基于全级配试件性能的大坝混凝土抗裂性分析

为了解大坝实体混凝土的抗裂特性,系统测试了分别用灰岩和花岗岩人工骨料制备的全级配混凝土(最大骨料粒径为150 mm)的力学性能、变形性能和热学性能,基于上述性能计算分析了全级配混凝土的抗裂指数,并与湿筛二级配混凝土(最大骨料粒径为40 mm)进行了对比分析。试验结果显示,全级配混凝土各项性能与湿筛二级配混凝土性能之间存在一定的比例关系:7～180 d龄期,抗压强度比在0.85～1.16之间,轴向抗拉强度比在0.49～0.70之间、极限拉伸值比在0.60～0.83之间。计算结果显示,不考虑干燥收缩作用,灰岩骨料、花岗岩骨料全级配混凝土的抗裂指数分别在0.79～1.17之间和0.53～0.75之间,高于湿筛二级配混凝土的抗裂指数。研究结果表明,由于全级配混凝土中骨料的体积比大于80%,骨料岩性、物理性能对混凝土极限拉伸值、徐变、热膨胀系数等性能起决定作用,因此对混凝土抗裂性能具有重要影响,灰岩骨料混凝土的抗裂指数高于花岗岩骨料混凝土,抗裂性能更好。

Fully-graded specimen performance-based analysis on crack resistance of dam concrete

In order to understand the anti-cracking characteristics of dam concrete，the mechanical properties，deformation performances and thermal properties of the fully-graded concretes ( with the maximum aggregate particle size of 150 mm) respectively mixed with limestone and granite artificial aggregates are systematically tested． Based on the performances mentioned above，the anti-cracking index of the fully-graded concrete is calculated and analyzed，for which a comparative analysis is made with the wetsieved secondary aggregate grading concrete ( with the maximum aggregate particle size of 40 mm) ． The experiment result indicates that a certain proportion relationship is there between all the performances of the fully-graded concrete and those of the wetsieved secondary aggregate grading concrete，i． e． the age of 7～ 18 d，the compressive strength ratio between 0. 85 and 1. 16，the axial tensile strength ratio between 0. 49 and 0. 70，the ultimate tensile value ratio between 0. 60 and 0. 83． The calculation result shows that without considering the drying shrinkage effect，the anti-cracking indexes of the fully-graded concretes mixed with both the limestone aggregate and the granite aggregate are between 0. 79 ～ 1. 17 and 0. 53 ～ 0. 75 respectively，which are higher than that of the wet-sieved secondary aggregate grading concrete． The study result demonstrates that as the volume of the aggregate in the fully-graded concrete is larger than 80%，the aggregate lithology and the physical performance have the decisive effects on the performances of the ultimate tensile value，the creep，the thermal expansion coefficient，etc． of concrete，thus have important effects on the anti-cracking performance of concrete，while the anti-cracking index of the limestone aggregate concrete is higher than that of the granite aggregate concrete with a better anti-cracking performance．