FINAL REPORT ON MINOR RESEARCH PROJECTpvpsiddhartha.ac.in/dep_civil/docs/asv_ugc.pdf · steps given in ACI 211.4 code. 3. OBJECTIVES OF THE FINAL REPORT: The following are the objectives

FINAL REPORT ON MINOR RESEARCH PROJECT

UGC Project title: “Production and development of Ultra high strength concrete (M150)”

Sanction Order No: F. MRP-6028/15, dated 31/10/2016

1. INTRODUCTION:

Strength is the most important characteristic of hardened concrete. Compressive, flexural

and split tensile are the most common type of concrete strengths. When the term

“strength” use with concrete it will express its compression strength. However there is no

specific classification limits according to strength but may be summarized as follow.

1. Normal strength concrete (10 Mpa – 40 Mpa)

2. High strength concrete (40 Mpa – 100 Mpa)

3. Ultra high strength concrete (100 Mpa – 800 Mpa)

2. THE WORK COVERED IN THE ANNUAL REPORTThe following work was carried out and the report was sent as Annual report

1. The Literature survey was conducted by referring many publications related to

High strength concrete, mechanical properties of concrete, concrete subjected to

elevated temperature etc.

2. The preliminary experiments were carried out on ingredients of concrete

3. The Mix proportion for M150 was derived as 1 : 0.73 : 1.44 : 0.25 by following the

steps given in ACI 211.4 code.

3. OBJECTIVES OF THE FINAL REPORT:The following are the objectives of the final report

1. The effect of temperature on compressive strength of concrete by heating the 28

days cured cubes at elevated temperature of 50, 100, 150, 200 and 2500C for 1, 2 and

3 hours.

2. The effect of temperature on split tensile strength of concrete by heating the 28 days

cured cylinders at elevated temperature of 50, 100, 150, 200 and 2500C for 1, 2 and 3

hours.

3. The effect of temperature on flexural strength of concrete by heating the 28 days

cured beams at elevated temperature of 50, 100, 150, 200 and 2500C for 1, 2 and 3

hours.

4. EXPERIMENTAL PROGRAM

Preliminary investigations were carried out to develop M150 grade concrete. The mix

proportion arrived as per ACI 211.4R was 1:0.454:1.527 by weight with w/c ratio of

0.25. The estimated batch quantities per cubic meter of concrete were: cement, 732 kg;

fine aggregate, 332.32 kg; coarse aggregate, 1118 kg and water, 183 litres. The optimum

dosages of mineral and chemical admixtures were identified as 6% and 1.5% of quantity

of cement respectively from the previous investigation.

An electric furnace is a thermally insulated

chamber used for the heating the elements. It

has a digital microprocessor controller, open

coil heater and double-wall construction with

glass fiber insulation and silicone door

gaskets minimize heat loss. Exterior surfaces

have scratch-resistant baked enamel coating

and stainless steel interiors as shown in Fig.1.

Furnaces have superior thermal uniformity

and a forced-air convection system with an

adjustable damper. Maximum temperature is

1200°C with capacity of 12”x12”x25”.

Tests were conducted on 100 mm size cubes, 150 mm diameter with 300 mm height

cylinders and 100x100x500 mm beam specimens. The specimens were heated to

different temperatures of 50, 100, 150, 200 and 250oC for different durations of 1, 2, 3

and 4 hour at each temperature which were cured for 28 days. After the heat treatment,

the specimens were brought to room temperature and tested for compressive strength,

split tensile strength and flexural strength.

Fig. 1 Heating the concrete element in furnace

Fig. 4 Testing the cylinder for split tensile strength

https://en.wikipedia.org/wiki/Heating

5. EXPERIMENTAL RESULTS:

a). Effect of temperature on compressive strength

The compressive strength of concrete at any age and exposed to any temperature is

expressed as the % of 28 days compressive strength at room temperature. This is termed

as Percentage residual compressive strength.

The cubes were casted, cured for 28 days

and heated at different temperatures for 1, 2,

3 and 4 h. The heated specimens are tested in

hot condition as shown in Fig.2 for

compressive strength according to IS: 516-

1959. The compressive strength of cubes

when exposed to elevated temperature of 50,

100, 150, 200 and 250oC at different

durations of 1, 2, 3 and 4 hours after 28 days

of curing. The variation of percentage

residual compressive strengths with the

increase in temperature is plotted in Fig.3.

0 50 100 150 200 250 30080

90

100

110

120

130

1401 hour duration

2 hours duration

Temperature (Degree Celsius)

% R

esid

ual C

ompr

essi

ve st

reng

th

Fig. 2 Testing the concrete cube for compressive strength

Fig. 3 Variation of % residual compressive strength of concrete with temperature for

different exposure duration

b). Effect of temperature on split tensile strength

The split tensile strength at any temperature is expressed as the % of 28 days split tensile

strength at room temperature and that is known as residual split tensile strength. The

residual splitting tensile strength of

concrete is found to be influenced by the

temperature to which it was exposed and

the duration of exposure. The testing of

cylinder for splitting tensile strength and

its failure surface are represented in Fig. 4.

