Nano-Al2O3 was found to be very effective to increase the modulus of elasticity of cement mortar. With 5% nano- Al2O3 (~ 150 nm particle size), the elastic modulus increased by 143% at 28 days whereas the increase of compressive strength was not very obvious [Zhenhua Li et al. 2006]. A proper mixing procedure was selected in order to ensure adherence of nano- Al2O3 particles on the sand surfaces. It is believed that during cement hydration, these nano-alumina particles were available to fill the pores at the sand-paste interfaces and created a dense ITZ with less porosity. Effective densification of ITZ by nano- Al2O3 particles was mainly responsible for significant increase of elastic modulus of mortars. With the increase of nano-alumina contents, the elastic modulus of mortars increases when nano-alumina content is less than 5%. At higher replacement level (e.g., > 5%), agglomeration of nano-particles caused ineffective densification of ITZ and as a result, the elastic modulus of mortars decreases.
Was this article helpful?