%28 days: 6100 psi (42 MPa); COV = 6%________________*COV = coefficient of variation, determined from testing performance of 40 concretedeliveries.

Owner: Université de SherbrookeConcrete producer: Demix béton, Sherbrooke


CHAPTER 2—FRESH PROPERTIES2.1—Terminology relative to SCC

SCC is highly flowable, nonsegregating concrete that canspread into place, fill formwork, and encapsulate reinforcementwithout any mechanical consolidation. SCC rheology ischaracterized by a low yield stress to ensure high deformabilityand moderate plastic viscosity to maintain homogeneoussuspension of solids, hence reducing interparticle collision,segregation, and flow blockage. The main requirements ofSCC involve securing high levels of deformability whilemaintaining a highly stable mixture. These characteristicsare further elaborated on and defined as follows.

Rheology refers to the science of deformation, and flow ofmatter is fundamental to understanding the flow of freshSCC. Concrete rheology is evaluated using special rheometersthat enable one to relate variations in shear stress to shearrate. SCC is sometimes described as a Bingham fluid inwhich the shear stress can be expressed as

τ = τ0 + μp · γ

where τ is the shear stress (Pa); τ0 is the yield stress (Pa); μpis the plastic viscosity (Pa·s); and γ is the shear rate. Theyield stress corresponds to the minimum shear stressrequired to initiate flow. Below such value, the mixture doesnot undergo any deformation and, therefore, does not flow.The constant of proportionality between shear stress andshear rate is referred to as the plastic viscosity and refers tothe resistance of the plastic material to undergo a given flow.A video clip of both a low and high viscosity SCC mixturesis included in Table 2.1.

Workability describes the ease with which concrete canbe mixed, placed, consolidated, and finished. Workability ofSCC is described in terms of filling ability, passing ability,and stability, and is characterized by specific testing methods.

The filling ability (unconfined flowability) describes theability of SCC to flow into and fill completely all spaceswithin the formwork, under its own weight. This property isof importance when selecting the casting technique anddetermining spacing between filling points.

The passing ability (confined flowability) refers to theease with which concrete can pass among various obstaclesand narrow spacing in the formwork without blockage.Blockage refers to the condition that can arise from localaggregate segregation in the vicinity of the obstacles thatgive rise to interlocking and blockage of the flow in theabsence of any mechanical vibration. SCC can exhibit highfilling capacity if it can achieve the levels of both fillingability and passing ability required to readily fill a predeter-mined section under the sole action of gravity.

Stability of concrete describes the ability of a material tomaintain homogeneous distribution of its various constituentsduring its flow and setting. There are two types of stabilitycharacteristics that are important for SCC: dynamic andstatic stability.

Dynamic stability refers to the resistance of concrete tothe separation of constituents during placement into theformwork. Adequate dynamic stability is required for SCC

when the application has requirements such as flowingthrough closely spaced obstacles and narrow spaces. It is alsoimportant if the SCC will be transported without agitation.

Static stability refers to the resistance of concrete tobleeding, segregation, and surface settlement after castingwhile the concrete is still in a plastic state.

In some cases, VMAs or higher powder contents will beused to promote stability. A VMA is an admixture used forenhancing the rheological properties of cement-basedmaterials in the plastic state to reduce the risk of segregationand washout.

2.2—Performance requirements of SCCIn general, the performance requirements of SCC are

complex and depend on several parameters, including serviceloading and environmental conditions, intended placementmethod, labor skill, and quality assurance and quality controlmeasures.

The required workability for placing concrete dependson the type of construction, selected placement andconsolidation methods, complexity of the formwork, andstructural design details that affect the degree of congestionof the reinforcement.

Figure 2.1 shows the many variables that influence thedesired fresh properties of SCC (Khayat and Daczko 2002).Not only are project and raw material variables accountedfor, but economic variables should also be considered. Asshown in Fig. 2.1, an initial perceived value drives the userto try SCC; however, the real question is, “is the actual value,which is determined after evaluation, equivalent to the initialperceived value?” This is where the mixture qualificationprocess becomes important, and by committing oneself to thetime required to investigate these variables, the most cost-effective solution will be determined.

2.3—GeneralIt is the fresh, plastic properties of SCC that differentiate

the material from conventional concrete.In outlining and defining the fresh properties, two points

of view can be used. The first is in evaluating the funda-mental rheological properties of the SCC mixture. The

Fig. 2.1—Variables involved in establishing the requiredfresh SCC properties.


rheology of fresh concrete was introduced earlier and ismore fully defined elsewhere (Tattersall and Banfill 1983;Ferraris 1999; Ferraris and Brower 2001). The secondmethod of defining the fresh properties of SCC is to evaluatethem strictly based upon practical field-related requirements.These practical characteristics are: stability, filling ability,and passing ability. Relationships of responses obtainedfrom various practical test methods to assess both the staticand dynamic stability of SCC in conjunction with rheologicalparameters have been reported (Khayat et al. 2004). Therheological properties of SCC influence the characteristics ofstability, filling ability, and passing ability. This document,

however, focuses its attention on the practical, rather thanthe rheological, characteristics of SCC.

2.4—CharacteristicsThe degrees of stability, filling ability, and passing ability

of SCC are dictated by the application. For example, passingability is only important for reinforced concrete applicationsand in sections that will restrict the flow of concrete intoplace. The level of passing ability is dictated by the amountand spacing of reinforcement in the proposed structure. Inaddition to the application, the availability of quality rawmaterials will influence the levels of performance achievable.Placing methods and formwork should also be reviewed

Table 2.1—Test methods for measuring SCC characteristics*

Characteristics Test method Description

Filling ability (deformability) and stability

Click here for related video 1.

Click here for related video 2

ASTM C 1611/C 1611MSlump flow of SCC

The slump flow test is a measure of mixture filling ability. This test isperformed similarly to the conventional slump test using the standardASTM C 143/C 143M slump cone. Instead of measuring the slumpingdistance vertically, however, the mean spread of the resulting concretepatty is measured horizontally. This number is recorded as the slumpflow. The visual stability index (VSI) is determined through rating theapparent stability of the slump flow patty (Daczko and Kurtz 2001).

Passing ability

J-ring

The J-ring consists of a ring of reinforcing bars that will fit around thebase of a standard ASTM C 143/C 143M slump cone. The slump cone isfilled with concrete and then lifted in the same fashion as if one wereconducting the slump flow test. The final spread of the concrete ismeasured, and the difference between the conventional slump flow valueand the J-ring slump flow value is calculated.

Passing ability

Click here for related video.

L-box

The L-box test consists of an L-shaped container divided into a verticaland horizontal section. A sliding door separates the vertical and hori-zontal sections. An obstacle of three reinforcing bars can be positionedin the horizontal section adjacent to the sliding door. The vertical sectionof the container is filled with concrete and the sliding door is immedi-ately removed, allowing the concrete to flow through the obstacle intothe horizontal section. The height of the concrete left in the verticalsection (h1) and at the end of the horizontal section (h2) is measured. Theratio of h2/h1 is calculated as the blocking ratio.

Stability

Column segregation

This test evaluates the static stability of a concrete mixture by quantifyingaggregate segregation. This test consists of filling a 26 in. (610 mm) highcolumn with concrete. The concrete is allowed to sit for 15 minutes afterplacement. Each section is removed individually, the concrete from thatsection is washed over a No. 4 (4.75 mm) sieve, and the retainedaggregate is weighed. A nonsegregating mixture will have consistentaggregate mass distribution between the top and bottom sections. Asegregating mixture will have a higher concentration of aggregate in thelower section.

*To view related video, go to http://www.concrete.org/COMMITTEES/CommVideo/com_video.htm


(these are discussed in Chapter 6). Tables 2.2 to 2.4 provideinsight into the mixture and application variables that influencethe characteristics of filling ability, passing ability, and stability.

2.5—Target guidelines for fresh propertiesDevelopment of an acceptable SCC for each application

starts with trial mixtures. To effectively accomplish this task,test methods that quantify filling ability, passing ability, andstability should be used. Table 2.1 shows the test methodscurrently under development in ASTM that relate to thethree aforementioned characteristics.

Establishing the initial target value for slump flow is thefirst step in developing an SCC mixture. Table 2.5 providesguidance for choosing the initial target (Daczko andConstantiner 2001). Based on the application, the mixturedesigner rates the characteristics of an element as low,medium, or high. The dark areas are potential problem areasand should be avoided. For example, if the applicationpresents a high level of reinforcement, SCC with a slumpflow lower than 22 in. (550 mm) is not recommended. Initialtargets should be chosen from the white areas. In general, thelowest slump flow consistency should be chosen to reducethe potential for instability and optimize the performance/cost relationship.

Once the initial slump flow target is set, trial mixturesshould be proportioned with those materials that will be usedfor the intended project. As these mixtures are evaluated,

testing for the other SCC properties, such as passing abilityand stability, should be conducted. The relationship betweenslump flow consistency and the stability properties can beused as a predictor of the stability requirements of the SCCmixture during the quality-control process, allowing for lessfrequent stability testing in the field (Daczko 2004).

2.6—Quality controlQuality control is critical for SCC. The appropriate

quality-control parameters should be determined during themixture qualification stage or should be based on perfor-mance history. Quality-control testing should be performed

Table 2.2—Variables influencing filling abilityApplication variables Influence

Reinforcement level High reinforcement level inhibits flow

Intricacy of the element shape Intricate shapes are more difficult to fill

Wall thickness Narrow section inhibit flow

Placement techniqueSlow, discontinuous pouring decreases

placement energy

Element length Longer distances are more difficult to fill

Mixture variables

Fluidity (slump flow) level High fluidity improves filling ability

Viscosity levelViscosity that is too high can limit filling

ability

Table 2.3—Variables influencing passing abilityApplication variables Influence

Reinforcement levelTight reinforcement can cause aggregate

bridging and blocking of concrete

Narrowing of formworkNarrow sections in formwork can cause

aggregate bridging and blocking of concrete

Mixture variables

Fluidity (slump flow) level

Fluidity that is too low may not allow for enough deformability, while fluidity that is too high may cause instability and mixture

separation

Viscosity levelViscosity level should be gauged in light of

fluidity level

Coarse aggregate sizeAggregate size that is too large will increase

blocking tendency

Coarse aggregate contentToo much coarse aggregate will increase

blocking tendency

Table 2.4—Variables influencing stabilityApplication variables Influence

Placement techniqueHigh placement energy can cause materials to

separate

Reinforcement levelIf concrete falls or flows through reinforcement,

separation of materials can occur

Element heightThe depth of an element is proportional to its potential for aggregate settlement and bleed

Mixture variables

Fluidity (slump flow) levelAll other things being equal, as fluidity level

increases, stability decreases*

Viscosity level As viscosity increases, stability increases*Highly fluid SCC mixtures must be proportioned to be stable.

Table 2.5—Slump flow targets(Daczko and Constantiner 2001)

Slump flow

<22 in. (<550 mm)

22 to 26 in.(550 to 650 mm)

>26 in.(>650 mm)

Reinforcement level

Low

Medium

High

Element shape intricacy

Low

Medium

High

Element depth

Low

Medium

High

Surface finish importance

Low

Medium

High

Element length

Low

Medium

High

Wall thickness

Low

Medium

High

Coarse aggregate content

Low

Medium

High

Placement energy

Low

Medium

High

Note: SCC mixtures with slump flows less than 22 in. (550 mm) may require minorvibration.

Mem

ber

char

acte

rist

ics


by experienced personnel. At present, there is no applicableACI certification program for SCC testing. It is thereforerecommended that, at minimum, the personnel be certified asan ACI Level 1 Field Testing Technician.

