Early-age durability and semi-destructive strength evaluation of rapid-hardening latex-modified concrete overlays

This study investigates the early-age durability and strength of rapid-hardening latex-modified concrete (LMC) overlays, with a focus on field-applicable semi-destructive testing. Five mixtures using acrylic and styrene-butadiene rubber (SBR) latexes were tested for compressive strength, freeze–thaw resistance, and abrasion at early ages. All mixtures retained over 80 % of dynamic modulus after 300 freeze–thaw cycles, and abrasion resistance improved after 4 h. Break-off and pull-out tests were conducted in laboratory and field conditions to evaluate in-situ strength. The pull-out test showed R² = 0.8857 correlation with compressive strength across insert sizes and ages, while the break-off test showed depth sensitivity and reduced reliability. A log-transformed orthogonal regression model based on lab pull-out data was applied to field results, enabling strength prediction without core testing. The findings confirm that rapid-hardening LMC overlays achieved sufficient early durability and strength, and that the pull-out method was a practical tool for early-age quality control in concrete repair.