self curing and self compacted concrete

DEVELOPMENT OF SELF CURING SELF COMPACTED CONCRETE

By

VEKARIYA SANKETKUMAR M(120070720006)

PROF. NANAK J. PAMNANIPrinciapal,

H.b.patelpolytehnic,Limbodara,

Lunawada, (dist. Mahisagar)

DR. DARSHANA R. BHATTAssociate professor,

Department of structural engineeringBvm engineering college, vvn

A Dissertation Phase-I (730003) Submitted toGujarat Technological University

In Partial Fulfillment of the Requirements forThe Degree of Master of Engineering

In Structural Engineering

December 2013

BIRLA VISHVAKARMA MAHAVIDYALAYA ENGINEERING COLLEGEVALLABH VIDYANAGAR

I

CERTIFICATE

This is to certify that research work embodied in this dissertation entitled “DEVELOPMENT OF SELF CURING SELF COMPACTED CONCRETE” was carried out by Mr. VEKARIYA SANKETKUMAR M (120070720006) at Birla Vishvakarma Mahavidyalaya (BVM) Engineering College for Dissertation Phase-I (730003) of M.E Structural Engineering. This research work has been carried out under our supervision and is to our satisfaction.

Date:

Place:

Signature of Guide Signature of Co-Guide

(PROF. NANAK J PAMNANI) (DR. DARSHANA R. BHATT)

II

ACKNOWLEDGEMENT

With great pleasure & deep sense gratitude I would like to extent out sincere thanks to

almighty GODfor his peace and blessings for granting me the chance and the ability to

successfully complete this study.

I would like to take this opportunity to thank my guidesPROF. NANAK J

PAMNANI,princiapal, h.b.patelpolytehnic, limbodara, lunawada, (dist. mahisagar). DR.

DARSHANA R. BHATT,associate professor,department of structural engineering, Birla

VishvakarmaMahavidyalayaEngineering College, VallabhVidyanagar, Whose timely and

persistent guidance has played a key role in making my dissertation a success.

I express sincere thanks to DR.F.S.UMRIGAR, Principal, Birla

VishvakarmaMahavidyalayaEngineering College, VallabhVidyanagar andPROF. A.K.VERMA,

Associate Professor and Head, Structural Engineering, Birla

VishvakarmaMahavidyalayaEngineering College, VallabhVidyanagar for giving us an

opportunity to undertake this research study.

Special thanks to MY FAMILY members for their everlasting love and financial support

throughout my numerous academic years. Without their support, I would not have been

able to accomplish my dreams.

I would also like to thank all MY FRIENDS who have directly or indirectly provided their

unerring support throughout the course of this dissertation work, without whom none of

this would have been possible.

VEKARIYA SANKETKUMAR MANSUKHBHAI

M.E. STRUCTURAL ENGINEERING

ENROLLMENT NO: 120070720006

III

TABLE OF CONTENTS

TITLE PAGE …I

CERTIFICATE …

II

ACKNOWLEDGEMENT …

III

TABLE OF CONTENTS …

IV

LIST OF FIGURES …

VI

LIST OF TABLES …

VII

Chapter 1: INTRODUCTION …1

1.1 General …2

1.2 Need for study …3

1.3 Objective …3

1.4 Scope of work …3

1.5 Study pattern and resources …4

Chapter 2: LITERATURE REVIEW …5

2.1

2.2

2.2.1 V-funnel Test

2.2.2 Slump Test

IV

2.2.3 L-box Test

2.2.4 U-box Test

2.3

2.4

2.5

V

TABLE OF FIGURE

Figure 2.1 …7

Figure 2.2 …8

Figure 2.3 …9

Figure 2.4 …

10

Figure 2.5 …

12

Figure 2.6 …

12

Figure 2.7 …

17

VI

LIST OF TABLE

Table-2.1 …

15

Table-2.2 …

16

Table-2.3 …16

VII

CHAPTER 1

INTRODUCTION1.1 GENERAL

Self-compacting concrete (SCC), which flows under its own weight and does not

require any external vibration for compaction, has revolutionized concrete placement.

Adequate curing is essential for concrete to obtain structural and durability properties

and therefore is one of the most important requirements for optimum concrete

performance in any environment or application. Curing of concrete is the process of

maintaining the proper moisture conditions to promote optimum cement hydration

immediately after placement

Enough water needs to be present in a concrete mix for the hydration of cement to

take place. However, even mix contains enough water, any loss of moisture from the

concrete will reduce the initial water cement ratio and result in incomplete hydration

of cement especially with the mixes having low water cement ratio. This results in

very poor quality of concrete. When the concrete is exposed, water evaporates from

its surface. Evaporation from the freshly placed concrete results in plastic shrinkage

cracking. The poor surface characteristics lead to high permeability on the surface of

concrete which increases the risk of carbonation and heightens the susceptibility of

corrosion to the steel.

Curing techniques and curing duration significantly affect curing efficiency.

According to Gowripalan (JUNE- 2012) , the mechanism of self curing can be

explained as follows:

“Continuous evaporation of moisture takes place from an exposed surface due

to the difference in chemical potentials (free energy) between the vapour and liquid

phases. The polymer added in the mix mainly form hydrogen bonds with water

molecules and reduce the chemical potential of the molecules which in turn reduces

the vapour pressure. Physical moisture retention also occurs. This reduces the rate of

evaporation from the surface”

DEVELOPMENT OF SELF CURING SELF COMPECTED CONCRETE 1

1.2 CHARACTERISTICS OF SELF-CURING CONCRETE

Today concrete is most widely used construction material due to its good

compressive strength and durability. Plain concrete needs an atmosphere by providing

moisture for a minimum period of 28 days for good hydration and to attain desired

strength.

The present study involves the use of shrinkage reducing admixture

polyethylene glycol (PEG 400) in concrete which helps in self curing and helps in

better hydration and hence strength.

It was also found that 1% of PEG 400 by weight of cement was optimum for

M20, while 0.5 % was optimum for M40 grade concretes for achieving maximum

strength without compromising workability.

Defination :

Self-curing or internal curing is a technique that can be used to provide

additional moisture in concrete for more effective hydration of cement and

reduced self-desiccation.

Methods of self curing :

Currently, there are two major methods available for internal curing of concrete.

1. Saturated porous lightweight aggregate (LWA) in order to supply an

internal source of water, which can replace the water consumed by chemical

shrinkage during cement hydration.

2. Poly-ethylene glycol (PEG) which reduces the evaporation of water from

the surface of concrete and also helps in water retention.

Mechanism of Internal Curing:

Continuous evaporation of moisture takes place from an exposed

surface due to the difference in chemical potentials (free energy) between the

vapour and liquid phases. The polymers added in the mix mainly form

hydrogen bonds with water molecules and reduce the chemical potential of the


molecules which in turn reduces the vapour pressure, thus reducing the rate of

evaporation from the surface.

Potential Materials for Internal Curing (IC) :

a) Lightweight Aggregate (natural and synthetic, expanded shale)

b) Super-absorbent Polymers (SAP) (60-300 nm size)

c) SRA (Shrinkage Reducing Admixture) (propylene glycol type i.e.

polyethylene-glycol)

Advantages of Internal Curing :

a) Internal curing (IC) is a method to provide the water to hydrate all the cement,

accomplishing what the mixing water alone cannot do.

b) Provides water to keep the relative humidity (RH) high.

c) Eliminates largely autogenous shrinkage.

Maintains the strengths of mortar/concrete at the early age (12 to 72 hrs.) above the

level where internally & externally induced strains can cause cracking.

Can make up for some of the deficiencies of external curing, both human related

(critical period when curing is required in the first 12 to 72 hours) and hydration.

1.3 NEED FOR STUDY

Proper Curing for freshly placed concrete is required and in general practice

many times concrete does not get proper water for the process of hydration.

Hence, internal curing with different method if achieved than it is very

effective.

As same way proper vibration during placing of concrete in beam and in other

formwork can not done properly

And it leads to the improper casting of concrete in beam and in other

formwork


Hence, if both self curing, self compacting properties if achieved than this

problem can be solved easily and its comes out very effective.

In general, a newly placed concrete is compacted by vibrating

equipment to remove the entrapped air, thus making it dense and homogeneous;

Compaction is the key to producing good concrete with optimum strength and

durability but while we use Admixtures compaction is eliminated, the internal

segregation between solid particles and the surrounding liquid is avoided which

results in less poroustransition zones between paste and aggregate &a more even

colour of the concrete also it's Improved strength, durability and finish of SCC can

therefore be anticipated.

1.4 OBJECTIVE

Finding out appropriate chemical compound for self curing

Development of mix design for medium strength SCC

Development of self curing, self compacted concrete

Mix design for medium strength NVC

Development of mix design for self compacted NVC

Finalization of optimum dosage for self curing properties in SCC & NVC

Find out optimum dosage of chemical compound for self curing

1.5 SCOPE OF WORK

Identify appropriate admixtures and its proportion to achieve pumpability and

self compatibility of concrete.

Mix-design for M30 & M50 grade Self Compacted Concrete (SCC).

