Durability of high and ultra-high strength concretes subjected to aggressive chemical environments

摘要

During the recent years, ultra-high strength concretes (UHSCs) are being used in lieu of high strength concretes (HSCs) for applications demanding higher tensile strength (such as pre-stressed bridges, thin sections and others) and longer service life with zero or least maintenance cost. Concretes used for such applications are often subjected to aggressive chemical attacks due to the penetration of chlorides, sulfates, etc. from atmosphere, thereby indicating the need for highly durable concretes. This paper compares the durability of three concretes namely, HSC, high performance concrete (HPC) and UHSC. The durability tests conducted include water absorption, porosity, chloride permeability, and strength/weight loss due to exposure to different chemical solutions. Results from this investigation indicated that the water absorption and porosity of UHSC were substantially lower than that of HSC. In acid resistance test, the 90-day strength loss of UHSC was lower than that of HSC by 44%, 62% and 48% under hydrochloric, nitric and sulfuric acid attacks, respectively, with sulfuric acid causing the highest deterioration. Similar trends were observed in sulfate resistance test also, with the 'alternate wetting and drying' method causing higher deterioration than the 'continuous immersion' method. In the salt resistance test, all concretes showed minimal damage. In the chloride permeability test, the HSC was in the 'very low' range while HPC and UHSC were in the 'negligible' range. Overall, the UHSC showed superior performance than others and therefore, is anticipated to perform well in applications demanding long term durability.