PDF(Pubmed)
Abstract：
The ductility and exhibition of the multiple, fine, self-controlled cracking of strain-hardening cementitious composites (SHCCs) under tension has made them attractive for enhancing the durability of civil infrastructure. These fine cracks are key to preventing the ingress of water and harmful chemicals into the structure and thereby achieving steel reinforcement. However, several studies have suggested that the short-term fine cracks shown in the laboratory may end up exceeding the acceptable crack widths that are specified in design codes when SHCC members are subjected to sustained constant loads. In real structures, however, the load is also shared by the steel reinforcement in the member, so the SHCC within may not be under a constant load; therefore, the crack widening will not be as severe. This study focuses on the creep behaviour of SHCCs when they are applied as an external layer on reinforced concrete to enhance durability. A novel approach to simulate various stress-strain regimes in such systems is developed by using a fixture to share a sustained moment exclusively between a reinforcement member and SHCC. The developed load-sharing system allows stresses within the reinforcement and SHCC to be monitored against time during the imposed loading, while ensuring access to the SHCC layer for instrumentation and monitoring of strain/cracking. The time-dependent widening of cracks in the SHCC layer is found to be much less significant than that under constant loading, so resistance to water/chemical penetration can still be ensured in the long term. The obtained information on the variation in stress, strain, and crack opening with time will be useful for the development of a general model for the creep behaviour of SHCC members.
摘要：
多重性的延展性和展开性，好,应变硬化水泥基复合材料（SHCC）在张力下的自控开裂使它们对提高民用基础设施的耐久性具有吸引力。这些细小的裂缝是防止水和有害化学物质进入结构并从而实现钢筋加固的关键。然而,多项研究表明，当SHCC构件承受持续恒定载荷时，实验室中显示的短期细裂纹最终可能超过设计规范中规定的可接受裂纹宽度。在真实的结构中，然而,荷载也由构件中的钢筋分担，因此，内部的SHCC可能不会处于恒定负载下；因此，裂缝扩大不会那么严重。这项研究的重点是SHCC在钢筋混凝土上用作外层以增强耐久性时的蠕变行为。通过使用固定装置在加固构件和SHCC之间仅共享持续力矩，开发了一种模拟此类系统中各种应力-应变状态的新颖方法。开发的载荷分担系统允许在施加载荷期间对钢筋和SHCC内的应力进行监控。同时确保进入SHCC层进行仪表和应变/裂纹监测。与恒定载荷下相比，SHCC层中裂纹的随时间变化的加宽程度要小得多，因此，从长远来看，仍然可以确保耐水/化学渗透。获得的应力变化信息，应变，随着时间的推移，裂纹张开将有助于开发SHCC构件蠕变行为的通用模型。