When producing SCC, at least the slump flow and visualstability index (VSI) tests should be performed each day bytesting the first batch of SCC, and then consecutive batchesuntil two consecutively produced batches are within specifi-cation, as outlined in the initial mixture qualification process(NPCA 2006). Thereafter, slump flow and VSI testingshould be performed as per the project requirements. Testingshould be performed as outlined in ASTM C 1611/C 1611M.Furthermore, standard tests, such as the unit weight and aircontent, should be assessed at the job site for quality assurance.

Varying moisture content of aggregate and changes inaggregate gradation will have a greater impact on the work-ability of SCC than in conventional concrete. For SCC, whenmoisture probes or meters are used with automatic mixingwater adjustment systems, the aggregate moisture contentshould be determined at least once a day before making thefirst SCC batch. Moisture confirmation tests should beperformed according to ASTM C 70 or C 566. Samples formoisture tests should be taken as close as possible to the areawhere the probe is located. For SCC made without moistureprobes or meters and automatic mixing water adjustmentsystems, the aggregate moisture content should be determinedat least once a day before making the first SCC batch. There-after, it should be determined once every 4 hours of elapsedtime after the first batch, while SCC is being mixed.

CHAPTER 3—HARDENED PROPERTIES3.1—General

While some of the fresh properties of SCC differ signifi-cantly from those of conventional concrete, hardenedconcrete properties of SCC may be engineered through themixture proportion to be similar to, or better than, those of aconventional concrete mixture.

If specific key properties are important in a particularapplication, these should to be considered when developingSCC mixtures.

Hardened properties discussed in this chapter mainlyinvolve SCC that is properly designed to minimize anysegregation and bleeding. Effects of bleeding and segregationon the various hardened properties of SCC will be coveredwhen applicable. Special emphasis will be given to the impor-tance of the stability of SCC and its impact on the homogeneityof mechanical properties (including bond to reinforcement),transport/diffusion properties, and dimensional stability.

3.2—Mechanical propertiesGiven the same raw material sources and the same specified

compressive strength, the engineering properties of SCCshould be similar to those of conventional concrete. Toverify this, the same test methods and procedures employedfor conventional concrete should be used for SCC. Thereader should refer to applicable ACI documents andASTM standards. SCC is sometimes made with supplementarycementitious materials and, similar to conventional concrete

using supplementary cementitious materials, may be testedafter 91 days of age to allow for the development ofmechanical properties.

In columns, long-span elements, cantilevers, and similarapplications where hardened concrete properties such asmodulus of elasticity, creep, or shrinkage parameters arecritical, relevant tests should be performed to verify that thedesired performance of the SCC is achieved. This is espe-cially true when the proportions of coarse aggregate or pastecontent of the SCC mixtures vary significantly from those ofconventional mixtures for which the producer has a historyof performance.

3.2.1 Compressive strength—Quality SCC requires thatthe concrete be highly flowable, yet cohesive enough toresist segregation. This often necessitates the use of a water-cementitious material ratio (w/cm) that is lower than thattypically used for comparable conventional concrete. As aresult of a low w/cm, higher compressive strengths areachieved. SCC typically used for precast can be proportionedwith a w/cm of 0.32 to 0.40. Mixtures with a greater w/cm(higher than 0.40) are sometimes employed for cast-in-placeand repair applications, and have strength characteristicssimilar to conventional concrete.

Mixture proportion adjustments may be needed to ensureadequate stability. Because w/cm is a key component indetermining the compressive strength of concrete, otherchanges in mixture proportions compared with conventionalconcrete may affect the rate of development and ultimatecompressive strength. These can include sand-total aggregate(s/a) ratio, the type and amount of supplementary cementitiousmaterials and fillers, and the combination of chemicaladmixtures. For example, SCC mixtures proportioned with apolycarboxylate-based high-range water-reducing admixture(HRWRA) can develop higher early strength gain and ultimatestrength than similar SCC mixtures made with naphthaleneor a melamine-sulfonate-based HRWRA.

The lower w/cm that is sometimes selected to enhancefresh concrete characteristics will normally yield a higher28-day compressive strength than typical values required bythe design of the concrete structure.

Measured compressive strength, as opposed to specifiedcompressive strength, should be used when estimating othermechanical properties that are calculated using a value ofcompressive strength. Even at the same w/cm, properlydesigned SCC can exhibit higher compressive strength. Thereduction of the risk of bleeding and segregation along withthe lack of mechanical vibration can further promote a moreuniform microstructure and less porous interface zonebetween the cement paste and aggregate and embeddedreinforcement (Zhu et al. 2001). The compressive strengthof the concrete should be determined in accordance withASTM C 39/C 39M by an ACI certified technician.

3.2.2 Flexural strength—Like conventional concrete, theflexural strength of SCC depends on the w/cm, coarse aggregatevolume, and the quality of the interface between the aggregateand cement paste. SCC flexural strength may be higher thanthat of conventional concrete with similar mixture proportions(Sonebi and Bartos 2001). The flexural strength should be


determined in accordance with ASTM C 78 or C 293 by anACI certified technician.

3.2.3 Modulus of elasticity—Elastic modulus of concreteis related to compressive strength, aggregate type andcontent, and unit weight of the concrete. Adjustments inmixture proportions, especially the s/a, will influence theelastic modulus of the SCC. Some observations have shownthat for equal compressive strength, the elastic modulus ofSCC can be as much as 10 to 15% lower than that ofconventional concrete of similar compressive strength dueto the required adjustments of mixture proportions to makeSCC (Bennenk 2002). Other studies have shown the opposite—that at an equal compressive strength, the elastic modulus ofSCC coincides well with that of conventional concrete(Persson 1999). Mortsell and Rodum (2001) found that SCCand conventional concrete for housing applications with thesame mixture proportioning, developed with a relatively lowbinder content for SCC (650 lb/yd3 [385 kg/m3]), developthe same elastic modulus.

In applications where the modulus of elasticity is not criticalto the concrete element, the ACI equation Ec = wc

1.5 ·0.043 (MPa) (or Ec = wc

1.5 · 33 to determine Ec inpsi) should be used for concrete with unit weight wc varyingbetween 90 and 155 lb/ft3 (1500 and 2500 kg/m3). Fornormal-density concrete, Ec can be calculated as 4700(MPa) (or 57,000 to determine Ec in psi).

In applications that require a specific modulus of elasticityor a specific relationship of the modulus of elasticity andcompressive strength, the elastic modulus should be determinedin accordance with ASTM C 469 from the same trialmixtures using the mixture proportions of SCC to be used onthe project.

3.2.4 Autogenous, drying, and plastic shrinkage3.2.4.1 Autogenous shrinkage—Autogenous shrinkage

can be particularly high in mixtures made with a relativelylow w/cm, high content of cement, and supplementarycementitious materials exhibiting a high rate of pozzolanicreactivity at an early age. Special attention should be givento protect SCC at early ages to minimize desiccation.

Song et al. (2001) showed that for SCC mixtures madewith 0.34 w/cm and 40% replacement of cement by GGBFS,the increase in the Blaine fineness of the GGBFS from 400to 600 or 800 m2/kg can lead to greater autogenous shrinkage.After 28 days, the SCC made without any GGBFS and theSCC made with 40% GGBFS with a Blaine fineness of400 m2/kg had similar autogenous shrinkage values. Thesevalues were considerably greater (about 2.5 times) after 28 dayswhen the Blaine fineness of the GGBFS increased from 400to 600 or 800 m2/kg. The GGBFS fineness also had a signif-icant effect on the rate of autogenous shrinkage for the first28 days. The finer GGBFS particles have a larger surfacearea for the pozzolanic reaction, leading to a faster reactionand greater autogenous shrinkage.

Khayat and Morin (2002) reported autogenous shrinkagevalues on the order of 100 to 50 × 10–6 m/m for SCC mixturesused in repair applications proportioned with a w/cm of 0.38.

3.2.4.2 Drying shrinkage—Drying shrinkage is relatedto the water and paste contents, as well as aggregate volume,

size, and stiffness. High paste volumes and reduction inaggregate content can lead to greater potential for dryingshrinkage. Paste volumes can be optimized during themixture-proportioning process through the selection ofaggregate content, composition, and admixtures.

Drying shrinkage has been reported to be similar to orlower than that of conventional concrete of similar compressivestrength (Persson 1999; Sonebi and Bartos 1999). Mortselland Rodum (2001) reported that the drying shrinkage ofSCC developed for housing applications made with 615 and35 lb/yd3 (365 and 20 kg/m3) of cement and silica fume,respectively, and 265 lb/yd3 (157 kg/m3) of water wasessentially the same as that of conventional concrete with thesame mixture proportions.

For SCC, as for other types of concrete, the higher the w/cm(other parameters being comparable), the lower the autogenousshrinkage, and the higher the drying shrinkage.

3.2.4.3 Plastic shrinkage—SCC can be prone to plasticshrinkage cracking given the fact that these mixtures mayexhibit little or no surface bleeding. SCC should be protectedfrom rapid moisture loss just like conventional concrete thatexhibits little or no surface bleeding. Protection is thenrequired to prevent surface drying during the first 24 hours(Gram and Piiparinen 1999; Turcry et al. 2002).

In applications where the shrinkage characteristics are animportant design parameter, this aspect of the SCC mixtureshould be considered in design and verified by testing.Drying shrinkage should be determined according to ASTMC 157/C 157M.

3.2.5 Creep in compression—Creep is mostly affected bythe rigidity of the cement paste and concrete as well as coarseaggregate volume and stiffness, curing time, curing method,temperature, relative humidity, and concrete age at the timeof load application. As in the case of drying shrinkage, creepof SCC is highly dependent on the mixture composition,paste volume, and aggregate content. For the same mixtureproportions as those for conventional concrete, creep of SCCis expected to be similar to that of conventional concrete.When the SCC is proportioned with greater paste volume,however, it can exhibit higher creep than conventionalconcrete with a similar compressive strength. Certain testresults have shown that the creep coefficient of mature SCCcoincided well with the same property of conventionalconcrete when the strength at load application was similarand was held constant (Persson 1999).

Song et al.(2001) showed that early-age SCC specimenscontaining finer GGBFS (Blaine fineness of 600 or 800versus 400 m2/kg, as inch-pound units are never used forBlaine fineness) results in greater autogenous shrinkage, butsmaller specific creep, for the first 28 days. The overalleffect of the fineness of GGBFS on the creep behavior ofSCC is variable with the age at which loading occurs. Whenthe specimens are loaded at early ages, the effect of finenessis more pronounced, while at later ages, the effect of finenessbecomes very small.

Attiogbe et al. (2002) found that SCC had specific creepvalues similar to conventional steam-cured precast mixtures.For air-cured precast concrete, the specific creep was

fc′ fc′

fc′

fc′


slightly higher. Analysis of drying shrinkage and creep dataindicated that the combined effects on long-term prestresslosses would be similar for both mixtures.

In applications where the creep characteristic is an importantdesign parameter, it should be considered in design andverified by testing in accordance with ASTM C 512.

3.2.6 Bond to reinforcing steel and prestressed strand—Properly designed SCC bonding characteristics are equal toor better than conventional concrete. SCC flows easilyaround the reinforcement, and bonds well. The bond strengthof reinforcing bars in SCC may be up to 40% higher whencompared with conventional concrete (Sonebi and Bartos1999; Chan et al. 2003). This may be due to the lower watercontent and the higher powder volume in the SCC mixturesrelative to the reference mixtures, which reduces the accumula-tion of bleed water under horizontally embedded reinforcingbars. In normal concrete, bleed-water accumulation canincrease the local w/cm under the bar and weaken thestrength of the bond (Sonebi et al. 2001).

Bond to reinforcement can be compromised by excessivebleeding and lack of stability in poorly designed SCCmixtures, especially in upper sections containing reinforce-ment. The phenomenon of a greater reduction in bond in theupper levels of reinforcement is known as top-bar effect. Thetop-bar effect was shown to increase with the increase inmixture settlement determined from the surface settlement test(Khayat 1998). Properly proportioned SCC can develop lesstop-bar effect than fluid conventional concrete (Khayat 1998).

