Creep Model Of Fly Ash Concrete With Time And Load Dependant Mechanical Properties

The mechanical properties of concrete will develop as the curing ages increase. Because of the secondary hydration caused by the fly ash, the increasment is particularly considerable. When a permanent load is applied, the development of some mechanical properties of the concrete will be affected. However this phenomenon has not been paid enough attention yet, the influence of the mechanical properties of fly ash concrete varies as time and load varies on the creep of fly ash concrete also has not been studied thoroughly. Nearly every country’ codes and popular models always assume the mechanical properties are fixed, so the corresponding results lack not only the exact physical significance but also the necessary accuracy.Based on the existing theories and experiment data, a fly ash concrete compressive strength prediction model and an elastic modulus prediction model considering the action of sustained loads were established, which would be applicable for the creep model of fly ash concrete. Each prediction model has considered many essential factors, such as water to cement ratio, the content of fly ash, air content, cement density, curing temperature, stress levels, age of loading and so on. Compared with experimental data, the regression precision of the prediction model is validated.According to the two mechanical properties prediction models of fly ash concrete, a creep prediction model of fly ash concrete based on B3model was proposed, which considerates the mechanical properties vary as time and load varies. Through regression of much experiment data, the coefficients in the B3model have been modified. The prediction of the new models has a good agreement with the test results. At last, the effect of the varied mechanical properties with time and load on each parts of the creep strain has been analyzed by the new creep model.