超高韧性水泥基复合材料干缩性能及其对抗裂能力的影响

新近研制的超高韧性水泥基复合材料（Ultra High Toughness Cementitious Composite,简称UHTCC,国外称之为Engineered Cementitious Composites，简称ECC）具有优良的韧性和能量吸收能力，在直接拉伸荷载作用下表现出应变硬化和多点开裂等特性。本文通过干燥收缩试验，在与素混凝土、纤维混凝土进行对比的基础上，评价了UHTCC的干缩性能。试验结果表明：UHTCC的干缩主要发生在早期；早期的湿养护可避免UHTCC水分的过快蒸发，减小其干缩速度，但是却使其最终的干缩值大大增加；PVA纤维对UHTCC的干缩值影响不大。通过抗裂能力参数，结合已完成的约束收缩试验结果，对较大的干缩量并不有利约束条件下材料抗裂能力的传统概念进行了修正，指出对修复材料来说干缩量的大小仅仅表征了材料性能的一个物理参数，决定其材料抗裂能力的是其非线性变形能力的大小。最后给出了符合UHTCC干缩变形的收缩表达式。

Study on Drying Shrinkage behavior of Ultra High Toughness Cementitious Composites and its influence on the cracking capacity

Ultra High Toughness Cementitious Composites(UHTCC) ,which shows the observed strain-hardening behavior and multiple cracking under the uniaxial tensile load, has excellent toughness and remarkable energy absorption ability. Through the experiment of drying shrinkage, drying shrinkage property of UHTCC at early age was investigated and compared with plain concrete and traditional fiber reinforced concrete. The experimental results indicated that drying shrinkage of UHTCC mainly occurred at early age and the evaporation speed of water contained in the UHTCC can be slowed down by wet curing at early age, which leads to a reduction in the rate of drying shrinkage of UHTCC at early age but a increase in ultimate drying shrinkage deformation, moreover, and that PVA fiber has little influence on the drying shrinkage of UHTCC. Combined cracking potential parameter with the test results of restrained shrinkage which has been done, the traditional concept which higher drying shrinkage strain has no avail on the cracking capacity of restrained materials is revised. It can be considered that drying shrinkage strain is just a physics parameter for repair materials and it is the plastic straining performance that determines the cracking capacity of materials. Finally the expression for describing the drying shrinkage deformation of UHTCC is present.