Cracking Controlled in Massive, Reinforced Structural Concrete by Ap·plication of Mass Concrete Practices

It was concluded that massive concrete structural sections of powerplants and pumping plants could be made more crack-free and more watertight if cold concrete of lowest feasible cement content was used and if the opportunity was taken to require a minimum number of construction and contraction joints. Together with this, a special effort was made to secure watertightness of horizontal construction joints by special attention to requirements for cleanup and bonding. Placement of the special concrete selected is discussed. The lean concrete is shown to be ample in strength. Performance reports, after nine of the ten plants have been exposed two to six cold seasons, indicate very few cracks between contraction joints spaced at a minimum of 70 ft (21 m), and little or no leakage into submerged pumping plants, as com­ pared with others where the special procedures described were not followed.