To study effect of extreme weather condition curing on various properties of

fresh and hardened Self Compacted Concrete (SCC).

To identify best curing condition for Self-curing of SCC.

1.6 STUDY PATTERN & RESOURCE

Literature review


Literature pertaining to self curing, self-compacting concrete will be

reviewed from published papers of journals and codes practice.

Data collection

Data will be collected by for identifying appropriate admixtures for

self curing and self compacting concrete. And than by using different

proportion of different self curing compound and after that compressive

strength of different proportion will be calculated.

Data analysis

Based on the data collected during literature review and practical, we

will be able to find out optimum ratio of different chemical admixture used for

self curing in self compacting concrete.

Conclusions

Based on the analysis relevant conclusions will be made and scope for

the future work will be suggested.


CHAPTER 2

LITERATURE REVIEW

Y.B. Raghavendra, M.U. Aswath (JUNE- 2012)[1] : give research on experimental

investigation on concrete cured with various curing methods and From the results of

the investigation, it can be concluded that the concrete cured with self curing

compound and membrane curing compound have an efficiency of 92.5% and 90%

respectively when compared to conventionally cured standard water curing method

whereas Non standard water curing and air curing method have an efficiency of 75%

and 70% respectively when compared to Standard water curing method. Therefore

non standard water curing and air curing methods has to be avoided at the

construction sites otherwise which may leads to loss in strength of concrete. Hence

curing of concrete with self curing compound and membrane curing can be adopted

efficiently where ‘performance specifications’ are important than ‘prescriptive

specifications’ for concrete. Self curing method of curing is most suitable for concrete

at inaccessible areas of the structure like high rise buildings especially columns.

AGGARWAL Paratibha, SIDDIQUE Rafat, AGGARWAL Yogesh (June 2008)[2] :

give

Procedure for Mix Design of Self-Compacting Concrete and conclude that


1. At the water/powder ratio of 1.180 to 1.215, slump flow test, V-funnel test and L-

box test results were found to be satisfactory, i.e. passing ability, filling ability and

segregation resistance are well within the limits.

2. SCC could be developed without using VMA as was done in this study.

3. The SCC1 to SCC5 mixes can be easily used as medium strength SCC mixes,

which are useful for most of the constructions; the proportions for SCC3 mix

satisfying all the properties of Self-Compacting Concrete can be easily used for the

development of medium strength self compacting and for further study.

4. By using the OPC 43 grade, normal strength of 25 MPa to 33 MPa at 28-days was

obtained, keeping the cement content around 350 kg/m3 to 414 kg/m3. As SCC

technology is now being adopted in many countries throughout the world, in absence

of suitable standardized test methods it is necessary to examine the existing test

methods and identify or, when necessary to develop test methods suitable for

acceptance as International Standards. Such test methods have to be capable of a

rapid and reliable assessment of key properties of fresh SCC on a construction site. At

the same time, testing equipment should be reliable, easily portable and inexpensive.

A single operator should carry out the test procedure and the test results have to be

interpreted with a minimum of training. In addition, the results have to be defined and

specify different SCC mixes. One primary application of these test methods would be

in verification of compliance on sites and in concrete production plants, if self-

compacting concrete is to be manufactured in large quantities.

M.V.Jagannadha Kumar, M.Srikanth, Dr.K.Jagannadha Rao(SEP 2012)[3] :

give

strength characteristics of self-curing concrete and from the experiments and test

results i found that The optimum dosage of PEG400 for maximum strengths

(compressive, tensile and modulus of rupture) was found to be 1% for M20 and 0.5%

for M40 grades of concrete. As percentage of PEG400 increased slump increased for

both M20 and M40 grades of concrete. Strength of self curing concrete is on par with


conventional concrete. Self curing concrete is the answer to many problems faced

due to lack of proper curing.

A.Aielstein Rozario, Dr.C.Freeda Christy (April – 2013)[4] : gives Experimental

Studies on Effects of Sulphate Resistance on Self-Curing Concrete and from this it

came to know that The permeability of concrete decreases with increase in the

replacement of fly ash with cement and in addition of P.E.G dosages. So the

penetration of chemicals is decreased with the addition of PEG and the concrete is

safe against sulphates. The percentage of weight loss of the concrete specimens are

also decreased for every grades of concrete. From the results, we know that the

selfcuring concrete has the ability to resist the sulphates present in the soils and in the

sea waters. It is very economical also, So it can be adoptable for the constructions.

C. Selvamony, M. S. Ravikumar (March 2010) [5] : investigations on self-

compacted self-curing concrete using limestone powder and clinkers and From the

experimental investigation, it was observed that both admixtures affected the

workability of SCC adversely. A maximum of 8% of lime stone powder with silica

fume, 30% of quarry dust and 14 % of clinkers was able to be used as a mineral

admixture without affecting the self compactability. Silica fume was observed to

improve the mechanical properties of SCC, while lime stone powder along with

quarry dust affected mechanical properties of SCC adversely.

C. Chella Gifta, S. Prabavathy and G. Yuvaraj Kumar[6] : study on internal curing of

high performance concrete using super absorbent polymers and light weight

aggregates and Based on the results of these investigations the following conclusions

can be drawn.


(i) The internal cured specimens are proved to better than conventional cured

specimens

in all means.

(ii) The addition of internal curing agent increases the degree of hydration, producing

a

denser microstructure leading to better results.

(iii) Compressive strength results reveals that compressive strength of internal cured

specimens at 7days and 28 days are greater but at the age of 3 days the strength is

lower than

conventionally cured specimens. SAP specimens shows a significant improvement of

about

6.88 % increase in compressive strength and LWA specimens are found to be 12.35%

on 28

days compressive strength than the control concrete mix. Hence ,the incorporation of

Internal Curing components in high performance concrete by means of LWA has

proven to

be effective than internal cured HPC using SAP with respect to strength.

(vi) The durability studies have showed that internal curing by means of SAP has less

chloride penetration than internal cured specimens using LWA.

(vii) The RCPT value for the control mix was 783 coulombs which was greater than

both

the internal cured specimens, while the mix using SAP had lower RCPT value of 483

coulombs which proved to be the best.

(viii) The coefficient of permeability of mix M2 was 13.68 x10-12 m/sec which was

lesser than all the other mixes. Lesser the coefficient of permeability betters the

results.


Fareed Ahmed Memon, Muhd Fadhil Nuruddin (2011) [7] : studied Effect of

Curing Conditions on Strength of Fly ash-based Self-Compacting Geopolymer

Concrete

In this experimental work, the effect of curing conditions on the compressive strength

of fly ash-based self compacting geopolymer concrete was investigated. Test results

indicate that curing time and curing temperature significantly affect the compressive

strength of hardened concrete. Based on the test results reported here, the following

conclusions can be drawn.

1. Longer curing time improves the geopolymerisation process resulting in higher

compressive strength. Increase in compressive strength was observed with increase in

curing time. The compressive strength was highest when the specimens were cured

for a period of 96 hours; however, the increase in strength after 48 hours was not

significant.

2. Compressive strength of concrete increased with the increase in curing temperature

from 60°C to 70°C; however an increase in the curing temperature beyond 70°C

decreased the compressive strength of selfcompacting geopolymer concrete.

A.M.M. Sheinn, C.T. Tam (August 2004)[8] : done comparative study on hardened

properties of selfcompacting concrete (scc) with normal slump concrete (nsc)

Through the investigations and comparisons between Self-compacting Concrete

(SCC) and

Normal Slump Concrete (NSC) in this study, the following observations and

concluding remarks can

be made.

a) With similar water/cement ratios and coarse aggregate content, SCC and NSC can

be


expected to have similar mechanical properties.

b) Incorporation of fine filler could reduce the porosity in the concrete through the

filling

effect and subsequently improve the interfacial zone properties. Thus the concrete of

similar compressive strength, the splitting tensile strength of SCC is possible to be

higher than that of normal concrete.

c) Drying shrinkage and creep deformations of SCC are similar to that of normal

slump

concrete if both types of concrete are of similar compressive strength level.

d) With similar mix proportions and strength level, there is no Significant difference

in

mechanical properties and long-term deformation between SCC and NC. Thus,

existing structural design code for normal slump concrete can be used to design the

structural applications of SCC.

M. M. Rahman, M. H. Rashid, M. A. Hossain, F. S. Adrita (AUGUST 2011)[9] :

have done research on mixing time effects on properties of self compacting concrete

and This work gives attention to an effect, which affects the performance of SCC mix

adversely and hence, its hardened properties also. This effect is the time delay or the

time elapsed during the mixing process.

As soon as water applied to the cement, chemical reaction starts simultaneously

between them. During long mixing time of SCC, some portion of water are used in

the hydration of cement and some portion of water evaporate to the atmosphere and

that’s why, amount of added water is increased with long mixing time for maintaining

constant workability.


After adding water for maintaining constant flowability, the amount of water/cement

ratio increases in SCC for prolonged mixing time, which affects the cohesion among

the constituents of concrete. So, compressive and tensile strength of SCC decreases

with this water quantity.

