Effects of Supplementary Cementing Materials on the Mechanical Properties of Concrete

 

M. Vijaya Sekhar Reddy¹*, Dr. I.V. Ramana Reddy², K. Madan Mohan Reddy¹, C.M Ravi Kumar³, K. Chandra Sekhar Reddy⁴

¹Department of Civil Engineering, Srikalahasteeswara  Institute of Technology, Srikalahasti, AP, India,

²Department of Civil Engineering, Sri Venkateswara University College of Engineering, Tirupati, AP, India,

³Department of Civil Engineering, VTUBTDC, Davanagere, Karnataka, India.

⁴Department of Civil Engineering, Siddharth Institute of Engineering & Technology, Puttur, Chittoor, A.P

*Corresponding Author E-mail: skitce.hod@gmail.com

 

ABSTRACT:

In today’s competitive environment it is becoming important to reduce the construction cost in one or other way. Now a day’s OPC is widely used and it is the costly ingredients in the production of concrete. However many countries have severe shortage of cement although there requirements are vast. The manufacture of OPC is expensive and skill intensive process, besides polluting the environment heavily production is associated with the emission of carbon dioxide which is a significant source of global warming. Pozzolanic materials are widely used in concrete and mortars for various reasons particularly for reducing the amount of cement required for making concrete and mortar which lead to a reduction in construction cost. This paper presents the results of study under taken to investigate the feasibility of using Supplementary Cementing Materials (SCMs) as partial replacements of cement. The effects of replacing cement by these SCMs on compressive strength, split tensile strength are evaluated in this work. Both compressive and spilt tensile strength is evaluated at 7days, 28 days, 90 days and 180 days.

 

 

INTRODUCTION:

The addition of pozzolanic materials with OPC, a century old practice, is an alternative practice in the construction industry to improve the durability performance of concrete. Industrial by-product based SCMs like FA, SF, and Metakaoline etc., are worldwide accepted pozzolanic materials and employed for making blended cement concrete. Now-a-days the use of blended cement concrete is growing rapidly mainly due to the considerations of cost and energy saving, environmental protection and conservation of resources. It is generally recognized that the addition of pozzolanic material reduces the calcium hydroxide content in cement concrete and improves the impermeability of concrete. This helps to increase the strength properties and durability properties of concrete.

 

The investigation results from various parts of the world indicate that the replacement of cement by FA reduces the initial strength development rate and increases the setting time of concrete due to the slower pozzolanic reactions where as the strength and durability during the later age improved by reducing the pore size of the concrete.

 

Efforts have been made to promote the initial strength development rate and reduce the setting time of concrete.

 

Established a testing regime to optimize the strengths and durability characteristics of a wide range of high-performance concrete mixes. The intent of the selected designs was to present multiple solutions for creating a highly durable and effective structural material that would be implemented on Pennsylvania bridge decks, with a life expectancy of 75 to 100 years. One of the prime methods of optimizing the mixtures was to implement supplemental cementitious materials, at their most advantageous levels. Fly ash, slag cement, and microsilica all proved to be highly effective in creating more durable concrete design mixtures.¹

 

An application of the method of the simplex-lattice design for predicting the properties of cement-based composites on the basis of the compressive Strength, its use was demonstrated on ternary paste systems composed of cement, silica fume and fly ash with constant water to binder ratio and a mass fraction of mineral admixtures not exceeding 30%².

Table 1. Physical Properties of Zuari-53 Grade Cement

 

Table 2 . Physicochemical properties of Flyash sample.

 

Defines that a high performance concrete element is that which is designed to give optimized performance characteristics for a given set of load, usage and exposure conditions, consistent with requirement of cost, service life and durability. [3]

 

Materials used in the present study

Cement

Ordinary Portland cement Zuari-53 grade conforming to IS: 12269-1987 [4] were used in concrete. The physical properties of the cement are listed in Table 1.

 

Aggregates

A crushed granite rock with a maximum size of 20mm and 12mm with specific gravity of 2.60 was used as a coarse aggregate. Natural sand from Swarnamukhi River in Srikalahasthi with specific gravity of 2.60 was used as fine aggregate conforming to zone- II of IS 383-1970 [5]. The individual aggregates were blended to get the desired combined grading.

