Effect of Fine Materials on the Compressive Strength and Workability of Concrete

Abstract

This paper studies the effect of different ratios of clay addition on the concrete properties. Most of the standards limit the ratio of the clay in aggregates due to its harmful effect on the concrete properties. For example, ASTM C33  limits the fine contents in fine aggregate to 5% whereas the ratio of clay lumps is limited to 0.5% as deleterious substances included in the fine materials as  very fine substances .This study has considered many ratios of clay addition(0%,2%,3%,4% and 5%) of the total aggregate weight to the concrete mixes and observed the governed values of compressive strengths and workability. A series of cube groups were fabricated with different water-cement ratios (0.45,0.5 and 0.55) and different mix ratios(1:1:2,1:1.5:3 and 1:2:4).It is seen that as the ratio of clay increases, slump decreases; therefore, more water will be needed to reach a reasonable workability while the compressive strength is severely affected in high ratios of clay existence. There is no effect of age on the ratio of strength decrease when a high ratio of clay is added or existed. The strength will decrease by about 33% if a 5% of clay is available in fine material. This study has come as a result of investigating the reasons behind the continuous deterioration in concrete cubes that came to the laboratory for the aim of testing through local construction companies and contractors who are working in most of projects all over the middle region governorates in Iraq.