Stress-strain relationship of fibre reinforced concrete exposed under elevated temperatures

A research had been done to study the stress-strain relationship of fibre reinforced concrete (FRC) exposed under elevated temperature. The FRC used were single fibre concrete and hybrid fibre concrete which is combination of two different properties of fibres i.e. steel (SF) and polypropylene (PPF) by applying fibres volume fraction at 1.5%. At the same time, the fibres proportion of steel-to-polypropylene ranged in the following percentages: (100-0), (75-25), (50-50), (25-75) and (0-100). Cylinder samples of 150 mm diameter x 300 mm high were used and subjected to a compressive load to determine the relationship. All samples were casted and then water cured for 28 days before exposing them to the desired temperature i.e. 200ºC, 400ºC, 600ºC and 800ºC for 1 hour. For the control specimens, the cylinders were left at room temperature (27ºC) until the test day. Before placing the cylinders into the compression testing machine, they were left to cool naturally. All test results were tabulated and the stress-strain relationships were compared between the variations of the elevated exposure temperature. The findings show that the addition of fibres only improve the Elastic Modulus of concrete at room temperatures (27ºC), but when exposed under elevated temperatures, the Elastic Modulus decreased especially above 400º. High temperature