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The purpose of this paper is to evaluate high strength concrete (HSC) containing polypropylene fibers (PP-fibers) at high temperature under a compressive load.

The use of PP fibers in HSC is known to reduce and at times eliminate the risk of spalling. HSC containing 0, 1 and 2 kg/m³ of PP-fibers were subjected to various temperatures from 20°C to 150°C, 300°C and 450°C and evaluated in a “hot condition”. One group of specimens was in a non-stressed condition during heating (unstressed hot), while a second group was subjected to an initial preload of 40 per cent of the room temperature compressive strength during the heating (stressed hot).

Results showed that stressed concrete containing PP-fibers had lower thermal gradients (the temperature difference between the surface and center temperatures as a function of radial distance) and a decrease in relative porosity. However, the compressive strength of stressed specimens was improved with or without fibers as compared to that of the unstressed HSC. The increased stress levels due to concrete expansion at elevated temperature were also reported. The PP-fibers did not have a significant effect on the compressive strength of stressed concrete as compared to the unstressed state.

This paper reports the compressive strength of PP-fibers in HSC at elevated temperature with and without a pre-load.