Impact of Clay and Non-clay Microfines on Various Concrete Properties

High amounts of microfines (particles less than 75 µm in size) are unavoidable in sand manufacturing. In addition, due to the manufacturing process and clayey soil strata in rocks, sometimes clay intermingles with manufactured sand (M-sand). Therefore, it is necessary to identify clay and non-clay microfines in M-sand. The present study uses a methylene blue value (MB-value) test for differentiating clay and non-clay particles. Furthermore, the current research examines the effect of clay and non-clay microfines on concrete workability, mechanical strength, and abrasion resistance. Results showed that the MB-value of M-sand is affected by the clay microfines but not by the non-clay sandstone microfines. Clay particles significantly decrease the workability of concrete. Microfines of clay improve the mechanical strength up to an MB-value of 6. Beyond that, a higher superplasticizer dose used to achieve workability deteriorates the strength. Abrasion resistance of concrete also decreases with increase in clay particles.