ABSTRACT
For cement factor in kilograms per cubic meter, multiply the tabulated value in sacks (94 lb) percubic yard by 55.767.
For aggregate size in millimeters, multiply values in inches by 25.4.
5.1 BUILDING MATERIALS
5.1.1 Concrete
Table 5.1.1-1 CONCRETE FOR VARIOUS TYPES OF CONSTRUCTION
Portland cement is a mixture consisting mainly of calcium and silicon oxides (as calcium silicates) in powder form with particle sizes largely in the range 10 to 50 μm. While the composition is approximately 65% CaO, 21% SiO2, and 7% Al2O3 (balance from other oxides), the actual compounds are 3CaO·SiO2, 2CaO·SiO2, 3CaO ·Al2O3, and 4CaO·Al2O3·Fe2O3. The proportions of these actual compounds will vary with the type of cement. When water is added and the mixture hardens, the heat of hydration is
approximately 100 cal/g cement (180 Btu/lb). The heat is released gradually as hydration proceeds, with a shrinkage of about 8% compared with the total volume of cement-plus-water in the original mix. Shrinkage is minimal if original water content is low. To accelerate the setting of cement, especially in cold weather, calcium chloride (2% or less of weight of cement) often is added. In very hot weather retarders are sometimes used to delay hardening.
