A novel test method for characterizing tempo-spatial variations in elastic modulus of underwater concrete

• Published in: Journal of Building Engineering Vol. 76; p. 107096
• Main Authors: Yang, Fujian, Li, Ruixin, Hu, Dawei, Iqbal, Sayed Muhammad, Zhou, Hui, Guo, Feng
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.10.2023
• Subjects: Coupling erosion; Durability testing; Elastic modulus; Indentation technique; Stress state; Elastic modulus; Durability testing; Stress state; Indentation technique; Coupling erosion
• ISSN: 2352-7102; 2352-7102
• DOI: 10.1016/j.jobe.2023.107096

Concrete structures used in underwater engineering, such as immersed tube tunnels, are subject to a range of challenging coupling circumstances including mechanical load (M), fluid flow (F), fluid pressure (P), and chemical attack (C). Concrete in different areas also experiences compressive or tensile stress under mechanical load. However, most experimental setups only consider limited coupling scenarios, such as M-C, M-F-C, or M-P-C, and the sample is typically in a single stress state, either compressive or tensile. To overcome these limitations, a novel stress-seepage-chemical coupling erosion setup (SSC-CES) was developed to perform durability tests on concrete. This setup allows for simulation of the service conditions of an immersed tube tunnel, including M-F-P-C coupling and distribution of compressive and tensile stresses. This study presents also a detailed description of the setup's components, configurations, and working principles, and discuss how sealing and alignment problems for the sample were addressed to ensure accurate fluid pressure and stress loading. The indentation technique was furthermore applied to obtain the local mechanical properties of different erosion areas, enabling analysis of tempo-spatial variations in elastic modulus. Finally, a test was conducted to examine the M-F-P-C coupling effect using the developed SSC-CES and indentation technique. Results indicated that the elastic modulus weakened from the erosion surface and gradually approached the initial value with increasing depth. Additionally, it showed a transition from slight increase to gradual decrease with erosion time. Notably, the elastic modulus in the tensile stress area was considerably lower than that in the compression stress area. These test results confirm the reliability of the developed SSC-CES and the rationality of the analysis method using micro-indentation technology. The system effectively supports the study of durability evaluation of immersed tube tunnels under M-F-P-C coupling. •A novel setup was developed to perform the durability tests for the concrete material.•Mechanical load-fluid flow-fluid pressure-chemical attack coupling effect is considered.•Influence of the stress state on the durability of concrete is considered.•Tempo-spatial variations in elastic modulus is shown using indentation technique.•Elastic modulus in tensile stress area is considerably lower than that in compression stress area.