• Post-tensioning keeps the concrete in compression, which controls shrinkage
cracking and reduces the possibility of opening up of construction joints. When tensile stresses do develop in a post-tensioned member, their magnitude is much smaller than in an equivalent reinforced concrete member. A post-tensioned floor, therefore, has better watertightness than a reinforced concrete floor. This is particularly important in car parks where de-icing salts often cause corrosion of reinforcement in a reinforced concrete floor. The hairline cracks over supports in a reinforced concrete continuous floor may allow water to penetrate and freeze, causing spalling of concrete.