Evaluation of mechanical and durability properties of engineered cementitious composites exposed to sulfate attack and freeze–thaw cycle

In this study, different engineered cementitious composite (ECC) designs were proposed with ground granulated blast slag (GGBS) combined with metakaolin (MK), micro silica (MS), and carbon nanotube (CNT) reinforced with polyvinyl alcohol (PVA) and polypropylene (PP) fibers. The specimens were cured in water, magnesium sulfate solution and exposed to freeze–thaw cycles to test the specimens' durability. Then, compressive strength, displacement in the middle of span, residual strength, and modulus of rupture of the specimens in different environments were compared. The results indicated that addition of MK had a significant effect on the reduction of permeability. Moreover, replacement of PP fibers with PVA fibers decreased the strength and increased the porosity of the specimens. It was found that the specimen containing 0.015% CNT had better performance compared to other samples. The results of samples cured in aggressive environments indicated that the specimen containing 0.015% CNT had the lowest loss in the value of compressive strength, modulus of rupture, displacement and residual strength in comparison to other mixtures. Furthermore, the use of CNT along with PVA fibers in ECC significantly increased the energy absorption capacity, indicating the CNT's ability to bridge and close the micro-cracks in a case of suitable distribution.