外文翻译---波特兰水泥的分法及生产.docxVIP

外文资料译文Portland cement of its Types and Manufacture of Portland cementPortland cement is made by heating a mixture of limestone and clay, or other materials of similar bulk composition and sufficient reactivity, ultimately to a temperature of about 1450°C. Partial fusion occurs, and nodules of clinker are produced. The clinker is mixed with a few percent of gypsum and finely ground to make the cement. The gypsum controls the rate of set and may be partly replaced by other forms of calcium sulfate. Some specifications allow the addition of other materials at the grinding stage. The clinker typically has a composition in the region of 67% CaO, 22% SiO2, 5% Al2O3 , 3%Fe2O3 , and 3% of other components,and normally contains four major phases,called alite , belite , aluminate phase and ferrite phase . Several other phases, such as alkali sulfates and calcium oxide, are normally present in minor amounts.Alite is the most important constituent of all normal Portland cement clinkers,of which it constitutes 50%--70%.It is tricalcium silicate (Ca3SiO5)modified in composition and crystal structure by incorporation of foreign ions, especially Mg2+, Al3+ and Fe3+. It reacts relatively quickly with water, and in normal Portland cement is the most important of the constituent phases for strength development at ages up to 28 days, it is by far the most important. Belite constitutes 15%---30% of normal Portland cement clinker. It is declaim silicate (Ca2SiO4) modified by incorporation of foreign ions and normally present wholly or largely as theβ polymorph. it reacts slowly with water , thus contributing little to the strength during the first 28 days ,but substantially to the further increase in strength that occurs at later ages .By one year, the strength obtainable form pure alit and pure belite are about the same under comparable conditions.The aluminates phase constitutes 5%--10% of most normal Portland cement clinkers. it is Tricalcium aluminates (Ca3Al2O6), substantially mo