NaOH碱激发煤矸石胶砂试块力学性能及微观结构

Mechanical properties and microstructure of coal gangue mortar blocks excited by NaOH Alkali

碱激发煤矸石胶凝材料是一种新型低碳环保材料,将成为未来硅酸盐水泥体系的潜在替代材料。为探讨NaOH碱性激发后煤矸石的活性,研究0%,2%,4%质量掺量下的NaOH活性激发后煤矸石胶砂试块的力学性能,对鄂尔多斯地区煤矸石的理化性质进行了测试,测定了不同NaOH掺量的煤矸石胶砂试块抗压强度和抗折强度,并采用X-射线衍射分析和扫描电子显微镜对其微观结构进行分析,揭示了宏观力学性能变化规律的微观机理。结果表明相较于未掺入NaOH激发剂的煤矸石胶砂试块,2%NaOH的煤矸石胶砂试块在28 d的抗压强度降低了13%,4%NaOH的煤矸石胶砂试块抗压强度降低了21%,这是由于过高的碱性环境溶解了铝硅酸和硅酸盐而导致煤矸石强度的降低;同时,试块中NaOH浓度的增加会抑制水化产物C-S-H,AFt和CH的形成,且水化产物中会含有较多孔隙,从而降低其力学性能。由此可见,NaOH对于该地区煤矸石激发效果较差。

A new eco-friendly low-carbon material,Alkali-activated coal gangue cementing material will become a potential substituted material for the future portland cement system.In order to investigate the activity of coal gangue activated by NaOH Alkaline,the mechanical properties of NaOH activated coal gangue mortar blocks with 0%,2%,4%mass contents were studied.In this paper,the physical and chemical properties of coal gangue in Ordos were tested.The compressive and flexural strength of coal gangue mortar blocks with different NaOH content were measured.The X-ray diffraction analysis and scanning electron microscope were used to explore the microstructure of the blocks,which reveals the micro-mechanism of the macro-mechanical property change law.The results showed that compared with the coal gangue mortar block without NaOH activator,the compressive strength of the coal gangue mortar block with 2%NaOH was reduced by 13%at 28 days,and the compressive strength of 4%NaOH coal gangue mortar blocks was decreased by 21%,or the dissolution of alumino silicate and silicate in an excessively alkaline environment led to the reduction in the strength of coal gangue.At the same time,the XRD and SEM showed that the NaOH concentration in the test block increasing the amount of hydration products would inhibit the formation of C-S-H,AFt and CH,and the hydration products would contain more pores,thereby reducing their mechanical properties.It can be seen that NaOH has a poor excitation effect on coal gangue in this area.