DURABILITY OF PORTLAND CEMENT SYSTEMS IN AGGRESSIVE ENVIRONMENTS

摘要

Portland cement systems are now commonly used for the construction of structures and buildings for residential, commercial and industrial applications. In many instances, these elements are exposed to severe environments, and their long-term performance is of concern. The main results of a comprehensive investigation of deterioration processes that may affect the behavior of Portland cement systems exposed to chemically-aggressive environments is presented. As part of this investigation, well-cured cement paste discs were exposed to deionized water, sodium sulfate and sodium chloride solutions. Degradation experiments were conducted under saturated and unsaturated conditions. At the end of the exposure period, microstructural alterations were investigated by microprobe analyses, scanning electron microscope observations and energy-dispersive X-ray analyses. Test results provide information on the basic aspects of various degradation phenomena such as chloride penetration, decalcification and external sulfate attack. For each phenomenon, the influence of factors such as water/cement ratio, type of cement and water transport is reviewed. The implication of these results on the prediction of the long-term performance of hydrated cement systems in chemically aggressive environments is discussed.