3.3—Long-term durability3.3.1 Resistance to freezing and thawing and deicer salt

scaling—Saturated concrete exposed to severe environ-ments requires a satisfactory air-void system, sufficientmaturity, and proper aggregates. When a proper air-voidsystem is provided, SCC can exhibit excellent resistance tofreezing and thawing and to deicing salt scaling (Persson2003; Khayat 2000; Beaupré et al. 1999). For example, SCCmixtures with 0.45 to 0.50 w/cm made with 710 to 885 lb/yd3

(420 to 525 kg/m3) of ternary binders, containing combina-tions of silica fume and fly ash or GGBFS, were shown todevelop favorable air-void systems with spacing factors lessthan 0.008 in. (200 μm) and excellent resistance to freezingand thawing. The mean longitudinal elongation after 300 cyclesof freezing and thawing was limited to 0.025% (250 μm/m)(Khayat 2000).

The resistance to freezing and thawing and surface scalingshould be determined in accordance with ASTM C 666/C 666M and C 672/C 672M.

3.3.1.1 Air-void system—Proper air volume can beproduced and remain stable in SCC. High fluidity and highamounts of HRWRA, however, may, in certain cases, imparta large amount of coarse air bubbles in SCC. If coarse bubblesare obtained, an air-entraining agent may be used to achieve anadequate air-void system. A change in design proportions or achange in the selection of admixtures such as HRWRA, air-entraining agents, or VMAs may obtain small bubbles andachieve proper air-void parameters.

It is difficult to stabilize air voids in segregating concrete. Insuch cases, increasing the concrete viscosity by use of a VMAor by changing the mixture proportions (through the additionof more powder, a reduction of water, or both), is necessary toreduce segregation and ensure adequate air-void distribution(Khayat and Assaad 2002). The air-void parameters should bedetermined in accordance with ASTM C 457.

3.3.2 Paste microstructure—When properly designed,SCC can develop microstructure with fine capillary porositythat reduces transport properties. Zhu and Bartos (2003)reported that, compared with conventional concrete that isvibrated into place, SCC exhibited significantly lower valuesof the coefficient of air permeability and water absorption.The tested SCC mixtures were proportioned with 605 to925 lb/yd3 (360 to 550 kg/m3) of powdered materials(combinations of cement and fly ash or limestone filler)made with water-powder ratios of 0.33 to 0.58. Two conven-tional concrete reference mixtures were proportioned with0.57 w/cm and 575 lb/yd3 (340 kg/m3) of cement as well aswith 0.48 w/cm and 475 and 200 lb/yd3 (280 and 120 kg/m3)of cement and fly ash, respectively. The coefficient of chloridemigration was shown to depend on the type of powder in use.Both the reference conventional concrete and the SCCmixtures made with fly ash had much lower values of migrationcoefficient than the other mixtures that did not contain fly ash.

The typically lower w/cm of SCC, combined with thebetter homogeneity characteristics when compared withconventional concrete, can improve the interface zone ofcement paste and aggregate, improve surface quality that resultsin fewer bugholes and air voids, and enhance impermeability.Care should be taken to ensure that the powder materials andchemical admixtures used in proportioning SCC do not havean adverse effect on permeability and electrical resistivityproperties. For testing of rapid chloride-ion permeability,refer to ASTM C 1202.

3.3.3 Resistance to carbonation—SCC is expected to havethe same resistance to carbonation as conventional concrete.For testing, refer to MNL-116 and ASTM test methods(Assié et al. 2005).

3.4—AestheticsOne benefit of SCC is that it provides improved surface

appearances and aesthetics in finished concrete. Pour lines,bugholes, honeycombs, and other surface imperfections arelargely reduced (Gaimster and Foord 2000). For more infor-mation on how placement techniques for SCC can affect theappearance of concrete, refer to Chapter 6.

The fluidity of SCC and the elimination of vibration willresult in improved aesthetics. Selection of form-release agentsis very important in achieving the desired smooth finish.

CHAPTER 4—GUIDE FOR SELECTING PROPORTIONS FOR SCC

4.1—GeneralThis chapter presents generally applicable methods for

selecting mixture proportions for SCC and for optimizingmixture proportions on the basis of trial batches. Discussionis limited to SCC produced with conventional materials and


production methods. The use of fly ash, silica fume, andGGBFS have been used to produce quality SCC and haveshown to be beneficial by enhancing both plastic and hardenedproperty values of SCC.

SCC can be considered high-performance concrete in theplastic state. The fresh properties of SCC have a much higherdegree of workability and self-consolidation than anyconventional concrete. The workability attributes of SCC arecharacterized with the following properties: filling ability,passing ability, and stability (segregation resistance). Referto Chapters 2 and 8 for further information on these character-istics and methods for measuring them.

The aforementioned attributes should be present for theconcrete to be considered SCC. To achieve these properties,the SCC mixture should be carefully proportioned, takinginto account the application and the placement technique.For example, SCC in a noncongested footing applicationcould contain a higher percentage of coarse aggregate andlower slump flow requirements than SCC being used in acongested column application. The congested column wouldrequire greater passing ability to flow around reinforcement,enhanced stability to minimize segregation, and sufficientstrength to meet the load requirements. The proportions offine and coarse aggregate and powder content (cement,supplementary cementitious materials, finely dividedpowders) for SCC should be balanced to achieve the desiredfresh and hardened properties. To ensure the passing abilityof SCC, concrete being placed in a highly congested reinforcedcolumn may require a different mixture proportion than aslab-on-ground with widely spaced reinforcement. Therefore,the intended application of the SCC can significantly affectthe mixture proportions. The quantity, size, and spacing ofsteel reinforcement in a structure, if any, and method of SCCdelivery and discharge play a major role in determining thefilling ability, passing ability, and stability requirements.

This chapter is intended to supplement the standard practicefor selecting proportions for concrete mixture proportions asdiscussed in ACI 211.1. The chapter will cover severalapproaches for proportioning SCC for air-entrained and non-air-entrained concrete, with a wide range of compressivestrengths. The special rheological properties of SCC arehighly dependent on the individual components; thisproportioning procedure is meant to illustrate a process forproducing submittal mixture proportions based on theperformance of adjusted laboratory and field trial batches.

4.1.1 Mixture proportion methodology—The committee isaware of three basic mixture-proportioning approaches fordeveloping SCC mixtures:

• High powder content and HRWRA;

• Low powder content, HRWRA, and VMA; and

• Moderate powder content, HRWRA, and moderateVMA dose (stability can be controlled throughblending of aggregates, lowering water content, or byusing a VMA).

In some cases, VMAs or higher powder contents will beused to promote stability.

4.2—Performance requirementsBefore starting the proportioning of SCC, the project

specifications should be reviewed. The review will establishthe specified required slump flow (Table 2.5), strength, agewhen strengths are to be attained, and testing methods foracceptance of the SCC properties of stability, filling ability,and passing ability. SCC is proportioned to meet a targetslump flow range and a required compressive strength and tofulfill any specific application requirement. Establishing theinitial target value for slump flow is the first step in developingan SCC mixture. Table 2.5 provides guidance for choosingthe initial slump flow target (Daczko and Constantiner2001). Based on the application, the characteristics of anelement should be rated as low, medium, or high. The darkareas of the table are potential problem areas that should beavoided. Other test methods for evaluating the filling ability,passing ability, and stability characteristics of the SCCmixture are discussed in Chapters 2 and 8 of this document.

4.2.1 Test age—Typically, 28-day age strengths arespecified. The selection of mixture proportions, particularlythe cementitious composition, can influence the strength fora given age. The use of fly ash, GGBFS, and silica fume maybe used to improve the plastic and hardened properties ofSCC as well as control heat of hydration.

4.3—Materials4.3.1 Cement—Cements allowed should meet one of the

following specifications: ASTM C 150, C 595, or C 1157.4.3.2 Finely divided powders and supplementary

cementitious materials—Combining finely divided powders,admixtures, and portland cement can enhance the behaviorof SCC (filling ability, passing ability, and stability). Themain target is to enhance the grain-size distribution andparticle packing, thus ensuring greater cohesiveness. Inbinary and ternary mixtures, each constituent’s particle-sizedistribution, volume fraction of the particles, particle formand shape, and chemical composition influence the rheolog-ical property of the paste. For SCC, it is important to seek acombination of constituents that provides the mortar theappropriate yield stress for the application while maintainingadequate viscosity to ensure passing ability and segregationresistance. These characteristics are influenced by theproperties of each constituent material and the physical andchemical reaction between them.

The reduction in free water content and increase in thevolume of powder increases the stability of SCC. Althoughthe inert filler does not meet any published specification, itoften improves the quality of SCC. Inert filler, obtained bygrinding limestone or siliceous aggregates, can be used toenhance the portland cement particle-size distribution andachieve a better packing density. The fine fraction of thesefillers will increase the specific surface of the blend, whilecoarse fractions can help bridge the gap between the sandand portland cement. The replacement of a portion of cementwith finely ground limestone filler is shown to improvefilling ability and stability without affecting the 1-daycompressive strength. The concrete can exhibit up to 10%lower 28-day strength compared with similar concrete


without filler. Proper selection of ground materials canenhance the packing density of solid particles and enable thereduction of water or HRWRA demand required to achievehigh filling ability (Ghezal and Khayat 2002). The replacementof part of the cement with a less reactive powder may provebeneficial when project requirements limit the heat ofhydration.

4.3.2.1 Silica fume—Silica fume can increase thestability of SCC mixtures. The mixture stability is increasedby the silica fume’s ability to reduce the mobility of the waterwithin the concrete matrix. At relatively low replacementrates—5% or below—plastic viscosity of SCC decreases.The replacement rate required will be generally affected bythe size, shape, and distribution of the cement particles. Athreshold replacement rate, with respect to a decrease orincrease in plastic viscosity, may be established throughlaboratory trials using the T50 test method for slump flow(Chapter 8). When low replacement rates are established andincorporated in to the SCC mixture, silica fume’s small sizeand rounded shape reduces friction between the largercement particles, in essence lubricating the paste matrix.

4.3.2.2 Fly ash—Most fly ash particles are sphericalwith a smooth surface that can act as a ball bearing within thepaste of the SCC mixture. Because of this, fly ash mayenhance the workability and slump flow of SCC. Slump flowvalues are increased when the replacement rates are between20 and 40% of portland cement (Fang et al. 1999). Optimumreplacement values are dictated by job specifications, materialcompatibility, and cost (Sonebi et al. 2003). Generallyspeaking, fly ash density is lower than GGBFS; therefore, fora given mass, a larger volume can be incorporated into theSCC design, ultimately increasing paste volume and stability.

4.3.2.3 Ground-granulated blast-furnace slag—GGBFSmeeting ASTM C 989 is hydraulic cement and can be usedto replace a portion of the portland cement. The percentageof the replacement is specified and should be agreed to beforeSCC placement. The increased Blaine, relative to mostcements, can also add stability to the mixture. Optimumreplacement values will be determined by job specifications,overall compatibility with the cementitious system, or both.

4.3.3 Aggregate selection—The nominal maximum sizeof the coarse aggregate should be chosen with respect toobtaining an acceptable passing ability and stability of theplastic concrete. Coarse aggregate size and the volume ofcoarse aggregate are influential in obtaining the passingability of the concrete. Therefore, the nominal maximumsize of the coarse aggregate may be one size smaller thansuggested in ACI 301 to improve the passing ability. Particleshape of the coarse aggregate is also significant in terms ofaffecting the workability of SCC. A rounded coarse aggregatewill impart greater filling ability for the same water contentof a mixture compared with a crushed stone of similar size.The blending of different sizes of stones can often be beneficialto improving the overall characteristics of the mixture. As aguideline to minimize blocking of SCC through the reinforce-ment, if the coarse aggregate is greater than 1/2 in. (12.5 mm)nominal maximum size, then the absolute volume of coarseaggregate should be in the range of 28 to 32% of the volume

of concrete for congested formwork. For applicationswithout aggregate blocking or passing ability concerns, thepercentage of total volume of coarse aggregate may be greater.

