An Experimental Study on Partial Replacement of River Sand by Manufactured Sand in Self-Compacting Concrete

Abstract

SCC was first developed in Japan to achieve durable concrete structures in 1980’s. Self-compacting concrete (SCC) is an innovative concrete which can be placed and compacted under its own weight with little or no vibration effect and at the same time cohesive enough to be handled without segregation or bleeding. Adoption of SCC offers substantial benefits in enhancing construction productivity, reducing overall cost, and improving work environment. Cost reduction in the building is the primary objective in developing countries like India. This paper puts forward the applications of manufactured sand as an attempt towards sustainable development in India. It will help to find valuable solution to the declining availability of natural sand to make eco-balance. Manufactured sand is one among such materials to replace river sand, which can be used as an alternative fine aggregate in mortars and concretes. The use of manufactured sand in concrete is gaining momentum these days. The present experimental investigations have been made on concrete using manufactured sand as fine aggregate and observed the effects of crushed manufactured sand on strength properties of concrete. The application of concrete meeting the specification is of paramount importance, to ensure construction of durable R.C.C. structure. A well processed manufactured sand as full replacement to river sand is the need of the hour as a long-term solution in Indian concrete industry until other suitable alternative fine aggregate are developed.

Introduction

I. INTRODUCTION

Concrete Concrete technology has made tremendous strides in the past decade. The development of specifying a concrete according to its performance requirements, rather than the constituents and ingredients has opened innumerable opportunities for producers of concrete and users to design concrete to suit their specific requirements. One of the most outstanding advances in the concrete technology over the last decade is “Self-Compacting Concrete” (SCC). Self-compacting concrete (SCC) was first developed in Japan in 1988.  Self-Compacting Concrete is an innovative concrete that does not require vibration for placing and compaction. It is able to flow under its own weight, completely filling formwork and achieving full compaction, even in the presence of congested reinforcement.  The improved construction practice and performance, combined with the health and safety benefits, make self-compacting concrete a very attractive solution for civil engineering construction. The use of SCC is increasing.

Concrete is a widely used construction material around the world, and its properties have been undergoing changes through technological advancement. Numerous types of concrete have been developed to enhance the different properties of concrete. So far, this development can be divided into four stages. The earliest is the traditional normal strength concrete which is composed of only four constituent materials, which are cement, water, fine and coarse aggregates. At the way to achieve the high compressive beginning, reducing the water cement ratio was the easiest way to achieve the high compressive strength. Thereafter the fifth ingredient a water reducing agent or super plasticizer was indispensable. But now a day the cost of sand has been increasing beyond imagination which is resulting in the increase in concrete cost. This is because demand for sand is more than its supply to overcome this problem the experiment on concrete by partial replacement of river sand by manufactured sand in self-compacting concrete. We can reduce the cost of concrete and enhance the strength of concrete also M-sand can reduce ecological imbalance in nature. To study the mechanical properties of both SCC and manufactured sand as a replacement material in various percentages to the mix. A study has been done on the compressive, flexural and split tensile strength with these various mix Self-compacting mixes are designed to have fresh properties that have a higher degree of workability than convectional concrete. Workability is a way of describing the performance of concrete in the plastic state.

II. ADMIXTURES USED

A. Chemical Admixtues

Chemical admixtures reduce the cost of construction, modify properties of hardened concrete, ensure quality of concrete mixing/transporting/placing/curing, and overcome certain emergencies during concrete operations. Chemical admixtures are used to improve the quality of concrete during mixing, transporting, placement and curing. Superplasticizers are well known chemical admixtures for concrete used in the reduction of water to cement ratio without affecting workability, and to avoid particle aggregation in the concrete mixture. These are also known as high range water reducers (HRWR), fluidifiers, and dispersants as these are capable of reducing water to cement ratio by 40.0%. These chemical admixtures are added in the concrete just before the concrete is placed. These admixtures help to improve strength and flow characteristics of the concrete. Flow characteristics and slump of concrete varies with type, dosage, and time of addition of concrete superplasticizer. Superplasticizers can be classified into four types such as,

1. High Range Water Reducing Admixture (HRWA),
2. Viscosity Modifying Admixture (VMA),

B. High Range Water Reducing Admixture (HRWA)

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. The conventional method used for obtaining high workability is by improving the gradation or by the use of relatively higher percentage of fine aggregate or by increasing cement content.

