BEHAVIOR OF NORMAL, HIGH AND ULTRA- HIGH STRENGTH … · relevant to the shear load with the inclusion of mode of failure and final strength. Direct shear samples with an inverted

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International Journal of Civil Engineering and Technology (IJCIET)

Volume 9, Issue 2, February 2018, pp. 349–360, Article ID: IJCIET_09_02_034

Available online at http://http://www.iaeme.com/ijciet/issues.asp?JType=IJCIET&VType=9&IType=2

ISSN Print: 0976-6308 and ISSN Online: 0976-6316

© IAEME Publication Scopus Indexed

BEHAVIOR OF NORMAL, HIGH AND ULTRA-

HIGH STRENGTH CONCRETE IN DIRECT

SHEAR

Dr. Qassim Ali Al-Quraishy

Doctor, Lecturer, Civil Engineering Department,

AL-Mansour University College, Baghdad, Iraq

ABSTRACT

The construction and manufacture of high buildings and the increasing demands

of owners and designers have directed to the increasing and growing demand for

“high” and "ultra-high strength" (HSC and UHSC) concrete. This innovative concrete

technology was designated with extremely high (f'c) compressive strength. This paper

displays and presents an experimental work that focuses on structural performance in

relevant to the shear load with the inclusion of mode of failure and final strength.

Direct shear samples with an inverted "L" shape has been tested to the shear failure

level using "normal", "high", and "ultra-high-strength" concrete with the impact of

steel fibers. The test (shear strength test) taken here, where are the sample

preparation and testing process can be simpler and through the same corresponding

and particular time guarantees steady and compatible results. The experimental

search results and conclusions display that the steel fiber samples exhibit a ductile

manner with the improvement in the ultimate strength, in counting, and significantly

improve in structural integrity. The variants that were considered were compressive

strength (f'c) and steel fiber (vf) volume fraction. It was discovered that the addition

and inclusion of steel fiber enhance and improve the ultimate shear capacity and

capability of the concrete compared to conventional plain concrete.

Key words: Normal, high, ultra-high, shear strength and steel fiber.

Cite this Article: Dr. Qassim Ali Al-Quraishy, Behavior of Normal, High and Ultra-

High Strength Concrete in Direct Shear. International Journal of Civil Engineering

and Technology, 9(2), 2018, pp. 349-360.

http://www.iaeme.com/IJCIET/issues.asp?JType=IJCIET&VType=9&IType=2

1. INTRODUCTION

High strength (HSC) and ultra-high-strength (UHSC) concrete is generally and commonly

used with a compressive strength (f'c) greater than (100 MPa) [Dili, A. S. and Manu

Santhanam, (2004), Wille, K. et. al., (2011), A. Logan, et. al., (2009)]. These types of

concrete are considered and recognized to be nearly and comparatively as a brittle behavior

material. Ultra-high strength (UHSC) concrete is a concrete that has a very low ratio of water

to cement, high binder content, and optimal packing density to eliminate capillary pores and



provide dense matrix. It is a high strength material developed from a special combination of

constituent materials [Voo, Y.L. et. al., (2012), Habel, K., (2004)]. This material has the

ability to maintain deformation and resists bending and tensile strength, even after the initial

cracking [C.Wang, et. al., (2012), M. Ismeik (2009)]. The shearing strength of the concrete is

one-layer resistance with concern or regard to the others; throughout the slip in the contacted

surface area. Adding fiber to the concrete makes the concrete transpose its behavior from

brittle characteristics to ductile one and with isotropic and homogenous manner. At time of

cracking of concrete, the randomly oriented fibers, function and operate to arrest and restrain

micro-cracking, therefore, develop the shear strength crack and considerably increased. In

terms of structure performance, insertion and addition of discrete fibers in a concrete matrix

can stop the cracks and thus control the propagation of the crack.

There are several methods to find shear strength found by many researchers. In this study

the shear strength was found by setup suggested by [Bairagi, N. K. and Modhera, C. D.,

(2004)] those who designed a practical method to find shear force in the absence of the usual

or standard methods of shear force. Researchers have experimented with their design in a

practical way in the laboratory and their work has been compared with (JSCE) method, but it

was found that the proposed method of their design gives a 10% higher than (JSCE) method.