4.3.3.1 Fine aggregate—The fine aggregate componentshould be well-graded concrete sand; it may be beneficial toblend natural and manufactured sand to improve SCC plasticproperties. In some cases, VMA or higher powder contentswill be used to promote stability.

4.3.4 Admixtures—There is a variety of commerciallyavailable HRWRAs that can be used to produce SCC. Poly-carboxylate-based HRWRAs are the most typical admixturematerials used for developing and proportioning SCC.VMAs are also beneficial materials for adjusting theviscosity and improving the stability of SCC.

In general terms, HRWRAs impart fluidity, while VMAsprovide an increase in viscosity (cohesiveness) to improvethe stability of the mixture. In some cases, HRWRAs willplay a dual role by providing fluidity while maintaining theviscosity of SCC. The admixtures, along with otherproportioning techniques such as combined gradation ofaggregates, increasing the fine aggregate content, powdercontent, or both, are controlled to impart stability.

Not all HRWRA or VMA products have the same properties.Some HRWRAs impart the characteristics of stability andcohesiveness; others do not. A VMA used with a HRWRAimproves the viscosity and increases the ability of themixture to tolerate variations in batch water adjustment. Theuse of a VMA is not always necessary, but a VMA can beadvantageous when using lower powder contents and gap-graded or demanding aggregates. Because VMAs do notincrease the overall paste content, the passing ability of amixture developed using a lower powder content andVMA for use in an application with dense reinforcementshould be evaluated before the start of the project. Thesuppliers of admixture products should be consulted fordosage and point-of-addition recommendations.

Recommended values for slump flow are given in Table 2.5.Although SCC has been produced successfully withoutmeasurement of the initial slump, an initial slump beforeadding the HRWRA is recommended for trial batch control.As an initial guideline, a water content should be selected toobtain an initial slump less than 4 in. (200 mm).

When performing trial batches, the water sensitivity of themixture should be established with additional trial mixtures.This is accomplished by taking the selected concrete mixtureproportions and adding successive amounts of water to themixture and recording the stability level after each wateraddition. The amount of added water that causes the mixtureto become unstable defines the mixture’s water sensitivity.This water sensitivity range should be designed to bewithin the capabilities of the concrete producer.

4.4—Mixture proportioning procedureEstimating the required batch weights involves a sequence

of steps. These steps fit a proportioning procedure thatcovers a combination of: selection of aggregates to providethe desired passing ability; a cementitious (powder)-waterratio and mortar-paste fraction ratio that have been histori-


cally proven to produce SCC with the required slump flow;and stability. These steps, in combination with the additionof the appropriate admixture technology, should yield a trialbatch with the desired fresh SCC properties.

The following is a summary of steps for determiningperformance requirements and proportioning of SCC.• Step 1: Determine slump flow performance requirements

(Table 2.5);• Step 2: Select coarse aggregate and proportion (ACI 211.1

and 301);• Step 3: Estimate the required cementitious content and

water;• Step 4: Calculate paste and mortar volume;• Step 5: Select admixture;• Step 6: Batch trial mixture;• Step 7: Test. When assessing the workability attributes

of SCC (stability, filling ability, and passing ability),the slump flow test as well as a test to evaluate stabilityand passing ability (such as column segregation, J-ring,or L-box) should be run; and

• Step 8: Adjust mixture proportions based on the testresults and then rebatch with further testing until therequired properties are achieved.

4.4.1 Establishing coarse aggregate content—The abilityof the SCC to flow through openings between steel reinforcingbars is related to both the nominal maximum size of thecoarse aggregate and the volume of the coarse aggregate inthe mixture proportion. The goal is to use the greatestvolume and largest coarse aggregate possible while stillproviding good stability, filling ability, and passing ability ofthe fresh SCC. The factors that influence the size and amountof coarse aggregate are:

1. The clearance between reinforcing bars;2. Texture of the aggregate surface—natural aggregate with

rounded smooth surface versus crushed angular aggregate; and3. Gradation of the coarse aggregate.All other mixture parameters being equal, a concrete

mixture containing well-rounded natural gravel could beused at a higher volume of coarse aggregate than that withangular crushed aggregate with the same gradation.

This guide will separate the nominal maximum aggregateinto two categories:• Category I: 1/2 in. (12.5 mm) and larger nominal

maximum size of aggregate; and• Category II: nominal maximum size smaller than 1/2 in.

(12.5 mm)4.4.1.1 Coarse aggregate content for Category I—As an

initial starting point in determining the aggregate content,the bulk dry density of the coarse aggregate should bemeasured. Fifty percent of the total concrete volume shouldbe filled with that bulk volume of coarse aggregate(Okamura and Ouchi 1999).

Example—Given the bulk dry-rodded unit weight ofcoarse aggregate at 100 lb/ft3, the pounds of dry coarseaggregate are calculated as

27 × 0.50 × 100 = 1350 dry lb/yd3

Metric: Given the bulk dry-rodded unit weight of coarseaggregate of 1600 kg/m3, the kilograms of dry coarseaggregate are calculated as

0.50 × 1600 kg/m3 = 800 kg/m3

As a starting point, in terms of absolute volumes, approx-imately 28 to 32% (7.5 to 9 ft3) of the total absolute volumeof a cubic yard would be coarse aggregate 0.5 in. (12.5 mm)and larger nominal maximum size. Again, size, gradation,and surface texture will influence the volume of coarseaggregate that will enable an acceptable passing ability ofthe plastic SCC concrete. To improve its fresh properties,such as passing and filling ability, SCC may have a lowercoarse aggregate content than is typical for normal concrete.

Using the methodology of blending the aggregates to apower of 0.45 curve may benefit the workability of themixture and lower water demand (ACI 302.1R). A fulldiscussion of the use of this technique is outside the scope ofthis document.

4.4.1.2 Coarse aggregate content for Category II—Thissize range of coarse aggregate is used with very congestedsteel reinforcement or challenging concrete placing condi-tions. An initial proportion of 50% sand and 50% coarseaggregate (3/8 in. [10 mm]) by volume would be a reason-able starting point for the first trial batch. Once the plasticproperties of the trial batch are assessed, the sand-aggregateratio may be adjusted.

4.4.2 Powder and water content—Powder includescement, fly ash, GGBFS, limestone fines, material crushed toless than 0.125 mm (No. 100 sieve), or other noncementitiousfiller. The relationship between the w/c or w/cm and compres-sive strength of concrete is well documented; refer to ACI211.1, Table 6.3.4. With SCC, the compressive strengthrequirements may not be the decisive factor when selectingthe amount of cementitious material. The fineness andvolume of the cementitious powder in conjunction with thefines in the aggregate help create a matrix that supports thecoarse aggregate in the cementitious mortar, thus addingstability (segregation resistance) to the concrete. An appropriatepowder content for initial testing is 650 to 800 lb/yd3. Whenperforming trial batches, it may be more prudent to start withhigher cement (powder) contents, and then optimize themixture for improved economy. To achieve higher slumpflows and prevent segregation, it may be necessary toincrease paste content by increasing water, powder contents,or both. The ratio of water to powder may stay relativelyconstant, but the volume of water plus powder increases.Generally, as the desired slump flow increases (increasedfilling ability), the powder contents required to achievepassing ability and stability will also need to increase, asshown in Table 4.1.

4.4.3 Paste and mortar volume—For this document, thefollowing definitions apply: paste volume is the volume ofcementitious and other powder, water, chemical admixtures,and air. Mortar volume is the paste volume plus the volumeof fine aggregate (material passing a No. 8 sieve).


Both paste and mortar volumes are expressed in percenttotal volume of the concrete mixture.

Example:

Paste volume of 38% = 0.38 × 27= 10.26 ft3 of paste/yd

(0.38 × 1 m3 × 1000 L/m3 = 380 L/m3)

Common target ratios:

Paste volume ratio: 0.34 to 0.40 (10 to 11 ft3 of paste)Mortar volume ratio: 0.60 to 0.70

The percent volumes of paste and mortar will generally begreater than for conventional concrete. It is the fluidity of thepaste and the ability of the mortar to carry the coarse aggregatethat convey the overall filling ability, passing ability, andstability of the concrete. Increasing paste and mortar volumehas a significant effect on slump flow, irrespective of admix-ture adjustment. The mortar volume of the mixture will alsoinfluence the passing ability of the SCC. Table 4.2 has asummary of proportioning guidelines. The values suggestedare only initial targets for trial mixtures, and will vary withlocal materials.

4.5—Examples of SCC mixture proportionsTable 4.3 provides examples of successful SCC mixture

designs. These examples are provided to illustrate the principlesdiscussed in this chapter.

The SCC mixture proportions provided in this chapter areexamples of mixtures that have been successfully used inactual projects. These mixture proportions should not becopied or used in a project without first performing fieldtrials; local materials may have a considerable effect on theproportioning of SCC concrete. It should always be verifiedthat the desired performance will be achieved. The reader is

cautioned that SCC mixture development should take intoaccount the local materials, desired application, requiredperformance, and expected environmental conditions at thetime of concrete placement. These examples, however, canbe used as a starting point for developing SCC mixtures.

CHAPTER 5—PRODUCTION5.1—General

SCC needs to be both fluid and stable. The required levelof fluidity is greatly influenced by the particular applicationbeing considered (Daczko and Constantiner 2001; Daczkoand Attiogbe 2003). The production of SCC requires carefulselection and control of the raw materials. This chapter willprovide some guidelines regarding the influence of materialcomposition on the SCC performance.

5.2—Production issues that influence fresh SCC properties

5.2.1 Raw materials—Changes in material characteristicscan have a significant impact on the SCC mixture performance.A consistent source of all raw materials should be usedthroughout the duration of a project. Strict control of thematerials characteristics is paramount. Refer to Chapter 4 fordetails on how to select materials.

5.2.2 Batching and mixing—Optimum batching andmixing procedures need be determined for the SCC propor-

Table 4.1—Suggested powder content ranges*

Slump flow of < 22 in.

(<550 mm)

Slump flow of 22 to 26 in.

(550 to 600 mm)

Slump flow of>26 in.

(>650 mm)

Powder content, lb/yd3 (kg/m3)

600 to 650(355 to 385)

650 to 750(385 to 445)

750+(458+)

*or as needed for strength.

Table 4.2—Summary of SCC proportioning trial mixture parameters

Absolute volume of coarse aggregate*28 to 32% (>1/2 in. [12 mm] nominal maximum size)

Paste fraction (calculated on volume)34 to 40% (total mixture volume)

Mortar fraction (calculated on volume)68 to 72% (total mixture volume)

Typical w/cm 0.32 to 0.45

Typical cement (powder content)650 to 800 lb/yd3

(386 to 475 kg/m3)(lower with a VMA)

*Up to 50% (3/8 in. [10 mm] nominal maximum size).

Table 4.3—Examples of successful SCC mixture proportionsSlump flow 26 in. 26 in. 26 in. 33 in. 27 in. 26 in.

