Effect of Clay Contamination on the Compressive Strength of Concrete

This study examined the impact of clay contamination in fine aggregates on the compressive strength of concrete. Clay particles present in aggregates can disrupt the bond between the cement paste and aggregate surfaces, leading to reduced strength and durability. In this research, concrete mixes were prepared with varying clay contents (0%, 2%, 4%, 6% and 8% by weight of fine aggregate). Standard cube specimens were cast, cured and tested for compressive strength at 7days and 28days. The results revealed a consistent decline in compressive strength with increasing clay content. At 28days, concrete with 8% clay showed a strength reduction of over 40% compared to the control mix. These findings highlight the critical importance of clean, clay – free aggregates in ensuring the structural integrity of concrete. Fine aggregates should therefore, be tested and confirmed to contain less than 3% clay by weight, as recommended by ASTM C33 and IS 383, to ensure adequate concrete strength and durability.