In normal or high and ultra-high strength concrete, especially when concrete grade is

increased, the shear failure is of a brittle failure type. Therefore, many researchers have

introduced and used steel fiber to increase the shear force capacity and concrete ability and

strength to obtain ductile type of failure [J. Zatloukal,et. al., (2012), C. Bywalski, et.al.,

(2004)]. There many additives to concrete that effects the concrete behavior such as steel

fiber, fiber type and silica fume with different ratios. The definition of shear force as sliding

surface on another surface or one layer on another layer. This method of slip on the joint

surface of the contact gives a clear picture of shear force transmitted through concrete

[Khaloo R. and Nakeseok kim., (1997), A. Khanlou, et. al., (2013), Y. Voo, et. al., (2006)].

Experimental study on the direct shear force of normal materials, high and ultra-strength

concrete using a simplified and reliable testing test suggested by [Bairagi, N. K. and Modhera,

C. D., (2004)] were presented here. The effect and influence of steel fiber (vf) ratios of (0, 1.0

and 2.0%) on concrete shear strength were studied. This type of experimental test for direct

shear calculation represented the most, efficient and the simplest test and also more

convenient and accessible to indicate a realistic and effective sliding mechanism in shear.

2. SPECIMENS AND TEST PREPARATIONS

This test study, presented the effect and influence importance of steel fiber variations upon the

concrete shear strength of (normal; high and ultra-high strength concrete) were studied. One

size of the L-shape mold is used to prepare samples as shown and presented in Figure (1).

Three different ratios of steel fiber (0, 1.0 and 2.0%) were added and combined to the mixture

and the concrete shear strength was compared to every type and sample of concrete.

Figure 1 L-shape testing and experimentation set-up and dimensions of the specimen for the direct shear test.

Behavior of Normal, High and Ultra-High Strength Concrete in Direct Shear


3. EXPERIMENTAL TEST AND MATERIALS USED

Experimental laboratory work for this research study consists of casting, examining and

testing of (normal, high and ultra-high concrete samples) tested in direct shearing load. Three

(3) samples for each concrete type are made for each separate mixture, and take the mean

value. Details and organizations for every laboratory experimental work test are displayed in

the subsequent:

3.1. Cement

Normal Portland cement (type I) was used and adopted throughout and during the

experimental laboratory work of this study. This cement complies with [Iraqi Standard

Specification No. 5/1984]. Figure (2) display and shows the sample of cement used.

3.2. Fine Aggregate

Natural sand was used for normal concrete mixtures while for high and ultra-high silica sand

known as glass sand are used as shown in Figures 3 and 4. Fine grades satisfy to B.S.

specification No.882/1992 and Iraqi Specification No.45/1984]. Table (1) shows the

classification of fine aggregates.

Table 1 Grading of fine aggregate.

Type Natural Sand Silica sand

Sieve

Size

(mm)

Passing

%

Limits of Iraqi specification

No.45/1984, zone 2

Passing

%

Limits of Iraqi

specification

No.45/1984, zone 4

4.75 100 90-100 100 95-100

2.36 80 75-100 98 95-100

1.18 68 55-90 98 90-100

0.60 48 35-59 86 80-100

0.30 18 8-30 18 15-50

0.15 5 0-10 8 0-15

3.3. Coarse Aggregate

Crushed aggregate was used with maximum particle size of 10 mm for the normal and high

strength concrete mixes. The coarse aggregate classification used is consistent with [Iraqi

specifications No. 45/1984] as shown and displayed in Table (2) and Figure. (5).

Table 2 Grading of Coarse Aggregate

Sieve Size (mm) Cumulative Passing (%) Limits of Iraqi

SpecificationNo.45/1984.

10 98 100

4.75 90 85-100

2.36 20 0-25

1.18 0 0-5



Figure 2 Sample of cement

used.

Figure 3 Sample of sand

used. Figure 4 glass sand

used.

Figure 5 Sample of

aggregate used.

