Behaviour of steel and polyproylene fibers in high strength concrete subjected to elevated temperature

Abstract

Concrete are widely used in the construction industry and with the increase in demand of high strength properties and long life span, High Strength Concrete (HSC) is more commonly used as compared to other types of concretes. The mechanical properties of HSC are more superior to Normal Strength Concrete (NSC) at room temperature but deteriorate rapidly and spall under fire conditions.

The purpose of the study is to know the feasibility of incorporating fibers and the content in HSC to reduce explosive spalling. The investigation will be on the behaviour of Steel and Polypropylene (PP) fibers in HSC under elevated temperatures.

The study was carried out by casting HSC with steel and PP fibers of 0.08%, 0.14% and 0.20% and tested at ambient, hot and residual temperatures of 250C, 350C and 550. Compressive and splitting tensile strengths of the specimens were obtained using compression test and splitting tensile strength test.

It was found that the strengths of HSC increased with higher PP and steel fibers content and were higher for residual temperature as compared to hot temperatures. PP fibers were found to be more effective in preventing explosive spalling as compared to steel fibers since it has the ability to create additional pathways and relieve the pore pressure in the HSC at high temperatures.

To conclude, PP fibers are effective in minimizing spalling while steel fibers are good at increasing the toughness of the concrete but spall more violently at high temperatures.