Polycarboxylate (PC) Yes Yes Yes Yes Yes Yes

Air entraining Yes Yes Yes Yes Yes Yes

Water reducer Yes — — Yes — —

VMA — — — Yes Yes Yes

Total cementitious material, lb/yd3* 750 680 780 797 700 700

Cement 600 680 620 345 700 600

Fly ash 150 — — 140 — 100

GGBFS — — 160 312 — —

w/cm 0.37 0.42 0.39 0.34 0.41 0.40

s/a (volume) 49 49 46 61 53 48.2

Percent paste fraction 37.1 36.5 38.1 36 34.7 35

Percent mortar fraction 64.6 68.3 63.4 64 59.5 65.6

Percent volume of coarse aggregate

35.6 31.7 36.6 36 31 33.5

Total gradation (sieve size), percent retained

1.0 in. (25 mm) — — — — — —

3/4 in. (19 mm) 2.3 — 0.7 0.75 3 9

1/2 in. (12.5 mm) 9.2 — 11.3 5.6 15 19

3/8 in. (9.5 mm) 5.1 — 6.5 11.8 14 8

No. 4 (4.75 mm) 25.4 26.6 23.6 26.2 15 14

No. 8 (2.36 mm) 14.4 23.3 16.9 12.4 16 4

No. 16 (1.18 mm) 9.5 10 5.7 12.5 14 12

No. 30 (600 μm) 11.1 12.5 8.2 20.1 10 13

No. 50 (300 μm) 12.2 14.2 18.4 8.5 8 14

No. 100 (150 μm) 7 11.2 7.1 1.5 3 6

Pan 3.9 2.3 1.4 0.24 1 1*1 lb/yd3 = 0.5932764 kg/m3.


tions being tested. An important qualification procedure forSCC mixtures is to perform trial batches from productionmixers and adjust the mixture as necessary to attainhomogeneity. In some cases, SCC may require an additional30 to 90 seconds of additional mixing versus conventionalconcrete. Refer to the applicable sections of ACI 304R foradditional guidance on concrete batching and mixing.

5.3—Performance targets5.3.1 Fresh properties—The fresh SCC properties developed

as a result of the use of the tables presented in Chapter 4should be confirmed in actual production conditions. Themixture proportions and performance should be adjusted asrequired.

5.3.2 Hardened properties—The SCC should meet orexceed project specifications.

5.3.3 Tolerances—Quality-control tolerances should beestablished for the range of plastic and hardened concreteproperties to be expected. These tolerances should beestablished through mixture proportioning qualification inthe context of the project specifications.

5.3.4 Mixture robustness—Mixture robustness is theoverall tolerance of the fresh concrete properties to fluctuationscaused by variations in raw materials, moisture contentconditions, concrete temperatures, or a combination of these.SCC mixtures are more sensitive to consistency fluctuationsduring production than conventional concrete. Fluctuationsin aggregate gradations and free moisture contents can havedramatic influence on the stability of the concrete mixtures(Daczko and Attiogbe 2003; Emborg and Hedin 1999;Daczko and Consantiner 2002). Batching fluctuations canalso significantly affect both stability and fluidity. Duringthe mixture qualification process, it is recommended toinvestigate the sensitivity of the particular design and theraw materials being used to fluctuations in fluidity level(slump flow) and moisture content (extra water).

5.3.5 Fluidity instability—Because the level of fluidity hasa direct impact on the stability of a mixture, once a suitablemixture has been developed, the level of fluidity (slumpflow) at which the mixture becomes unstable should bedetermined (Daczko and Attiogbe 2003; Daczko 2002). Thisshould be done initially with an HRWRA, but it can also bedone with water. When examining this characteristic, thefact that some HRWRA will lose slump flow more rapidlythan others should be taken into consideration. A mixtureshould be batched; slump flow, T50 (relative flow rate) andVSI (stability) measured; and successive amounts ofHRWRA or water added, measuring slump flow and VSI ateach addition. The level of slump flow or water content atwhich the mixture becomes unstable should be recorded.Other stability test methods, such as the column stability testor bleed test (ASTM C 232), can be used instead of the VSIfor quantitative assessment of this characteristic.

5.4—Mock-upIt is recommended that, as part of the mixture proportion

qualification/development, each SCC mixture be subject toactual production-based confirmation. This is accomplished

by running the proportioned SCC mixture through plantproduction equipment and, when possible, casting into aform similar to that which will be used on the project.

5.4.1 Test pieces—The actual performance of an SCCmixture in a test piece can be used to confirm productionmethods and ensure that the SCC mixture results in a homo-geneous element without segregation. Test placements ofcomplex portions of elements can be used to optimizeplacing techniques and details of the element itself to assuresuccessful use of SCC on the full-scale production unit.

5.4.2 Diagnostic analyses—Careful hardened testing ofthe cast piece should be coordinated as part of the trialprocedure. This includes taking cores from various locationsto ensure uniform distribution of the materials, air-voidsystems, permeability, and compressive strength.

5.4.3 Confirm mixture performance through performancehistory—The correct quality-control test parameters shouldbe established by understanding the values generated bythese tests and determining the minimum and maximumvalues needed to achieve a good performance. These quality-control parameters should be identified based on sufficientexisting mixture proportion history or performance fromproduction trials and finished product performance, or both, toensure production regularity and to satisfy job requirements.

5.5—Employee trainingBecause this is a new technology, those employees

associated with the testing or use of SCC should be trained,tested, and qualified appropriately.

5.5.1 Quality control—The day-to-day production ofquality SCC requires that all inspection testing personnel beproperly trained. At the time this document was written,there is no known certification program; therefore, trainingshould be provided by the producer. As a baseline, personnelshould have certification as an ACI Field Technician andConcrete Special Inspector. The objectives, methods, unifor-mity of practice, inspection, and record keeping required inthe production of SCC are no less important than any otherfacet of the quality-control program.

5.5.2 Quantitative and qualitative analyses—Everyquality-control inspector involved in the production andtesting of SCC should be trained and qualified in the propertesting procedures for various test methods. In addition tounderstanding how to properly conduct the tests, the quality-control personnel should also be able to evaluate the resultsof those tests. If the desired quality and value of a SCCmixture is to be realized, the quality-control personnelshould understand the engineering properties, placementtechniques, element characteristics, and raw materialsconsiderations that were used to determine mixture proportionsand fresh concrete properties.

5.5.3 Production personnel—To produce SCC thatachieves the desired quality, it is imperative that productionpersonnel receive training on the effect that productionmethods can have on these properties. Production personnelshould understand that each self-consolidating mixture hasbeen carefully designed to take into account all aspects ofmaterial selection, form condition, placement methods, and


engineering properties. Well-trained production personnelcan provide valuable input in developing effective correctiveaction plans whenever the specified SCC quality or perfor-mance is not being achieved. When quality or performance isnot being achieved, the contribution of knowledgeableproduction personnel is vital to taking proper corrective action.

CHAPTER 6—TRANSPORT, PLACEMENT,AND FINISHING

6.1—GeneralDue to the unique rheology of SCC, factors such as form

characteristics, method of concrete discharge, and volumeand rate of supply of the concrete during discharge can affectthe placement of the concrete. Therefore, proper knowledgeof these factors and careful planning is required.

This chapter contains methods and techniques used tosuccessfully place SCC mixtures in numerous applications,including columns, double tees, beams, modules and walls,repairs, and slabs. This overview of SCC placement in avariety of applications will help those transporting, placing,and finishing SCC mixtures.

6.2—TransportSCC can be transported using all of the conventional

concrete devices, but some precautions should be considered.6.2.1 Transit mixer—SCC can be delivered to a job site by

a concrete truck. Because of the fluidity of SCC mixtures,the volume of SCC placed into a truck should not exceed ofthe 80% capacity of the drum (ASTM C 94/C 94M). Thistype of monitoring is important to ensure that SCC does notspill out of a concrete truck (rear or front discharge) when-ever the truck goes up or down a steep incline. Concretetruck operators should keep the revolving drum turning in themixing mode direction while in transport. Alternatively,some suppliers have delivered the mixtures to the project ata conventional concrete consistency and added an HRWRAto bring the mixture to an SCC consistency. When SCC isdelivered and placed by a concrete truck where the speed ofdischarge and volume of concrete delivered is high andcontinuous, the mixture will experience further flowingdistances and improved filling capacities. A concrete truck isan effective method of placing SCC mixtures with slumpflow levels of 18 to 30 in. (455 to 760 mm) (Bury andBüehler 2002).

6.2.2 Hopper or bucket—SCC mixtures can be transportedto forms by concrete truck, hopper or bucket transporters, orother specialized devices. When hopper-type vehicles areused, SCC mixtures do not receive any additional mixingand should be very stable to resist segregation from vibratoryforces encountered during transport from the batch plant to aform. SCC transported by bucket from an overhead liftreceives minimal or no vibration, and does not require the samelevel of stability as SCC transported in a hopper-type vehicle.Bolting rubber strips or pads to the clam shell discharge pointof buckets is an effective method to prevent leakage of low-viscosity SCC mixtures during transport to forms. A chuteattached below the bucket opening will direct the flow of theSCC toward specific areas of the form to be filled.

When casting SCC using a hopper or bucket placementmethod, a limited volume of SCC can be placed at any onetime, thus reducing the rate of concrete placement. This canresult in discontinuous discharge rate of flow of concretecompared with placement by truck chute, where a largevolume of concrete can be continuously cast. These factorscan have direct consequences on the required flow charac-teristics of the concrete. SCC placed using a mobile hopperor bucket should have relatively high slump flow. Transportmethods that employ a screw to convey the SCC from thehopper to the form should be operated with the screwconveyor turning. When the screw conveyor is heldstationary, the paste may separate from the coarse aggregates,causing segregation. The use of larger volume transportvehicles, such as concrete trucks, rather than hopper orbucket transporters, is advantageous in rapidly filling forms.In the case of a relatively large section, this can avoid theproduction of multiple batches of concrete. SCC placementby bucket has a high discharge rate, and is discontinuous.SCC transported to a form by bucket should have a slumpflow of 24 to 28 in. (610 to 710 mm) to help facilitate place-ment by increasing flow distance and permitting consolida-tion with consecutive loads. The use of a deflector or a chutehelps to direct the flow of the SCC to the desired positionwithin the form.

6.2.3 Pump—One of the advantages of SCC is its abilityto flow long distances without any mechanical consolidation.Such distance is typically limited to 33 ft (10 m) to limit thesegregation of the concrete while ensuring self-consolidatingproperties. On jobs where there is minimal access for concreteplacement, SCC can eliminate the need for pumping becauseit can flow to the desired location. In hard-to-reach areas,pumping is needed to place concrete. SCC can easily bepumped in place without mixture segregating. The followinglists benefits from pumping SCC over conventional concrete:• Pump pressures are significantly reduced;• Pumping at truck idle minimizes wear and tear on

equipment;• Air contents remain stable;• Slicking pump lines with slurry if a pump line is 3 in.

(75 mm) or smaller; if the pump line is larger than 3 in.(75 mm), priming with slurry is not necessary; and

• Pumping beginning with very low pressures; highinitial pressures can cause the coarse aggregates in SCCto segregate from the paste, which can cause plugging.

The committee is not aware of any restrictions to pumpingSCC using conventional pumping equipment as long as themixture is stable.

6.3—Discharge of SCC for slabs or open-top molds for factory-type precast elements

Unlike conventional concrete, SCC is cast into placewithout any mechanical consolidation and human interventionto spread the concrete into place. The flow of SCC and fillingof the slab or open-top molds for factory-type precastelements is affected by the placement method and thecharacteristics of the concrete discharge into the mold orformwork. Proper planning and consideration of these


parameters is essential in designing the fluidity and stabilitycharacteristics of the SCC. Specific conditions related to thedischarge of the SCC will affect placement duration,construction cost, and ultimate concrete properties. Therefore,it is important to consider the actual placement method anddischarge conditions in planning SCC construction activities.

