Effect of Nanoclay on Expansive Potential of Cement Mortar due to Alkali-Silica Reaction

The impact of partial substitution of cement particles with nanoclay on the expansive potential of cement mortar due to alkali-silica reaction (ASR) was investigated. Portland cement was replaced by 0.5%, 1%, and 2% montmorillonite nanoclay. The effect of ASR on compressive strength, chemical composition, and microstructure of nanoclay-cement composites was evaluated. The accelerated mortar-bar method was followed to perform the ASR test according to ASTM C1567. The experimental results showed that the expansion of cement mortar due to ASR can be reduced by the addition of nanoclay. Two percent nanoclay was the only dosage among others used in this study that can mitigate the expansion. Furthermore, the ASR caused a marginal enhancement in compressive strength of mortar compared to the specimens cured in water. The gain in strength reached up to 10% for mortars contacting 2% nanoclay. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis did not detect the formation of any secondary products due to the ASR, revealing the similarity between ASR and the pozzolanic reaction for the first 14 days of the reaction. However, the microstructure of the mortars became denser and more homogeneous when apart of cement was replaced by nanoclay.