Application of ultrasonic pulse velocity for assessment of thermal expansion coefficient of concrete at early age

Abstract

Early age deformations, in concrete, may lead to cracking reducing its mechanical properties and service live. Cracking risk analysis is an essential part of a concrete design, and coefficient of thermal expansion of concrete is indispensable for this purpose. In this paper, an approach that utilizes ultrasonic pulse velocity measurements for assessment of thermal expansion coefficient of concrete at the early age is proposed. An expression for the calculation of the coefficient of thermal expansion was derived based on the theory of poromechanics. Free shrinkage and ultrasonic pulse velocity of cement paste with water to cement ratio of 0.33 were measured starting from the casting, in order to validate the formula. The calculated values were in an agreement with the data found in the literature, though the effect of self-desiccation was not captured. In addition, the calculated value of thermal expansion coefficient was used for decoupling of autogenous and thermal shrinkage of cement paste. Decoupled linear autogenous shrinkage was compared to the autogenous shrinkage measured by volumetric method.