Portland-limestone cement (PLC) is a low-carbon, green alternative binder that can substitute for ordinary Portland cement (OPC) to support the development of eco-friendly infrastructure solutions. The building's energy consumption and strength retention efficiency can be improved by effectively enhancing the cementitious matrix properties of the rendering materials.
In this study, the residual mechanical strengths and microstructure of OPC and PLC mortars before and after exposure to elevated temperatures of up to 800 °C were experimentally investigated. Tested specimens were prepared using 0%, 5%, 10% and 15 wt.% of limestone as a replacement for OPC. The fire-resistance performance of the prepared rendering mixtures was evaluated through their residual strengths, X-ray diffraction, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM).
Based on the results, the mechanical properties of all mortars improved at 250 °C, due to internal autoclaving and pore pressure effects. At 800 °C, the major phases observed in OPC and PLC mortars were calcium silicate and quartz. Large wollastonite and gehlenite crystalline phases were observed in PLC mortars; thus, the matrix structure was severely damaged, and this damage was more pronounced in PLC mortars.
Several studies have concentrated on this area, and numerous investigations into the fire-resistance performances of cement-based mortars have been reported. Nevertheless, limited investigations focused have focused on the residual strengths of rendering mortars made with PLC as a sustainable alternative to Portland cement; and therefore, have not been acknowledged to date.