The residual splitting tensile strength of all

heated specimens at any exposure time

was expressed as the percentage of 28 days

split tensile strength of unheated concrete

specimens. The variation of its % residual

split tensile strength with the increase in

temperature at different duration of

exposure is plotted is shown in Fig. 5.

Fig. 4 Testing of cylinder for split tensile strength

0 50 100 150 200 250 30060

70

80

90

100

110

120

130

140 1 hour duration 2 hours duration 3 hours duration 4 hours duration

Temperature (oC)

% R

esid

ual S

plit

tens

ile s

treng

th

c. Effect of temperature on flexural strength / modulus of rupture

Flexural strength is one way of measuring the tensile strength of concrete. It is a measure

of an unreinforced concrete beam or slab to resist failure in bending. It is measured by

loading 100 x 100 mm concrete beams with a span length at least three times the depth. In

this study, the concrete beams of 100 x 100 x 500 mm size are used. These specimens of

beams are exposed to elevated temperature of

50, 100, 150, 200 and 250oC for 1, 2, 3 and 4

hours duration after 28 days of curing. The

testing of beam for flexural strength is shown

in Fig.6. The flexural strength of M150

concrete was noticed to increase continuously

up to 150oC and beyond that there is a rapid

decrease in modulus of rupture. The residual

modulus of rupture is also calculated at

different temperatures. The variation of

modulus of rupture with respect to temperature

is shown in Fig.7.

Fig. 6 Testing of beam for flexural strength

Fig. 5 Variation of % residual split tensile strength of concrete with

temperature for different exposure duration

0 50 100 150 200 250 30060

70

80

90

100

110

120

130

140

150

160 1 hour duration2 hours duration3 hours duration4 hours duration

Temperature (oC)

% R

esid

ual F

lexu

re s

treng

th

6. CONCLUSIONSAfter investing the effect of temperature and its duration on M150 concrete, the following conclusions were drawn.

1. The mix exhibited a slump of 70 mm with Chemical admixture (920SH) of 2% byweight of cement.

2. The mix proportion for M150 concrete by ACI method is derived as 1:0.454:1.527:0.25.

3. The compressive strengths of M150 concrete are increased initially upto a temperature of 100oC and beyond that they got reduced rapidly with increasing the temperature.

4. The compressive strengths are lost very much when they are heated at 250oC.

5. The max compressive strength of 170 N/mm2 was obtained when the cubes were heated at 100oC for 1 hour duration.

6. It is noticed that both compressive and split tensile strengths increased continuously when the concrete heated upto 100oC and beyond that those values get reduced.

7. It was observed that major part of loss in split tensile strength is taking place in the first 1 hour exposure.

8. The flexural strength values were continuously increased upto 150oC and then they were noticed to get reduced.

9. It was observed that the variation of flexural strength for different exposure duration is very less upto 100oC temperature and beyond that the variation in strengths is considerable.

10. The concrete get hardened at faster rate at early ages than at later ages since the major quantity of heat of hydration get neutralized before 7 days of curing.



PUBLICATIONS

1. A. Sreenivasulu 2018, “Design and Development of M150 grade Concrete”, published in the “International Journal of Research and Scientific Innovation (IJRSI)”, Volume V, Issue VIII, August 2018, ISSN 2321–2705. pp. 52-55.

2. A. Sreenivasulu 2018, “The effect of temperature on mechanical properties of M150 Concrete”, published in the “International Journal of Research and Analytical Reviews (IJRAR)” – An UGC recognized Journal, Volume 5, Issue 4, December 2018,ISSN 2349–5138. pp. 172-177.

(Dr. A. Sreenivasulu)

International Journal of Research and Scientific Innovation (IJRSI) | Volume V, Issue VIII, August 2018 | ISSN 2321–2705

www.rsisinternational.org Page 52

Design and Development of M150 Grade Concrete

A. Sreenivasulu

Associate Professor, Department of Civil Engineering, PVP Siddhartha Institute of Technology, Vijayawada, Andhra Pradesh,

India

Abstract:-Concrete is easy to work with, versatile, durable, and

economical. By taking a few basic precautions, it is also one of

the safest building materials known. The use of high strength

concrete results in many advantages such as reduction in beam

and column sizes and increase in the building height with many

stories. High strength concrete is usually considered to be a

concrete with 28 days compressive strength of at least 40 MPa.

But in recent years, it is defined as the concrete having a

minimum 28 days compressive strength of 60 MPa. In many

developed countries, the concrete producers arbitrarily having

28 days compressive strength of above 45 MPa when normal

weight of aggregate is used. High strength concrete has been

widely used in Civil Engineering in recent years. High strength is

made possible by reducing porosity, non homogeneity and micro

cracks in concrete and the transition zone. It can be achieved by

using super plasticizers and supplementary cementing materials

such as silica fume, granulated blast furnace slag and natural

pozzolana. High strength concrete has a high modulus of

elasticity. High performance concrete with a very low

permeability ensures long life of structure exposed to such

conditions. The durability is not a problem under extreme

conditions of exposure. Preliminary experiments have been done

on Cement, Fine aggregate and Coarse aggregate. In the present

investigation, Silica fume is used as mineral admixture and

920SH is used as chemical admixture. The w/c ratio for M150

concrete is considered as 0.25. By following the design procedure

given by ACI Method, the mix Proportion for M150 grade

concrete is derived as 1 : 0.454 : 1.527. The compressive and split

tensile strengths are identified for the concrete after exposed to

elevated temperature ranging from 50 to 250oC with the

exposure duration of 1 to 4 hours.

