Assessment of the relationship between the initial temperature of concrete and the time intervals between layers of concrete placement to control early thermal cracking

Introduction. This article presents the results of a study on the development of a concrete mix incorporating fly ash, blast furnace slag, a superplasticizer, and a temperature-rise inhibitor to produce concrete with a compressive strength of 60 MPa after 28 days. The concrete mixture is intended for use in a massive concrete foundation measuring 4 meters by 4 meters by 4 meters. Methods and materials. Laboratory tests were conducted to determine the compressive and tensile strength of the concrete. Additionally, tests were performed to evaluate the temperature rise under adiabatic conditions. Results. Using numerical simulation, the study investigated the influence of two factors on the temperature regime for the given concrete composition, Vietnamese climatic conditions, and the selected mass concrete structure: the temperature of the placed concrete and the time interval between the placement of adjacent blocks forming the mass. Discussion. Based on the requirement that the temperature difference between the center and the surface of the concrete mass should not exceed the permissible limit of 20 °C, an equation has been derived relating these two factors. Graphs of the corresponding functions have also been constructed. Conclusion. The research results can serve as practical guidelines for the construction of monolithic concrete foundations, helping to minimize the risk of thermal cracking and ensure the durability and quality of the structure.