Effect of Soda Residue Addition and Its Chemical Composition on Physical Properties and Hydration Products of Soda Residue-Activated Slag Cementitious Materials

Soda residue (SR), the solid waste of Na2CO3 produced by ammonia soda process, pollutes water and soil, increasing environmental pressure. SR has high alkalinity, and its main components are Ca(OH)2, NaCl, CaCl2, CaSO4, and CaCO3, which accords with the requirements of being an alkali activator. The aim of this research is to investigate the best proportion of SR addition and the contribution of individual chemical components in SR to SR- activated ground granulated blast furnace slag (GGBS) cementitious materials. In this paper, GGBS pastes activated by SR, Ca(OH)2, Ca(OH)2 + NaCl, Ca(OH)2 + CaCl2, Ca(OH)2 + CaSO4, and Ca(OH)2 + CaCO3 were studied regarding setting time, compressive strength (1 d, 3 d, 7 d, 14 d, 28 d), hydration products, and microstructure. The results demonstrate that SR (24%)-activated GGBS pastes possess acceptable setting time and compressive strength (29.6 MPa, 28 d), and its hydration products are calcium silicate hydrate (CSH) gel, calcium aluminum silicate hydrates (CASH) gel and Friedel&rsquo
s salt. CaCl2 in SR plays a main role in hydration products generation and high compressive strength of SR- activated GGBS pastes.