Keywords: High strength concrete, Silica fume, Pozzolana,

Mineral admixture, Chemical admixture

I. INTRODUCTION

oncrete is a product obtained by hardening of the mixture

of cement, sand, gravel and water in predetermined

operations. Concrete is one of the most widely used

construction materials throughout the world. Many desirable

properties such as high compressive strength, excellent

durability and fire resistance contributed toward its wide

range of applicability. The most advantageous and unique

feature of concrete is that it can be produced using locally

available ingredients as aggregates. Therefore, in countries

where steel is not readily available, as in Bangladesh, concrete

is the most used construction material. These days concrete is

being used for wide varieties of purposes to make it suitable

in different conditions. In these conditions ordinary concrete

may fail to exhibit the require quality performance or

durability. In such cases, Admixtures are used to modify the

properties of ordinary concrete so as to make it more suitable

for any situation.

1.1. High Strength Concrete

In recent years, the terminology "High-Performance

Concrete" has been introduced into the construction industry.

The American Concrete Institute (ACI) defines high-

performance concrete as concrete meeting special

combinations of performance and uniformity requirements

that cannot always be achieved routinely when using

conventional constituents and normal mixing, placing and

curing practices. The specification of high-strength concrete

generally results in a true performance specification in which

the performance is specified for the intended application, and

the performance can be measured using a well-accepted

standard test procedure.

1.2. Admixtures

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 material, which is added at the time of grinding

cement clinker at the cement factory. It will be slightly

difficult to predict the effect and the results of using

admixtures because, many a time the change in the brand of

cement, aggregate grading mix proportions and richness of

mix after the properties of concrete. Sometimes many

admixtures affect more than one property of concrete. Some

times more than one admixture is used in the same mix. The

effect of more than one admixture is difficult to predict.

Therefore, one must be cautious in the selection of admixtures

and in predicting the effect of the same in concrete.

For high-strength concretes, a combination of mineral and

chemical admixtures is nearly always essential to ensure

achievement of the required strength.

1.2.1. Silica fume

Silica fume is one of the mineral admixtures. It is a byproduct

of producing silicon metal or ferrosilicon alloys. One of the

most beneficial uses for silica fume is in concrete. Because of

its chemical and physical properties, it is a very reactive

pozzolana. Concrete containing silica fume can have very

high strength and can be very durable. Silica fume is available

from suppliers of concrete admixtures and, when specified, is

simply added during concrete production. Placing, finishing,

and curing silica-fume concrete require special attention on

the part of the concrete contractor.

C



1.2.2. 920SH

920 SH is a chloride free, super plasticizing admixture based

on selected sulphonated naphthalene polymers. It is supplied

as a brown solution which instantly disperses in water. 920SH

disperses the fine particles in the concrete mix, enabling the

water content of the concrete perform more effectively. The

very high levels of water reduction is possible by allowing

major increase in strength to be obtained.

II. LITERATURE REVIEW

The following literature gives an idea on various design codes

used for design mix proportioning of high strength concrete

and the advantages for the use high strength concrete.

i. Mohamed bhai (1986) [1] carried out tests on 100 mm concrete cubes heated to temperatures in the range of 200-

800oC, to determine the effect of varying time of exposure

and rates of heating and cooling on the residual

compressive strength of concrete. These variables were

found to have a significant effect on concrete heated to the

lower range of temperatures, but their effect became less

pronounced at high temperatures. It was reported that

almost all the loss of compressive strength occurred within

two hours of exposure to the maximum temperature. It

was observed that the exposure time beyond one hour had

a significant effect on the residual strength of concrete, but

the effect diminished as the level of exposure temperature

increased, where as the loss of strength in bulk occurred

within first two hours of exposure. It was also observed

that the effect of exposure time on coral-sand concrete is

similar to that on basalt-sand concrete. It was also noticed that the rates of heating and cooling had no effect on the

residual compressive strength of concrete heated to lower

temperature.

ii. Srinivasa Rao et al (2006) studied the effect of elevated temperatures on compressive strength of concrete. In this

study, M60 grade of concrete was generated with water

cement ratio 0.25 using Ordinary Portland Cement of 53

grade. Part of the cement is replaced with flyash. At

different ages of 1, 3, 7, 28, 56 and 91 days of curing, the

compressive strength of concrete is obtained after exposed

to temperatures 50-250oC for 3 hours duration. The size of

the concrete specimen is 100 mm. The rate of heating is

maintained as 1oC/min and the specimens are tested in hot

condition. From the test results it is concluded that

retention of residual compressive strength is more in PPC

than OPC. The residual strengths decreased as the

temperature increased at different ages. For earlier ages

the decrease in strength is 10 to 30% for OPC and PPC

concrete with exposure duration, 3 hours. At 250oC, the

maximum decrease in strength for OPC concrete is 40%

and for PPC, it is 18%. As age of concrete increased,

residual compressive strength increased.

iii. Khan and Abbas (2015) studied the behavior of high volume fly ash concrete at varying peak temperatures.

