ECC材料力学性能与本构关系研究进展

混凝土在国内外应用广泛,但普通混凝土材料存在抗拉强度低、韧性差和脆性特征明显等缺点。自20世纪90年代采用性能驱动设计方法(PDDA)成功配制工程水泥基复合材料(ECC)后,仅在几年时间里,ECC材料受到了研究者的广泛关注。相比普通混凝土,采用PDDA得到的ECC的外掺纤维与基体界面有良好的粘结作用,这使得ECC材料具有应变硬化和多缝开展等重要特征。由于ECC优异的力学性能,使用其替代混凝土便成为解决混凝土脆性、裂缝开展等相关问题的一种有效的新途径。 然而, ECC的制备极不容易,由于基体胶凝材料产地不同或者纤维种类不同,某一地区配制成功的配合比大多无法适用于其他地区。因此,根据当地情况进行ECC材料的配合比设计仍然是各国学者青睐的课题。一方面,欲使用ECC代替混凝土用于建筑结构等,就必定要深入研究ECC材料层面的基本力学性能。建立ECC的本构模型对ECC构件甚至结构层面的研究都十分重要,但相关研究较少。另一方面,由于ECC材料良好的裂缝控制能力,国内外学者也致力于使用ECC材料进行结构加固修复的研究。 各国学者先后成功配制极限拉应变大于3%的ECC,这为进一步广泛开展ECC的研究和应用创造了很好的条件,用于配制ECC的纤维种类也更加丰富。在ECC拉伸、压缩、弯曲和剪切等大量的材料试验研究基础上,近几年,一些科研团队开始尝试用ECC部分甚至完全代替混凝土来浇筑梁、柱等构件,然后进行ECC构件层次的力学性能和耐久性等研究；另有部分研究人员也致力于建立ECC的本构模型,开展数值模拟分析。此外,由于ECC优异的力学性能,也有学者提出可以采用3D打印技术来建造无筋ECC建筑。 本文从ECC材料层面的单轴单调拉压力学性能、单轴循环拉压滞回性能、多轴力学性能及破坏准则、ECC与普通钢筋和纤维增强塑料(FRP)筋两种筋材的粘结性能方面进行综述,相应介绍了几种本构模型并简要对其进行评价,以期为用ECC代替混凝土进行建筑结构设计、选取本构模型进行数值模拟分析、编制规范和技术规程等提供参考。最后,对今后进一步开展ECC力学性能研究、建立本构模型提出展望。

A Survey on Mechanical Behavior and Constitutive Model ofEngineered Cementitious Composite

It is universally known that concrete is widely used in construction over the world. Yet ordinary concrete materials possess the disadvantages of low tensile strength, poor toughness, and obvious brittleness. Since 1990s, engineered cementitious composite(ECC) has been successfully prepared by employing the performance driven design approach (PDDA), and then ECC has captured extensive research attention in only a few years. Compared with ordinary concrete, there is a favorable interaction between fibers and matrix of ECC obtained by PDDA, which endows ECC with unique features like strain hardening and multiple cracks development. Thanks to the excellent mechanical behaviors of ECC, replacing concrete with ECC has become an effective approach to resolve the problems associated with the brittleness and crack development of concrete. Nevertheless, the preparation of ECC is extremely difficult. Due to the origin diversity of the cementitious materials or the different types of fibers, successful mix proportion for preparing ECC in a certain region cannot be applied to other regions usually. Therefore, proportion design of ECC materials according to the local conditions has become a popular topic among researchers all over the world. On the one hand, in order to use ECC as a substitute for conventional concrete in building structures, it is necessary to study the basic mechanical properties of ECC in depth. Establishing the constitutive model of ECC is quite important to the study of ECC components and structures, but there is few related studies. On the other hand, due to the great crack control capability of ECC, scholars at home and abroad are also devoted to the study of structural reinforcement and repair by ECC. The ECC with ultimate tensile strain larger than 3% has been successfully prepared by foreign and domestic scholars successively, which has laid a good foundation for the extensive research and application of ECC. And the types of fibers which can be used for preparing ECC are also more abundant. On the basis of numerous tensile, compression, bending and shearing test of ECC materials, some research teams begin to use ECC to partially or completely replace concrete in construction of beams, columns and other components in recent years. Then, the mechanical behaviors and durability of the ECC components can be studied. Other researchers also dedicated to the establishment of the ECC constitutive model and carried out numerical simulation analysis. In addition, due to the excellent mechanical properties of ECC, some scholars have proposed that 3D printing technology can be used to construct steel free ECC building. In terms of ECC materials, this article reviews the uniaxial monotonic tension or compression behavior, the uniaxial cyclic tension and compression hysteresis behavior, the multi-axial mechanical behavior and failure criterion, the bond behavior of ECC with steels or FRP bars. Several corresponding constitutive models are briefly introduced and evaluated, aiming at providing references for the structural design of buildings with ECC instead of concrete, selection of constitutive model for numerical simulation, and compi-lation specifications and technical regulations. Finally, further study on the mechanical behavior of ECC and the establishment of constitutive models are prospected.