Spalling sensitivity and mechanical response of an ecofriendly sawdust high strength concrete at elevated temperatures

•Modification of HSC with sawdust shows promising performance against spalling.•Intrusion of SD in HSC results in improved thermo-mechanical performance at high temperatures.•Structurally applicable strength (45 MPa) was achieved with optimal replacement of SD.•Optimal use of SD improves the energy characteristics of host matrices at elevated temperatures.•SD-HSC offers a suitable ecofriendly yet cheap alternative against spalling. An eco-friendly high strength concrete (HSC) was developed with integration of wood waste (0, 5, 10, and 15%) in replacement to weight content of fine aggregate. Wood waste (sawdust) potentially a thermally degradable fiber was incorporated to enhance the fire endurance of high strength concrete. Mechanical strength and durability parameters of controlled and modified samples were explored along with the degradation on exposure to elevated temperatures. The investigated formulations were subjected to a maximum temperature of 800 °C on 5 °C/min ramp and then tested in the ambient conditions for the residual properties. Results depicted significant retention in compressive strength of sawdust high strength concretes (SD-HSC) at elevated temperatures with limited spalling sensitivity. Visual assessment along with micro-forensic evidences illustrate that SD-HSC exhibits reduced thermal cracking in macro, micro and the nano phase, in comparison with HSC. The experimental trends obtained from material property tests were used to develop simplified mathematical relationships that are helpful in performing analytical fire resistant studies for HSC formulations bearing sawdust grains. Conclusively, sawdust has been effectively utilized to develop an ecofriendly and fire resistant structurally applicable high strength concrete.