Experimental Investigation on the Effect of Clay in Sand for Flexural Behavior of R.C.C. Beams

Abstract

In the present day construction industry in developing countries, concrete has emerged as the most common building material. Hence careful consideration must be given to factors that affect its strength. For sand having above 3.4% of clay content used in a 1: 1: 2 (M-25) mix of concrete resulted in the production of concrete with target compressive strength less than 31.75N/mm2. The sand sample was divided into two parts. First part of the sand sample was washed free of clay and slit and sun dried, while clay and silt were sieved out of the second part using 2.36 mm sieve. The washed sand sample was divided into 8parts in such a manner that from each part, at least 3 cubes of 150mmx 150mm x 150mm can be made. Therefore, this study was conducted to investigate suitability of soil in place of sand in producing conventional concrete.

This research work mainly consist of two parts, In the first part, substitution of natural sand partially by clay/silt in concrete is done with replacement of 0%, 1%, 2%, 3%, 4%, 5%, 10% and 15%. The optimum value obtained for 3%-4% replacement of clay/silt content. The 28 days average compression strength was observed to increase by about 0.3% - 27.6%, split tensile strength by 10.5% - 30.6% when compared with control mix.  In the second part, the flexural behavior of reinforced concrete beams with optimum clay/silt content is studied. The reinforced beam specimens used were 150 x 180 x 1200 mm, and tests were done at the curing age of 28 days. The reinforcement is varied from 0.62% - 0.89% in the flexure zone and the parameters like deflection, surface strain, cracking load, ultimate load and crack width of reinforced concrete beams was experimentally noted and compared with theoretical values as per code IS: 456-2000. 

Finally, it is concluded Due to high water absorption rate of clay W/C ratio was increased as replacement percentage increases and compression and tensile strength of concrete was decreases. The sieved clay/silt is added to each of the parts of the washed sand from1% to 15% by weight of the sand. It was discovered that the higher the clay/silt content, the strength of concrete is decreases.