With long mixing time of concrete, the pores in concrete are increased. That is why

the water absorption and the chloride ion permeability increase with increase in

mixing time.

Martin Hunger; H.J.H. Brouwers [10] : give research on Development of Self-

Compacting Eco-Concrete.

In this study a new design tool for SCC based on the controlled grading of the entire

solid mix was introduced. It has been shown that grading has a fundamental effect on

both fresh and hardened concrete properties. Here an improvement of various

parameters was found for mixes with low cement contents and decreasing values of

the distribution modulus q. Only viscosity was affected by too low q values. An

optimum in regard to the workability was found for 0.30 < q < 0.35. Furthermore the

mechanical and porosity parameters were strongly enhanced by optimized packing.

Dense packed granular blends showed good workability since less void fraction had to

be filled with water and on the other hand also high strength values due to a dense

packed granular skeleton. In this connection a raise of the compressive strength of

more than 60 % in average based on the introduced cement efficiency was registered.

Furthermore it was shown that broad grain size distributions with as many

overlapping fractions as possible (within the bounds of practical possibility) and

intermediate fractions (e.g. gravel 2-8) result in good packed mixes. The application

of a broadly graded unwashed sand 0-4 (so including the fines) of broken granite also

proved promising. On the basis of sound indirect parameters of durability as well as

on the compressive strength the minimum cement contents required by the standards

seem to be a little outdated. The same applies for the water cement ratio for which it is

recommended to replace it by a water/powder ratio. All these observations strongly

suggest a change from the present prescriptive.


CONCLUSIONS FROM LITERATURE REVIEW

a) The proportions for SCC mix satisfying all the properties of Self-Compacting

Concrete can be easily used for the development of medium strength self-

compacting.

b) There are many methods for self curing among that use of chemical

compound is very effective

c) For self curing widely used methods include use of Light Weight Aggregate

(LWA), and Poly-ethylene glycol

d) Silica fume was observed to improve the mechanical properties of SCC

e) The selfcuring concrete has the ability to resist the sulphates present in the

soils and in the sea waters.

f) SCC has a significant contribution in shrinkage reduction, enhancing

durability and hence improving overall concrete performance.

CHAPTER 3

MATERIALS USED IN EXPERIMENT

3.1 INTRODUCTION:


In this chapter include information about materials used for development of

self curing, self compacting concrete

3.2 MATERIALS USED IN CONCRETE:

Concrete is a homogeneous mixture of cement, coarse aggregate, fine aggregate and

water and admixtures

3.3 CEMENT(IS: 8112 – 1989)

In the most general sense of the word, cement is a binder, a substance

that sets and hardens independently, and can bind other materials together. The most

important use of cement is the production of mortar and Concrete the bonding of

natural or artificial aggregates to form a strong building material that is durable in the

face of normal environmental effects. Concrete should not be confused with cement,

cement

aggregate

admixture & construction

chemicalwater

fly ash


because the term cement refers to the material used to bind the aggregate materials of

concrete. Concrete is a combination of cement, aggregate and water.

Cement is a powder manufactured from limestone that is mixed with

other aggregates, notably sands, gravels and stone, to produce mortars and concretes.

The vast majority of cement used in the India is Portland Cement, sometimes referred

to as Ordinary Portland cement or OPC, although there are also specialist cements,

such as Sulphate-Resistant Cement (SRC) which is often used for sub-surface works,

and High-Alumina Cement (HAC).

3.3.1 ORDINARY PORTLAND CEMENT (OPC) (IS 269: 1976)

Portland cement is the most common type of cement in general usage. It is a basic

ingredient of concrete, mortar and plaster. English masonry worker Joseph Aspdin

patented Portland cement in 1824; it was named because of its similarity in colour to

Portland limestone, quarried from the English Isle of Portland and used extensively in

London architecture. It consists of a mixture of oxides of calcium, silicon and

aluminium. Portland cement and similar materials are made by heating limestone (a

source of calcium) with clay and grinding this product (called clinker) with a source

of sulfate (most commonly gypsum).The Ordinary Portland Cement of 53 grade

conforming to IS: 8112 is be use.

FIG 4.1, Sanghi Cement (OPC 53 GRADE)


Table-4.1 Physical Properties of Portland cement

PROPERTY VALUE IS CODE IS : 8112 - 1989

Specific Gravity 3.15 3.10-3.15

Consistency 28% 30-35

Initial setting time 35min 30min minimum

Final setting time 178min 600min maximum

Compressive strength at 7 days N/mm2 38.49 N/mm2 43 N/mm2

Compressive strength at 28 days N/mm2 52.31 N/mm2 53 N/mm2

Table-4.2 Chemical Properties of Portland cement

OXIDE CONTENT By %

Lime CaO 60-67

Silica SiO2 17-25

Alumina Al2O3 3-8

Iron Oxide Fe2O3 0.5-0.6

Magnesia MgO 0.5-4

Alkaline K2O, Na2O 0.3-1.2

Sulphates SO3 1.0-3.0

Source: SICART lab, V.V.N

3.4 AGGREGATE

The aggregates normally used for concrete are natural deposits of sand

and gravel, where available. In some localities, the deposits are hard to obtain and

larger rocks must be crushed to form the aggregate. Crushed aggregate usually costs

more to produce and will require more cement paste because of its shape. More care

must be used in handling crushed aggregate to prevent poor mixtures and improper

dispersion of the sizes through the finished concrete. At times, artificial aggregates,

such as blast-furnace slag or specially burned clay are used.

TYPES OFAGGREGATE — Aggregates are divided into two types as

follows:


3.4.1 FINE AGGREGATE (SAND) (IS: 383-1970)

Sand is a naturally occurring granular material composed of finely

divided rock and mineral particles. The composition of sand is highly variable,

depending on the local rock sources and conditions, but the most common constituent

of sand is silica (silicon dioxide, or SiO2), usually in the form of quartz.

TABLE 4.3 Properties of Sand or fine Aggregate

Sr.no Particulars Value of Sand

1 Source Bodeli, Gujarat

2 Zone Zone II

3 Specific Gravity 2.55

4 Fineness Modulus 2.87

5 Bulk Density 1776.29 kg/m3

6 Colour Yellowish White

3.4.1.1 USES

Concrete: Sand is often a principal component of this critical construction

material.

Brick: Manufacturing plants add sand to a mixture of clay and other materials

for manufacturing brick.

Mortar: Sand is mixed with cement and sometimes lime to be used in masonry

construction.

Glass: Sand is the principal component in common glass.

Aggregate

FineSand

below 4.75mm

CourseGrit

4.75mm to 12.5mm

Gravel12.5mm to 20mm


Landscaping: Sand makes small hills and slopes (for example, in golf

courses).

Paint: Mixing sand with paint produces a textured finish for walls and ceilings

or non-slip floor surfaces.

Railroads: Train operators use sand to improve the traction of wheels on the

rails.

Roads: Sand improves traction (and thus traffic safety) in icy or snowy

conditions.

3.4.2 COURSE AGGREGATE

As a basic raw material aggregates can be put to many uses, although

certain tasks may require a specific type of aggregate.

The largest proportion of the primary aggregate was used to manufacture concrete

(36%), with a further 10% used to manufacture the cement that is also used in the

concrete. Used in roads was the second largest category (26%), while 20% of

aggregates were used in other construction uses & fills and another 2% were used for

railway ballast.

Aggregates are the most mined material in the world. Aggregates are a component of

composite materials such as concrete and asphalt concrete; the aggregate serves as

reinforcement to add strength to the overall composite material. Due to the relatively

high hydraulic conductivity value as compared to most soils, aggregates are widely

used in drainage applications such as foundation and French drains, septic drain

fields, retaining wall drains, and road side edge drains.

Aggregates are also used as base material under foundations, roads, and

railroads. In other words, aggregates are used as a stable foundation or road/rail base

with predictable, uniform properties (e.g. to help prevent differential settling under the

road or building), or as a low-cost extender that binds with more expensive cement or

asphalt to form concrete.

3.4.2.1 COURSEAGGREGATE (GRIT) (IS: 383)

Another granular material that can be thought of as a transition stage between a coarse

sand and small pebbles. Generally 4.75mm-12.5mm in size, grit has limited uses in


the construction industry on its own, other than as a surface dressing. However, over

recent years with the development in block paving specifications, it has become a

viable alternative bedding material for permeable paving and other forms of elemental

paving used in areas of high water ingress.

TABLE 4.4 Properties of Grit or Course Aggregate


1 Source Sevalia, Gujarat




5 Colour Greyish Black

3.4.2.2 COURSEAGGREGATE (GRAVEL) (IS: 383 – 1989)

A granular material which can be of almost any rock type. It is usually

between 60mm and 2mm in size which may be rounded, if from a marine or fluvial

source, or angular if a quarried and crushed product. Gravels are sold in mixed sizes,

e.g. 20-5mm or closely graded to a specific size, such as 10mm.

