Studies And Procedures For The Control Of Cracking In Mass Concrete Structures

Studies and Procedures for the Control of Cracking in Mass Concrete Structures

Studies and Procedures for the Control of Cracking in Mass Concrete Structures

Studies and Procedures for the Control of Cracking in Mass Concrete Structures

Cracking occurs in mass concrete when tensile stresses exceed the tensile strength of the concrete. Most of these stresses are caused by restraint against volume change; others occur because of loading conditions and the configuration of the structure. To estimate future tensile stresses, temperature studies must be made to determine the temperature changes which will occur in a structure from the time concrete is first placed in the structure until the structure is in normal operation. These temperature changes are made a part of the design and construction of the structure. The range or amplitude of mean concrete temperature in a mass concrete structure is of primary interest, but temperature gradients are also investigated. The heat of hydration of the cement, the concrete mix proportions, the diffusivity of the concrete, amplitudes of air and reservoir temperatures, and solar radiation affect the concrete temperatures. Knowing the concrete temperatures and temperature changes to be encountered, the width and length of the construction block is determined, the precooling and/or artificial cooling measures are selected, and construction requirements are determined. Included in the latter are surface treatments, operation of cooling systems, height differentials, and foundation irregularities. (Author).