Applicability Of Equivalent Age Method For Concrete Thermal Cracking Control At Early Ages

Quality control during construction is one of the challenges of today's engineering practice, with regard to both the loss of durability and the functionality of the structures being built. In concrete technology, cracking is a cause of major concern. As a result of temperature gradients and restraint conditions, thermal stress occurs and may induce cracks in concrete.Determining whether the cracks may develop is complicated by the fact that both the stress development and strength evolution are related to curing temperature and time. The equivalent age method based on the Arrhenius law can be applied successfully to predict the characteristics which are needed to control the risk of cracking in concrete through the use of numerical tools such as the finite element program ANSYS.The four main parts included in this thesis are as the following:1. The theoretical basis of the equivalent method is introduced and using the equivalent age method ,an aging model is established to describe the evolution of the mechanical properties of the material during the hydration process.2. The hydration heat model of concrete is established using the concept of equivalent age and the finite element program ANSYS is used to calculate the temperature field in concrete structures.3. The thermal stress field is calculated using the elasticity modulus which is calculated by the average equivalent age in concrete structures.4. The risk of thermal cracking is estimated by comparing induced thermal stress with concrete tensile strength and possible corrective actions to limit it are demonstrated.The study of this thesis has demonstrated the following conclusions: 1. The equivalent age method is perfectly suitable to predict the evolution of concrete mechanical properties even in constant temperature.2. With the hydration heat model based on the equivalent age concept, the temperature field of early age concrete structure can be successfully calculated.3. The equivalent age method is extended successfully to the concrete cracking control in structures through the use of the finite element program ANSYS.