Concrete cylinders of 100 × 200 mm were prepared by

replacing the cement with fly ash in the range of 40-60%

by weight. These concrete specimens, after 28 days

curing, were exposed to varying peak temperatures

ranging from 100 to 900oC to investigate the influence of

temperature on the behavior of fly ash concrete. The

compressive and split tensile strength of concrete

increased initially with an increase in the temperature up

to 300oC, however, further increase in the exposure

temperature caused reduction in both strengths. The loss

of weight of the concrete increased with increase in the temperature as well as the fly ash content.

iv. Muhammad Masood Rafi et al (2017) Conducted experimental testing programme on cylindrical specimens

of 100 × 200 mm size. They were heated at temperatures

which were varied from 100°C to 900°C in increment

of 100°C. Similar specimens were tested at ambient

temperature as control specimens. The compressive and

tensile properties of heat treated specimens were

determined. The colour of concrete started to change

at 300°C and hairline cracks appeared at 400°C. Explosive

spalling was observed in few specimens in the temperature

range of 400°C-650°C which could be attributed to the

pore pressure generated by steam. Significant loss of

concrete compressive strength occurred on heating

temperatures larger than 600°C, and the residual

compressive strength was found to be 15 per cent

at 900°C. Residual tensile strength of concrete became

less than 10 per cent at 900°C. The loss of concrete

stiffness reached 85 per cent at 600°C. Residual Poisson’s

ratio of concrete increased at high temperatures and

became nearly six times larger at 900°C as compared to

that at ambient temperature.

III. MIX DESIGN PROCEDURE

The ACI Standard 211.4 code “Guide for selecting

proportions for High-Strength Concrete with Portland cement

and Flyash” is used for mix design

3.1.1 Design Stipulations

Grade of concrete : M150

Size of aggregate : 10 mm

Degree of workability : 0.76 (compaction factor)

Degree of quality control : good

Type of exposure : moderate

Cement : Portland Pozzolana Cement

(PPC)

3.1.2 Test Data for Materials

Specific gravity of cement : 3.15

Specific gravity of fine aggregate : 2.68

Specific gravity of coarse aggregate : 2.72

tel:100tel:200tel:100tel:900tel:100tel:300tel:400tel:400tel:650tel:600tel:900tel:900tel:600tel:900



Water absorption of fine aggregate : 1.2%

Water absorption of coarse aggregate : 0.8%

Bulk Density of coarse aggregate : 1720 kg/m3

Aggregate Impact value : 8.4% (Exceptionally Strong)

3.1.3 Sieve Analysis

Fine aggregate : Sand zone II according to IS: 383 -1970

Coarse aggregate : Confirming to IS: 383 -1970

Trial strength

fcr = Trial Mix Strength

fck= Specified Compressive Characteristic Strength =

150 N/mm2

S = Standard deviation (from ACI 211.4) =10

1) fcr= fck+1.34*S = 150 + 1.34*10=163.4 N/mm2

Or

2) fcr= 0.9*fck+2.33*S=0.9*150+ 2.33*10=158.3 N/mm

2

Larger Value out of these two is taken as fcr

Therefore, the Value of fcr = 163.4 N/mm2

Step-1 Choice of slump

The value of slump height is taken from the table

4.3.1 of ACI 211.4R based on the type of work. Slump Height

is considered as 50 mm.

Step-2 Choice of maximum size of aggregate

The ACI method is based on the principle that the

Maximum size of aggregate should be the largest available so

long it is consistent with the dimensions of the structure.

When high strength concrete is desired, best results may be

obtained with reduced maximum sizes of aggregate as they

produce higher strengths at a given w/c ratio. The maximum

size of Coarse aggregate is taken as 10 mm from the Table

4.3.2 of ACI 211.4R code.

Step-3 Estimation of mixing water and air content

From the Table 4.3.4 of ACI 211.4R, the quantity of

water required (for 50 mm Slump and 10 mm aggregates) =

183 kg/m3

Step-4 Selection of water/cement ratio

Let the water/cement ratio = 0.25

Step-5 Calculation of cement content

Water/cement ratio = 0.25 & Water content = 183 kg/m3

&

Specific gravity = 3.15

=> Cement content = 183 / 0.25

= 732 kg

Step-6 Estimation of coarse aggregate content

From the Table 4.3.3 of ACI 211.4R, the volume of

oven dry rodded coarse aggregate per unit of volume of

concrete = 0.65 for 10 mm aggregate with fineness modulus

of fine aggregate as 2.68.

