Строительные материалы

- 88 -Строительные материалы / Building materials5. PORTLAND CEMENTPlan5.1. The composition of Portland cement.5.2. Mineralogical composition of Portland cement clinker. The influence of the mineralogical composition of Portland ce-ment clinker on its properties.5.3. Physical and mechanical properties of Portland cement. Types of Portland cement.5.1. The composition of Portland cementGeneral characteristics and material composition of Portland ce-ment. Portland cement was invented in 1824 by Englishman Joseph Aspdin and simultaneously with it the Russian industrialist Egor Alievym. Portland cement is a hydraulic binder, which is 70–80 % of highly basic calcium silicate, obtained by firing at a temperature of 1450 °C the raw mix of limestone and clay followed by grinding product calcination (clinker) in fine powder together with gypsum and mineral additives.Natural gypsum is added to clinker during grinding in the amount of 4–5 % of the clinker. The addition of gypsum plays an important role as a regulator of setting time. Without addition of gypsum ce-ment will be very quick to grab and have a reduced strength.When grinding the clinker in an amount up to 20 % can be added the active mineral additives. Use additives of a sedimentary origin: diatomite, Tripoli (can be entered up to 10 %); volcanic – volcanic ash, tuff, pumice (15 %), and the domain granulated slag (to 20 %). Depending on the content of mineral additives Portland cement has a key: PC-D0 (without additions), PC-D5 (5 % additives), MI-D20 (up to 20 % of additives).Chemical composition of Portland cement clinker expressed by the content of oxides (by weight). The main ones are: СaO 63–66 %, ЅіО2 – 21–24 %, of Al2O3 4–8 % and Fе2О3 – 2–4 %, the total con-tent of which amounts to 95–97 %. In small amounts in the various compounds may include MgO, Na2O, K2O, TiO2, Cr2O3, P2O5, play a role in the properties of Portland cement. The mineral composi-