Consolidation Characteristics and Sulfate Resistance of Alkali-activated Slag Cementitious Materials
SUN Daosheng1, YE Zhe1, LIU Kaiwei1, WANG Aiguo1, GUAN Yanmei1, CHEN Dong2
1 Anhui Key Laboratory of Advanced Building Materials, School of Materials and Chemical Engineering, Anhui Jianzhu University, Hefei 230022, China 2 School of Civil and Engineering, Anhui Jianzhu University, Hefei 230022, China
Abstract: As a kind of low-carbon and environment-friendly cementing material for roadbed and foundation reinforcement, alkali-activated geopolymer grouting material not only has no calcium hydroxide in its hydration products, but also some hydration products can provide adsorption of sulfate ions, with excellent anti-sulfate erosion effect and broad application prospect. In this experiment, the consolidation properties and sulfate resistance of magnesia-activated slag (GGBS-MgO), calcium oxide-activated slag (GGBS-CaO) and cement (PC) were studied by appearance, unconfined compressive strength, mass change, the change of mineral composition and microstructure. The results show that slag activated by CaO obtains a higher pH value than MgO activated slag. Higher pH value is beneficial to the fracture of vitreous O-Si-O and O-Al-O bonds in slag, which causes a better consolidation characteristic as more hydration products. The unconfined compressive strength of sand samples stabilized by GGBS-MgO and GGBS-CaO increases 42.2% and 101.2% respectively after curing for 28 d. When the sand samples were immersed in 5wt% Na2SO4 solution for 150 d, sulfate ions react with calcium hydroxide to form ettringite and gypsum in PC, which results in more pores and obvious cracking. After 150 d of immersion, the unconfined compressive strength of PC is decreased to 0.41 MPa while the unconfined compressive strength of GGBS-MgO and GGBS-CaO continuously increases due to the formation of hydrotalcite. As a result of adsorption of sulfate ions by hydrotalcite, the sulfate resistance of GGBS-MgO and GGBS-CaO is better than PC.
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2020, Vol. 34 
