Abstract:With the rapid development of mine filling technology, the research and development of green and inexpensive filling materials have become an industry trend.As the main cementitious material for mine backfill paste, cement has the problems of high resource consumption and high cost.To find cement substitute materials with excellent performance, this paper takes gangue-cement-based backfill paste as the research object. Backfill paste samples with zeolite contents of 0%, 5%, 10%, 15%, 20% and 25% are prepared, and compressive strength and flexural strength tests on backfill paste with different zeolite contents are carried out.Combined with scanning electron microscope (SEM) microscopic test and X-ray diffraction (XRD) phase analysis, the influence of zeolite content on the mechanical properties of backfill paste and its action mechanism are explored from three aspects: the variation law of mechanical properties, the composition characteristics of hydration products, and the morphology of microstructure.The results indicate that, With the increase of zeolite content, the compressive strength and flexural strength show a trend of first increasing and then decreasing. The mechanical properties of backfill paste can be significantly improved by incorporating appropriate amount of zeolite.Under the curing condition of 28 days, the mechanical properties of backfill paste are the best when the zeolite content is 15%. The compressive strength and flexural strength reach 5.42 MPa and 3.63 MPa respectively, which are increased by 5.86% and 9.3% compared with the paste samples without zeolite.After the incorporation of zeolite, the types of hydration products in the backfill paste remain unchanged, but the contents of ettringite (AFt) and calcium hydroxide are significantly reduced compared with the group without zeolite, and the content of C-S-H gel is significantly increased.In terms of microstructure, the C-S-H gel transforms from a loose network to a dense cotton-like framework, the pore structure is optimized, and it interweaves with calcium hydroxide crystals to form a more uniform composite system. Zeolite realizes the improvement of the mechanical properties of the backfill paste by coordinately regulating the generation process of C-S-H gel, ettringite (AFt) and calcium hydroxide, and optimizing the internal pore structure of the paste.This paper provides a theoretical basis for the application of zeolite as a cementitious material, which is of great significance for promoting the research on new green cementitious materials.

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