Thermal and Mechanical Performance of Sawdust High Strength Concretes at Elevated Temperatures

Abstract

The performance of high strength concrete (HSC) under fire conditions is an established concern in concrete industry. The kinetics and mechanisms involved in processes that affect the fire behavior of HSC are mostly controlled by its mechanical and material properties, thermo-mechanical interactions, and type of structural component exposed to fire. The weaknesses of HSC in infrastructure under fire conditions preclude its applications in fire resistance applications unless significant modifications are done either to concrete mix or the structural design. For many years, polypropylene fibers have been used to attain a certain amount of essential porosity in HSC under fire resistance applications. Sawdust high strength concrete (SD-HSC) however, can provide a suitable alternative to conventional HSC under fire conditions, especially due to its improved thermal properties in hardened state. An experimental program was designed to study the performance of sawdust high strength concrete at elevated temperatures in 23 to 800°C temperature range. In this study, material and thermal properties of sawdust high strength concrete (SD-HSC) were investigated with various content of sawdust (5, 10 and 15%) replacement as the total dry volume wt of sand and compared with control HSC under residual fire testing condition. Mechanical tests such as compressive and splitting tensile strength, stress-strain response, elastic moduli, compressive toughness and spalling behaviour under a heating rate of 5°C/min were studied. Additionally, visual inspection, mass loss and ultra-sonic pulse velocity test (UPV) was carried out on control and sawdust modified high strength concrete specimens. Forensic analysis was also carried out to asses to microstructure and cracking behavior of concrete specimens. Results shows that 10SD-HSC performed better at elevated temperature with improved residual mechanical properties compared to that of reference HSC and the spalling mitigation at elevated temperatures. Conversely, an increase in sawdust showed a minor degradation in the mechanical properties at ambient temperature conditions.