Influence Of Sustained Load On Freeze-thaw Properties Of Fly Ash Concrete

As admixture mixed into the concrete, fly ash can reduce the dosage of cement and reduce the cost, and thereby protect the environment and save resources; what's more, it can also lower the hydration heat and reduce the shrinkage and creep, according to which the internal structure of the concrete will be improved. Consequently, it has become an important ingredient of the concrete. And great importance and close attention have been attached to its performance by researchers and engineers in and outside China.Researchers have done pretty much study on the physical properties and mechanical properties of fly ash concrete. And it has been much developed in the theoretical aspect; while in the practical applications, it has to take the environmental factors into consideration, which mainly concerns its frost resistance after loading. Frost resistance is an important factor affecting the durability of the concrete, especially in north China. Due to the insufficiency of test types and data, and also the inadequacy of theory, researches in this aspect are comparatively deficient. As a result, it is urgent to perform some relevant studies in this area.Based on the theoretical foundation and experimental study, this paper practically conducts an in-depth study on the freeze-thaw performance of the fly ash concrete after sustained load. By comparing of the freeze-thaw damage of the concretes with a fly ash mixture of 0%,20% and 40% separately after sustained load and not sustained load, it is concluded that the frost resistance of the concrete is improved a lot in the concrete with a 20% fly ash mixture, comparing with the ordinary concrete without any fly ash; but the degree of peeling is more serious than the ordinary one. And the results also show that the concrete with a 40% fly ash mixture has the lowest degree of frost resistance, and the highest degree of peeling. However, sustained load has the greatest influence on the freeze-thaw performance of the concrete with a 20% fly ash mixture, followed by the concrete with a 40% fly ash mixture. The sharp degradation point and the freeze-thaw damage points are both advanced. The concrete with a 40% fly ash mixture shows serious cracks in the freeze-thaw process, and the 20% one also show slight cracks. While all in all, the degree of goodness in the freeze-thaw performance still shows the following sequence:the concrete with a 20% fly ash mixture, the concrete with a 0% fly ash mixture, and the concrete with a 40% fly ash mixture. The paper also gives some corresponding explanations on the working mechanisms of fly ash and sustained load on the performance of the concrete, and the paper also offers a relevant evaluation model. Testified by the experiments, the results prove to be comparatively credible.