Long-term behaviors of phosphate-based rapid repairing material for concrete shafts in coal mines.

INTRODUCTION: Concrete structures in shaft linings are apt to deteriorate prematurely and therefore prompt restoration is required. In considering this, desulphurization fly ash and machine-made tuff sand are employed to fabricate a phosphate-based rapid repairing material.

METHODS: The long-term efficiency of the material is evaluated based on combined factors, so drying shrinkage, interfacial bonding strength, corrosion resistance, and combustibility of the specimens are tested and researched in this paper.

RESULTS: Experimental results showed that, under a dry circumstance, the material goes through a minor expansion at an early stage. It goes into a stage of rapid contraction after one day and a stable contraction after seven days. After 28 days, the total deformation is 67 micro-strains. On the other hand, the fabricated material manifests an excellent mechanical property. The one hour bending strength and compressive strength were 9.2 MPa and 32.6 MPa, respectively. A long-term mine water flushing simulation demonstrates that only 10% bending strength is lost and the corrosion resistance coefficient stays above 0.8, so a very good corrosion resistance is thus achieved.

CONCLUSIONS: What is more, this repairing material retains its stability even at a high temperature of 1000°C, revealing its good thermo-stability. All these prominent properties make it a good prospective material for real restoration applications.