There are difficulties and limitations to obtain high workability in the field for a given set of conditions. The addition of excess water will only improve the fluidity or the consistency but not the workability of the concrete. The excess water will not improve the fluidity or the consistency but not the workability of the concrete. High range water reducing admixture helps to solve the problem by giving required workability at lower water content. It has become to use high range water reducing admixture for all reinforced concrete and mass concreting to reduce the water requirement for making concrete of higher workability. The use of HRWA permits the reduction of water to an extent up to 30% without reducing workability. The water/cement ratio can be low as 0.35 or even lower and flowing concrete can have strength of the order of 120 MPa.

C. Viscosity Modifying Admixture (VMA)

A Self-compacting concrete should have high workability and viscosity. The fluidity of the mix increases as there is no internal friction between the particles and the concrete flows freely. Segregation occurs when the components of the concrete separates out into the mortar ad large aggregates. Reaching a right balance between fluidity and resistance to segregation is essential for Self-compacting concrete. This balance is lacking when the fluidity of the concrete is obtained by adding water. Even through HRWA gives high fluidity, the required property of the Self-compacting concrete is not ensured. Therefore, there is a need for Viscosity Modifying Admixture to attain required property.

VII. ACKNOWLEDGEMENT

First and foremost, I would like to thank the Almighty God for giving me the power to believe in myself and achieve my goals. I sincerely remit my due respect to my project guide Mr. U.G. Arunrajan, M.E., (Ph.D)., Assistant Professor in Agricultural Engineering for his encouragement and guidance throughout the project. I extend my sincere thanks to all faculty members, non-teaching staff and my friends for their help and support in completing this project work.

Conclusion

Today, the engineering industry in India is growing very fast. The infrastructure growth is phenomenal which demands new innovative methodologies in execution of the projects. Effective handling and quicker completion of the projects are very important to achieve the proposed growth of the country. The civil engineering fraternity all over the world in general and in India is working to find new innovative materials which would help in achieving the targets. Such innovation has to be with materials which are easily available, ecofriendly, economical and satisfies the technical requirements. Self-compacting concrete (SCC) is one such innovations of type of concrete that has excellent fluidity in the fresh state with high resistance to segregation and can be placed in intricate geometry and gets compacted under its own self weight without applying vibration. The requirement of concrete in India is increasing day by day but at the same time, the resources like river sand is depleting. More use of river sand also would affect the water table in the river beds which in turn will have a detrimental effect on the environment. At this juncture, it is all the more important to find a suitable alternative to river sand which can perform equally. In this context, this study was aimed at developing and investigating SCC with the use of manufactured sand replacing natural river sand. Design and development of SCC were done using European Federation for Specialist Construction Chemicals and Concrete Systems (EFNARC) Norms. Following criteria was followed in the study. The SCC mix proportion that was obtained using EFNARC 2005 guidelines is capable of achieving the SCC characteristics. Cement and coarse aggregate is kept as constant throughout this study. Fine aggregate is partly replaced as Manufacture sand in the percentage of 25%, 50% and 75%. The recommended dosage of super plasticizer admixture (Glenium B233) is kept as 1percent and 2 percent by weight of powder content for the various mixes of concrete and the Viscosity modifying agent (Glenium stream 2) is fixed as 0.2 percent of weight of powder content. The test results of the workability investigations are summarized in table. Based on the test results we can conclude that the table values satisfied the requirement criteria mentioned in table. The hardened concrete test results are summarized in table. It is observed that with the increase in percentage of Fly ash and Rice husk ash there is reduction in strength parameters. And also compared to the 7 days strength of concrete, the 28 days compressive strength and split tensile strength of concrete are increased by 41% and 55%.

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Copyright

Copyright © 2023 Thirukumaran G S, Arunrajan U G, Gokulnath N. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.