Developing of High Temperature Resistance Cementitious Composites by Using CNC Milling Waste

The reuse of waste materials that are released in large quantities is crucial for environmental health. A reasonable solution is to embed waste materials in concrete, since concrete is the most consumed material after water. In this study, CNC (Computer Numerical Control) milling waste, which is generated in large quantities worldwide, was utilized as steel fiber. The waste was added to cementitious mortar mixtures in three different volume ratios. The mortars were exposed to temperatures of 400 °C, 600 °C, and 800 °C, and their post-temperature properties were investigated. Physical analysis, compressive strength, flexural strength, ultrasonic pulse velocity (UPV), and mass loss experiments were conducted. The CNC milling waste (CNCW) showed excellent compatibility with the mortar structure due to its physical and chemical properties. They maintained this accordance against elevated temperatures and provided superior residual properties. Due to their rough and irregular shape, the waste exhibited crack-resistant behavior and prevented the occurrence of temperature-induced cracks. As the amount of waste used and the level of temperature exposure increased, the contribution of the waste to strength also improved. Compared to the control specimens, the CNCW protected the compressive strength, flexural strength, UPV, and mass loss of the mortars by up to 70.74%, 85.10%, 22.63%, and 14.24%, respectively. Finally, this study has demonstrated that CNCW can be effectively used as steel fiber in mortars and that the incorporation of CNCW enhances the high-temperature resistance of these mortars.