Effects of nano-TiO2 on strength, shrinkage and microstructure of alkali activated slag pastes

Abstract

For alkali-activated slag (AAS), high drying shrinkage is an obstacle which impedes its application as a construction material. In this investigation, nano-TiO2 was added to AAS, and its mechanical properties and shrinkage were tested to examine its effect on hardened alkali-activated slag paste (AASP). To understand the impact of nano-TiO2 on AASP at micro scale, FTIR, MIP and SEM were carried out. Experimental results indicate that the addition of nano-TiO2 to AAS enhances the mechanical strength, and decreases the shrinkage of AASP. FTIR and SEM results demonstrated that the addition of nano-TiO2 into the AASP accelerates its hydration process, resulting in more hydration products and denser structure. MIP results showed that the addition of nano-TiO2 reduces the total porosity of AASP and changes the pore structure. The porosity of 1.25-25 nm mesopores, which is believed to be responsible for the high shrinkage of AASP, is remarkably reduced due to the addition of nano-TiO2.