微膨胀抗冲磨混凝土早期徐变理论与试验研究

Study on calculation starting point of autogenous volume deformation based on thermal stress test

早期徐变特性是开裂敏感性评价中很重要的因素,为建立精度更高的微膨胀抗冲磨混凝土早期徐变模型,提高早期混凝土应力计算精度、裂缝预测和控制的能力,本文基于丹麦标准TI-B102(95)的徐变试验测试方法,针对混凝土早龄期徐变测试需要,将初始加载龄期从3d提前到20h左右、将龄期3d前的加卸载周期加密至1 d左右和每10 min自动采集变形数据3个方面,对丹麦技术研究所提出的早期徐变测试方法做进一步改进;通过间歇式加卸荷载的特殊加载方式,在大量试验数据的拟合和优化基础上,得到早期徐变模型的黏性和弹性系数,获得了拟合相关性系数大幅度提高(达到0.96)的早期黏弹性模型。该方法的引用和改进,可以弥补目前国内在早期徐变测试领域的空白。

Focusing on the point problem involved in the calculation of autogenous volume deformation by the standard test method,this paper takes the micro-expansive abrasion-resistant concrete as the research object and improves the ASTM C1074method for activation energy tests.In this paper,a more accurate calculation is devised for the activation energy of hydration reaction of cementitious materials,from which the equivalent age of the specimen under the actuual temperature conditions can be obtained.Using the characteristics of thermal stress tests and adopting the equivalent age corresponding to the first zero stress as the effective starting point,we establish an improved autogenous volume deformation model based on the one put forward by the Japan Concrete Institute.With the Maximum expansion value of autogenous volume deformation as a cutoff point,the improved model has the unique ability to simulate the deformation before and after the point separately,which provides a good reference for the establishment of a more accurate anti-crack model.