Development Of Mechanical Properties Of Fly Ash Concrete With Age Under Sustained Loading

The mechanical properties of fly ash concrete will develop as the curing ages increase, which also reflects a maturing process of concrete. When a permanent load is applied, the development of some mechanical properties will be affected. However this phenomenon has not been paid enough attention yet. The study of the influence of sustained loads on the development of compressive strength and elastic modulus of fly ash concrete will have a profound significance on pre-stressed structures and other concrete structures that have to withstand long-term sustained loads. At the same time, it will also benefit the later maintenance and reinforcement. In this paper, the experimental and theoretical research of compressive strength and elastic modulus of fly ash concrete under the action of sustained loads is carried.The experimental study of fly ash concrete with a permanent load applied is carried. The stress level is0.2of their compressive strength during seven days, and four different ages are selected. Compressive strength and elastic modulus are tested at every age, and then they are compared with those specimens without any loads applied. Test results show that:the compressive strengths of fly ash concrete with0.2fractions stress applied are higher than those without stress applied at all ages, and the growing rate is faster as the age increases; As to the elastic modulus, it is also higher of specimens with stress applied than those without, but it is not obvious when companied to compressive strength.According to the test results, a theoretical exploration is made. First, the enhancing effect of sustained loads to compressive strength and elastic modulus is explained from the mechanism. Second, based on the compressible packing model (CPM) of fly ash concrete compressive strength prediction model and elastic modulus triple sphere model, new models considered the action of sustained loads are established. Third, parameters' fitting in new-models is done by using test results. Fourth, parameter analysis and experimental verification of new models are made. Analysis shows that the prediction of new models has a good agreement with the test results.