Study of concrete mixes (M20 and M30) with optimum cement consumption using 100% crushed sand and effect of silt content in the crushed sand on strength and workability of the concrete

Abstract

Now a day, as there is scarcity of natural sand, it is essential to replace it with some other constituent to make concrete. The natural sand is now being replaced by crushed sand(crushed sand is obtained from quarry by crushing stones to required size).Civil engineers and contractors are using crushed sand for making concrete as river sand is now not available and comparatively the crushed sand is cheaper.However, it is imperative to verify its effects on strength, workability and cost of concrete but before using crushed sand for making concrete.The civil engineers and contractors in rural parts of western Maharashtra region have strong belief that the use of crushed sand for making cement concrete results in increase of cement consumption per cubic meter of concrete.Also, the percentage of fine particles (less than 150 µm termed as silt) in the crushed sand considerably affects the strength of the concrete.This paper represents the experimental study carried out to design the concrete mixes for achieving the desired strength at optimum cement consumption. Also, the effect of percentage silt content in the crushed sand, on the strength of concrete was studied. After the experimentation it was found thatthe strength of M20 grade concrete cast using crushed sand was 43.38% more than M20 grade concrete cast using natural sand, whereas the corresponding percentage increase in the cement consumption per cubic meter of concrete was observed to be 16.03%. The paper indicates that with further more trials of design mix the cement consumption can be optimised for use ofcrushed sand,without adversely affecting the strength of concrete compared to the concrete cast using natural sand. The results obtained in this study will encourage the engineers and contractors to use the crushed sand for making the concrete.