Influence of Temperature in the Early-age Elastic Modulus Evolution of Cement Pastes and Concrete

抄録

The influence of temperature on the hydration of cementitious materials has been traditionally modelled using the maturity concept and Arrhenius law. This approach yields a single material property, called apparent activation energy (E_a), that describes the whole temperature dependence. Determining E_a experimentally has sparked controversy, such as whether the different properties (e.g., compressive strength, tensile strength, E-modulus) exhibit different E_a, whether a single E_a value exists for the entire hydration process, or whether cement paste and concrete possess the same E_a. Furthermore, studies measuring E_a from elastic modulus measurements are truly scarce, likely due to experimental challenges with measuring this property at early-ages. This work investigated the influence of temperature on the elastic modulus evolution of cement paste and concrete. A single mix for each material was tested with the EMM-ARM (Elasticity Modulus Measurement through Ambient Response Method) methodology under three different isothermal conditions. The resulting elastic modulus evolution curves were used to derive E_a evolution curves from two traditional computation methods: the ‘speed’ method and the ‘derivative of speed’ method. Results showed that the elastic modulus evolution of both materials initially presented a constant E_a, independent of temperature and hydration development as preconized by the classical Arrhenius law. However, as hydration progressed to later stages, the activation energy exhibited evident dependencies on both temperature and hydration levels. Cement paste and concrete consistently exhibited different E_a values throughout hydration, with concrete having higher values. The use of the E_a curves to superimpose the different experimental elastic modulus evolution curves by means of the equivalent age concept led to near-perfect superpositions, strengthening the validity of this concept when applied to elastic modulus evolution.