Preparation and performance study of rapid-hardening curing materials based on orthogonal design

Abstract

This study systematically investigates the effects of water-to-binder ratio (A), binder-to-sand ratio (B), ultrafine mineral admixture content (C), and lithium carbonate content (D) on the mechanical properties and durability of rapid-hardening curing materials using an orthogonal design. Range analysis, chloride penetration tests, and microscopic characterization (SEM, XRD, TG) reveal the mechanisms governing early and late strength. Early strength is primarily controlled by lithium carbonate content, whose catalytic effect promotes ettringite formation. Late strength is dominated by the filling effect and pozzolanic activity of the ultrafine admixture. The optimal mix proportion is: water-to-binder ratio 0.24, binder-to-sand ratio 0.70, ultrafine admixture 20%, and lithium carbonate 0.04%. Under this mix, compressive strengths reach 59.7 MPa at 3 h, 73.55 MPa at 1 d, and 87.875 MPa at 28 d, with no strength regression, demonstrating excellent rapid-hardening performance and long-term stability. Microscopic analysis shows that needle-like ettringite (AFt) crystals form an early-age skeleton, later enveloped by C-S-H gel to create a dense microstructure, significantly enhancing performance and durability. This study provides a theoretical basis for mix optimization and engineering application of rapid-hardening repair materials.