Mechanical and physical behavior of cement paste and mortar incorporating nano-CaO

The aim of this work is to experimentally investigate the effect of properties of nano-CaO in cement-based materials. Mortars and paste samples were produced by using nano-CaO in 2.5, 5, and 7.5% ratios instead of cement. The initial and final setting times and volumetric autogenous shrinkage tests of paste samples and 7, 28, and 360days' compressive strength, the ultrasonic pulse velocity, heat of hydration, and linear autogenous shrinkage of mortar samples were determined. In addition, the micro-structures of paste samples were characterized by X-ray-diffraction and SEM. As a result, the shrinkage and setting times were reduced with the increase of nano-CaO content. CaO with nano size increased the compressive strength (about 10-22%) and the heat of hydration. The compressive strength of mixture containing 7.5% nano-CaO was lower than that of 2.5 and 5% nano-CaO at 360days of curing duration. The heat of hydration increased for all the mixtures containing nano-CaO at an early stage and very rapidly between 4 and 16hr.