Transformation of Singular Joint Deformations in Concrete Elements into Plural Cracks

接缝是板形混凝土构件的组成部分，例如工业区、停车场和交通区、挡土墙等，以避免不必要的裂缝。混凝土构件的热或湿致变形集中在这些接缝中。同时，关节必须紧密。传统接缝密封胶的耐久性只有几年，导致维护成本高。因此，关节是这个系统固有的弱点。在应用的研究项目中，应研究一种替代概念，即在无钢筋/仅弱钢筋混凝土构件的接缝上覆盖薄的碳筋混凝土层（CRC）。其基本思想是将基构件中相对较大的单一关节运动转化为覆盖层中多个较小的裂缝。这种薄的crc层在这种应用中受到特殊的应力，既在轴向，由于节理的运动，也垂直于它，例如，由于土压力或交通荷载。为了达到这个目的，必须在接头的两侧中断粘结，使其保持一定的距离，以便产生相应的扩展范围，使细裂纹能够发展。为了评价这种混凝土层对桥梁接缝的适用性，一方面需要研究混凝土层在相应的高应变下的裂纹发展情况，另一方面需要研究在相应的暴露条件下混凝土层在基础构件上的粘结行为。应该考虑到这些板/层中的应力是双轴的，并且由于节理运动，crc层中可能出现拉应力和压应力。具体而言，拟进行以下研究：•在CRC层：—在双轴拉压应力下CRC层的承载和变形行为—碳筋与混凝土之间的双轴粘结建模•在接缝区域的复合体系：-复合材料体中crc层在拉伸应力（打开接头）下与粘结制动变化的微裂纹的形成-压缩应力（关闭接头）下与粘结制动变化的crc层的稳定性-在该区域的循环应力情况下发生渐进分层的风险。

Joints are integral part of slab-shaped concrete components, e.g. industrial areas, parking and traffic areas, retaining walls, etc., in order to avoid undesired cracking. Thermally or hygrically induced deformations in the concrete component are concentrated in these joints. Simultaneously, joints must be tight. The durability of conventional joint sealants is limited to only a few years, resulting in high maintenance costs. Therefore joints are inherent weak points in this system. In the research project applied, an alternative concept shall be investigated in which the joints in unreinforced / only weakly reinforced concrete components are covered with thin, carbonreinforced concrete layers (CRC). The basic idea is that the relatively large singular joint movements in the base component are converted into plural, considerably smaller cracks in the covering layer. Such thin CRC-layers are subjected to special stresses in this application, both in the axial direction due to the joint movement and perpendicular to it, e.g. due to earth pressure or traffic loads. For this purpose, the bond must be interrupted at both sides of the joint for a defined distance in order to create corresponding expansion ranges in which the fine cracks can develop. In order to evaluate the suitability of such CRC-layers for bridging joints, on the one hand the crack development in CRC-layers at correspondingly high straining, and on the other hand the bond behaviour of this layer on the base component under the relevant exposures shall be investigated. It should be taken into account that the stresses in such slabs / layers are of two-axial nature and that tensile as well as compressive stresses can occur in the CRC-layer as a result of the joint movements. In concrete terms, following studies are intended: • At the CRC layers: – Load-bearing and deformation behaviour of CRC-layers under biaxial tensile and compressive stresses – Modelling of the biaxial bond between carbon reinforcement and concrete • At the composite system in the joint area: – Formation of micro-cracks in the CRC-layer in composite bodies under tensile stress (opening joint) with variations in bond braking – Stability of the CRC-layer under compressive stress (closing joint) with variations in bond braking – Risk of progressive delamination in case of cyclic stresses in this area.