Bulk Density of Coarse aggregate = 1720 kg/m3

Per 1m3 of Concrete, the Volume of C.A = 0.65 m

3

The quantity of C.A = 1720*0.65 = 1118 kg

Step-7 Estimation of Fine Aggregate Content

Volume based calculation

Volume of water = 183/1000 = 0.183 m3

Volume of Cement = 732 / (3.15*1000) = 0.232 m3

Volume of Coarse aggregate

= 1118 / (2.72*1000) = 0.411 m3

Volume of entrapped air = 0.05 m3

Volume of Fine aggregate

= 1 - 0.183 - 0.232 - 0.411 - 0.05

= 0.124 m3

Fine Aggregate Content = 0.124x2.68x1000

= 332.32 kg

Step-8 Adjustments for Aggregate Moisture

Aggregate quantities actually to be weighed out for

the concrete must allow for moisture in the aggregates.

Usually the air-dry condition for the coarse aggregate is close

enough for use in laboratory, but the fine aggregate is often

2% or 3% above or below SSD.

This means that a correction must be made before a

laboratory batch of concrete is made.

Step-9 Trial Batch Adjustments

The ACI method is written on the basis that a trial batch of

concrete will be prepared in the laboratory, and adjusted to

give the desired slump, freedom from segregation,

finishability, unit weight, air content and strength.

Table 1: Mix Proportion of M150 Grade Concrete

Cement Fine Aggregate Coarse

Aggregate Water

732 kg 332.32 kg 1118 kg 183 kg

1 0.454 1.527 0.25

Water / Cement ratio = 0.25

IV. EXPERIMENTAL TEST RESULTS

By conducting the workability slump test, it is found that the

amount of 920SH required for getting the slump height 50

mm = 2% (total weight)



4.1 Determination of Compressive Strength: The cubes of 100

mm size are used for measuring the compressive strength of

M150 concrete.

S. No. % of Silica

Fume % of 920SH

Average Compressive

Strength (28 days) N/mm2

1 0 2 122.65

2 5 2 133.42

3 10 2 145.19

4 15 2 152.06

5 20 2 147.15

6 25 2 139.30

Fig 1: The graph shows the variation of 28 days compressive strength of

concrete with the variation of % of silica fume.

V. CONCLUSIONS

1. The mix exhibited a slump of 70 mm with Chemical admixture (920SH) of 2% by weight of cement.

2. The mix proportion for M150 concrete by ACI method is derived as 1:0.454:1.527:0.25.

3. By maintaining the w/c ratio as 0.25, the 28 days compressive strength of the concrete is achieved as

152.06 N/mm2 at 15% of silica fume and 2% of

920SH.

REFERENCES

[1]. Arshad, A. Khan, William, D. Cook and Denis Mitchel, “Tensile strength of low, medium and high strength concretes at early

ages”, ACI Materials Journal, Sept-Oct 1996, pp. 487-493.

[2]. Eugen Brihwiler and Emmanuel Denarie (2008), “Rehabilitation of concrete structures using Ultra-High Performance Fibre

Reinforced Concrete”, Department of civil Engineering, Lausanne,

Switzerland.

[3]. Faghani Nobari, H., Ejlaly R., “Punching Shear Resistance of High Strength Concrete slabs”, Asian Journal of Civil Engineering

(Building and Housing), Vol.4, No.1 (2003), pp. 55-63. [4]. Flyod slate, O., Arthur Nilson H., and Salvador Martinez,

“Mechanical properties of High strength Concrete”, ACI Journal,

July-August 1986, pp. 606-613. [5]. Gupta, S.M., Sehgal, V.K., Kaushik, S.K., “Study on Shrinkage of

High Strength Concrete”, ACI Journal proceedings, 1884, Vol. 81,

No.4 pp. 364-411. [6]. Klaus Holschemacher, Sven Klotz (2003); “ Ultra High Strength

Concrete under Concentrated Load”, Department of Civil

Engineering, HTWK Leipzig. [7]. Parrot, I.J (1969), “Properties of High Strength Concrete,”

Technical Report No. 42.417, Cement and Concrete Association,

Wexham Springs. [8]. S.Nagataki and A.Yonekura (1978), “Studies of the Volume

Changes of High Strength Concrete with Superplastizer,” Journal, Japan Prestressed Concrete Engineering Association Tokyo.

[9]. S.M.Gupta, V.K.Sehgal, S.K.Kaushik (1884); “Study on Shrinkage of High Strength Concrete”, ACI Journal proceedings Vol. 81, No.4 pp. 364-411.

[10]. Z. Wadud and S. Ahmad (2001); “ACI method of concrete mix design- A parametric study”, The Eighth East Asia-Pacific Conference on Structural Engineering and Construction, Nanyang

Technological University, Singapore

80

90

100

110

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140

150

160

0 5 10 15 20 25 30

Co

mp

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stre

ngt

h (

N/m

m2 )

% of Silica Fume

© 2018 IJRAR December 2018, Volume 5, Issue 4 www.ijrar.org (E-ISSN 2348-1269, P- ISSN 2349-5138)

IJRAR1905044 International Journal of Research and Analytical Reviews (IJRAR) www.ijrar.org 172

THE EFFECT OF TEMPERATURE ON

MECHANICAL PROPERTIES OF M150

CONCRETE

A. Sreenivasulu

Associate Professor

Department of Civil Engineering

PVP Siddhartha Institute of Technology, Vijayawada

Andhra Pradesh State, India _______________________________________________________________________________________________________

