THEORETICAL PREDICTION OF DRYING SHRINKAGE OF CONCRETE

The water potential that controls moisture movement in concrete is a kind of stress that also causes concrete to shrink and to expand. An explicit equation that shows the relationships between water potential and drying shrinkage was derived through a mathematical process. In this study, only two micromechanisms that are valid when the relative humidity is over 50% are considered among the three shrinkage mechanisms. The theory developed shows that the magnitude and the shape of the drying-shrinkage curve depends on the compressibility of the ingredients, the amount of aggregate, and the pore structure of the cement. The relationship between drying shrinkage and water potential is found to be a logarithmic curve. Thermocouple psychrometers are embedded in a concrete slab to measure the water potential. The test results prove the validity of the theory, and show how to use the derived equation.