Table 6.1 (Daczko and Constantiner 2001) shows anoverview of the traditional ways that concrete is placedand, for each technique, a relative rating is given for fourunique categories:• Discharge rate: The volume of concrete is being

discharged over a set time period;• Discharge type: The manner in which the concrete is

being supplied during placement;• Single discharge volume: The relative volume of

concrete continuously placed from a given vessel; and• Flow momentum: An overall flowability rating deter-

mined as a combination of the other three categories.For the discharge rate, single discharge volume, and flow

momentum categories, a relative rating of high, medium, orlow is given to describe the concrete characteristics. Thedischarge type is determined to have either a continuous ordiscontinuous descriptive rating. The relative ratings assumeidentical drop heights and mixture densities, which wouldaffect the amount of flow momentum of the concrete.

The flow momentum rating and its relation to the form-work geometry may have an impact on the type of SCCmixture required. For example, in a specific applicationusing identical mixture proportions, a contractor using aplacement technique with a high flow momentum rating willexperience further flowing distances and improved fillingcapacities of SCC when compared with a placement techniquewith a low flow momentum rating. Using this example, aconcrete producer, aware of a contractor using a placementtechnique with a high flow momentum rating, could producea lower level of slump flow for a project, thereby potentiallyreducing the cost of the concrete mixture.

6.4—Formwork, element characteristics,and reinforcement

6.4.1 Form characteristics—Forms or molds assembled toreceive SCC come in different sizes and shapes. The formcharacteristics will have an effect on the target fluidity andstability performance of the SCC mixture (Daczko andConstantiner 2001). Formwork should be watertight(nonleaking) and grout-tight when placing SCC, especiallywhen the mixture has relatively low viscosity. The need todesign the formwork for water tightness is greater thanconventional formwork so as to avoid honeycombs andsurface defects.

6.4.1.1 Form pressure—The highly fluid nature of SCCmay lead to higher formwork pressure than conventionalconcrete, especially when the casting rate is high. As a resultof the highly fluid nature of SCC, a high placement rate islikely and should be anticipated. This is especially the casewith the wall and column elements of restricted sections. Themaximum initial lateral pressure and its rate of drop in timeafter casting are affected by the rheology, thixotropy, initial

consistency of the concrete, casting rate, and concrete andambient temperatures (Assaad 2004). Key mixtureproportioning characteristics affecting formwork pressure ofSCC include the coarse aggregate volume, binder type andcontent, and the type and dosage of HRWRA (Assaad 2004).Formwork designs that accommodate the expected liquidhead formwork pressures can allow unrestricted placementrates and permit the contractor to take full advantage of a fastcasting rate of the SCC. It is recommended to design theformwork for full liquid head, especially when the castingrate is high. SCC formwork needs to be designed usingEq. (2-1) in ACI 347. This conservative approach is requireduntil published, documented research is available to designby another equation.

As the rate of SCC placement increases, however, so doesthe pressure. When filling the form is accomplished by apump attached to the bottom of the form, formwork pressureis about twice as high as when filling from the top withoutpressure (Brameshuber and Uebachs 2002). A researchprogram initiated by the Insulated Concrete Forms Associationstudied the effect of SCC on form pressure in ICF construction.The results showed that SCC exerts equal or less pressurethan conventional concrete with 8 to 10 in. (200 to 260 mm)slump that is vibrated (Gajda and Dowell 2003). Thecommittee is aware that this is one area where the concreteindustry needs very specific guidance. Committees 237 and347 have created a joint task group to thoroughly compileand analyze all of the published research on the topic offormwork pressures for SCC. The task group will thendisseminate the information through a special publication, astate-of-the-art report on SCC.

6.4.2 Element shape intricacy—The more intricate theform shape, the more difficulty a concrete mixture will haveduring the filling process to flow into place and produce anelement without voids or honeycombing. Because of a lackof edges or corners, for example, a round column is easier toproduce with fewer surface voids than a square column. Theelement intricacy is a variable to consider when designingthe flow level of the SCC mixture. In general, a higher levelof form intricacy and reinforcement congestion will requirea higher slump flow and possibly a lower viscosity to allowair to escape from the form surfaces.

Table 6.1—Relative comparison of placement techniques and flow momentum (Daczko and Constantiner 2001)

Placement technique

Discharge rate

Discharge type

Single dis-charge volume

Flow momentum rating

Truck chute High Continuous High High

PumpMedium/

highContinuous Medium Medium/high

Conveyor Medium Continuous High High

Buggy Medium Continuous Low Low

Crane and bucket

High Discontinuous Low Low/medium

Auger Low Continuous Medium Medium

Drop tube High Discontinuous High High


6.4.3 Element depth—SCC has a greater potential forsegregation in column applications than slab applicationsdue to the increase in the depth of the form. The deeper theelement depth, the higher the required level of dynamicstability during placement and static stability after placementof SCC.

6.4.4 Element length and width—Long forms generallyrequire SCC mixtures with a slump flow greater than 24 in.(610 mm) and high stability to minimize moving of theplacement equipment. SCC placed in narrow forms achievesbetter flowing potential because the discharge is concentratedin one area, creating a head of SCC that facilitates flow in thelonger direction. Therefore, SCC placed in smaller-widthforms need not have as high of a slump flow. Prior planningis essential to ensure that equipment discharging SCC can gainaccess to forms at points appropriate for letting concrete flowand consolidate into itself from previously placed concrete.

6.4.5 Element size—Production coordination is essentialfor larger placements to ensure an adequate and timelysupply of SCC. In an application that will require a largequantity of concrete (multiple batches), each batch should bemade available within a short time frame because of SCC’scapacity to discharge quickly over a large area. When a largesurface area of SCC is exposed to adverse weather conditions,steps should be taken to protect it against premature moistureevaporation that can cause plastic shrinkage cracking. Aninadequate or intermittent supply of SCC, when placed indrier and warmer ambient conditions, may result in pourlines. Pour lines appear as dark, thin lines that can distinguishedbetween layers of concrete placed. These pour lines can bemerely cosmetic or can indicate cold joints.

6.4.6 Surface finish—An SCC mixture with the consistencyand look of peanut brittle indicates a mixture with higherviscosity and should be suitable for placement in heavilysteel-reinforced applications. The finishing technique andthe type of finish applied influence the overall look of thefinished concrete. By contrast, an architectural panel orcolumn surface is formed and mainly controlled by the flowproperties of the concrete. For SCC, an improved surfaceappearance is generally obtained with slump flow valuesgreater than 24 in. (610 mm) with controlled rheologicalproperties and minimal to no bleeding characteristics.

High volumes of SCC can be placed over a short period oftime. For slab applications, it is necessary to ensure the avail-ability of a sufficient finishing workforce that can accom-modate the area to be finished. Typically, because of fasterplacement times, SCC will yield a larger concrete surfacearea ready for finishing at a given point in time whencompared with conventional concrete. A field trial before thestart of a project is recommended to determine the placement,setting time characteristics, and finishing techniques for themixture.

6.4.7 Degree of reinforcement—When a form containsreinforcing steel, there is a minimum clear spacing betweendifferent sections of reinforcing steel as well as between thereinforcing steel and the form wall. The more congested theform, the higher the potential for aggregate bridging andblocking that can lead to segregation of the SCC mixture. For

congested steel-reinforced forms, a smaller coarse aggregatetop size is required to minimize or eliminate this phenomenonduring placement. The SCC mixture should also be stable toreduce the potential of aggregate separation from thepaste as the mixture flows between reinforcing bars orprestressing strands.

6.5—Placement techniquesAs with any concrete placement for a given application, a

field trial or mock-up should be performed to ensure that thedesired performance is achieved. Generally speaking, it isimportant not to overfill the form. When screeded, SCCmixtures with a low viscosity have a tendency to roll underthe screed; this requires multiple passes by the finishingcrew to level the SCC to the form edge.

Whenever possible, SCC should be deposited continuouslyand in layers of such thickness that no fresh SCC is placedon concrete that has hardened enough to cause a seam orplane of weakness. Because of its thixotropic characteristic,SCC can be placed onto previously placed SCC that hasgelled but has not yet achieved initial set. In this case, it isacceptable to use an internal or external vibrator for a 2- to3-second duration to avoid pour lines in the piece. If asection cannot be placed continuously, construction jointsshould be provided.

The SCC placement techniques for each of the applica-tions described in Sections 6.5.1 through 6.5.7 represent asummary of information learned from actual field experi-ences in North American applications (Bury and Bühler2002). When possible, SCC should be discharged in thedirection of desired flow to maximize the distance of travel.

6.5.1 Double tee production—One placement techniquefor double tee production is to place the stems of each doubletee first, and then proceed with the flange portion. This tech-nique is generally used when auger-type equipment is themethod for placement. Placement can start from the middleof the bed, allowing the SCC mixture to flow into place onits own toward the ends of the bed (Bury and Bühler 2002).

Concrete trucks can also be used to cast the SCC in doubletee production. Transit mixers usually have larger concretecapacity than auger-type equipment. This could reduce thenumber of deliveries per bed of double tee production. Aslump flow of 23 to 26 in. (585 to 650 mm) will generally beadequate for double tees; however, values outside this rangecan be acceptable. During placement, a vibrating screed, usedat a very low setting, can take the place of the raking,screeding, and bullfloating operations if it is carefully guidedover the surface of the concrete.

Another proven method for SCC placement by hopper-type vehicles is to start filling one stem and flange portion onone side of the tee and move forward along the form to theother end of the section as the concrete fills the tee form. Thesame process is repeated for the other stem and flange side.The final finish should be applied as appropriate. Thismethod does not require a mechanical screed.

6.5.2 Beams—Many different configurations of structuralbeams can be produced using SCC. The production ofrelatively deep beams reaching heights of 8 ft (2.4 m) and the


casting of heavily reinforced beams, however, can presentsome difficulties. For tall beams, refer to Section 6.5.4 onmodules and walls. Ideally, the point of SCC filling shouldbe near one end of a beam and remain there until it is filledcompletely. For heavier reinforced taller beams, slump flowvalues of 24 to 28 in. (610 to 710 mm) are effective (Buryand Bühler 2002).

6.5.3 Slabs—Slab placement using SCC is different thanconventional concrete mixtures because of its self-levelingcharacteristics. SCC should be discharged at one point andallowed to flow as far as practical before moving the point ofplacement. SCC used in casting slabs should be dischargedat one point and allowed to flow into place before moving thepoint of placement. The maximum allowable horizontalspread distance will depend on the stability of the concrete,and is typically limited to 33 ft (10 m). Long-flow distanceof the SCC will allow the mixture to fill the form and self-level, thereby minimizing the degree of screeding and bull-floating typically required to level slabs.

6.5.4 Modules and walls—These elements are typicallyvery thin in nature and are often less than 4 in. (100 mm)thick. Vibration, used for consolidation of conventionalconcrete in walls, moves entrapped air bubbles toward theform surface rather than driving them out toward the top ofthe form. There has been no documented benefit in vibratingSCC in this type of application. On modules containing acore, SCC should be placed onto the core and then allowedto run over the edge and into the wall. On walls withoutcores, specially manufactured deflectors or breaker boardsattached to the forms or the discharge container can guideconcrete into place to avoid direct freefall that could entrapair. A continuous supply of concrete flowing into the formwill build its own column of transport, operating much likean invisible tremie pipe. It is very important to create alateral flow within such structures, as horizontal SCCmovement can fill the unit without entrapping air.

Another method to fill modules and walls is to pump themfrom the bottom of the form, permitting the concrete to builda wall and push the air out of the form. For complex modulessuch as jail cells, it is advantageous to pump from multiplelocations.

In modules such as rectangular septic tanks, the deflectorshall be positioned so that the SCC flows in one directionrather than falls straight down into the form. This permits theSCC to have higher discharge energy in one direction, allowingeasier escape of air from form surfaces and limiting the turbu-lence created when SCC freefalls in a concentrated area.

