Compressive stress-strain model and residual strength of self-compacting concrete containing recycled ceramic aggregate after exposure to fire

Abstract

The present study uses recycled ceramic aggregates (RCAs) as a partial replacement of natural coarse aggregate (NCA), to produce two self-compacting concrete (SCC) types, the first containing Portland cement, and the second a calcium-aluminate cement. The residual behavior in compression, after heating to five reference temperatures (110, 200, 400, 600, and 800 °C) is investigated, besides the behavior at room temperature. For both SCC types, three mixes were prepared with different substitution ratios (RCA/NCA = 0, 25 and 50% by mass), and such properties as slump flow and flow time (at the fresh state), and compressive strength, modulus of elasticity and strain at the peak stress (after hardening) were measured. The results confirm that using calcium-aluminate cement brings in a sharp decrease in the mechanical properties at high temperature and indicate that adding RCA has a negligible effect on the mechanical performance at high temperature (with an improvement at 800 °C, 16–86%), but slightly decreases the flowability at the fresh state. For each reference temperature, the stress-strain curves in compression were measured after cooling, but - besides the gain in terms of compressive strength - the general shape of the curves was affected by the substitution ratio. Comparisons are made too with code provisions and previous studies. Last but not the least, predictive equations taken from the literature are used to fit the stress-strain curves to incorporate the effect of recycled ceramic aggregate in SCC in compression at high temperature, and the fitting of the test results appears to be very satisfactory.