Abstract : The Concrete has emerged as widely used construction material of modern era and it is an

excellent fire proofing material. The effect of high temperature on the properties of concrete depends mainly

on various factors related to its quality and the level of temperature exposure. As concrete is exposed to

elevated temperature in accidental building fire, an operating furnace, coke oven batteries or a nuclear

reactor, its mechanical properties such as compressive strength, split tensile strength and flexural strength

of concrete may be decreased reasonably. The present study investigated the effect of elevated temperature

ranging from 50 to 250oC with different durations of 1, 2, 3 and 4 hours on the compressive, flexural and

splitting tensile strengths of M150 concrete. The effect of elevated temperature with different duration of

exposure on the concrete specimens was evaluated by measuring the residual compressive, flexural and

split-tensile strengths. The results were analyzed and the effect of elevated temperature on these three

properties was presented. The compressive and split tensile strengths of M150 concrete are increased

initially up to a temperature of 100oC and beyond that they got reduced rapidly with increasing the

temperature. Flexural strength increased gradually up to a temperature of 150oC and beyond that it is also

observed to decrease continuously.

Key Words: High Strength Concrete, compressive strength, flexural strength, split tensile strength, temperature ________________________________________________________________________________________________________

I. INTRODUCTION

Concrete is generally an excellent fire proofing material. Fire is one of the most severe conditions when

the structures are exposed for it. Mechanical properties such as compressive strength, split tensile strength

and flexural strength are considerably reduced during exposure, potentially resulting in undesirable

structural failures. Therefore, the residual properties of concrete are still important in determining the load

carrying capacity and the further use of fire damaged structures. Previous investigations have shown that

concrete type, concrete strength, aggregate types, test types, maximum exposure temperature, exposure

time, type and amount of mineral admixtures affect the residual properties of concrete after exposure.

Degradation of concrete strength due to short-term exposure to elevated temperature has been studied as

early as the 1950s. Among the early studies were those of Abrams, Malhotra and Schneider. Results of these

studies constituted the technical basis for the provisions and recommendations for determining concrete

strength at elevated temperature in many existing codes and authoritative design guides. While these studies

provided valuable information on the variation of concrete strength as a function of temperatures, almost all

used specimens made with normal strength concrete (NSC, according to the current ACI definition. Thus, in

light of the results of recent studies, which have shown that high-strength concrete (HSC) behavior at

elevated temperature may be significantly different from that of NSC. The behavioral differences between

HSC and NSC are found in two main areas: (1) strength loss: HSC has been found to have higher strength

loss in the intermediate temperature range than NSC when exposed to the same heating condition, and (2)

explosive spalling: HSC specimens are prone to explosive spalling, even when heated at a relatively slow

heating rate (≤ 5oC/min)

The increase in concrete strength reduces its ductility. The higher the strength of concrete, the lower is its

ductility. Concrete undergoes changes in its chemical composition, physical structure and water content

when it is exposed to high temperature. These changes take place primarily in the hardened cement paste

and also in the aggregate. At normal temperature, the evaporable water in the capillary pores and gel pores

in hardened cement paste is held in equilibrium (i.e., protected against evaporation). However, at elevated

http://www.ijrar.org/



temperature, the loss of evaporable water occurs. At temperatures of above 105◦C, even the chemically

combined water (i.e., non-evaporable water) starts evaporating. The dehydration of calcium-silicate-hydrate

gel and calcium hydroxide starts at a temperature in the range of about 100 - 200 ◦C and continues at further

higher temperature levels causing coarsening of the pore structure resulting in the loss of strength and other

properties of concrete.

1.1 OBJECTIVE

The objective of this work is to understand the behavior of M150 concrete when exposed to elevated

temperatures at different duration. The experiments were carried out to study the changes in compressive,

flexural and splitting tensile strengths of Ultra high strength concrete subjected to elevated temperatures for

different durations of exposure.

1.2 RESEARCH SIGNIFICANCE

Concrete properties are changed by fire exposure. The properties such as compressive, flexural and split

tensile strengths must be accurately predicted after the fire as they are crucial for the further usage of

concrete structures affected by fire. Despite the fact that certain models have already been proposed for the

prediction of compressive strength and split tensile strength loss, they have limitations or lower statistical

performances. A unique and comprehensive empirical model is needed to predict compressive and split

tensile strength losses with high statistical values for which the database of test results is required. This

study aims to fulfill the need. The mechanical properties must accurately be predicted after the fire as they

are crucial for the further usage of concrete structures affected by heat. Despite the fact that certain models

have already been proposed for the prediction of compressive strength loss, they have limitations or lower

statistical performances.