The advent of modern blasting methods enabled the development of quarries,

which are now used throughout the world, wherever competent bedrock deposits of

aggregate quality exist. In many places, good limestone, granite, marble or other

quality stone bedrock deposits do not exist. In these areas, natural sand and gravel

are mined for use as aggregate. Where neither stone, nor sand and gravel, are

available, construction demand is usually satisfied by shipping in aggregate by

rail, barge or truck. Additionally, demand for aggregates can be partially satisfied

through the use of slag and recycled concrete. However, the available tonnages and

lesser quality of these materials prevent them from being a viable replacement for

mined aggregates on a large scale.

TABLE 4.5 Properties of Gravel or Course Aggregate



1 Source Sevalia, Gujarat




5 Colour Greyish Black

3.5 FLY ASH

The Fly Ash story begins 2000 years ago...

When the Romans built the Colosseum in the year 100 A.D. - that still

stands the test of time!!

The ash generated from Volcanoes was used extensively in the

construction of Roman structures. Colosseum is a classic example of

durability achieved by using volcanic ash. The building constructed 2000

years ago and still standing today!

Only difference is, Fly Ash is generated in artificial volcanoes - non

other than coal fired.

TABLE 4.6 Physical Properties of fly ash “CLASS C”

Sr.no Physical Properties Test Result

1 Colour Grey



3.5.1 So what is so special in fly ash that makes our concrete so durable?

Fly ash has a high amount of silica and alumina in a reactive form.

These reactive elements complement hydration chemistry of cement. Let us

take a quick tour through this exciting world of hydration chemistry.

When cement reacts with water, we say that hydration of cement has

begun.

On hydration, cement produces C-S-H Gel.


This C-S-H Gel binds the aggregates together and strengthens our concrete!

However, one more compound is produced on hydration that is so

different in behaviour. It is non-other than the Calcium Hydroxide Ca(OH)2.

In our construction industry, it is generally referred to as Free Lime.

Aggressive environmental agents like water, sulphates,CO2 attack this

free lime leading to deterioration of the concrete.

3.5.2 FROM MASS CONCRETE TO MASS APPLICATIONS

In the beginning of the twentieth century, fly ash was used only for the

mass concrete applications—to delay the heat of hydration. However, in the

early 80’s, with the advent of the high strength cements, the undesirable side

effects of free lime started surfacing.

TABLE 4.7Chemical Properties of fly ash “CLASS C”

Sr. No Constituents Weight % by

1 Loss on ignition 4.17

2 Silica (SiO2) 69.40

3 Iron Oxide (Fe2O3) 3.44

4 Alumina (Al2O3) 28.20

5 Calcium Oxide (CaO)

2.23

6 Magnesium Oxide (MgO)

1.45

7 Total Sulphur (SO3) 0.165

8 Insoluble residue -

9ALKALIES

Sodium Oxide (Na2O)

Potassium Oxide (K2O)

0.581.26


3.5.3 IS FREE LIME REALLY BAD FOR CONCRETE?

No a certain amount of free lime is necessary to keep our concrete

alkaline.


The problem arises when our new generation - 53 grades - cements

produce excessive lime which leads to the deterioration of concrete,

leading to corrosion.

The cement technologists observed that the reactive elements present

in fly ash convert the problematic free lime into the beneficial C-H-S Gel.

Ca(OH)2 + SiO2 => C-S-H Gel

Ca(OH)2 + Al2O3 = C-Al-H Gel

OR

Problem + Fly Ash => Durable Concrete

The analysis on fly ash production from coal based thermal power

stations indicates that 82 power stations, as of today, produce about 175

million tons per year by 2012 A.D. with 15% annual rise in the thermal power

generation slated for the decade.

In India, it is estimated that 125-145 million tons of fly ash is

generated by 70 major thermal power plants of which only 6-10 % is utilized

by cement, construction and road industries.

3.5.4 WHAT MAKES FLY ASH SO DURABLE?

Fly ash has a high amount of silica and alumina in a reactive form.

These reactive elements complement hydration chemistry of cement.

Hydration chemistry of Cement: When cement reacts with water, the

hydration of cement begins. On hydration, cement produces C-S-H Gel. This

C-S-H Gel binds the aggregates together and strengthens the concrete.

However, one more compound is produced on hydration that is so different in


behaviour. It is none other than the Calcium Hydroxide Ca(OH)2. In

construction industry, it is generally referred to as Free Lime. Aggressive

environmental agents like water, sulphates, CO2 attack this free lime leading to

deterioration of the concrete.

It is not only the chemistry provided by fly ash that compliments

chemistry of cement, but also the physical properties of fly ash improve the

rheology and microstructure of concrete by a great extent. Fly ash, on itself,

cannot react with water, it needs free lime, produced on hydration of Portland

cement, to trigger off its Pozzolanic effect. Once it is triggered, it can go on

and on. In simple words, it means a much longer life for concrete structure.

Specific benchmarks have been set up to evaluate the performance of

concrete with respect to durability - mainly Strength and Permeability. This

means to produce a durable and long lasting concrete, it must possess: High

strength and Low permeability.

3.5.6 Fly ash makes concrete denser, and hence less permeable, mainly

by:

Reducing water demand in concrete

Improving microstructure of concrete

At the same time, fly ash improves long term strength of concrete due

to the continued Pozzolanic reaction as discussed earlier.

3.5.7 BENEFITS OF USING FLY ASH

It delays the heat of hydration and hence reduces the thermal cracks

in concrete.

It improves the workability of concrete.

It makes the mix homogeneous and hence reduces segregation and

bleeding.

The concrete finish is improved due to perfectly spherical fly ash

particles.


The concrete permeability is substantially reduced which enhances

the life of the structure.

Fly ash contributes to the long term strength in concrete.

3.6 ADMIXTURES

GENERAL: Admixture is defined as a material, other than cement, water and

aggregates, which is used as an ingredient of concrete and is added to the

batch immediately before or during mixing. Additive is a material which is

added at the time of grinding cement clinker at the cement factory.

Plasticizer

Superplasticizer

Retarders and Retarding Plasticizers

Accelerators and Accelerating Plasticizer

Air-entraining Admixtures

Damp-proofing and Waterproofing Admixtures

Gas forming Admixture

Workability Admixture

Grouting Admixture

Bonding Admixture

Colouring Admixture

3.6.1 PLASTICIZER

Requirement of right workability is the essence of good concrete.

Concrete in different situations require different degree of workability. A high

degree of workability is required in situations like deep beams, thin walls of

water retaining structures with high percentage of steel reinforcement, column

and beam junctions, tremie concreting,pumping of concrete, hot weather

concreting, for concrete to be conveyed for considerable distance and in ready

mixed concrete industries. The conventional methods followed for obtaining

high workability is by improving the gradation, or by the use of relatively

higher percentage of fine aggregate or by increasing the cement content. There

are difficulties and limitations to obtain high workability in the field for a


given set of conditions. The easy method generally followed at the site in most

of the conditions is to use extra water unmindful of the harm it can do to the

strength and durability of concrete.

The harmful effect of using extra water than necessary. It is an abuse, a

criminal act, and unengineering to use too much water than necessary in

concrete. At the same time, one must admit that getting required workability

for the job in hand with set conditions and available materials is essential and

is often difficult. Therefore, engineers at the site are generally placed in

conflicting situations. Often he follows the easiest path and that is adding extra

water to fluidise the mix. This addition of extra water to satisfy the need for

workable concrete is amounting to sowing the seed of cancer in concrete.

Today we have plasticizers and superplasticizers to help an engineer

placed in intriguing situations. These plasticizers can help the difficult

conditions for obtaining higher workability without using excess of water. One

must remember that addition of excess water, will only improve the fluidity or

the consistency but not the workability of concrete.

The excess water will not improve the inherent good qualities such as

homogeneity and cohesiveness of the mix which reduces the tendency for

segregation and bleeding. Whereas the plasticized concrete will improve the

desirable qualities demanded of plastic concrete. The practice all over the

world now is to use plasticizer or superplasticizer for almost all the reinforced

concrete and even for mass concrete to reduce the water requirement for

making concrete of higher workability or flowing concrete. The use of

superplasticizer has become almost an universal practice to reduce

water/cement ratio for the given workability, which naturally increases the

strength. Moreover, the reduction in water/cement ratio improves the

durability of concrete. Sometimes the use of plasticizers is employed to reduce

the cement content and heat of hydration in mass concrete.

The organic substances or combinations of organic and inorganic

substances, which allow a reduction in water content for the given workability,

or give a higher workability at the same water content, are termed as


plasticizing admixtures. The advantages are considerable in both cases : in the

former, concretes are stronger, and in the latter they are more workable.

3.6.1.1 THE BASIC PRODUCTS CONSTITUTING PLASTICIZERS:

(i) Anionic surfactants such as lignosulphonates and their modifications

and

derivatives, salts of sulphonates hydrocarbons.

(ii) Nonionic surfactants, such as polyglycol esters, acid of hydroxylated

carboxylic

acids and their modifications and derivatives.

(iii) Other products, such as carbohydrates etc.

