There have been notable negative experiences when alkali-reactive aggregates have been used. A low alkali cement is normally needed to protect against the destructive expansion of the concrete which generally occurs due to the alkali-aggregate reaction. (a chemical reaction between the alkalis in the cement and the reactive aggregates. Another means of controlling the reactions alkali-aggregates is the use of suitable fly ash or natural pozzolan. If it is necessary to use a highly reactive aggregate, a low alkali cement and pozzolan should be used. Another design recommendation is the type of cement to be used. Type 2 cement is normally used by the Bureau of Reclamation in mass concrete dams. Limitations on the heat of hydration of this cement are specified when deemed necessary to minimize cracks in the concrete structure generally reduces the heat of hydration of cement to an acceptable level, particularly when Type 2 cement is used in conjunction with other heat reduction methods. These include using a lower cement content and using pozzolan as part of the cementitious material, using a pipe cooling system, and using a specified maximum temperature for placing concrete, which can be up to 50 degrees F Using all or some of these methods usually reduces or eliminates the need for stringent limitations on the heat of hydration of concrete. However, a 58% limitation on tricalcium aluminate plus type 2 tricalcium silicate content is required where the heat of hydration must be kept low. Further limitation on the heat of hydration, if more rigorous control of the heat requirement is required can be achieved with a type 2 cement by providing a maximum limitation on the cement of 70 calories per gram at 7 days or 80 calories per gram at 28... ... half of the paper ...... for the transportation of concrete whose aggregate size is less than 7.5 cm. Concrete pumping must be done in such a way as to provide concrete without air pockets or interruptions. Placing Concrete: Concrete should be placed at a uniform rate throughout concrete placement. Each layer is compacted well before laying the other layer. Generally the thickness of the layers must not exceed the following limits. Reinforced concrete-25 cm. Vibrated concrete-45 cm. Hand compacted concrete - 30 cm. The concrete is placed vertically on top of the other layer so as to avoid damage, segregation and air pockets. Compaction must be carried out as quickly as possible after installation. When concrete is placed in forms, the temperature may increase, as suggested by some previous studies, so measures must be taken to reduce such effects. They are