Concrete, or cement, is composed of different ingredients to create an approved American Society for Testing and Materials (ATSM) specified formula. Each concrete formula falls under specific classifications determined for certain uses. Concrete mixes must pass rigorous testing through ATSM before they can be used as a building materials. The testing determines the viability and longevity of the cement, as well as the application most suitable.
Hydraulic Cements
Most cement types are composed of a hydraulic cement base. Hydraulic cements, in themselves, are used for broad applications in general construction. Type GU is for general use and can be applied in sidewalks, driveways, and other more common buildings. Type HE is for high early strength applications. It is a lighter weight cement designed for height specific uses. Type MS has a moderate sulfate resistance, making it appropriate for light to medium sulfate infused environments. Type HS has a high sulfate resistance making it usable in extreme sulfate environments. Type MH is for moderate heat of hydration making it good for climates with wide ranging temperatures. Type LH is for low heat of hydration used in average climates.
Portland Cements
Portland cements possess mostly hydraulic calcium silicates. Ten types of cement are recognized by the ASTM. Types I and IA are essentially the same used in areas that do not require special propertied cements. The difference for Type IA is that it is an air retaining cement. All Portland types ending with "A" are air retaining, making them more porous. Types II and IIA are moderate sulfate resistant containing less than 8 percent tricalcium aluminate. Types II(MH) and II(MH)A contain both moderate heat of hydration characteristics combined with moderate sulfate resistance. Types III and IIIA are finely ground for denser strength and share the chemical make-up of Type I. Type IV has a slower strength development and is used for large concrete structures. Type V has a high sulfate resistance with less than 5 percent tricalcium aluminate.
Blended Cements
Blended cements are composed of two or fine materials such as hydrated lime, slag cements, calcined clay, fly ash, silica fume, Portland cements, other pozzolans, and pre-blended combinations of these materials. Type IS is for Portland blast furnace slag cement, which is a combination of slag cement and Portland cement. Type IP is for Portland-pozzolan cement, which is a combination of Portland cement and pozzolan that does not contain more than 40 percent pozzolan. Type IT is a ternary cement composed of 25 percent slag cement, 15 percent pozzolan, and a third ingredient subject to the application.
Expansive Cements
Expansive cements are designed to expand as they dry and set. There are three different types of expansive cements, although the United States only allows using one type on American soil--Type E-1(K). Type E-1(K) is comprised of lime, Portland cement, calcium sulfate, uncombined calcium oxide, and anhydrous tetracalcium trialuminosulfate. In applications where drying causes shrinkage, expansive cements are used to stabilize long-term dimensions of post-tensioned structures and to induce tensile stress in reinforcements.
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