 

Water

Potable water was used for mixing and curing of concrete cubes.

 

Supplementary Cementing Materials

Flyash

Fly ash was obtained directly from the M/s Ennore Thermal Power Station, Tamilnadu, India. The physicochemical analysis of sample was presented in Table 2.

 

Silica Fume

The silica fume used in the experimentation was obtained from Elkem Laboratory, Navi Mumbai. The chemical composition of Silica Fume is shown in Table 3.

 

Metakaoline

The Metakaoline was obtained from M/s. 20 Microns Limited, Baroda, India. The chemical composition of Metakaoline is shown in Table 4.

 

Super Plasticizer

VARAPLAST SP123 is a chloride free, Superplasticising admixture based on selected synthetic polymers. It is supplied as a brown solution which is instantly dispersible in water and also it can provide very high level of water reduction and hence major increase in strength can be obtained coupled with good retention of workability to aid placement.

 

RESULTS AND DISCUSSIONS:

In the present work, proportions for high strength concrete mix design of M₄₀ was carried out according to IS:10262-2009 [6] recommendations. The mix proportions are presented in Table 5.

 

The tests were carried out as per IS: 516-1959 [7] and IS: 5816-1999 [8]. The 150mm cubes and cylindrical specimens (15mm dia and 300mm height) of various concrete mixtures were cast to test compressive strength and split tensile strength. The cubes and cylindrical specimens after de-moulding were stored in curing tanks and on removal of cubes and cylinders from water the compressive strength and split tensile strength were conducted at 7days, 28days, 90 days and 180 days. The test results were compared with individual percentage replacements for M₄₀ grade concrete. Results of compressive strength and split tensile strength for M₄₀ were shown in Figure 1 and Figure 2.

 

Table 3. Chemical composition of Silica Fume.

 

Table 4. Chemical composition of Metakaoline

 

Table 5. Mix Proportion for M₄₀ Concrete.

 

Fig 1. Shows the Compressive Strength results of M₄₀ mix.

 

Fig 2. Shows the Split Tensile Strength results of M₄₀ mix.

 

CONCLUSIONS:

1.      In M₄₀ concrete mix design as water/cement ratio adopted is low, super plasticizers are necessary to maintain required workability. As the percentage of mineral admixtures is increased in the mix, the percentage of super plasticizer should also be increased, for thorough mixing and for obtaining the desired strength.

 

2.      Present investigation reveals that in the case of individual percentage replacement of mineral admixtures the maximum compressive strength achieved in M₄₀ grade concrete is 56.80 Mpa with replacement of 10% Silica Fume for 180 days curing period.

 

3.      In case of individual percentage replacement of mineral admixtures the maximum Split Tensile strength achieved in M₄₀ grade concrete is 4.76 Mpa with replacement of 10% Metakaolin for 180 days curing period.

 

REFERENCES:

1.       Kevin Smith M, Andrea Schokker J and Paul Tikalsky J. Performance of Supplementary Cementitious Materials in Concrete Resistivity and Corrosion Monitoring Evaluations. ACI Materials Journal. 101(5); 2004: 385-390.

2.       Chen HS, Sun W and  Stroeven P. Prediction of compressive strength and optimization of mixture proportioning in ternary cementitious systems. Materials and Structures.36(6); 2003: 396-401.

3.       Swamy RN. High Performance Durability Through Design. International Workshop on HighPerformance Concrete, ACI-SP. 159(14); 1996: 209-230.

4.       IS: 12269-1987, Specification for 53 Grade Ordinary Portland Cement, Bureau of Indian Standards, New Delhi, India, 1989.

5.       IS: 383-1970: specifications for Coarse and Fine Aggregates for natural sources of concrete, Bureau of Indian standards, New Delhi.

6.       IS: 10262-2009: Concrete Mix Proportioning-guidelines, Bureau of Indian Standards, New Delhi.

7.       IS: 516-1959: Methods of tests for strength of concrete, Bureau of Indian standards, New Delhi.

8.       IS: 5816-1999: Methods of tests for Splitting tensile strength concrete, Bureau of Indian standards, New Delhi.

 

 

 

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