Efflorescence inhibition of alkali-activated steel slag-slag material by nano SiO2

Abstract

Alkali-activated materials have significant shortcomings like poor volume soundness, easy efflorescence and so on, which have restricted their application to a certain degree. Nano modification is an important approach in solving the problem. Based on the test of hydration hardening characteristics, matrix porosity and the concentration of alkali ions leaching on the surface of the alkali-activated steel slag-slag material, the effects of the nano SiO2 on matrix compaction and efflorescence inhibition were studied. The results show that when the mixing amount of the nano SiO2 was 2.0 %, the growth rates of the compressive strengths of the specimen at 1 d and 28 d increased by 203.71 % and 39.29 %, respectively, when compared with the blank specimen. The nano SiO2 exerted filling and crystal nucleus effects, and a clustering fibrous C-S-H gel was generated around the nanoparticles. The matrix was compacted with an increase in the hydration products, and, as a result, the overall porosity of the matrix reduced by 7.06 %. Porosity improvement contributed in preventing internal alkali ions in the specimen leaching to the surface, and the ionic concentration of the leaching solution out of the specimen reduced by 32.57 % when compared with the blank specimen.