When walls are near full, a concrete contractor is temptedto walk around the perimeter of the structure and top it off.This is not necessary when a high-flowing SCC mixture iscombined with a slow, safe, and efficient placement procedure.A slump flow value of 26 to 30 in. (660 to 700 mm) worksbest for modules and walls because of its ability to flowaround corners and boxed-out areas. One concern regardingthe use of a fluid mixture in a deep section, such as a wallunit, is the increased potential for segregation. Although astable SCC mixture, resistant to segregation, can beproduced with various combinations of raw materials, a

mixture with a moderate s/a, moderate w/cm, optimizedcementitious quantity, and the use of a VMA has been shownto work exceptionally well in wall and module applications(Bury and Bühler 2002).

6.5.5 Vertical columns—As with modules and walls,vertical columns are also deep sections. SCC placement incolumns should consist of a continuous supply of concretebuilding its own column of transport and allowed to flowinto place. It is also possible to pump SCC mixtures into thebottom of a form column and let the concrete rise up into theform. The fluid nature of SCC makes this placement tech-nique possible with minimal bug holes and no segregation.

6.5.6 Horizontal columns—Some precast columns areproduced with the forms positioned horizontally. For thisapplication, SCC can be placed using the same methodologyused for beams by discharging the concrete at one end of theform and letting the SCC flow into place. It is critical in thisapplication to ensure that the SCC mixture does not bleedwhere water would collect on the inside top of the mold.Adjusting the mixture proportions, changing aggregate, orusing a VMA (that works through binding water) canproduce a nonbleeding SCC (Bury and Christensen 2002).

6.5.7 Freefall—As a general rule, allowing SCC mixturesto freefall into walls, column, or other deep sections shouldbe avoided whenever possible to avoid trapping air withinthe concrete. Vertical dropping of SCC directly into existinglayers of already placed concrete can produce a vortex ofnew concrete influx into the old, carrying a significantamount of entrapped air that will be retained within theconcrete. Any external vibration to remedy honeycombingor bug holes will do more damage than good, and can causebleeding, sand-streaking, and severe aggregate segregationwithin the unit.

In some cases, freefalling SCC must be properly designedto ensure high resistance to segregation under excessive free-fall conditions. This may be due to restricted access tofurther extend the placement device into the formwork. Forexample, during construction of the Rosenthal Contempo-rary Arts Center in Cincinnati, Ohio, 28 ft (8.5 m) tallcolumns containing acute angles were placed with a tremieextending into the column only 8 ft (2.4 m) (Johnston 2002).Successful SCC placements were made with the mixturefreefalling up to 19 ft (5.8 m) (Ohio Concrete 2002).

6.6—Finishing6.6.1 Double tees—During placement, a vibrating screed,

used at a very low setting, can take the place of raking,screeding, and bullfloating operations if it is carefully guidedover the surface of the concrete flange following dischargeof the SCC. This process adequately prepares the surface forbroom texturing or applying a tined finish. Applying aroughened finish too soon, however, will result in the SCCmixture flowing back to a smooth, level surface. Performinga setting-time test on the SCC mixture before placement willprovide the information necessary to establish the correcttiming of the final finish operation (ASTM C 403/C 403M).

6.6.2 Slabs—For finishing a slab made with SCC, theprocedures in ACI 302.1R should be followed. Because SCC


does not require vibration for consolidation, the steps toconsolidate the concrete may be omitted.

Many SCC mixtures are self-leveling, and the effortrequired to bring these mixtures to a final level condition isminimal. If some leveling is necessary, this can be accom-plished by using a screed. If desired, a vibrating screed maybe used at a low setting to level the SCC. The levelingprocess of SCC will tend to embed the coarse aggregate intothe surface, minimizing or eliminating the need to bullfloat.

SCC slabs can accept virtually any type of final finish,including, but not limited to, magnesium float swirl, broom,or steel trowel (Bury and Bühler 2002). Performing a fieldtrial slab test and a setting-time test on the SCC mixture,developed for the given project, before placement, willprovide the information necessary to establish the correcttiming for application of the final finish.

6.7—CuringSCC mixtures are made from the same materials as

conventional concrete except for certain HRWRAs designedspecifically for SCC, and sometimes VMAs. As a result,SCC is no different than conventional concrete mixtures interms of outside factors that affect performance. Changes infactors, such as high or low ambient temperatures, cementtype, aggregate gradations, water content, mixture proportions,and air content, will affect SCC in a manner similar to conven-tional concrete. Curing is essential, and early protection ofexposed surfaces is key to preventing rapid moisture loss thatcould lead to plastic shrinkage cracking. For SCC, the estab-lished guidelines for curing in ACI 308R should be followed.

6.7.1 Accelerated curing—SCC mixtures, and especiallythose used in the precast industry, are often produced usingpolycarboxylate-based high-range admixtures to achieve ahigh level of water reduction without interfering with thedevelopment of high early strength (Attiogbe et al. 2002). As aresult, accelerated curing techniques can potentially be reducedor eliminated in the production of some precast products thatrequire accelerated heat for early strength development.

CHAPTER 7—SCC SPECIFICATION GUIDELINES7.1—Concrete materials

7.1.1 Cementitious material—Cements should meetASTM C 150, C 595, or C 1157.

Supplementary cementitious materials can be used incombination with hydraulic cement for proportioning SCCmixtures. If supplementary cementitious material is used, itshould meet the requirements of ASTM C 618 or ASTM C989. If silica fume is used in SCC, it should meet the require-ments of ASTM C 1240.

7.1.2 Aggregates—Ideally, aggregates should be well-graded and meet the requirements of ASTM C 33. It may beacceptable to use an aggregate source that does not meet therequirements of ASTM C 33 if it produces a mixture thatmeets the performance targets for the fresh and hardenedconcrete. The difficulties encountered with challengingaggregates (for example, gap-graded or excessively harsh)may be improved by adding material from other sources(improving gradation), using fine powders such as limestone

fines, or using a VMA. A field trial should be mandatory fordetermining the suitability of an aggregate for a project.

7.1.3 Admixtures—HRWRAs should meet the requirementsof ASTM C 494/C 494M, Type F or G. Polycarboxylate-based HRWRAs are best suited to achieve water reductionfor specified strength and durability properties and slumpflow values of 18 to 30 in. (450 to 760 mm), which is acommon range for SCC mixtures. Admixture suppliersshould be consulted to ensure that the HRWRA is suited forproduction of SCC.

The use of a VMA is acceptable for producing SCC. Thereare no standard specifications for VMA. If a VMA is used,the admixture supplier should be consulted to ensure that itis suitable for the application.

In addition to HRWRAs and VMAs, other admixtures andadditives, such as air-entraining admixtures, normal andmid-range water-reducing admixtures, liquid and dry coloradmixtures, accelerating admixtures, retarding admixtures,extended set-control admixtures, corrosion-inhibitingadmixtures, shrinkage-reducing admixtures, and fibers canbe specified for use in SCC.

7.2—Execution7.2.1 Transportation and handling—Truck mixers or

agitators for transporting SCC should comply with ASTM C94/C 94M. The SCC should be completely discharged within1-1/2 hours after the water has been added to the cement or thecement has been added to the aggregates. This requirementcan be waived if the SCC is treated with a hydration-controllingadmixture. In such an event, no limits should be placed onthe time of discharge as long as the specified performancerequirements of the SCC for the project can be achieved. Toavoid spills during transport, the volume of SCC should belimited to the capacity of the drum or vessel.

7.2.2 Forms and placement—A preproduction trial shouldbe performed to evaluate the effect of SCC on formworkpressure for the established mixture proportions for thespecific application. This is especially critical for applicationswhere SCC is placed in a single lift in forms higher than 6 ft(1.8 m). If a trial evaluation is not performed, full hydrostaticpressure should be assumed to be exerted by the SCC on theform. SCC placement techniques or procedures outlined inChapter 6 of this document should be specified.

SCC placement techniques, other than those found inChapter 6, can be acceptable if they have been determined tobe successful by field trial evaluation.

7.2.3 Protection and curing—Freshly placed SCC shouldbe protected from premature drying, excessive cold or hottemperatures, and should be cured in compliance with ACI305R, 306R, and 308R.

CHAPTER 8—TEST METHODS8.1—Measuring SCC characteristics

The four main characteristics of SCC are:• Ability to fill a mold or form under its own weight;• Resistance to segregation (stability);• Ability to flow through reinforcing bars or other obstacles

without segregation and without mechanical vibration;


and• Surface quality and finishability.

ASTM Committee C09.47 is responsible for the developmentof standard test methods and developing a specification forSCC. Table 8.1 summarizes test methods being developed thatmeasure the main characteristics of SCC.

8.2—Slump flowThe slump flow test is a common procedure used to deter-

mine the horizontal free-flow characteristics of SCC in theabsence of obstructions. It was first developed in Japan tocharacterize fluid concrete mixtures for underwater placement.The procedure is based on ASTM C 143/C 143M, with amodification for determining the slump of conventionalconcrete. The test is easy to perform either at a concrete plantor on a job site.

8.2.1 Summary of test—The concrete is placed in one liftand not consolidated by any means of mechanical or manualagitation. The mold is raised, and the concrete is allowed tosubside. The average of two diameters measured perpendicularto each other of the resulting spread is reported as the slumpflow of the concrete.

8.2.2 Interpretation of results—The slump flow valueallows the comparison of the lateral flow and filling potentialof different SCC mixtures. A common range of slump flowfor SCC is 18 to 30 in. (450 to 760 mm). The higher theslump flow, the farther the SCC can travel under its ownmass from a given discharge point, and the faster it can fill aform or mold. The slump flow value can be also be used toassess the consistency of SCC, and should not differ by morethan 2 in. (50 mm) from load to load.

8.3—Visual stability indexThe visual stability index (VSI) test involves the visual

examination of the SCC slump flow spread resulting fromperforming the slump flow test. This test method is intendedto provide the user with a procedure to determine thestability of SCC mixtures (Daczko and Kurtz 2001). It isused to evaluate the relative stability of batches of the sameor similar SCC mixtures.

8.3.1 Summary of test—A sample of freshly mixedconcrete is placed in a mold shaped as the frustum of a cone.The concrete is placed in one lift and is not consolidated byany means of mechanical agitation. The mold is raised andthe concrete is allowed to subside. The average of twodiameters, measured perpendicular to each other, of theresulting spread is reported as the slump flow of the concrete.A visual observation of the concrete spread is noted tocharacterize the stability of the mixture. A VSI number of 0,1, 2, or 3 is given to the spread to characterize the stability ofthe mixture, as defined in Table 8.2.

8.3.2 Interpretation of results—A VSI rating of 0 or 1 isan indication that the SCC mixture is stable and should besuitable for the intended use. A VSI rating of 2 or 3 indicatespossible segregation potential and that a producer shouldtake action by modifying or adjusting the mixture to ensurestability. Because the VSI rating is determined visually, itcan be subjective. Therefore, the VSI rating is an excellent

quality-control tool for producing SCC, but should not beused for acceptance or rejection of a given mixture. The VSItest is most applicable to SCC mixtures that tend to bleed. Ifa mixture does not bleed, this test is less useful in identifyinga mixture’s tendency to segregate.

8.4—T50The flow rate of a SCC mixture is influenced by its

viscosity. When developing an SCC mixture in the laboratory,a relative measure of viscosity is useful. The time it takes forthe outer edge of the concrete spread, resulting from theprocedure described in the slump flow test, to reach a diameterof 20 in. (500 mm) from the time the mold is first raisedprovides a relative measure of the unconfined flow rate ofthe concrete mixture. For similar materials, this time period,termed T50, gives an indication of the viscosity of the SCCmixture.

