Study On Capability Of Long-term Resistance Sulphate Corrode OfⅡ Fly Ash Content High Performance Concrete

Considered the factors of varieties of cement,water-cement ratio,level of II fly ash,curing period, sulphate concentration and erosion age,the capability of resisting sulphate corrode of II fly ash content concrete unduer the long-term sulphate attack condition was studied by the erosion experiment for2years of portland cement concrete mortar specimens in the case that the water cement ratio were0.40,0.35and0.30, and the volume of Ⅱ fly ash were30%,40%and60%. And to evaluate the capability, the experiment of resisting sulphate corrode was also test for high sulphate resistant portland cement concrete,We also took macroscopic observation and microscopic observation methods of scanning electron microscope (SEM) and energy dispersion spectrum (EDS) to analysis and reveal the anti-erosion mechanism of II fly ash concrete. Results found in this research were as follows:(1)Main factors which affect the capability of resisting sulphate corrode of II fly ash content concrete were the water-cement ratio and the volume of Ⅱ fly ash.Especially, the quantum of II fly ash was the most significant factor. With the quantum of II fly ash increasing, while the water-cement ratio was unchanged, the corrosion resistance coefficient of the specimens were increased, especially when the fly ash content up to60%,both the specimens of standard curing (28d) and the specimens of short age curing (3d) can resist erosion of the high concentration sulphate solution. With the Water-cement ratio reducing, while the quantum of Ⅱ fly ash was unchanged, the corrosion resistance coefficient of the specimens were increased, especially when the Water-cement ratio down to0.30, both the specimens of standard curing (28d) and the specimens of short age curing (3d) can resist erosion of the high concentration sulphate solution. It’s indicated that the lower water-cement ratio and lager volume of II fly ash can improve the capability of resisting sulphate corrode of II fly ash content concrete well.(2)High sulphate resistant cement mortar specimen which can’t resist high concentrations of sulphate attack.also difficult to resist low concentrations of sulphate attack for a long time. It should be careful to use high sulphate resistant cement in the concrete engineerings which have sulphate attack problems. It must take some effective measures to improve it’s ability to resist erosion and some experiments to verify it’s erosion resistant reliability.(3)The mortar specimens in the case that the volume of Ⅱ fly ash is30%and40%soaked in different concentrations of sulphate solutions for6months have high ability to resist erosion, but with the ersion age extending, some mortar specimens which have higher water-cement ratio and lower volume of Ⅱ fly ash soaked in high concentrations of sulphate solution were damaged gradually. Explained that Describe the evaluation of the fly ash samples of sulphate corrosion resistance ability should pay full attention to the time effect of erosion, only through short-term (6months) erosion test is difficult to determine, have to do long-term trial research.(4)Use the mortar specimens which made in a low water-cement ratio after immersing in the high concentration of sulphate solution for a long time, the specific forms of erosion damage mainly occurs as the surface of mortar specimens configured at a low water cement ratio would be loose and break gradually, and the loose layer of materials contained a lot of gypsum crystallization, caused the specimen surface gradually loose damage.(5)In the short-term erosion of time (6months), fly ash is mainly effect on physical filling and chemical substitution to increase the density of concrete and reduce the internal chemical attack;but when the ersion age extended to2years, Ⅱ fly ash begins to play a secondary hydration.