RESIDUAL PROPERTIES OF HYBRID POLYPROPYLENE-STEEL FIBRE REINFORCED HPC EXPOSED TO HIGH TEMPERATURES

A current topic concerning the use of High Performance Concrete (HPC) in tunnels and underground structures is its performance in fire: this is because the steam produced inside the elements is not able to dissipate as easily due to the low porosity and permeability of HPC. The final result could be an explosive spalling of structure cover, with a quick decrease of residual strength. The behavior of concrete, after exposure to a high temperature, depends upon the specific concrete mix proportions, the constituents used and the physicochemical transformations that the heating generates. Sometimes, a combination of polymeric and steel fibers can be used, to adjust ductility and to ensure fire resistance. Within this context, the damage after thermal treatments, in HPC was studied using compression and three-point bending tests. Porosity determinations and microscopy analysis were also carried out, in order to evaluate the deterioration of the different compositions, as a function of the temperature. Four types of HPC were produced using different fiber combinations of polypropylene and steel fibers. The maximum temperature reached using an electric furnace was 750°C. Intermediate temperatures were set at 250°C and 500°C.

• INTRODUCTION

• EXPERIMENTAL TECHNIQUES

• EXPERIMENTAL RESULTS

• DISCUSSION

• CONCLUSIONS

• REFERENCES