TEMPERATURE CONTROL MEASURES IN MASS CONCRETE DAMS

Abstract

Temperature control in mass concrete dams has become a must these days due to the increase in dimensions of these structures and also the rapid rate of construction. The problem of cracking associated with the generation of heat of hydration in cement is twofold: (1) When a large difference in temperature exists between the interior of a mass and the surface, thermal cracking may result. (2) Even if the concrete attains its maximum tempera-ture without cracking, as it cools to its final stable temperature, the decrease in size which accompanies the cooling may result in cracking if the mass is restrained against movement by adjacent concrete or by the foundation. The solution for these is to restrict the maximum temperature attained by the concrete. This may be done by giving proper attention to any or all of the following measures ; selection of type and quantity of cement or other admixtures, control of lift thickness and time interval between lifts$ proper construction programme, precooling of the concrete ingredients, post-cooling Hof the concrete, its curing, insulation etc. All the above temperature control measures are discussed in detail in the chapters to come and much effort has been put in giving the examples of various dams throughout the World, mostly from U.S.A. and India. In Chapter II, the temperature studies have also been covered to a certain extent. The arrangements for cooling of concrete in some important projects has been dealt in Chapter VI. The projects chosen are having some or the other distinctions or peculiarities in them. The necessity of avoiding the longitudinal joints, if it is possible to do soy by putting the required effort in controlling tempera-ture through other ways has been advocated in the conclusion.