Among these, calcium, sodium and ammonium lignosulphonates are

the most used. Plasticizers are used in the amount of 0.1% to 0.4% by weight

of cement. At these doses, at constant workability the reduction in mixing

water is expected to be of the order of 5% to 15%. This naturally increases the

strength. The increase in workability that can be expected, at the same w/c

ratio, may be anything from 30 mm to 150 mm slump, depending on the

dosage, initial slump of concrete, cement content and type.

A good plasticizer fluidizes the mortar or concrete in a different

manner than that of the air-entraining agents. Some of the plasticizers, while

improving the workability, entrains air also. As the entrainment of air reduces

the mechanical strength, a good plasticizer is one which does not cause air-

entrainment in concrete more than 1 or 2%.

One of the common chemicals generally used, as mentioned above is

Lignosulphonic acid in the form of either its calcium or sodium salt. This

material is a natural product derived from wood processing industries.

Admixtures based on lignosulphonate are formulated from purified product

from which the bulk of the sugars and other interfering impurities are removed

to low levels. Such a product would allow adsorption into cement particles

without any significant interference with the hydration process or hydrated


Fig. 4.2.Effect of surface-active agents on deflocculating of cement grains.

products. Normal water reducing admixtures may also be formulated from

wholly synthetic raw materials. It is also observed that at a recommended

dose, it does not affect the setting time significantly. However, at higher

dosages than prescribed, it may cause excessive retardation. It must be noted

that if unrefined and not properly processed lignosulphonate is used as raw

material, the behavior of plasticizer would be unpredictable. It is sometimes

seen that this type of admixture has resulted in some increase in air-

entrainment. It is advised that users should follow the instructions of well-

established standard manufacturers of plasticizers regarding dosage

3.6.1.2 ACTION OF PLASTICIZERS

The action of plasticizers is mainly to fluidify the mix and improve the

workability of concrete, mortar or grout. The mechanisms that are involved

could be explained in the following way:

Tendency to flocculate in wet concrete. These flocculation entraps

certain amount of water used in the mix and thereby all the water is not freely

available to fluidify the mix.

Sources: Concrete Technology Book by M.S.Shetty


When plasticizers are used, they get adsorbed on the cement particles.

The adsorption of charged polymer on the particles of cement creates particle-

to-particle repulsive forces which overcome the attractive forces. This

repulsive force is called Zeta Potential, which depends on the base, solid

content, quantity of plasticizer used. The overall result is that the cement

particles are deflocculated and dispersed. When cement particles are

deflocculated, the water trapped inside the flocs gets released and now

available to fluidify the mix. Fig. 4.1 explains the mechanism.

RETARDING EFFECT: It is mentioned earlier that plasticizer gets

adsorbed on the surface of cement particles and form a thin sheath. This thin

sheath inhibits the surface hydration reaction between water and cement as

long as sufficient plasticizer molecules are available at the particle/solution

interface. The quantity of available plasticizers will progressively decrease as

the polymers become entrapped in hydration products.

Many research workers explained that one or more of the following

mechanisms may take place simultaneously:

Reduction in the surface tension of water

Induced electrostatic repulsion between particles of cement.

Lubricating film between cement particles.

Dispersion of cement grains, releasing water trapped within cement

flocs.

Inhibition of the surface hydration reaction of the cement particles,

leaving more water to fluidify the mix.

Change in the morphology of the hydration products.

Induced steric hindrance preventing particle-to-particle contact.

It may be noted that all plasticizer are to some extent set retarders,

depending upon the base of plasticizers, concentration and dosage used.

4.4.2 SUPERPLASTICIZERS (High Range Water Reducers) HRWR


Superplasticizers constitute a relatively new category and improved

version of plasticizer, the use of which was developed in Japan and Germany

during 1960 and 1970 respectively. They are chemically different from normal

plasticizers. Use of Superplasticizers permits the reduction of water to the

extent up to 30 per cent without reducing workability in contrast to the

possible reduction up to 15 per cent in case of plasticizers.

The use of superplasticizer is practiced for production of flowing, self

levelling, self-compacting and for the production of high strength and high

performance concrete.

The mechanism of action of superplasticizers is more or less same as

explained earlier in case of ordinary plasticizer. Only thing is that the

superplasticizers are more powerful as dispersing agents and they are high

range water reducers. They are called High Range Water Reducers

(HRWR) in American literature. It is the use of superplasticizer which has

made it possible to use w/c as low as 0.25 or even lower and yet to make

flowing concrete to obtain strength of the order 120 Mpa or more. It is the use

of superplasticizer which has made it possible to use fly ash, slag and

particularly silica fume to make high performance concrete.

The use of superplasticizer in concrete is an important milestone in the

advancement of concrete technology; it is widely used all over the world.

India is catching up with the use of superplasticizer in the construction of high

rise buildings, long span bridges and the recently become popular Ready

Mixed Concrete Industry. Common builders and Government departments are

yet to take up the use of this useful material.

4.4.2.1 SUPERPLASTICIZERS CAN PRODUCE:

at the same w/c ratio much more workable concrete than the plain

ones,

for the same workability, it permits the use of lower w/c ratio,

As a consequence of increased strength with lower w/c ratio, it also

permits a reduction of cement content.


The superplasticizers also produce a homogeneous, cohesive concrete generally without any tendency for segregation and bleeding.

4.4.2.2CLASSIFICATION OF SUPERPLASTICIZER

Following are a few polymers which are commonly used as base for superplasticizers.

Sulphonatedmalanie-formaldehyde condensates (SMF)

Sulphonated naphthalene-formaldehyde condensates (SNF)

Modified lignosulphonates (MLS)

Acrylic polymer based (AP)

Copolymer of carboxylic acrylic acid with acrylic ester (CAE)

Cross linked acrylic polymer (CLAP)

Polycarboxylateethers (PCE)

Multicarboxylatethers (MCE)

Combinations of above.

Out of the above new generation superplasticizersbased on carboxylic

acrylic ester (CAE) andmulticarboxylatether (MCE).

As far as our country is concerned, at present (2000 AD), we

manufacture and use the first four types of superplasticizers. The new

generation superplasticizers have been tried in recent projects, but it was not

found feasible for general usage on account of

high cost. The first four categories of products differ from one another

because of the base component or on account of different molecular weight.

As a consequence each commercial product will have different action on

cements. Whilst the dosage of conventional plasticizers do not exceed 0.25%

by weight of cement in case of lignosulphonates, or 0.1 % in case of

carboxylic acids, the products of type SMF or NSF are used considerably

high dosages (0.5% to 3.00%), since they do not entrain air.


FIG 4.3: Effect of 3rd generation PCE based super-plasticizer

The modified lignosulphonate (LS) based admixtures, which have an

effective fluidizing action, but at the relatively high dosages, they can produce

undesirable effects, such as accelerations or delay in setting times. Moreover,

they increase the air-entrainment in concrete.

Super plasticizer has been procured from BASF chemical (india) Pvt.

Ltd. With the brand name Glanium B276 Suretec (polycarboxylic either base).

The properties aregiven in TABLE 4.7.

TABLE 4.8 Properties of “GLANIUM B276 SURETEC”Aspect Light brown liquid

Relative Density 1.10 ± 0.02 at 25° CPh ≥6

Chloride ion content <0.2%

Plasticizers and superplasticizers are water based. The solid contents

can vary to any extent in the products manufactured by different companies.

Cost should be based on efficiencies and solid content, but not on volume or

weight basis. Generally in projects cost of superplasticizers should be worked

for one cubic meter of concrete.

4.4.2.3EFFECTS OF SUPERPLASTICIZERS ON FRESH CONCRETE

It is to be noted that dramatic improvement in workability is not

showing up when plasticizers or superplasticizers are added to very stiff or

what is called zero slump concrete at nominal dosages. A mix with an initial

slump of about 2 to 3 cm can only be fluidised by plasticizers or


superplasticizers at nominal dosages. A high dosage is required to fluidify no

slump concrete. An improvement in slump value can be obtained to the extent

of 25 cm or more depending upon the initial slump of the mix, the dosage and

cement content. It is often noticed that slump increases with increase in

dosage. But there is no appreciable increase in slump beyond certain limit of

dosage. As a matter of fact, the over dosage may sometime harm the concrete.

A typical curve, showing the slump and dosage is shown in Fig. 4.2.

Fig 4.4, Sources: Concrete

Technology Book by M.S.Shetty

4.4.2.4 COMPATIBILITY OF SUPERPLASTICIZERS AND CEMENT

It has been noticed that all superplasticizers are not showing the same

extent of improvement in fluidity with all types of cements. Some

superplasticizers may show higher fluidizing effect on some type of cement

than other cement. There is nothing wrong with either the superplasticizer or

that of cement. The fact is that they are just not compatible to show maximum

fluidizing effect. Optimum fluidizing effect at lowest dosage is an economical

consideration. Giving maximum fluidizing effect for a particular

superplasticizer and cement is very complex involving many factors like

composition of cement, fineness of cement etc.

Although compatibility problem looks to be very complex, it could be

more or less solved by simple rough and ready field method. Incidentally this

simple field test shows also the optimum dose of the superplasticizer to the

cement. Following methods could be adopted.


