高强混凝土收缩徐变试验及预测模型研究

通过苏通大桥连续刚构所用高强混凝土的收缩徐变试验,以及其他几组不同强度等级的高强混凝土收缩徐变试验,探讨了目前常用收缩徐变模型对高强混凝土收缩徐变的适用性。试验结果表明,高强混凝土的徐变系数一般低于常用的徐变模型预测值;而现桥规采用的CEB-FIP90收缩模型有低估高强混凝土收缩发展的危险,并且,随着混凝土抗压强度的提高,预测精度有降低的趋势。针对高强混凝土收缩徐变的特点,提出了考虑混凝土强度因素的修正收缩、徐变模型。最后运用B3变异系数法比较了这几种模型预测高强混凝土收缩徐变的精度,比较结果表明,修正收缩、徐变模型对高强混凝土收缩徐变预测的精度相对于现有模型有较大提高。

Shrinkage and Creep Tests and Prediction Model of High-strength Concrete

Based on the shrinkage and creep tests of high-strength concrete used in the continuous rigid frame of Sutong Bridge and other several groups of concrete with different strength grades, the applicability of existing prediction models of creep and shrinkage to the high-strength concrete was discussed. The test results show that (1) the measured creep coefficients are generally lower than the prediction values of the creep models; (2) if the CEB-FIP90 shrinkage model adopted in the existing specification is used, there is a risk in underestimating the shrinkage strains, and the prediction precision decreases with the increase of the concrete compression strength. Due to the shrinkage and creep characteristics of high-strength concrete, the modified prediction models for creep and shrinkage of high-strength concrete were presented, considering the concrete strength influencing on creep and shrinkage. At last, the prediction precision of the models for concrete creep and shrinkage of high-strength concrete was compared with the experimental results by the B3 coefficient of variation method. The results of the comparison indicate that the modified prediction models for creep and shrinkage match the test data well.