Compressive Strength and Microstructure of Cement Mortar with Nanosilica

Abstract

This research article presents the compressive strength and microstructure of cement mortar withnanosilica. The effects of nanosilica particle size and the replacement content are determined by varyingthe nanosilica particle size from 7, 12 and 40 nm and the replacement content from 3, 5, 8, 10 and 12%,respectively. For economic consideration, the use of nanosilica incorporating with silica fume is includedby partially replacing of nanosilica with silica fume 0, 30, 50, 70, and 100%, respectively.

The tested results indicated that nanosilica particle size affected directly on the compressivestrength development and microstructure of cement mortar. For the replacement content 3% and waterper binder ratio of 0.65, the mortar with nanosilica particles size of 7, 12, and 40 nm gave the highercompressive strength at age of 28 days than that of control cement mortar about 1.11, 1.21 and 1.69 times,respectively. The cement mortar with nanosilica particle size of 40 nm also presented the fully dense,uniform and homogenous microstructure corresponding with that of strength development. For thereplacement content of cement by nanosilica ranged from 0, 3, 5, and 8%, the compressive strength ofmortar was directly improved with the replacement content of nanosilica. For 8% replacement, themaximum compressive strength was higher than that of control mortar about 2.32 times. The compressivestrength became lower for higher replacement content of 10 and 12% based on the fact that the higherthan 8% of replacement content gave the mixture of mortar with low cement content. The lower cementcontents, the lower hydration reaction and calcium hydroxide were obtained and then affected directlyon the pozzolanic reaction and compressive strength of cement mortar. For the cement mortar with 8%of nanosilica, the fully dense, uniform and homogenous microstructure was also presented. For the useof nanosilica incorporating with silica fume, the ratio between nanosilica and silica fume affected on thecompressive strength and microstructure of cement mortar. The mortar with higher ratio of nanosilica gavethe higher compressive strength as well as fully dense, uniform and homogenous microstructure.

Keywords : Cement Mortar / Nanosilica / Silica Fume / Compressive Strength / Microstructure