Effects of artificial interior stone (AIS) sludge incorporation on strength enhancement of cement mortar after exposed to elevated temperatures

There has been increasing interest in developing recycling strategies for artificial interior stone (AIS) sludge in light of climate change, carbon neutrality objectives, and environmental concerns. In this study, a recycling strategy that incorporates AIS sludge into the production of interior and exterior wall materials with high early strengths is newly proposed. Additionally, this research is the first, to our knowledge, to investigate the thermo-mechanical properties of AIS sludge-incorporated cement mortar following exposure to elevated temperatures. Initially, the early strength of specimens was compared under three different curing conditions (i.e., air at 25°C and 60°C, and water at 90°C) to identify the optimal curing conditions. Subsequently, the specimens were exposed to elevated temperatures of 400, 600, and 800°C, and their strength degradation was assessed. The results were thoroughly analyzed using X-ray diffraction (XRD), thermogravimetric analysis (TGA), and permeable void measurements. The experimental results revealed a reduction in density of approximately 15 % across all specimens. Furthermore, the normalized specific flexural strength exhibited a significant increase, with improvements exceeding 800 % after exposure to a temperature of 800°C. The findings revealed that AIS sludge, when used as a replacement for sand in cement mortar, offers significant potential for producing lightweight, high-strength wall panels capable of withstanding elevated temperatures.