Preparation technology and mechanical properties of early-strength high-performance sleeve grout

An early-strength, high-performance grout was optimized with particular attention to the effects of admixture dosage and aggregate replacement ratio on its workability and mechanical properties. The hydration products and pore structure of grouts with varying replacement ratios were examined using scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), while the effects of rebar diameter, anchorage length, and grout type on the load-bearing capacity and failure modes of sleeve connections were investigated. The results indicate that an early-strength, high-performance sleeve grouting material can be achieved when sulfoaluminate cement, silica fume, ultrafine mineral powder, and steel fibers constitute 15%, 6%, 15%, and 1.5% of the binder, respectively, with tailings sand replacing 30% of quartz sand, a binder-to-sand ratio of 1:1, and a water-to-binder ratio of 0.24. The optimized formulation further incorporates 1% polycarboxylate superplasticizer, 0.1% defoamer, and 0.1% dispersant, yielding an initial flowability of 341 mm and a 30-min flowability of 328 mm, as well as compressive strengths of 60.4 MPa, 75.4 MPa, and 95.4 MPa at 1, 3, and 28 days, respectively. Microstructural analyses reveal the formation of a denser hydration framework and a continuous C-S-H gel network within the grout matrix, accompanied by abundant acicular and rod-like AFt phases that effectively fill pores and strengthen interfacial bonding. Uniaxial tensile tests show that all specimens prepared with this grout exhibit yield strengths exceeding 420 MPa and ultimate tensile strengths above 600 MPa, together with enhanced post-peak deformation capacity, indicating superior tensile performance and overall mechanical behavior.