The Role of Dilation in Shrinkage Cracking of Concrete

The aim of this investigation was to study the role of dilation in delaying shrinkage cracking of concrete and the possibility of producing shrinkage crack-free concrete. The experimental programme consisted of two parts. In the first part, end-restrained concrete beams were water-cured for one and three days before drying under controlled temperature (35 °C) and relative humidity (25%) conditions. In the second part, concrete beams were water-cured for one and three days before drying in outdoor summer conditions in Baghdad, Iraq. For all specimens, various parameters were measured, including free-shrinkage strain, tensile strain capacity, elastic tensile strain capacity, creep in tension and cracking time. The experimental results show that none of the concrete specimens dried under natural outdoor conditions cracked in spite of high temperatures (up to 60 °C) and low relative humidity (less than 15%). This is due to dilation in the form of increased creep in tension with variations in temperature and relative humidity. Increasing water-curing duration usually delays shrinkage and always delays or prevents cracking; it increases tensile strain capacity, which reduces the probability of cracking for all specimens dried in natural or controlled conditions.