Rheological, fluidity and mechanical performance of cementitious grouts with perlite powder

This study evaluates the feasibility of using perlite powder (PP) as a partial replacement for Portland cement in cementitious grouts for ground improvement applications. Grout mixtures were prepared with water-to-binder (w/b) ratios of 0.75, 1.00, 1.25 and 1.50, and PP replacement levels ranging from 0% to 30%. Fresh-state performance was assessed through rheological measurements, mini-slump, Marsh funnel viscosity and bleeding tests, while hardened-state properties were evaluated using bulk density, unconfined compressive strength (UCS) and ultrasonic pulse velocity. All mixtures exhibited Bingham-type flow behaviour. Increasing PP content increased yield stress and plastic viscosity, whereas higher w/b ratios improved flowability. PP replacement at 5–10% provided a favourable balance between injectability, stability and strength. At w/b = 1.00, 5% PP increased 28-day UCS by 23% compared to the control mixture. Higher PP contents (≥15%) reduced fluidity and strength due to increased water demand and cement dilution. The results indicate that incorporating 5–10% PP with w/b ratios between 1.00 and 1.25 offers an optimal performance range for sustainable grout applications.