Influence of fire on temperature gradient and physical-mechanical properties of macro-synthetic fiber reinforced concrete for tunnel linings

Abstract

Abstract This study aims to evaluate the effect of fire on the physical, mechanical, and microstructural properties of macro-synthetic fiber reinforced concrete. Results demonstrated that internal heating rate is constant through time and is a function of the distance from the fire. Temperature gradient values are nonlinear, reduce at greater distances from the heated surface and with the duration of the fire. Microstructural analysis shows the severe dehydration of hydrated products, which negatively influences the mechanical properties of the composite. Above 205 °C the formation of nesosilicates is verified. Residual flexural strength values reduce by over 85% after the fire exposure due to deterioration of the reinforcing mechanism. Compressive strength and elastic modulus drastically reduce with temperature increase. The present study contributes to the absent literature on the post-fire mechanical behavior of MSFRC, suggests an alternative approach to the post-fire evaluation of tunnel structures, and aids in the definition of post-fire safety parameters.