Hardening stresses are generated as concrete hardens when the volume shrinkage of the concrete mortar is restrained by the aggregates. In the early stages of concrete curing, random cracking tends to occur because the structural strength of a concrete structure is relatively low and is likely exceeded by the concrete shrinkage-induced hardening stress. This is the primary cause of the initial damage in concrete. To investigate the initial damage in concrete, an exponential model for strain hardening is combined with a spline interpolation method to characterize the anisotropic hardening process in a three-phase structure that consists of aggregates, cement mortar and an interfacial transition zone (ITZ). A nonlinear analysis using a stress/strain softening damage model is then performed to analyze the characteristics of the shrinkage-induced initial damage in the concrete and the influence of the aggregates on the structural damage. To calculate the magnitude of the initial damage in concrete, damaged and undamaged concrete specimens are subjected to uniaxial loads. The results show that the shrinkage-induced damage initiates at the surfaces of aggregate particles and in the ITZs and then propagates into the cement mortar. The initial damage to the concrete is influenced by the volume fraction and geometric characteristics of the aggregate. These characteristics are analyzed using a random aggregate model and compared with computed tomography images of a cross section of concrete.

Due to factors such as seasonal variations in the solar azimuth angle and the masking of a dam body by itself or by a mountain, different areas of a high arch dam absorb significantly different amounts of solar radiation, which is likely to result in an uneven temperature distribution on the surface of the high arch dam and, subsequently, in unfavorable stress during the high arch dam's construction and operation. Therefore, in calculations of the dam body's temperature and for crack control, the effect of solar radiation should be taken into account accurately. Based on the mask algorithm, as well as local meteorological conditions, the effect of solar radiation is included in simulations of temperature and for crack control in high arch dams in the southwestern region. The engineering examples show that when solar radiation is included, the calculation's accuracy improves significantly.

Purpose: At present, using the finite element method is difficult to efficiently and accurately construct the temperature field of mass concrete based on temperature measurement points. Thus, there is a need to propose a method for improvement.Design/methodology/approach: This study developed an implicit finite element method that digitally constructs the temperature field of mass concrete based on temperature measurement data. That is, in the proposed method of this paper, the temperature of the measuring point is also one of the boundary conditions, which real-time corrects the calculation error.Findings: In this method, during the digital construction of the temperature field, the computed temperature approaches the actual measured value at the point of measurement with increasing iteration steps. Using this method and sufficient temperature measurement data, the errors in calculation conditions (such as the boundary conditions, the initial casting temperature and material parameters) can be automatically corrected during the iterative computation process.Originality/value: This new method can improve calculation accuracy and allows the digitally constructed temperature field to converge to its true value with sufficient measurement data.

The adiabatic temperature rise of early-age concrete can be precisely tested by the device. However, the insufficient accuracy of testing device can lead to inaccurate measurements of adiabatic temperature rise of later-age concrete. The purpose of this paper is to create a model to predict the hydration heat of later-age concrete. Based on the previous studies, it is known that the heat release of the concrete is accomplished with the increment of the concrete strength and concrete strength can be accurately measured. Thus, a preliminary later-age hydration heat model was established. The correction of the model was verified through experiments.