2. REVIEW OF LITERATURE

Arshad Khan et al (1996) carried out an experimental study of early age tensile strength (i.e. modulus of

rupture) of low, medium and high strength concretes. In this study, low strength concrete indicates a 28 day

concrete compressive strength of 30 MPa, medium strength indicates a 28 day compressive strength of 70

MPa and high strength indicates a 28 day concrete compressive strength of 100 MPa. Tests for modulus of

rupture were carried out at frequent intervals during the first 3 days after casting to observe the influence of

concrete strength. The influence of three different curing conditions-temperature-matched curing, sealed

curing and air-dried curing- were investigated. It was found that the gain in modulus of rupture of

temperature of temperature-matched cured concrete beams was higher than that of sealed and air-dried

beams. After an initial retardation, the 70 and 100 MPa concretes showed a higher rate of flexural strength

gain than the 30 MPa concrete.

Sammy et al (1996) carried out investigations to compare the effect of high temperatures on high

strength concrete and normal strength concrete. Two normal strength concretes and three high strength

concretes with 28 day compressive strengths of 28, 47, 76, 79 and 94 MPa respectively were used to

compare the effect of high temperatures on high strength concrete and normal strength concrete. After being

heated to a series of maximum temperatures at 400, 600, 800, 1000 and 1200oC and maintained for 1-hour,

their compressive strengths were determined. It was reported that high strength concrete lost its mechanical

strength in a manner similar to or slightly better than that of normal strength concrete, when subjected to

high temperatures of up to 1200oC. Under the condition of electrical heating, there was no special danger of

spalling for high strength concrete, although the hardened cement paste within it was much densere than in

normal strength concrete. In the range of 20 to 400oC, HSC maintained its original strength while NSC lost

its strength slightly.

Venkatesh Kodur (2014): Fire response of concrete structural members is dependent on the thermal,

mechanical, and deformation properties of concrete. These properties vary significantly with temperature

and also depend on the composition and characteristics of concrete batch mix as well as heating rate and

other environmental conditions. In this chapter, the key characteristics of concrete are outlined. The various

properties that influence fire resistance performance, together with the role of these properties on fire

http://www.ijrar.org/https://www.hindawi.com/51518202/



resistance, are discussed. The variation of thermal, mechanical, deformation, and spalling properties with

temperature for different types of concrete are presented.

Jyotsna Devi and Srinivasa Rao (2014) investigated the performance of steel fibre reinforced concrete at

high temperatures. They aimed at comparing the flexural and split tensile strengths of normal (M30) and

high strength concrete (M60) when mixed with 1% volume fractions of steel fibres. To study flexural

strengths, prisms of size 100 x 100 x 500 mm were casted and to study splitting tensile strength, cylinders of

150 mm diameter and 300 mm length were casted. The samples are cured for 7, 28 and 91 days. After

specified period of curing, the specimens were air dried and then exposed to 100, 200, 300, 400 and 500oC

(apart from 27oC), for duration of one hour and then allowed to cool. The prisms are tested in Universal

Testing machine for flexure and cylinders are tested for split in compression testing machine. The use of

fibres in high strength concrete is of good advantage than using in normal strength concrete. By adding steel

fibres, the fracture resistance of concrete can be increased.

3. Experimental Program Preliminary investigations were carried out to develop M150 grade concrete. The mix proportion arrived

as per ACI 211.4R was 1:0.454:1.527 by weight with w/c ratio of 0.25. The estimated batch quantities per

cubic meter of concrete were: cement, 732 kg; fine aggregate, 332.32 kg; coarse aggregate, 1118 kg and

water, 183 litres. The optimum dosages of mineral and chemical admixtures were identified as 6% and 1.5%

of quantity of cement respectively from the previous investigation.

An electric furnace is a thermally insulated chamber used for

the heating the elements. It has a digital microprocessor

controller, open coil heater and double-wall construction with

glass fiber insulation and silicone door gaskets minimize heat

loss. Exterior surfaces have scratch-resistant baked enamel

coating and stainless steel interiors as shown in Fig.1. Furnaces

have superior thermal uniformity and a forced-air convection

system with an adjustable damper. Maximum temperature is

1200°C with capacity of 12”x12”x25”.

Tests were conducted on 100 mm size cubes, 150 mm

diameter with 300 mm height cylinders and 100x100x500 mm

beam specimens. The specimens were heated to different

temperatures of 50, 100, 150, 200 and 250oC for different

durations of 1, 2, 3 and 4 hour at each temperature which were

cured for 28 days. After the heat treatment, the specimens were

brought to room temperature and tested for compressive

strength, split tensile strength and flexural strength.

4. Experimental Results:

a). Effect of temperature on compressive strength The compressive strength of concrete at any age and exposed to

any temperature is expressed as the % of 28 days compressive

strength at room temperature. This is termed as Percentage residual

compressive strength. The cubes were casted, cured for 28 days and

heated at different temperatures for 1, 2, 3 and 4 h. The heated

specimens are tested in hot condition as shown in Fig.2 for

compressive strength according to IS: 516-1959. The compressive

strength of cubes when exposed to elevated temperature of 50, 100,

150, 200 and 250oC at different durations of 1, 2, 3 and 4 hours after

28 days of curing. The variation of percentage residual compressive

strengths with the increase in temperature is plotted in Fig.3.

