Properties of cement covered by API specificationsĬhemical properties and physical requirements are summarized in Tables 3 and Table 4, respectively. No additions other than calcium sulfate or water, or both, shall be interground or blended with the clinker during manufacture of Class H well cement.This product is intended for use as a basic well cement.No additions other than calcium sulfate or water, or both, shall be interground or blended with the clinker during manufacture of Class G well cement.Available in ordinary, O, MSR, and HSR grades (similar to ASTM Spec.This product is intended for use when conditions require high early strength.Available in both MSR and HSR grades (similar to ASTM Spec.This product is intended for use when conditions require moderate or high sulfate resistance.Available only in ordinary, O, grade (similar to ASTM Spec.This product is intended for use when special properties are not required.The different classes of API cements for use at downhole temperatures and pressures are defined next. The oil industry purchases cements manufactured predominantly in accordance with API classifications as published in API Spec. Sulfate-resistant grades are used to prevent deterioration of set cement downhole caused by sulfate attack by formation waters. Oilwell cements are also available in either moderate sulfate-resistant (MSR) or high sulfate-resistant (HSR) grades. API Classes G and H are the most widely used. API currently provides specifications covering eight classes of oilwell cements, designated Classes A through H.
For these reasons, different specifications were designed and are covered by API specifications. Cements used in wells are subjected to conditions not encountered in construction, such as wide ranges in temperature and pressure. These cements are designed to meet the varying needs of the construction industry. C150 provides for eight types of Portland cement: Types I, IA, II, IIA, III, IIIA, IV, and V, where the “A” denotes an air-entraining cement. Of these groups, the best known to the oil industry are ASTM, which deals with cements for construction and building use, and API, which writes specifications for cements used only in wells. In the U.S., there are several agencies that study and write specifications for the manufacture of Portland cement. Minor impurities in the raw material also must be taken into account, as they can have a significant effect on cement performance. Examples of such additives are:Ĭalculations also take into account argillaceous or siliceous materials that may be present in high proportions in some limestones, as well as from the ash produced when coal is used to fire the kiln. In some cases, additional or corrective components must be added to produce the optimum compositions. Portland cements are usually manufactured to meet certain chemical and physical standards that depend upon their application. Table 2-Typical Composition And Properties Of API Classes of Portland Cement When these clinkers hydrate with water in the setting process, they form four major crystalline phases, as shown in Table 1 and Table 2. After it cools, the clinker is pulverized and blended with a small amount of gypsum to control the setting time of the finished cement. These materials are blended together, either wet or dry, and fed into a rotary kiln, which fuses the limestone slurry at temperatures ranging from 2,600 to 3,000☏ into a material called cement clinker. Iron and alumina are frequently added if they are not already present in sufficient quantity in the clay or shale. The basic raw materials used to manufacture Portland cements are limestone (calcium carbonate) and clay or shale.
#Concrete compositions series
Proportioning of the raw materials is based on a series of simultaneous calculations that take into consideration the chemical composition of the raw materials and the type of cement to be produced: American Society for Testing and Materials (ASTM) Type I, II, III, or V white cement, or American Petroleum Institute (API) Class A, C, G, or H. Portland cements can be modified easily, depending on the raw materials used and the process used to combine them. 4 Properties of cement covered by API specifications.
0 kommentar(er)
