Enhanced physical, mechanical and microstructural properties of lightweight vermiculite cement composites modified with nano metakaolin

This article presents a study on the influence of nano metakaolin (NMK) on physical, mechanical and microstructural properties of high volume vermiculite blended white Portland cement (WPC). WPC was replaced with 70 vol% expanded vermiculite (EVM), NMK were incorporated at a rate of 2, 4, 6, 8 and 10% as partial replacement by weight of EVM. The density, thermal conductivity, compressive strength, flexural strength, and capillary water absorption of the blended mixes were determined in accordance with ASTM standards at 28 days of curing. Differential scanning calorimeter (DSC) was used to study the phase transitions. The microstructure characteristics of the hardened samples were investigated by scanning electron microscope (SEM). The experimental results revealed a significant enhancement in both compressive and flexural strength, enhancements of about 57 and 59%, respectively were obtained at 10% NMK replacement. The capillary water absorption generally decreases with increasing replacements of EVM by NMK. A considerable decrease of about 74% was observed at 10% NMK. No significant effect of the NMK content on density and thermal conductivity. NMK led to noticeable improvement in the microstructure characteristics of the hardened blends. (c) 2016 Elsevier Ltd. All rights reserved.