Fig. 1 Heating the concrete element in furnace

Fig. 2 Testing the concrete cube for compressive

strength

http://www.ijrar.org/https://en.wikipedia.org/wiki/Heating



b). Effect of temperature on split

tensile strength

The split tensile strength at any

temperature is expressed as the % of

28 days split tensile strength at room

temperature and that is known as

residual split tensile strength. The

residual splitting tensile strength of

concrete is found to be influenced by

the temperature to which it was

exposed and the duration of exposure.

The testing of cylinder for splitting

tensile strength and its failure surface

are represented in Fig. 4. The residual

splitting tensile strength of all heated

specimens at any exposure time was

expressed as the percentage of 28 days split tensile strength of unheated concrete specimens. The variation

of its % residual split tensile strength with the increase in temperature at different duration of exposure is

plotted is shown in Fig. 5.

c. E

effect of temperature on flexural strength / modulus of rupture

Flexural strength is one way of measuring the tensile strength of concrete. It is a measure of an

unreinforced concrete beam or slab to resist failure in bending. It is measured by loading 100 x 100 mm

concrete beams with a span length at least three times the depth. In this study, the concrete beams of

100 x 100 x 500 mm size are used. These specimens of beams are exposed to elevated temperature of

50, 100, 150, 200 and 250oC for 1, 2, 3 and 4 hours duration after 28 days of curing. The testing of

beam for flexural strength is shown in Fig.6. The flexural strength of M150 concrete was noticed to

increase continuously up to 150oC and beyond that there is a rapid decrease in modulus of rupture. The

residual modulus of rupture is also calculated at different temperatures. The variation of modulus of

rupture with respect to temperature is shown in Fig.7.

Fig. 3 Variation of % residual compressive strength of concrete with


Fig. 4 Testing of cylinder for split tensile

strength






5. Results and Discussion

The max compressive strength of 170 N/mm2 was obtained when the cubes were heated at 100oC for 1

hour duration. It is noticed that both compressive and split tensile strengths increased continuously when the

concrete heated upto 100oC and beyond that those values get reduced. The flexural strength values were

continuously increased upto 150oC and then they were noticed to get redueced. The concrete get hardened at

faster rate at early ages than at later ages since the major quantity of heat of hydration get neutralized before

7 days of curing.

6. Conclusions:

After investing the effect of temperature and its duration on M150 concrete, the following conclusions

were drawn.

1. The compressive strengths of M150 concrete are increased initially upto a temperature of 100oC and beyond that they got reduced rapidly with increasing the temperature

2. The compressive strengths are lost very much when they are heated at 250oC 3. It was observed that major part of loss in split tensile strength is taking place in the first 1 hour

exposure.

4. It was observed that the variation of flexural strength for different exposure duration is very less upto 100oC temperature and beyond that the variation in strengths is considerable

5. The compressive and Split tensile strengths are lost very much when they are heated at 250oC.

7. References

1. V. R. Kodur and M. A. Sultan (1998), “Thermal properties of high strength concrete at elevated temperatures,” American Concrete Institute, Special Publication, SP-179, pp. 467 – 480

2. Castilo C and Durrani A.J. (1990), “Effect of transient high temperature on high strength concrete, ACI Materials Journal, v.87, pp. 47-53.

3. Sujith Ghosh and Karim W. Nasser (1996), “Effects of high temperature and pressure on strength and elasticity of Lignite fly ash and Silica fume concrete”, ACI materials journal, volume

93, issue 1, pp. 41-50.

4. Said Iravani, “Mechanical properties of High Performance Concrete”, ACI Material Journal, Vol. 94, N0.5, 1996, pp. 416-426.

5. Klaus Holschemacher and Sven Klotz, “Ultra High Strength Concrete under Concentrated Load”, Department of Civil Engineering, HTWK Leipzig, 2003.

6. Wang S.D, and Read A.S., “Trials of grade 100 high strength concrete”, Magazine of Concrete Research, December 1999, 51, No.6, pp. 409-414.

Fig. 6 Testing of beam for flexural

strength






7. Brandt, A.M. and Kucharska L., “Mechanical properties and application of High Performance Concretes”, Proceedings of Inter Symposium on innovative world of concrete (ICI-IWC-93), 1993,

pp. KN3-KN2.

8. Klaus Holschemacher and Sven Klotz (2003); “Ultra High Strength Concrete under Concentrated Load”, Department of Civil Engineering, HTWK Leipzig.

9. Srinivasa Rao, K., Potharaju, M., Shoba, M., and Raju, P.S.N., “Effect of age on some mechanical properties of High Strength Concrete”, SERC Journal of Structural Engineering, Vol.32, No.3,

August –September 2005, pp-221-224.

10. Sammy Y.N. Chan, Gai-fei-Peng and John K.W. Chan, “Comparison between high strength concrete and normal strength concrete subjected to high temperature”, “Materials and Structures”,

Vol. 9, No. 10, December 1996, pp.616-619.

Documents

FINAL REPORT ON MINOR RESEARCH PROJECTpvpsiddhartha.ac.in/dep_civil/docs/asv_ugc.pdf · steps given in ACI 211.4 code. 3. OBJECTIVES OF THE FINAL REPORT: The following are the objectives