Ratnayake Karuna Arachchige Shan Dilruksha, Leung Christopher Kin Ying
Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong SAR, China.
Materials (Basel). 2024 May 17;17(10):2407. doi: 10.3390/ma17102407.
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.
应变硬化水泥基复合材料（SHCCs）在拉伸时具有延展性以及呈现出多条细密、可控的自裂纹，这使其在提高民用基础设施耐久性方面具有吸引力。这些细裂纹是防止水和有害化学物质进入结构从而实现钢筋防锈的关键。然而，多项研究表明，当SHCC构件承受持续恒定荷载时，实验室中显示的短期细裂纹最终可能会超过设计规范中规定的可接受裂纹宽度。然而，在实际结构中，构件中的钢筋也分担荷载，因此内部的SHCC可能不会承受恒定荷载；所以，裂纹扩展不会那么严重。本研究聚焦于将SHCCs用作钢筋混凝土外层以提高耐久性时的徐变行为。通过使用一种夹具在钢筋构件和SHCC之间专门分担持续弯矩，开发了一种模拟此类系统中各种应力 - 应变状态的新方法。所开发的荷载分担系统能够在施加荷载期间监测钢筋和SHCC内部的应力随时间的变化，同时确保能够接触到SHCC层以进行应变/裂纹监测。结果发现，SHCC层中裂纹随时间的扩展远不如在恒定荷载下显著，因此从长期来看仍可确保对水/化学物质渗透的抵抗力。所获得的关于应力、应变和裂纹张开随时间变化的信息将有助于建立SHCC构件徐变行为的通用模型。
