The construction of dams usually requires the placement of mass concrete many feet thick. The cement for this type of concrete should be carefully selected. Mass concrete issues usually require Type II cement, accelerating admixtures and cementitous materials in excess of 600 pcf. Thick concrete sections generate massive amounts of heat due to the hydration of the cement and can get trapped. There is a large temperature gradient between the interior of the concrete mass and the exterior sruface which generates thermal stresses and immediate cracking of the concrete.
In my opinion, 1" diameter pvc pipes should be placed within the concrete mass at 2 to 4 ft on center and pumped with very cold water to transfer the heat of hydration to the water. The water will come of the concrete mass at a very high temperature.
Optimal Concrete Mix Design:
Use low heat cement, Type II, not Type I/II, because it has the lowest heat of hydration
The concrete mix should contain flyash used to replace 25 to 40 percent of the cement because its heat of hydration is about half that of cement.
The water/cement ration should be as low as reasonably practicable. This increases the efficiency of the cementitous materials, and decreases the likelihood of bleeding and segregation. The minimum w/c ratio is in the order of 0.35 to 0.40, but achieving a workable mix at this w/c ratio will require the use of admixtures.
The total cementitous materials content should be as low as possible to achieve the required compressive strength at the required age. Acceptance criteria strength should be 42 or 56 days, not the usual 28 days.
Use larger and better graded aggregates. The max size of the aggregates should be about 3/4 of the smaller of rebar spacing and clear cover.
Aggregates such as limestone, granite, or basalt should be used to reduce the thermal expansion and potential for thermal cracking.