8.4.1 Summary of test—A sample of freshly mixedconcrete is placed in a mold shaped as the frustum of a cone.The concrete is placed in one lift and is not consolidated byany means of mechanical or manual agitation. The mold israised and the concrete is allowed to subside. The personperforming the test measures the time it takes, in seconds(T50), for any part of the outer edge of the concrete spread toreach a diameter of 20 in. (500 mm) from the time the moldis first lifted.

8.4.2 Interpretation of results—A longer T50 time indicates amixture with a higher viscosity; the opposite is true for ashorter T50 time. A T50 time of 2 seconds or less typicallycharacterizes a SCC with a low viscosity, and a T50 time ofgreater than 5 seconds is generally considered a high-viscosity SCC mixture.

Table 8.1—Test methods being developed that measure characteristics of SCC

Test name Category Characteristic What test measures

Slump flow Free flow Filling ability Flow distance

Visual stability index (VSI)

Static conditionResistance to segregation

Visual stability of the mixture

T50 Free flow Filling ability Rate of flow

J-ring Confined flow Passing ability Flow rate

L-box Confined flowPassing andfilling ability

Flow rateand distance

Columnsegregation test

Confined flowResistance to segregation

Segregation of aggregates

Table 8.2—Visual stability index (VSI) rating of SCC mixtures (Daczko and Kurtz 2001)

VSI value Criteria

0 = highly stable No evidence of segregation in slump flow spread

1= stableNo mortar halo or aggregate pile in the slump flow spread

2 = unstableA slight mortar halo (< 10 mm [3/8 in.]) or aggregate pile, or both, in the slump flow spread

3 = highly unstableClearly segregating by evidence of a large mortar halo (>10 mm [3/8 in.]) or a large aggregate pile in the center of the concrete spread, or both.


8.5—J-ringWhen SCC is placed in forms containing steel reinforcement,

the mixture should remain cohesive, and the aggregatesshould not separate from the paste fraction of the mixturewhen it flows between obstacles. This is a critical characteristicof the mixture when it is used in highly congested reinforcedstructures. The J-ring test is used to characterize the abilityof SCC to pass through reinforcing steel (Bartos et al. 2002;Sonebi and Bartos 1999). The test is easy to perform eitherat a concrete plant or on a job site.

8.5.1 Summary of test—A sample of freshly mixedconcrete is placed in a mold shaped as the frustum of a coneconcentric with the J-ring. The concrete is placed in one liftand is not consolidated by any means of mechanical ormanual agitation. The mold is raised and the concrete isallowed to pass through the J-ring, which consists of a steelring assembly containing reinforcing bars, and subside. Theaverage of two diameters of the resulting spread, measuredperpendicular to each other, is reported as the J-ring flow ofthe concrete.

8.5.2 Interpretation of results—The resulting slump flow isan indication of the passing ability of SCC through reinforcingsteel. The higher the J-ring slump flow, the farther the SCCcan travel through a reinforcing bar under its own mass froma given discharge point, and the faster it can fill a steel-reinforced form or mold. The difference between the J-ringslump flow and the unconfined slump flow is an indicationof the degree to which the passage of SCC through reinforcingbars is restricted.

This test method may also be used to determine the potentialfor blocking of a SCC mixture for a given application. If thereinforcing bars retain the coarse aggregates inside the ring,then the mixture has a high potential for blocking and shouldbe reproportioned for ensuring stability of the mixture.

8.6—L-boxThe development of the L-box test for SCC in normal

applications is based on a Japanese design to evaluate SCCplaced under water (Skarendahl 2001). The test assesses theconfined flow of SCC and the extent to which it is subject toblocking by reinforcement. The test method is suitable forperforming in the laboratory. The L-box test can be used forthe development of an SCC mixture for a given application.

8.6.1 Summary of test—The test apparatus consists of arectangular-section box in the shape of an L, with a verticaland horizontal section, separated by a moveable gate, infront of which vertical lengths of reinforcing bar are fitted.The vertical section is filled with SCC, and then the gatelifted to let the SCC flow into the horizontal section. Whenthe flow has stopped, the height of the SCC at the end of thehorizontal section is expressed as a proportion of thatremaining in the vertical section.

8.6.2 Interpretation of results—The minimum ratio of theheight in the horizontal section relative to the vertical sectionis considered to be 0.8. If the SCC flows as freely as water,it will be completely horizontal, and the ratio will be equal to1.0. Therefore, the nearer this ratio is to 1.0, the better theflow potential of the SCC mixture. This is an indication of

passing ability, or the degree to which the passage of SCCthrough the bars is restricted. Coarse aggregate behind thereinforcing bars (blocking) and segregation at the end thehorizontal section can be detected visually. SCC mixtureswith either of these characteristics should be reproportionedto ensure stability of the mixture.

8.7—Column segregationThe column segregation test is a laboratory method for

developing and assessing SCC for segregation resistance.8.7.1 Summary of test—A sample of freshly mixed

concrete is placed in a cylindrical mold. The concrete isplaced in one lift without tamping or vibration. The mold isseparated into four sections that represent different levels ofthe column. The concrete from the top and bottom sectionsis wet-washed through a No. 4 (4.75 mm) sieve, leaving thecoarse aggregate on the sieve. The mass of the coarse aggregatefrom the top and the bottom sections of the column aredetermined, and the percent segregation is calculated.

8.7.2 Interpretation of results—This test method isintended to provide the user with a procedure to determinethe stability of SCC mixtures. This test method should beused to develop stable SCC mixtures and determine suitabilityfor a specific application or project.

The following equation is used to determine the percentsegregation

S% = [(CAB – CAT)/((CAB + CAT)/2)] × 100, if CAB > CAT

S% = 0, if CAB < CAT

Table 8.3—Test methods to measure characteristics of SCC

Test name Category Characteristic What test measures

Flow coneV-shaped funnel

Orimet

Confined flow

Filling ability Flow rate

U-boxConfined

flowPassing andfilling ability

Flow rate anddistance

Surfacesettlement test

Confined flow

Resistance to segregation

Settlement of SCC sur-face

Rapid segregation test using penetration

apparatus

Confined flow


Segregation ofaggregates

Wet sieving testConfined

flowResistance to segregation

Segregation of aggre-gates and measurement

of laitance

Hardenedexamination

Staticcondition


Distribution of coarse aggregate

Surface quality and finish evaluation

Confined flow

Surface quality and finishability

Observation ofsurface quality

K-slumpConfined

flowSegregation resistance

Flow rate

Rheometers:IBB

Two-point testBTRHEOM

BML

Rotational rheometer

Filling ability Rheology

Slump meterRotational rheometer

Filling abilityTorque to turn truck

mixer


where S = percent segregation; CAT = mass of coarseaggregate in the top section of the column; and CAB = massof coarse aggregate in the bottom section of the column.

A specific threshold for determining when an SCC mixturehas tolerable segregation has not yet been established;however, SCC is generally considered to be acceptable if thepercent segregation is less than 10%.

8.8—Other testsOther test methods have been performed to measure the

characteristics of SCC. Table 8.3 summarizes a list of thesetests found in the literature (Cussigh et al. 2003; Sonebi et al.2003; Bartos et al. 2002; Brower and Ferraris 2002; Bui andShah 2002; Rooney 2002; Ferraris and Brower 2001;Hackley and Ferraris 2001; Ferraris 1999; Bui et al. 1998)

CHAPTER 9—REFERENCES9.1—Referenced standards and reports

The standards and reports listed below were the latesteditions at the time this document was prepared. Becausethese documents are revised frequently, the reader is advisedto contact the proper sponsoring group if it is desired to referto the latest version.

American Concrete Institute211.1 Standard Practice for Selecting Proportions for

Normal, Heavyweight, and Mass Concrete301 Specifications for Structural Concrete302.1R Guide for Concrete Floor and Slab Construction304R Guide for Measuring, Mixing, Transporting, and

Placing Concrete305R Hot Weather Concreting306R Cold Weather Concreting308R Guide to Curing Concrete347 Guide to Formwork for Concrete

ASTM InternationalC 33 Specification for Concrete AggregatesC 39/C 39M Test Method for Compressive Strength of

Cylindrical Concrete SpecimensC 70 Test Method for Surface Moisture in Fine

AggregateC 78 Test Method for Flexural Strength of

Concrete (Using Simple Beam with Third-Point Loading)

C 94/C 94M Specification for Ready-Mixed ConcreteC 143/C 143M Test Method for Slump of Hydraulic

Cement ConcreteC 150 Specification for Portland CementC 157/C 157M Test Method for Length Change of Hardened

Hydraulic-Cement Mortar and ConcreteC 232 Test Methods for Bleeding of ConcreteC 293 Test Method for Flexural Strength of

Concrete (Using Simple Beam withCenter-Point Loading)

C 403/C 403M Test Method for Time of Setting of ConcreteMixtures by Penetration Resistance

C 457 Test Method for Microscopical Determi-nation of Parameters of the Air-VoidSystem in Hardened Concrete

C 469 Test Method for Static Modulus of Elas-ticity and Poisson’s Ratio of Concrete inCompression

C 494/C 494M Specification for Chemical Admixturesfor Concrete

C 512 Test Method for Creep of Concrete inCompression

C 566 Test Method for Total Evaporable Mois-ture Content of Aggregate by Drying

C 595 Specification for Hydraulic CementsC 618 Specification for Coal Fly Ash and Raw or

Calcined Natural Pozzolan for Use inConcrete

C 666/C 666M Test Method for Resistance of Concrete toRapid Freezing and Thawing

C 672/C 672M Test Method for Scaling Resistance ofConcrete Surfaces Exposed to DeicingChemicals

C 989 Specification for Ground GranulatedBlast-Furnace Slag for Use in Concreteand Mortars

C 1157 Performance Specification for HydraulicCement

C 1202 Test Method for Electrical Indication ofConcrete’s Ability to Resist Chloride IonPenetration

C 1240 Specification for Silica Fume Used inCementitious Mixtures

C1611/ C1611M Test Method for Slump Flow of Self-Consolidating Concrete

These publications may be obtained from these organizations:

American Concrete InstitutePO Box 9094Farmington Hills, MI 48333-9094

ASTM International100 Barr Harbor DrWest Conshohocken, PA 19428

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Attiogbe, E.; See, H.; and Daczko, J., 2002, “EngineeringProperties of Self-Consolidating Concrete,” Proceedings of theFirst North American Conference on the Design and Use ofSCC, ACBM, Chicago, Ill., Nov. 12-13.

Bartos, P. J. M.; Sonebi, M.; and Tamimi, A., 2002,“Workability and Rheology of Fresh Concrete: Compen-


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Bui, V. K., and Shah, S. P., 2002, “Rapid Methods forTesting Quality of Fresh Self-Consolidating Concrete,”Proceedings of the First North American Conference on theDesign and Use of SCC, Chicago, Ill., Nov. 12-13, pp. 311-316.

Bury, M. A., and Bühler, E., 2002, “Methods and Tech-niques for Placing Self-Consolidating Concrete—An Over-view of Field Experiences in North American Applications,”Proceedings of the First North American Conference on theDesign and Use of SCC, ACBM, Chicago, Ill., Nov. 12-13.

Bury, M. A., and Christensen, B., 2002, “The Role ofInnovative Admixtures in Producing Self-ConsolidatingConcrete,” Proceedings of the First North AmericanConference on the Design and Use of SCC, ACBM,Chicago, Ill., Nov. 12-13.

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Daczko, J. A., and Constantiner, D., 2002, “QualityControl of Self-Consolidating and Rheodynamic Concrete,”ACI Fifth International Conference, Supplementary Papers,Cancun, Mexico, Dec.

Daczko, J. A., and Kurtz, M. A., 2001, “Development ofHigh-Volume Coarse Aggregate Self-Compacting Concrete,”Proceedings of the Second International Symposium onSCC, Oct. 23-25, Tokyo, Japan.

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Documents

ACI 237R 07 Self Consolidating Concrete (1)