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• GBFS, UCG and MFASB were used to synthesis the ternary OAGM. • Effects of various factors on flowability, setting time and strength were studied. • Borax is the optimal retarder for the ternary OAGM. • The ternary OAGM with BR has high compressive strength and great flowability. • Reaction product, microstructure and pore structure of different OAGMs were studied. To obtain an environment-friendly grouting material suitable for in situ application, the granulated blast furnace slag (GBFS), uncalcined coal gangue (UCG) and microscopic fly ash sinking beads (MFASB) were used to synthesis the one-part alkali-activated grouting material (OAGM). Firstly, OAGMs with different combination of precursors were prepared respectively, which are GBFS-based OAGM (the unitary OAGM), GBFS/UCG-based OAGM (the binary OAGM) and GBFS/UCG/MFASB-based OAGM (the ternary OAGM). The flowability, setting time and compressive strength of them were measured to analyze their applicability and feasibility in grouting engineering and obtain the OAGM with a reasonable combination of precursors. Next, the effects of different water to solid ratios (W/S ratios), different retarders, and the content of selected retarder on the OAGM were investigated to put forward its rational composition under the best overall performance. Finally, the reaction product, microstructure and pore structure of OAGMs were characterized to probe into their mechanism. Results show that compared with other OAGMs, the ternary OAGM with the retarder borax (BR) has the best overall performance. This material not only has the best flowability and the longest setting time, but also has high compressive strength, thus, it is more suitable for grouting engineering. Microstructural tests reveal that adding UCG and MFASB sequentially into GBFS-based OAGM makes important impacts on the formation of C-A-S-H gel, thus affecting the compressive strength. And adding MFASB into the binary OAGM increases the harmless pores, causing the ternary OAGM has higher porosity. However, the increase of porosity does not necessarily bring about the decrease of compressive strength. Besides, pore structure characteristics shows that adding BR increases the porosity of the ternary OAGM. This study can provide guidance for preparing environment-friendly OAGM suitable for in situ application and promote the recycling of industrial solid wastes. [ABSTRACT FROM AUTHOR]

As a promising sustainable building material, geopolymer/steel-slag composite materials have been poorly known in the field of the interfacial characteristics of geopolymer/steel-slag interface, especially at the molecular level. Herein, in this work, molecular dynamics simulation was employed to reveal the interfacial characteristics and mechanical behaviors of geopolymer binder with steel slag aggregate. The molecular models of two geopolymer binders (C-A-S-H and N-A-S-H) and three main minerals of steel slag aggregate (Ca 2 SiO 4 , Ca 2 Fe 2 O 5 and CaCO 3) were constructed and carried out. Then the wetting characteristics of different mineral surfaces, interfacial characteristics, interaction mechanisms and mechanical behaviors of various geopolymer/steel-slag interfacial systems were elucidated and compared. It is found that the Ca 2 SiO 4 , Ca 2 Fe 2 O 5 and CaCO 3 of steel slag aggregate show strong hydrophilicity, attracting water molecules to accumulated on its mineral surface and promoting the diffusion of Ca2+ and Na + at the interface. The interaction energy of geopolymer/steel-slag systems is mainly composed of electrostatic interaction energy. Thanks to the accumulation of water molecules on the mineral surface, the stronger hydrogen bond interaction occurs at the interface of the geopolymer/steel-slag system. The free metal cations from mineral surfaces and geopolymer binder respectively are coordinated with the accumulated water molecules to emerge hydrated ions, forming composite ionic clusters to stabilize the interfacial interaction. Mechanically, the interaction systems with C-A-S-H binder possess stronger interfacial tensile strength and shear strength. Steel slag with higher Ca 2 SiO 4 content can effectively form strong interfacial bonding, lowering the risk of interfacial tensile failure, whereas steel slag containing more Ca 2 Fe 2 O 5 can reduce occurrence possibility of shearing damage. CaCO 3 formed by carbonization of steel slag, is conductive to strengthening the interfacial interaction with geopolymer binder. [Display omitted] • MD simulation can reveal the interfacial behaviors of geopolymer/steel-slag. • The interfacial interaction of geopolymer/steel-slag is mainly composed of electrostatic interaction. • The water molecules at the interface produce hydrogen bond interaction. • The water molecules, Ca2+ and Na + migrate to the interface to form hydrated ions. [ABSTRACT FROM AUTHOR]