3.4. Silica Fume

The gray silica fume as shown in Figure (6) was employed as additives in mixtures to

improve and enhance its properties. [M. Mazloom, et. al., (2004), S. Allena et. al., (2010)]

The silica with fineness used is 200x103 m

2/kg and its chemical structure is shown and

displayed in Table (3).

Table 3 Chemical Analysis of Silica Fume.

Chemical

composition

Percent

%

SiO2 97

Fe2O3 0.02

Al2O3 0.015

MgO 0.012

CaO 0.25

Na2O 0

K2O 0.09

3.5. Superplasticizer

The ultra-high-superplasticizer commercially labeled as sika ViscoCrete PC-20 was used as a

concrete mixture. It has three functions, namely superplasticizer, viscosity modulation factor,

and a retarder which increases the compressive, tensile strength and flexural strength which

can be achieved by taking advantage of water reduction characteristics as specified in [ASTM

C109/C109M-05] and [ASTM C1240-03]. Figure 7 display and shows the superplasticizer

used.

3.6. Steel Fibers

Steel fibers with aspect ratio of (65) were used here as shown in Figure (8) which complies

with [ASTM A820/A 820M-04] provisions. Steel fibers typically range and vary from 0.25 to

2% in volume [R.Yu; et. al., (2014)]. Table (4) shows the properties and characteristics of the

used steel fibers. Table 4 Properties of steel fiber used.

Description

Length of fiber (L) mm 13

Diameter of Fiber (d) mm 0.25

Tensile strength (MPa) 2600

Modulus of Elasticity (Es) (GPa) 210

Density (kg/m3) 7800

Cross section Straight and Round

Aspect ratio L/D 65



Figure 6 Silica fume used. Figure 7 Sample of

superplasticizer used.

Figure 8 Sample of the steel fiber

used.

4. MIX PROPORTIONS

Three concrete types (normal, high HSC and ultra-high UHSC strength concrete) with

different percentage of steel fiber (Vf) (0, 1.0% and 2.0%) as shown and introduce in table (5)

which gives mixture of all concrete types used, with the proportion of components of ready-

mixed concrete as shown below:

For Normal strength concrete (1: 1.28: 1.96) (by weight of normal Portland cement OPC: Fine

aggregate S: Coarse aggregate G with w/c ratio of 0.45).

For High Strength HSC concrete (1: 1.77: 2.65) (by weight of normal Portland cement OPC:

Fine aggregate S: Coarse aggregate G with w/c ratio of 0.2).

For Ultra-high strength concrete (1: 1: 0) (by weight of normal Portland cement OPC: Fine

aggregate S: Coarse aggregate G with w/c ratio of 0.2).

Table 5 Mix proportions of (normal, high and ultra-high strength concrete).

Mix Cement

(kg/m3)

Sand

(kg/m3)

Aggregate

(kg/m3)

w/c superplasticizer

by weight of

cement

silica fume by

weight of

cement

steel fiber %

by volume

concrete

1 500 640 980 0.4

5

0 0 0 Normal

Concrete

2 500 640 980 0.4

5

0 0 1

3 500 640 980 0.4

5

0 0 2

1 450 797 1195 0.2 0.04 10% 0 High

strength

concrete

2 450 797 1195 0.2 0.04 10% 1

3 450 797 1195 0.2 0.04 10% 2

1 1000 1000 0 0.2 7 25% 0 Ultra-

high

strength

concrete

2 1000 1000 0 0.2 7 25% 1

3 1000 1000 0 0.2 7 25% 2

5. MIXING, CASTING AND CURING OF SPECIMENS

At first steel molds of dimensions (150*150*150mm width, length and depth) have been used

to cast all samples of (L-form shape). All parts of the molds should be fixed in their desired

position and therefore, the inner surface of the samples should be cleaned and lubricating with

oil liquids. Second, each part of the polystyrene is placed in the required steel molds to give

L-form shape in for the samples as shown and displayed in Figure 9.

All concrete types were mixed in a horizontal rotary mixer of types as shown in Figure 10.