Marsh cone test

Mini slump test

Flow table test

3.7 CONSTRUCTION CHEMICALS

Discussed the materials that are used as admixtures to modify the

properties of concrete. There are other chemicals not used as admixtures but

used to enhance the performance of concrete, or used in concrete related

activities in the field of construction. Such chemicals are called construction

chemicals or building chemicals. The following is the list of some of the

construction chemicals commonly used.

Concrete Curing Compounds

Polymer Bonding Agents

Polymer Modified Mortar for Repair and maintenance

Mould Releasing Agents

Protective and Decorative Coatings

Floor Hardeners and Dust-proofers

Ready to use Plaster

4.5.1 GENERAL CHARACTERISTICS

The clear or translucent compounds shall be colorless or light in color.

If the compound contains fugitive dye, it shall be readily distinguishable on

the concrete surface for at least 4 hours after application, but shall become

inconspicuous within 7 days after application, if exposed to sun light.

The white-pigmented compound shall consist of finely divided white

pigment and vehicle ready mixed for immediate use as it is. The compound

shall present in uniform white appearance where applied at the specified rate.

The liquid membrane forming compounds shall be of such consistency

that it can be readily applied by spraying, brushing or rolling at temperature

above 4°C.


The liquid membrane-forming compounds are generally applied in two

coats. If need be more than two coats may be applied so that the surface is

effectively sealed. The first coat shall be applied after the bleeding water, if

any, is fully dried up, but the concrete surface is quite damp. In case of formed

surfaces such as columns and beams etc., the curing compound shall be

applied immediately on removal of formwork.

The following types of compounds are included:

Clear or translucent without dye

Clear or translucent with fugitive dye

White pigmented.

4.5.2 MEMBRANE FORMING CURING COMPOUNDS

In view of insufficient curing generally carried out at site of work, the

increasing importance of curing for around good qualities of concrete, in

particular, strength and durability, the need for conservation of water and

common availability of curing compounds in the country, it is felt that detail

information is required on this vital topic - curing of concrete by membrane

forming curing compounds.

Availability of enough moisture in concrete is the essence for

uninterrupted hydration process. In fresh concrete, the moisture level in

concrete is much higher than the relative humidity of atmosphere. Therefore,

evaporation of water takes place from the surface of concrete. To recoup the

loss of water from the surface of concrete and to prevent the migration of

water from the interior of concrete to surface of concrete, that is to retain

adequate moisture in the concrete, certain measures are adopted. Such

measures taken are generally called curing of concrete.

4.5.3DRYING BEHAVIOUR

Drying behavior of concrete depends upon air temperature, relative

humidity, fresh concrete temperature and wind velocity.

4.5.4TYPES OF CURING COMPOUNDS


Liquid membrane forming curing compounds are used to retard the

loss of water from concrete during the early period of setting and hardening.

They are used not only for curing fresh concrete, but also for further curing of

concrete after removal of form work or after initial water curing for one or two

days. In the case of white pigmented curing compound it also reduces the

temperature rise in concrete exposed to radiation from sun. Curing compounds

are made with the following bases.

Synthetic resin based

Waxbased

Acrylicbased

Chlorinated rubberbased

4.5.4.1 SYNTHETIC RESIN & WAX BASED

Resin and wax based curing compounds seals the concrete surface

effectively. With time their efficiency will get reduced and at about 28 days

they get disintegrated and peel off. Plastering can be done after about 28 days.

If plastering is required to be done earlier, the surface can be washed off with

hot water. As per one set of experiments it has been revealed that the typical

curing efficiency was 96% for 24 hours, 84% for 72 hours 74% for 7 days and

65% for 14 days and the average efficiency of resin and wax based membrane

forming curing compound can be taken as about 80%.

Curing Compound has been procured from FAIR MATE chemical Pvt.

Ltd. With the brand name FAIRCURE WX WHITE (wax based). The

properties are given in TABLE 4.8.

TABLE 4.10FAIRCURE WX White Properties

Water retention 0.29% kg/m² as per ASTM

Reflectance 70 % as per ASTM C 309 : 06

Drying time < 90 min as per ASTM C 309 : 06

Water retention efficiency More than 90%

Curing efficiency 90%

4.5.4.2 ACRYLICBASED


Acrylic based membrane forming curing compound has the additional

advantage of having better adhesion of subsequent plaster. The membrane

does not get crumbled down or it need not be washed with hot water. In fact

on account of inherent characteristics of acrylic emulsion the bonding for the

plaster is better.

4.5.4.3CHLORINATED RUBBERBASED

Chlorinated rubber curing compounds not only form a thin film that

protects the concrete from drying out but also fill the minute pores in the

surface of concrete. The surface film will wear out eventually.

4.5.5APPLICATION PROCEDURE

The curing compound is applied by brush or by spraying while the

concrete is wet. In case of columns and beams the application is done after

removal of formwork. On the horizontal surface, the curing compound is

applied upon the complete disappearance of all bleeding water. In case of road

and Air field pavements where texturing is required, the curing compound is

applied after texturing. In case of Pune-Mumbai express highway, the

pavement is cast by slip form paver. In this process concrete is finished,

texturing is done and curing compound is sprayed all by mechanical means.

The young concrete is covered by tents to protect green concrete from hot sun

and drying winds. In the above express highway it is specified that the

concrete is also water cured after one day using wet hessian cloth. Water

curing over membrane curing is seemingly superfluous, but it may be helpful

in keeping the temperature down.

In case the concrete surface has dried, the surface should be sprayed

with water and thoroughly wetted and made fully damp before curing

compound is applied. The container of curing compound should be well stirred

before use.

At present we do not have Bureau of Indian Standard Specification and

Code of Practice for membrane forming curing compounds. It is under

preparation. Since curing compounds are used very commonly in our country


in many of the major projects, such as SardarSarovar dam projects, express

highway projects, etc., a brief description in respect of ASTM: C 309 of 81,

for "Liquid Membrane-forming Compounds for Curing concrete" and ASTM

C 156 of 80 a for "Water Retention by concrete Curing Materials"

SCOPE: The specification covers liquid membrane forming compounds

suitable for retarding the loss of water during the early period of hardening of

concrete. The white pigmented curing compound also reduces the temperature

rise in concrete exposed to radiation from sun.

4.6SELF-CURING

Today concrete is most widely used construction material due to its

good compressive strength and durability. Depending upon the nature of work

the cement, fine aggregate, coarse aggregate and water are mixed in specific

proportions to produce plain concrete. Plain concrete needs congenial

atmosphere by providing moisture for a minimum period of 28 days for good

hydration and to attain desired strength. Any laxity in curing will badly affect

the strength and durability of concrete. Self-curing concrete is one of the

special concretes in mitigating insufficient curing due to human negligence

paucity of water in arid areas, inaccessibility of structures in difficult terrains

and in areas where the presence of fluorides in water will badly affect the

characteristics of concrete.

Proper curing of concrete structures is important to meet performance

and durability requirements. In conventional curing this is achieved by

external curing applied after mixing, placing and finishing. Self-curing or

internal curing is a technique that can be used to provide additional moisture

in concrete for more effective hydration of cement and reduced self-

desiccation.

4.6.1 MECHANISM OF SELF–CURING

Continuous evaporation of moisture takes place from an exposed

surface due to the difference in chemical potentials (free energy) between the


vapour and liquid phases. The polymers added in the mix mainly form

hydrogen bonds with water molecules and reduce the chemical potential of the

molecules which in turn reduces the vapour pressure, thus reducing the rate of

evaporation from the surface, When the mineral admixtures react completely

in a blended cement system, their demand for curing water (external or

internal) can be much greater than that in a conventional ordinary Portland

cement concrete. When this water is not readily available, significant

autogenously deformation and (early-age) cracking may result. Due to the

chemical shrinkage occurring during cement hydration, empty pores are

created within the cement paste, leading to a reduction in its internal relative

humidity and also to shrinkage which may cause early-age cracking.

4.6.2 METHODS OF SELF-CURING

There are two major methods available for internal curing of concrete.

The first method uses saturated porous lightweight aggregate (LWA) in order

to supply an internal source of water, which can replace the water consumed

by chemical shrinkage during cement hydration. The second method uses

poly-ethylene glycol (PEG) which reduces the evaporation of water from the

surface of concrete and also helps in water retention.

Lightweight aggregate (LWA)

Poly-ethylene glycol (PEG)

4.6.2.1POLYETHYLENE GLYCOLS (PEG)

Polyethylene glycol is a condensation polymer of ethylene oxide and

water with the general formula H(OCH2CH2)nOH , the abbreviation (PEG) is

termed in combination with a numeric suffix which indicates the average

molecular weights. One common feature of PEG appears to be the water-

soluble nature. Polyethylene glycol is non-toxic, odorless, neutral, lubricating,

non-volatile and non-irritating and is used in a variety of pharmaceuticals.

PEG's below 700 molecular weight occur as clear to slightly hazy, colorless,

slightly hygroscopic liquids with a slight characteristic odour. PEG's Between 700-900

are semi-solid. PEG's over 1000 molecular weight are creamy white waxy solids,

flakes, or free-flowing powders. We are using PEG’s 600.


