早期预拌混凝土抗拉性能的试验研究

Experimental Research on the Tensile Property of Premixed Concrete at Early Ages

在混凝土工程中包括强度和极限拉伸的抗拉力学性能是很重要的指标,然而因轴心受拉试验存在难度以及国内外对极限拉伸没有统一的试验方法造成相关的试验研究结果离散.为较精确地得到混凝土轴心抗拉和劈裂强度之间的关系以及早期拉伸变形值,利用自行设计制作的混凝土轴心受拉试验装置成功地解决了试件对中困难的问题,并对工程中常用的三个强度等级的预拌混凝土进行了4个龄期(3d,7d,14d,28d)的试验,得出了预拌混凝土强度、轴拉弹性模量和极限拉伸值随龄期的变化规律以及极限拉伸变形值的估算公式.轴拉和劈裂强度之比随龄期增长而减小,二者微观破坏机理不同;拉压关系与规范公式符合较好.

The tensile property such as strength and the ultimate strain is an important index in the concrete engineering, yet for the difficulty of the axial tension test, the experimental methods of the ultimate tensile are not uniform and the experimental research about it is discrete at home and abroad. To get more precise tensile deformation of concrete at early ages and the relationship between the axial tension and splitting strength, the difficulty that the load is truly axial is successfully over come by the designed experimental apparatus for concrete of the direct tension. The experiment is performed on three different concrete mixes at 3 d, 7 d, 14 d, 28 d. The changing relationship of the strength, the axial tension modulus of elasticity and the ultimate tensile at early ages of the premixed concrete along with the ages is obtained, and the estimated formula of ultimate tensile deformation is given. The ratio of the axial tension to the splitting strength decreases along with the ages increasing, the microcosmic mechanism is different between the axial tension failure and the splitting strength failure. The relationship between the tension and the compression is well matched concrete standard formula.