An elastic model to quantify the effect of moisture on the mechanical properties of concrete at the time of test

This paper describes the detailed development of a mathematical model for d etermining the effect of moisture on the mechanical properties of concrete at the time of test. Based on the theory of elasticity it focuses on the st ress distribution around spherical cavities in concrete filled with differe nt types of inclusions. Results obtained from the mathematical model have a ssisted in interpreting a number of experimental phenomena that have been t he subject of long-term controversy. In particular the model explains why c ompressive strength tests yield higher measured values for dry concrete spe cimens than for otherwise identical wet specimens, while the measured value s of static modulus exhibit the opposite effect. It also provides an explan ation as to why measured tensile strength values obtained from direct tensi on, tensile splitting or torsion tests are largely independent of moisture content. The model provides an analytical tool for studying the interdepend ence between the mechanical properties of concrete and its moisture content . It also yields essential input for the computational simulation of the be haviour of concrete structures that are subjected to large changes of moist ure condition. Moreover; it provides a method for analysing the stresses at the surface of any type of inclusion but particularly for cavities filled with incompressible liquids under any stress field.