TABLE 4.11 Physical and Chemical Properties of PEG’s 600

Physical State And

Appearance

Liquid

Odor & Taste Not Available

Molecular Weight 1000 G/Mole

Ph (1% Soln/Water) 6

Specific Gravity 1.12

Dispersion Properties See Solubility In Water, Methanol, Diethyl Ether

Solubility Easily Soluble In Cold Water, Hot Water. Soluble In Methanol,

Diethyl Ether

Advantages of Internal Curing

Internal curing (IC) is a method to provide the water to hydrate all

the cement, accomplishing what the mixing water alone cannot do.

Provides water to keep the relative humidity (RH) high, keeping self-

desiccation from occurring.

Eliminates largely autogenous shrinkage.

Maintains the strength of concrete at the early age (12 to 72 hrs.)

above the level where internally & externally induced strains can

cause cracking.

Can make up for some of the deficiencies of external curing, both

human related (critical period when curing is required in the first 12

to 72 hours) and hydration.


CHAPTER4

METHEDOLOGY5.1 MIX DESIGN AND TRIAL MIXES

The proposed study is being carriedout to develop self-compacting

concrete using fly ash andcement in varying combinations for use in the Indian

conditions.Following guidelines of ‘European Federation of National

Associations Representing producers and applicators of specialist building

products for Concrete’ EFNARC. To identify the property of fresh self-

compacted concrete by mix design & trial mixes.


5.1.1 GENERAL

Mix design selection and adjustment can be made according to the procedure

show:

• Set required performance

• Select materials

• Design and adjust mix composition

• Verify or Adjust performance in laboratory

• Verify performance in concrete

5.1.2 TRIAL MIXES

There is no standard method for SCC mix design and many academic

institutions, admixture, ready-mixed, pre cast and contracting companies have

developed their own mix proportioning methods.Based on ‘European

Federation of National Associations Representing producers and applicators

of specialist building products for Concrete’ EFNARC specifications, was

adopted for mixed design. Different mixes were prepared by varying the

amount of coarse aggregate, fine aggregate, water powder ratio &

superplasticizers. After several trials, SCC mix satisfying the test criteria was

obtained.

To develop self-compacting concrete using cement with various

quantity of fly ash from partially replacing fine and coarse aggregate.

Following steps are followed to achieve the SCC.

Quantity of cement and amount of fly ash to be added are determinate

by EFNARC.

Fixing optimum dosage of Superplasticizer by Marsh cone test on

cement slurry.

After fixing W/P ratio and optimum dosage of Superplasticizer with

given content and fly ash, aggregate quantities are found out and mix is

done to verify the fresh properties of SCC.

Cubes, Cylinders & Beams are cast and checked for its strength by

performing destructive tests.


5.1.3 MIXING PROCEDURE

There is no requirement for any specific mixer type. Forced action

mixers, including paddle mixers, free fall mixers, including truck mixers, and

other types can all be used. The mixing time necessary should be determined

by practical trials. Generally, mixing times need to be longer than for

conventional mixes Time of addition of admixture is important, and

procedures should be agreed with the supplier after planttrials. If the

consistence has to be adjusted after initial mixing, then it should generally be

done with theadmixtures.

All concrete batches were prepared in rotating drum mixture. First, the

aggregate are introduced and then one-half of the mixing water was added and

rotated for approximate two minutes. Next, the cement and fly ash were

introduced with HRWR admixture already mixed in the remaining water.

Most manufactures recommend at least 5minutes mixing upon final

introduction of Admixtures.

Once, the mix was determined to have sufficient visual attributes of

SCC, the rheological tests were performed in quick succession.

5.2 REQUIREMENTS FOR SELF-COMPACTING CONCRETE

SCC may be used in pre-cast applications or for concrete placed on

site. It can be manufactured in a site batching plant or in a ready mix concrete

plant and delivered to site by truck. It can then be placed either by pumping or

pouring into horizontal or vertical structures. In designing the mix, the size

and the form of the structure, the dimension and density of reinforcement and

cover should be taken in consideration.

Due to the high content of powder, SCC may show more plastic

shrinkage or creep than ordinary concrete mixes. These aspects should

therefore be considered during designing and specifying SCC. Current

knowledge of these aspects is limited and this is an area requiring further


research. Special care should also be taken to begin curing the concrete as

early as possible.

The workability of SCC can be characterized by the following properties:

1) Filling ability

2) Passing ability

3) Segregation resistance

A concrete mix can only be classified as Self-compacting Concrete if

the requirements for all three characteristics are fulfilled.

5.2.1 TEST METHOD

Many different test methods have been developed in attempts to

characterize the properties of SCC. So far no single method or combination of

methods has achieved universal approval and most of them have their

adherents. Similarly no single method has been found which characterizes all

the relevant workability aspects so each mix design should be tested by more

than one test method for the different workability parameters.

NO Method Property

1 Slump-flow by Abrams cone Filling ability

2 T50cmslumpflow Filling ability

3 J-ring Passing ability

4 V-funnel Filling ability

5 V-funnel at T5minutes Segregation resistance

6 L-box Passing ability

7 U-box Passing ability

8 Fill-box Passing ability

9 GTM screen Segregation resistance

10 Orimet Filling ability

Table 5.1List of test methods for workability properties of SCC


For site quality control, two test methods are generally sufficient to

monitor production quality. Typical combinations are Slump-flow and V-

funnel or Slump-flow and J-ring. With consistent raw material quality, a single

test method operated by a trained and experienced technician may be

sufficient.

NO Method Unit Typical range of valueMinimum Maximum

1 Slump-flow by Abrams cone mm 600 800

2 T50cmslumpflow sec 2 5

3 J-ring mm 0 10

4 V-funnel sec 6 12

5 V-funnel at T5minutes sec 0 +3

6 L-box (h2/h1) 0.8 1.0

7 U-box (h2-h1) mm 0 30

8 Fill-box % 90 100

9 GTM screen % 0 15

10 Orimet sec 0 5

Table 5.2Acceptance criteria for Self-compacting Concrete

5.2.1.1SLUMP FLOW TEST AND T50cm TEST

Introduction

The slump flow is used to assess the horizontal free flow of SCC in the

absence of obstructions. It was first developed in Japan for use in assessment

of underwater concrete. The test method is based on the test method for

determining the slump. The diameter of the concrete circle is a measure for the

filling ability of the concrete.

Assessment of test

This is a simple, rapid test procedure, though two people are needed if

the T50 time is to be measured. It can be used on site, though the size of the

base plate is somewhat unwieldy and level ground is essential. It is the most

commonly used test, and gives a good assessment of filling ability. It gives no

indication of the ability of the concrete to pass between reinforcement without


blocking, but may give some indication of resistance to segregation. It can be

argued that the completely free flow, unrestrained by any boundaries, is not

representative of what happens in practice in concrete construction, but the test

can be profitably be used to assess the consistency of supply of ready-mixed

concrete to a site from load to load.

Fig 5.1 Slump flow test

Equipment

The apparatus is shown in figure 5.1

Mould in the shape of a truncated cone with the internal dimensions

200 mm diameter at the base, 100 mm diameter at the top and a height

of 300 mm.

Base plate of a stiff non absorbing material, at least 700mm square,

marked with a circle marking thecentral location for the slump cone,

and a further concentric circle of 500mm diameter.

Trowel

Scoop

Ruler

Stopwatch


Procedure

About 6 litre of concrete is needed to perform the test, sampled

normally. Moisten the base plate and inside of slump cone, Place base plate on

level stable ground and the slump cone centrally on the base plate and hold

down firmly. Fill the cone with the scoop. Do not tamp, simply strike off the

concrete level with the top of the cone with the trowel. Remove any surplus

concrete from around the base of the cone. Raise the cone vertically and allow

the concrete to flow out freely. Simultaneously, start the stopwatch and record

the time taken for the concrete to reach the 500mm spread circle. (This is the

T50 time). Measure the final diameter of the concrete in two perpendicular

directions. Calculate the average of the two measured diameters. (This is the

slump flow in mm). Note any border of mortar or cement paste without coarse

aggregate at the edge of the pool of concrete.

Interpretation of result

The higher the slump flow (SF) value, the greater its ability to fill

formwork under its own weight. A value of at least 650mm is required for

SCC. There is no generally accepted advice on what are reasonable tolerances

about a specified value, though ± 50mm, as with the related flow table test,

might be appropriate.

The T50 time is a secondary indication of flow. A lower time indicates

greater flow ability. The research suggested 3-7 seconds is acceptable for civil

engineering applications, and 2-5 seconds for housing applications.

In case of severe segregation most coarse aggregate will remain in the

centre of the pool of concrete and mortar and cement paste at the concrete

periphery. In case of minor segregation a border of mortar without coarse

aggregate can occur at the edge of the pool of concrete. If none of these

phenomena appear it is no assurance that segregation will not occur since this

is a time related aspect that can occur after a longer period.


5.2.1.2V-funnel TEST:

Introduction

The V-funnel test was developed in Japan and used by Ozawa, et al 5.

