Abstract
High-flow low-expansion backfill materials have been developed to improve difficult slurry pipeline transport and poor roof-contact effect of many filling materials. The fly ash content was fixed at 80%, with 8.5% - 9.5% mineral powder content, 8.5% - 9.5% lime, 2% - 3% desulfurized gypsum, 0.9% - 1.2% sodium carbonate, and 0.01% - 0.02% aluminum powder content. The prepared backfill material processed good fluidity, with the expansion rate of the hardened material reaching 2% - 3%, and compressive strength on 90 d reaching 4 MPa-5.5 MPa. SEM observations indicated that as the aluminum content increased, ettringite on bubble walls transformed from a fine-needle to needle-rod shape. Secondly, the hydration products of the system were mainly hydrated calcium silicate gel and ettringite, which interconnected and promoted the formation of the structure. The backfill material has extensive sources of raw materials, low cost, simple filling process, and good filling effect.
Highlights
When the fly ash amount was fixed at 80%, different amounts of mineral powder, lime, desulfurized gypsum, sodium carbonate, and aluminum powder were analyzed in order to
When the fly ash content was fixed at 80%, mineral powder was 8.5% - 9.5%, lime was 8.5% - 9.5%, desulfurized gypsum was 1% - 3%, with 0.9% - 1.2% sodium carbonate and 0.01– 0.02% aluminum powder
When water-to-material ratio was controlled between 0.60–0.70, the backfill material showed good fluidity
Summary
The fly ash has the potential pozzolanic activity. The wide source and low price of the fly ash are its advantage. The fly ash was selected as the main component of the backfill materials. Available fly ash was supplied by Shanxi Yang City Power Plant and used as the main backfill material. It had a density of 2.21 g/cm, a specific surface area of 332.1 m2/kg, and a water content of 0.05%. The SEM sample was taken from the specimens in uniaxial compression test, the sample was made by 1cm 1cm It was fixed on the metal plate with doublesided conductive adhesive, the metal plate was placed in a gold-spraying apparatus for gold spraying, drying and vacuuming, and placed in a SEM instrument for the experiment
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