Partial Replacement of Sand with Attapulgite in Concrete

Abstract

The research includes the use of attapulgite clays as a partial replacement of sand in concrete to study its properties. The effect of replacement on concrete properties (slump, density and compressive strength) has been studied for 7, 14, and 28 days; otherwise, the split tensile strength has been evaluated at 28 days. A series of concrete mixtures is done with a fixed mixing ratio of 1:2:4 by weight (cement: 1 sand: 2 gravel: 4) and water / cement ratio has been equal to 0.5. A partial of sand in concrete mix has been replaced by an attapulgite clay from 10%-50% to be compared with a reference mixture. The study has showed no significant change in compressive strength at 10% of attapulgite. The lowest decrease in compressive strength has been 6% when the replacement ratio has been 20% at 28 day. Therefore, the compressive strength is decreased by increasing the ratio of sand replaced. Meanwhile, the reduction in slump has been 28%. On the other hand, the use 1.2% superplasticizer improves the performance of the mixtures. Therefore, by adding superplasticizer, the slump of concrete mix with 50% of attapulgite is approximated equal to the slump of reference concrete mixture without a decrease in compressive strength, especially at 28 days. The slump, the compressive, and the splitting strength of the mixture containing 20% attapulgite have increased 10%, 12% and 18%, respectively, compared to the reference concrete mix by making the mixing ratio 1:1.5:4.5.