The equipment consists of a V-shaped funnel, shown in Figure 5.2. The funnel

is filled with concrete and the time taken by it to flow through the apparatus

measured. This test gives account of the filling capacity (flowability). The

inverted cone shape shows any possibility of the concrete to block is reflected

in the result.

Assessment of test

Though the test is designed to measure flowability, the result is

affected by concrete properties otherthan flow. The inverted cone shape will

cause any liability of the concrete to block to be reflected in theresult – if, for

example there is too much coarse aggregate. High flow time can also be

associated withlow deformability due to a high paste viscosity, and with high

inter-particle friction.While the apparatus is simple, the effect of the angle of

the funnel and the wall effect on the flow ofconcrete is not clear.

Fig 5.2, V-funnel test equipment (rectangular section)

Equipment


The apparatus is shown in figure 5.1

V-funnel

Bucket ( ±12 litre )

Trowel

Scoop

Stopwatch

Procedure flow time


normally.Set the V-funnel on firm ground.Moisten the inside surfaces of the

funnel.Keep the trap door open to allow any surplus water to drain.Close the

trap door and place a bucket underneath.Fill the apparatus completely with

concrete without compacting or tamping,simply strike off the concretelevel

with the top with the trowel.Open within 10 sec after filling the trap door and

allow the concrete to flow out under gravity.Start the stopwatch when the trap

door is opened, and record the time for the discharge to complete (theflow

time). This is taken to be when light is seen from above through the

funnel.The whole test has to be performed within 5 minutes.

Procedure flow time at T5 minutes

a

Do NOT clean or moisten the inside surfaces of the funnel again.Close

the trap door and refill the V-funnel immediately after measuring the flow

time.Place a bucket underneath.Fill the apparatus completely with concrete

without compacting or tapping, simply strike off the concretelevel with the top

with the trowel.Open the trap door 5 minutes after the second fill of the funnel

and allow the concrete to flow out undergravity. Simultaneously start the

stopwatch when the trap door is opened, and record the time for the

dischargeto complete (The flow time at T5 minutes). This is taken to be when

light is seen from above through the funnel.



This test measures the ease of flow of the concrete; shorter flow times

indicate greater flow ability. ForSCC a flow time of 10 seconds is considered

appropriate. The inverted cone shape restricts flow, andprolonged flow times

may give some indication of the susceptibility of the mix to blocking.After 5

minutes of settling, segregation of concrete will show a less continuous flow

with an increase inflow time.

5.2.1.3L BOX TEST METHOD

Introduction

This test, based on a Japanese design for underwater concrete, has been

described by Petersson. The test assesses the flow of the concrete, and also the

extent to which it is subject to blocking byreinforcement. The apparatus is

shown in figure 5.3

The apparatus consists of a rectangular-section box in the shape of an ‘L’, with

a vertical and horizontalsection, separated by a moveable gate, in front of

which vertical lengths of reinforcement bar are fitted.The vertical section is

filled with concrete, then the gate lifted to let the concrete flow into the

horizontalsection. When the flow has stopped, the height of the concrete at the

end of the horizontal section isexpressed as a proportion of that remaining in

the vertical section (H2/H1in the diagram). It indicates theslope of the

concrete when at rest. This is an indication passing ability, or the degree to

which thepassage of concrete through the bars is restricted.The horizontal

section of the box can be marked at 200mm and 400mm from the gate and the

times taken to reach these points measured. These are known as the T20 and

T40 times and are an indicationfor the filling ability.The sections of bar can be

of different diameters and spaced at different intervals: in accordance

withnormal reinforcement considerations, 3x the maximum aggregate size

might be appropriate.The bars can principally be set at any spacing to impose

a more or less severe test of the passing abilityof the concrete.

Assessment of test


This is a widely used test, suitable for laboratory, and perhaps site use.

It assesses filling and passingability of SCC, and serious lack of stability

(segregation) can be detected visually. Segregation may alsobe detected by

subsequently sawing and inspecting sections of the concrete in the horizontal

section.Unfortunately there is no agreement on materials, dimensions, or

reinforcing bar arrangement, so it isdifficult to compare test results. There is

no evidence of what effect the wall of the apparatus and theconsequent ‘wall

effect’ might have on the concrete flow, but this arrangement does, to some

extent,replicate what happens to concrete on site when it is confined within

formwork.

Two operators are required if times are measured, and a degree of

operator error is inevitable.

Equipment

L box of a stiff non absorbing material see figure 5.3.

Trowel

Scoop

Fig 5.3 L-box test


Procedure


normally.Set the apparatus level on firm ground, ensure that the sliding gate

can open freely and then close it.Moisten the inside surfaces of the apparatus,

remove any surplus waterFill the vertical section of the apparatus with the

concrete sample.Leave it to stand for 1 minute.Lift the sliding gate and allow

the concrete to flow out into the horizontal section.Simultaneously, start the

stopwatch and record the times taken for the concrete to reach the 200 and

400mm marks.When the concrete stops flowing, the distances “H1” and “H2”

are measured.Calculate H2/H1, the blocking ratio.The whole test has to be

performed within 5 minutes.


If the concrete flows as freely as water, at rest it will be horizontal, so

H2/H1 = 1. Therefore the nearerthis test value, the ‘blocking ratio’, is to unity,

the better the flow of the concrete. The EU research teamsuggested a

minimum acceptable value of 0.8. T20 and T40 times can give some

indication of ease offlow, but no suitable values have been generally agreed.

Obvious blocking of coarse aggregate behindthe reinforcing bars can be

detected visually.

5.3COMPRESSIVE STRENGTH TEST

150 mm × 150 mm × 150 mm concrete cubes are cast. Specimens with

ordinary Portland cement (OPC) and OPC replaced with and fly ash. the

specimens is remove from the mould and subjected to water curing for up to

90 days. After curing, the specimens are tested for compressive strength using

a calibrated compression testing machine of 2,000 KN capacities.


PROCEDURE:

The 3 days, 14 days, 28 days& 90 days compressive strength of cube

were tested in the following manner.

After cleaning the bearing surface of the compression testing machine,

the concrete cube was placed on its smooth face side. The axis of the

specimen was carefully aligned with the centre of the lower pressure

plate of compression testing machine. Then an upper pressure plate

was lowered till the distance between pressure plate and the top surface

of the specimen achieved. No packing used between face of the

pressure plates and cube.

The load was applied without shock and increased gradually at the rate

of kg/cm2/min until the specimen was crushed.

The compressive strength calculated in kg/cm3 from the max. Load

sustained by the cube before failure.


Fig 5.4 compression testing

Compressive strength= P/A load

Where, P = failure load

A=cross sectional area

Average of three values was taken for determining compressive

strength of concrete.


CHAPTER 5

SCHEDULING OF WORK

Identify appropriate admixtures and its proportion to achieve self

curing property and self compactibility of concrete.

Mix-design for M30 grade Self Compacted Concrete (SCC).

Mix-design for M30 grade Self Compacted Concrete (NVC).

To identify admixtures for Self-curing of SCC.

STEP 1 DETERMINE RESEARCH SCOPE AAND OBJECTIVES

STEP 2 DETERMINE RESEARCH METHODOLOGY

STEP 3 LITERATURE REVIEW

STEP 4 TRIAL MIX FOR SCC AND NVC

STEP 5 CASTING AND TESTING OF CONCRETE BLOCK

STEP 5 ANALYZE THE RESULT

STEP 6 DOCUMENTATION


Adding different percentage of Admixtures by volume of cement.

Decide optimum percentage of chemical admixture

WORK TO BE DONE IN NEXT PHASE II

Future scope of work

Testing the Concrete cubes at different interval of days with some

tests and prepares the documentation on it.

Then comparison between self curing SCC and self curing NVC

Decide optimum percentage of chemical admixture

I have completed my research work up to step-4 Trial Mix.

Preparing Scheduling for casting and testing of Self Curing Self

Compacted Concrete.

SCHEDULING FOR CASTING OF CONCRETE BLOCK

Grade M30 SELF CURING SELF COMPECTED (GLYCOL – 600) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24

Grade M30 SELF CURING SELF COMPECTED (GLYCOL – 1500) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24

Grade M30 SELF CURING NVC (GLYCOL – 600) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24


Grade M30 SELF CURING NVC (GLYCOL – 1500) Total Ratio 0 0.3 0.4 0.5 0.6 0.7 0.8 1No. Of cube 3 3 3 3 3 3 3 3 24

6.5SCHEDULING FOR TESTING OF CONCRETE BLOCK

compression testDay 0 3 7 28

1 M36(24) 2 M315(24) 3 M36N(24) 4 M315N(24) M36(8) 5 M315(8) 6 M36N(8) 7 M315N(8) 8 M36(8) 9 M315(8)

10 M36N(8) 11 M315N(8) 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 M36(8)29 M315(8)30 M36N(8)31 M315N(8)

TABLE: 6.3 SCHEDULING FOR TESTING OF CONCRETE BLOCK


CHAPTER 6

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self curing and self compacted concrete