For normal concrete mixture, concrete is combined and blended into normal procedures. The



coarse aggregates and sand were first mixed and homogenized for 2 minutes, then cement was

added and the dry ingredients were mixed and homogeneous for about 3 minutes to achieve

and get a homogeneous dry blend. The water was introduced and added during and

throughout the mixing process for another 3 minutes or until a homogeneous mixture was

obtained.

For high HSC and ultra-high UHSC strength concrete blending procedures adopted in this

experimental study is proposed by [Wille et al. 2011]. The cement and silica fume were

combined and mixed for the first time for 4 minutes, then fine sand was introduced and the

dry ingredients were added and blended for 5 minutes. For HSC gravel then added and mixing

continuous for about 3 minutes. In these mixes superplasticizer should be added to the water,

then the combined water and superplasticizer have been added to the dry mixture and the

mixing process has lasted for at least 3 minutes. Finally, steel fibers were inserted and added

during mixing in two minutes. Pour the samples by placing the concrete set in the molds

continuously into three layers including each layer being vibrated using a vibrator table to get

a compact concrete. With each mix control samples arranged and prepared to determine and

obtain the mechanical properties of the concrete. Control samples include 3 cylinders

(100mmx200mm) and 3 cubes (100mmx100mmx100mm) for compressive strength. After the

full casting process have been complete, all samples were covered with nylon layer for 24

hours to prevent moisture loss, figure (11) shows concrete curing treatment. After one day

from casting, all prepared samples were removed, transported and placed in water containers

tanks to be treated and cured.

Figure 9 Preparation of the concrete samples.

Figure 10 Mixing of concrete. Figure 11 Curing of the

concrete samples.



6. TESTING OF COMPRESSIVE STRENGTH TEST FOR CONTROL

SPECIMENS

A design mix is a method to identify the most suitable material from concrete, prepare the

corresponding portions to reach and attain the expected strength. The compressive strength

test was implemented with [ASTM C39 / C39M-01] for (cylinder 100mm × 200mm) and

(cube 100x100mmx100mm) for 28 days for all concrete using a 2000kN pressing machine as

shown in Figure (12). Three samples were prepared and used to determine and achieve the f'c

compression strength of all mixtures.

Figure 12 Compressive strength test of the samples.

7. RESULTS AND DISCUSSIONS

7.1. Compressive Strength

The results of mechanical properties (compressive strength) for (normal, high and ultra-high

strength concrete) were presented and displayed in Table (6) and Figures (13, 14 and 15). The

table shows the increasing percentage of compressive strength f'c with increasing the fiber

content of all types of concrete.

For normal concrete (when steel fiber increases from (0, 1 and 2%) an increase in average

compressive strength f'c of about (0, 6 and 10%).

For high strength (HSC) concrete (when steel fiber increases from (0, 1 and 2%) an increase in

average compressive strength f'c (0, 10 and 19%).

For ultra-high (UHSC) strength concrete (when steel fiber increases from (0, 1 and 2%) an

increase in average compressive strength (0, 18 and 42%).

Table 6 Compressive strength of (normal, high and ultra-high strength concrete).

Mix Concrete

Type

Cylinder Compressive

strength (MPa)

Increasing percentage (%) in

compressive strength

1 Normal 35 0

2 37 6

3 38.5 10

1 High 59 0

2 65 10

3 70 19

1 Ultra-High 72 0

2 85 18

3 102 42



Figure 13 Effect of fiber content on

compressive strength of normal concrete.

Figure 14 Effect of fiber content on

compressive strength of high strength concrete.

Figure 15 Effect of fiber content on compressive strength of Ultra high strength concrete

7.2. Shear Strength

The effect of steel fiber variation on shear strength (normal, high and ultra-high strength

concrete) were studied. Three different ratios of steel fibers (0, 1.0 and 2.0%) were added to

the mixture and the shear strength was compared for all samples. Differences and Variations

in shear strength gained from steel fiber variation. The experimental test results in Table (7)

show and display that the ultimate shear strength of the concrete with the inclusion and

addition of the fibers increases significantly over the plain concrete. With the addition of

fiber, the samples do not suddenly fail and the failure load is higher than the plain concrete

load. The amount of fiber used in plain concrete samples does not significantly influence the

first cracking load but has a significant and important impact on the crack propagation rate

