Influence of ground granulated blast furnace slag on the early hydration and microstructure of alkali-activated converte
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Influence of ground granulated blast furnace slag on the early hydration and microstructure of alkali‑activated converter steel slag binder Yuqi Zhou1,2 · Jianwei Sun2 · Yanwu Liao3 Received: 24 April 2020 / Accepted: 29 August 2020 © Akadémiai Kiadó, Budapest, Hungary 2020
Abstract Alkali-activated materials are low-environmental-impact binders that can be obtained from the alkaline activation of industrial wastes. In this study, converter steel slag as the major raw material and ground granulated blast furnace slag (GBFS) as the modified material were activated by water glass with a modulus of 1.5 and a Na2O dosage of 4%. The hydration process, microstructure and compressive strength of alkali-activated composite materials were investigated. The results show that adding GBFS accelerates the initial dissolution of the particles, leading to higher first exothermic peaks. But adding GBFS decelerates the formation of hydration products, resulting in the delay of the second exothermic peaks. Adding GBFS has no significant effect on the cumulative hydration heat, Ca(OH)2 content and the type of gel in the alkali-activated steel slag systems. However, with increasing GBFS content, the Ca–Si ratio in the gel decreases, and the Al–Si ratio increases. Adding GBFS can refine the pore structure and produces more Si–O–Si bonds in gels, resulting in a significant increase in the compressive strength. The improvement effect of GBFS on the compressive strength is more obvious at a later stage than at an earlier stage. Keywords Alkali-activated steel slag · GBFS · Hydration · Microstructure · Pore structure
Introduction Alkali-activated materials (AAMs) are called clinker-free cement and are alternative green materials compared to conventional ordinary Portland cement (OPC) [1, 2]. AAMs are generally prepared by various aluminosilicate precursors and alkaline sources without the need for the calcination process. Sodium hydroxide and sodium silicate are common alkaline activators. The alkali activation of precursors can be called “a complex process of structural destruction and polycondensation of hydration products” [2]. Currently, the emission of substantial industrial solid wastes is increasing * Jianwei Sun [email protected] 1
China Construction First Group Construction and Development Co., Ltd, Beijing 100102, China
2
Department of Civil Engineering, Tsinghua University, Beijing 100084, China
3
Sichuan Mianzhu New Materials Co., Ltd, Sichuan 618200, China
rapidly due to the fast-growing metallurgical industry. More studies have confirmed that some types of industrial wastes can be converted into potential precursors for AAMs resulting from their high activity under alkali activation [3–6]. If AAMs are widely used as building materials, they will not only meet the requirements of sustainable development but also conserve natural resources and preserve the environment. Ground granulated blast furnace slag (GBFS), fly ash and metakaolin are the most generated aluminosilicate precursors. It has been reported t
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