Fibras de polipropileno e sua influência no comportamento de concretos expostos a altas temperaturas: revis？o

the fire resistance of a structural concrete is evaluated by the time length that the element keeps performing its functions under high temperature conditions. it is usually believed that the concrete has an excellent durability before fire; however, in practice the stability of this material is reduced by high temperatures. unfortunately, under such circumstances, concrete elements present excessive damages or even catastrophic failures. when exposed to high temperatures, cement based materials undergo physicochemical changes that damage their mechanical properties and spoil their resistance to heat transfer. although the thermal features of a high strength concrete are similar to those of a conventional concrete, this material has a greater sensibility to high temperatures due to its reduced porosity, showing a higher relative loss of the mechanical properties and explosive spalling in the temperature range between 100 oc and 400 oc. the spalling can be avoided by adding polypropylene fibers in concrete: when melted and partially absorbed by the cement matrix, the fibers generate a permeable network that allows the outward gas migration, decreasing the pore pressure in the material and, consequently, eliminating the possibility of explosive spalling occurrence. thus, in the present paper, a review regarding the behavior of concretes exposed to high temperatures, as well as the influence of polypropylene fibers have been addressed for concretes applied in the civil engineering area.