高性能混凝土板式构件的早期收缩特性及预测模型

Prediction model and shrinkage character of high performance concrete plate component at early age

以桥面板等高性能混凝土板式构件为研究对象,通过实验测试了板式构件不同截面厚度位置处早期收缩分布情况,探讨混凝土早期收缩变形与温度、湿度发展过程。结果表明,混凝土板式构件的内部厚度方向不同位置处的相对湿度随龄期都呈现逐渐减小趋势,并呈现两阶段特征,同时,混凝土板式构件早期收缩变形厚度方向不同步,导致板式构件表面产生拉应力,当拉应力大于当时混凝土的抗拉强度时,混凝土表面就会出现浅层裂缝,这与实际工程中发现的板式构件表面开裂情况相吻合。混凝土板式构件早期收缩变形与相同配合比混凝土的早期自由收缩变形进行比较,引入相对约束度并建立了混凝土板式构件早期收缩变形的预测模型,并验证了该模型的准确性,其特点是能预测高性能混凝土板式构件不同截面厚度位置的早期收缩变形,对控制混凝土桥梁板式结构的早期收缩裂缝具有实际意义。

Shrinkage distribution on the early-age in different height of high performance concrete plate component and the developing process of early-age shrinkage,temperature and humidity with age are investigated.The results showed that relative humidity is decreased and presenting two stage features with age in different height of high performance concrete plate component.At the same time,the early-age shrinkage is out-sync along different height of high performance concrete plate component,what generates surface tensile stress of plate component.When the tensile stress is larger than the tensile strength of concrete,it products surface shallow cracks in plate component.This is the same as surface cracking situations found in actual engineering.Meanwhile,by comparing the early-age shrinkage of concrete platecomponents and the early-age free shrinkage of the same concrete,prediction model of early-age shrinkage of plate components introducing degree of relative constraint is established,and the accuracy of the prediction model is verified.This model can predict the early-age shrinkage deformation in different height of high performance concrete plate component.This result has practical significance to control the early-age shrinkage crack of concrete bridge plate.