evaluation of hybrid fiber reinforced concrete exposed to severe environmental conditions

Hybrid fiber reinforced concrete (hfrc) consisting of two or more different types of fibers has been widely investigated because of its superior mechanical properties. in the present study, the effect of the addition of steel (0.25%, 0.5%, 0.75% and 1% of concrete volume) and polypropylene (0.2%, 0.4% and 0.6% of concrete volume) fibers on the surface scaling resistance of concrete, depth of penetration of water, and compressive strength of concrete is investigated. the permeability test is conducted for all the specimens to measure the depth of penetration of water under pressure. moreover, scaling resistance of concrete subjected to freezing and thawing cycles in the presence of salt solution is assessed to simulate the durability of concrete under field exposure conditions. the results showed that the addition of fibers increases the permeability of concrete. however, it enhances the scaling resistance and compressive strength of concrete. the mixture containing 0.4% of polypropylene (pp) fibers and 0.75% of steel fibers demonstrated the highest scaling resistance since the scaled materials in this mixture were almost half weight of the materials scaled from the control mixture after 84 cycles of freezing and thawing. increasing the scaling resistance of concrete leads to a better long-term serviceability performance of hfrc compared to plain concrete, making these composites a great choice for application in environments exposed to cold weather.