Page - 1507 - in Book of Full Papers - Symposium Hydro Engineering

on the manufacturer’s certificates. In the early phases of construction, it may be prudent to arrange for comprehensive testing of the cement at frequent intervals until there is full confidence in the manufacturer’s test results. After that, physical tests should be carried out periodically. The tests that can realistically be performed at site are related to setting time and temperature. Table 2 shows QC chart of cementitious material. Table 2 Quality control chart of cementitious material 2.3. ADMIXTURES A number of chemical admixtures are available to improve the properties of fresh concrete and RCC. Admixtures commonly used in RCC and concrete are set retarders and water reducing/workability enhancing chemicals and air- entraining agents. Admixtures are available that combine more than one of these properties. For RCC dams, the effects of admixtures have to be tested with the various RCC mixes. These tests are typical setting times and workability (VeBe test). Poor or undesirable results can arise with particular products because of incompatibility with cement or pozzolan and with some types of aggregates and may arise with seasonal variations in air temperature. These cases require a change of type or brand of admixture. Such tests should be carried out periodically throughout the construction period. 2.4. WATER Water quality for RCC mixing should satisfy an appropriate standard with respect to the content of contaminants. Potable water is preferred for RCC as it has been filtered for contaminants. When potable water is not available, tests should be made with the precise source of construction water to validate the mix design and RCC properties. Any source of water may be used if the 7 and 28-day strengths of 5-cm cubic mortar specimens be at least 90 percent of the index mortar made using distilled water according to ASTM C109. Besides, the setting 1507