界面过渡区对混凝土徐变性能的影响

Influence of Interface Transition Zone on Creep Properties of Concrete

为分析界面过渡区对混凝土徐变性能的影响,运用Laplace变换原理,建立了考虑界面过渡区黏弹性的混凝土徐变模型,将该模型与不考虑界面过渡区的混凝土徐变预测模型进行对比和实验验证。结果表明:考虑界面过渡区的混凝土徐变模型与实验数据吻合较好,该模型能够反映界面过渡区在混凝土徐变中的作用,加载龄期为365 d时,界面过渡区使粉煤灰掺量为0、30%、60%的混凝土徐变度分别提高了45.7%、25.1%、66.7%。根据该模型,分析了不同加载龄期时3种粉煤灰掺量的界面过渡区对混凝土徐变贡献度。掺加粉煤灰的界面过渡区在早期对混凝土徐变贡献度高于不掺的基准组,后期基准组的界面过渡区对混凝土徐变贡献度不断增加,这是由于界面过渡区在荷载作用下不断弱化导致。而掺加粉煤灰的2组,随加载龄期的增长,粉煤灰二次水化反应使界面过渡区不断增强,界面过渡区对混凝土徐变贡献度不断降低。通过分析界面过渡区参数对混凝土徐变的影响发现,当界面过渡区弹性常数0.0001<E_(itz)<0.01,黏性系数0.1<η_(itz)<10时,可以较好地描述不同界面过渡区的混凝土徐变。

A creep prediction model of concrete considering the viscoelasticity of interface transition zone was proposed based on the Laplace transform principle to analyze the influence of interface transition zone on the creep performance of concrete.The proposed model was compared with a model of concrete creep non-considering interface transition zone and verified by the related experiments.The results show that the data predicted by the concrete creep model considering the interfacial transition zone is consistent with the experimental results.The model can be used to analyze the effect of interface transition zone on the creep properties of concrete besides the experiments.The specific creep of concrete specimens with different fly ash contents(i.e.,0,30%and 60%)is increased by 45.7%,25.1%and 66.7%,respectively,when the loading age is 365 d due to the interface transition zone.The contribution of the interface transition zone of concrete specimens with different fly ash contents to the creep of concrete at different loading ages was analyzed via the prediction by the model.The interfacial transition zone of concrete with fly ash to the concrete creep contributes greater than that without fly ash.The interface transition zone of the baseline group in the later period has an increasing contribution to the concrete creep due to the continuous weakening of the interface transition zone under the load.For the concrete specimens with fly ash,the interface transition zone continuously enhances and the contribution of the interface transition zone to the creep of concrete c ontinuously reduces with the increase of loading age because of the fly ash secondary hydration.The analysis of the influence of interface transition zone parameters on the concrete creep indicates that the concrete creep of different interface transition zones can be well described when the interface transition zone elasticity constant is in the range of 0.0001<E_(itz)<0.01 and the viscosity coefficient is in the range of 0.1<η_(itz)<10.