Influence of superfine ettringite on the properties of sulphoaluminate cement-based grouting materials

Superfine ettringite (S-ettringite) synthesized in this research presents same structure with the ettringite produced by the hydration of cement, which is expected to promote the hydration of sulphoaluminate cement-based materials. There are few literature reports on laboratory synthesis of superfine ettringite. In this paper, preparation of S-ettringite via separate nucleation and aging steps method by introduction of citric acid is presented. The effect of the S-ettringite on hydration, microstructure and properties of CSA cement-based grouting materials (CBGM) was experimentally investigated. Results show that specimens containing S-ettringite displayed a significant improved performance with regard to compressive strength at early and later ages and setting time. Compared to the control specimen, 4-h compressive strength increased by 380% and initial setting time shortened by 55.6% when 4 wt% S-ettringite was added, respectively. Due to the crystallization inducting effect and seed effect, the addition of S-ettringite changed the morphology of ettringite, and meanwhile promoted the hydration exothermic rate and increased the amount of hydration products, which thus generate higher compressive strength and shorter setting time. (C) 2018 Elsevier Ltd. All rights reserved.