and a load of failure. The tests indicated that samples specimens without fiber have a brittle

failure compared to ductile failure for specimens with fiber. The brittle failure has one major

crack while the presence of fiber leads to multiple small cracks and shear failure in a brittle

mode does not notice. Steel fiber works inside the concrete as a cracks restrainer and confiner

which arrested the concrete cracks and pulling-out the fibers from the matrix is observed at

the final load step. Figure 16 shows the test procedure and the shape pattern of the failure of

concrete samples. Typical variation of shear strength was made with respect and regard to the

fiber volume fraction has been planned and plotted in Figure (17 to Fig 28). It should be noted

that the maximum and the highest increase in shear strength was found for 2% fiber volume

fraction adding in the plain concrete samples.

For normal concrete, when steel fiber increases from (0, 1 and 2%) an increase in shear

strength of about (0, 51.8 and 117.2%).

For high strength (HSC) concrete, when steel fiber increases from (0, 1 and 2%) an increase in

shear strength of about (0, 60.4 and 124.0%).

For ultra-high (UHSC) strength concrete, when steel fiber increases from (0, 1 and 2%) an

increase in shear strength of about (0, 71.5 and 136.3%).



Table 7 Shear strength of (normal, high and ultra-high strength concrete).

Mix Shear strength (MPa) Increasing percentage (%) in shear strength

1 Normal 4.44 0.0

2 6.74 51.8

3 9.64 117.2

1 High 5.76 0.0

2 9.24 60.4

3 12.90 124.0

1 Ultra-High 6.36 0.0

2 10.91 71.5

3 15.04 136.3

Figure 16 Testing procedure and shape of failure of concrete specimens in shear.

Figure 17 Shear strength relationship with

compressive strength for normal concrete.

Figure 18 Shear strength relationship with fiber

content (%) for normal concrete.


compressive strength f’c for high strength concrete.


content (%) for high strength concrete.




compressive strength for ultra-high strength concrete.


content (%) for ultra-high strength concrete.


compressive strength for all types of concrete.


content (%) for all types of concrete.


compressive strength f'c for all types of concrete with

(0% fiber content).


compressive strength f'c for all types of concrete with

(1.0% fiber content).


compressive strength for all types of concrete with

(2.0% fiber content).

Figure 28 Shear strength for all types of concrete with

(0, 1.0 and 2.0% fiber content).



8. CONCLUSIONS

The test results and conclusions show that the setting of the proposed test by [Bairagi, N. K.

and Modhera, C. D., (2004)] is very simple to find shear strength.

The experimental test work on inverted “L” samples shows that the samples specimens

without fibers failed and fractured into a brittle behavior manner type. While the presence and

occupation of fiber in the specimen’s samples indicates multiple visible cracks and the failure

turn to ductile failure.

Due to and because of fibers presence, shear failure in a brittle mode does not notice and the

cracks restrained and confined by fibers and this lead to appear of multiple cracks in concrete.

In fact, fiber arrested the cracks and finally at the ultimate load, pulling-out the fibers from the

matrix is observed

When concrete strength changes to high and ultra-high strength and with regard to the fiber

presence; ductile failure was observed. Changing in concrete properties with the inclusions of

material additives all these components leads to optimal packing density.

For normal concrete, when steel fibers increase from (0, 1 and 2%), the average compressive

strength f'c increases by (0, 6 and 10%), while for high (HSC) strength concrete an increase in

average compressive strength f'c of (0, 10 and 19%) and for ultra-high (UHSC) strength

concrete, an increase in average compressive strength f'c (0, 18 and 42%) is achieved.

The presence and insertions of fibers increased shear strength of about (0, 51.8 and 117.2%)

for normal concrete and about (0, 60.4 and 124.0%) for high strength (HSC) concrete and

about (0, 71.5 and 136.3%) for Ultra high strength (UHSC) concrete, when the steel fibers (vf)

increases from (0, 1 and 2%).

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Documents

BEHAVIOR OF NORMAL, HIGH AND ULTRA- HIGH STRENGTH … · relevant to the shear load with the inclusion of mode of failure and final strength. Direct shear samples with an inverted