Analysis of the resistance to fire of solid concrete boards with polypropylene microfibers and long curing time

Abstract Reinforced concrete elements with long curing ages tend not to present spalling when subjected to high temperatures since heat transfer in concrete is influenced mostly by the materials constituting its composition. Polypropylene microfiber-reinforced concrete presents more porosity and higher thermal insulation as the fibers melt when exposed to high temperatures. Therefore, this study aimed to assess the influence of the addition of polypropylene microfibers on the resistance to fire of reinforced concrete boards. The mechanical tests required crafting 18 boards and 3 walls in real scale, which measured 3.15x3.00 m. The analysis comprised 3 types of systems, being the reference reinforced concrete and the concretes with polypropylene microfiber ratios of 0.97 kg/m³ and 1.94 kg/m³. Were extract 18 specimens for the axial compression test. The fire test was performed in a vertical furnace under the ISO 834 curve. None of the 3 walls displayed spalling and the boards with higher microfiber ratios presented better fire performance, with smaller maximum displacements. The wall with 1.94 kg/m³ microfiber ratio obtained a gain of 23.5 min in thermal insulation compared to the reference reinforced concrete wall. It was also perceived that the incorporation of polypropylene microfibers in the concrete reduces its compressive strength.