Abstract
Soda residue (SR), an industrial solid waste, pollutes the environment due to its high alkalinity and chloride ion content. SR can be used as an alkali activator of ground granulated blast furnace slag (GGBFS). This study investigated the effects of four types of SR-activated GGBFS cementitious materials (pastes) with different mass ratios of SR to GGBFS (8:92, 16:84, 24:76, 34:68) on the physical properties, mechanical strength, and chloride binding capacity. The hydration mechanism of the pastes was also studied. Results showed that with the increasing addition of SR, the density of the pastes decreased, and more white aggregates of SR appeared causing the increase of water absorption and porosity of the pastes. The pastes with 16% SR addition had the maximum compressive strength (34.1 MPa, 28 d), so the optimum proportion of SR addition in the pastes was 16%. With the increases of SR addition, the amount of chloride element in the initial pastes increases. When the proportion of SR addition is 8%, the mass percentage of free chloride ion in the pastes at 28 d is 0.13%. The main hydration products of the pastes were C–S–H gels, ettringite, and Friedel’s salt, and the amount of ettringite varied with the amount of SR addition and curing time.
Highlights
Received: 10 May 2021Accepted: May 2021Published: May 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Soda ash (Na2 CO3, called sodium carbonate) is an important chemical raw material widely used in the chemical industry
The main hydration products of the pastes were C–S–H gels, ettringite, and Friedel’s salt, and the amount of ettringite varied with the amount of Soda residue (SR) addition and curing time
Density of the pastes decreases with the increasing proportions of SR addition
Summary
Received: 10 May 2021Accepted: May 2021Published: May 2021Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.Soda ash (Na2 CO3 , called sodium carbonate) is an important chemical raw material widely used in the chemical industry. Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The Solvay process, developed into its modern form by Ernest Solvay during the 1860s, generates more than 60% of the soda ash in China [1]. It produces Na2 CO3 from brine (as a source of NaCl) and from limestone (as a source of CaCO3 ) [2,3]. The overall process is shown in Equation (1). The Solvay process produces solid waste, mainly including soluble matter (CaCl2 , NaCl) and suspended matter (CaCO3 , CaSO4 , Ca(OH) , SiO2 , and Al2 O3 ) [4]
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