A case study on early-age cracking of high-strength concrete construction by coupled thermal-mechanical analysis and field monitoring

• Published in: Case Studies in Construction Materials Vol. 21; p. e03436
• Main Authors: Wen, Tzu-Han, Yuen, Terry Y.P., Li, Victor K.S., Yeung, Albert T.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.12.2024; Elsevier
• Subjects: Autogenous shrinkage; Coupled thermal-mechanical analysis; Early-age crack; Field measurements; Heat of hydration; High-strength concrete (HSC); Large-diameter bored pile; Optical fiber temperature sensors; Stress-relaxation; Transient heat transfer; Large-diameter bored pile; Field measurements; High-strength concrete (HSC); Early-age crack; Heat of hydration; Optical fiber temperature sensors; Transient heat transfer; Coupled thermal-mechanical analysis; Autogenous shrinkage; Stress-relaxation
• ISSN: 2214-5095; 2214-5095
• DOI: 10.1016/j.cscm.2024.e03436

The use of high-strength concrete (HSC) in constructing high-rise reinforced concrete buildings and their deep foundations is becoming more popular because of the significant reduction in member size and, thus, self-weight in structural members. However, the higher cement content in HSC may result in increased heat of hydration and autogenous shrinkage, growing concerns about forming early-age cracks in HSC structural members. This case study assessed the early-age cracking of HSC in bored pile construction of high-rise buildings. A nonlinear transient coupled thermal-mechanical response analysis was performed to evaluate the potential of early-age cracking caused by the heat of hydration generated in the HSC using ABAQUS and two subprograms, USDFLD and UEXPAN. A 3-D finite element model was developed considering thermal effects, time-dependent evolution of early-age strength and stiffness of HSC, crack strain development, autogenous shrinkage, and stress-relaxation in the analysis. Field measurements were carried out on a 3-m diameter bored pile constructed using Grade C50/60 HSC (fck,cube = 60 MPa) for a high-rise building project in Hong Kong to evaluate the validity of the numerical model. Optical fiber sensors were used to monitor the temperature changes of the pile for approximately 380 hours after casting. The temporal and spatial temperature distributions measured in the field measurements agree well with the simulations. Large thermal gradients and high tensile stress zones were observed across the horizontal cross-sections of the pile, resulting in the formation of vertical annular cracks. Based on the results of the analysis, the maximum crack widths were predicted and compared with the durability crack width limits. •A novel coupled thermal-mechanical model was developed for the early-age cracking assessment of high-strength concrete piles.•The effects of hydration heat, transient thermal gradients, and autogenous shrinkage are rigorously considered.•Field temperature monitoring data acquired by optical fiber sensors are used to evaluate the validity of the model.•The evolutions of the temperature distribution, the stress, and strain fields were thoroughly investigated.•The formation mechanism of early-age annular cracks is proposed and its engineering implications are discussed.