Study on Microstructure of Long-Age Concrete with HCSA Expansive Agent

The microstructure of high-volume fly ash and long-age concrete with HCSA expansive agent at different curing time is studied by means of scanning electron microscope and energy dispersion spectrum analysis. The result shows that wet curing is benefit to the generation of ettringite which is the hydration product of HCSA expansive agent, and also is benefit to the hydration of cement and fly ash, which can fundamentally improve compactness of concrete. For the concrete which mix 6% amount of HCSA expansive agent a 60% amount of fly ash, when it is not cured, the average ratio of Ca to Si is 1.8, and the value is 0.36 after 28d curing. Since the ration of Ca to Si is lower, the hydration rate of binding material is faster.