CEMENT
cement,binding material used in construction and engineering, typically made by heating a mixture of limestone and clay until it almost fuses and then grinding it to a fine powder. When mixed with water, the silicates and aluminates in to it undergo a chemical reaction; the resulting hardened mass is then impervious to water. It may also be mixed with water and aggregates (crushed stone, sand, and gravel) to form concrete
Modern portland cement is made by mixing substances containing lime, silica, alumina, and iron oxide and then heating the mixture until it almost fuses. During the heating process dicalcium and tricalcium silicate, tricalcium aluminate, and a solid solution containing iron are formed. Gypsum is later added to these products during a grinding process. Cement with a high aluminate content is used for fireproofing, because it is quick-setting and resistant to high temperatures; this with a high sulfate content is used in complex castings, because it expands upon hardening, filling small spaces.
10 precautions must be taken in storing cement Following 10 precautions must be taken in storing cement : Portland cement is a finely ground material. It, therefore, readily absorbs moisture even from the atmosphere. It is therefore essential to protect it from dampness during storage. Lack of proper care may cause setting of cement or reduction in its strength due to partial setting. (i) Walls, roof and floor of the building in which cement is to be stored should be completely waterproof. (ii) In case the cement store is newly constructed then its interior should have been thoroughly dried before cement is stored in it. (iii) Doors and windows should be properly fitted and should be kept shut. (iv) Except in case of dry concrete floor the cement bags should be stacked on wooden planks. (v) The bags should be stacked away from walls. A space of 25 cm all…
Learn : Different kinds of cement as per IS code :Rapid hardening or high early strength,Quick setting,High alumina,portland slag,Low heat,Air entraining Portland etc cement Different kinds of cement as per IS code Following are some of the Different kinds of cement as per IS code manufactured to suit the different requirements. Important Different kinds of cement as per IS code 1. Rapid hardening or high early strength cement. This cement gains strength faster than the ordinary Portland cement. Its initial and final setting times are the same as those of ordinary cement. It contains more of tri-calcium silicate and is more finely ground. It gives out more heat while setting and is as such unsuitable for mass concreting. It is used for such structures as are to be subjected to loads early e.g. repair of bridges and roads etc. It is more costly than the ordinary cement. It is…
Learn : Pozzolana, Natural Pozzolanas, Artificial Pozzolana,Clay pozzolana,cement sand mortars, Pozzolana when added to lime make it hydraulic and the resulting mortar will be stronger. POZZOLANAS These are siliceous materials having siliceous material but no binding values within themselves, will chemically react with Calcium hydroxide at ordinary temperatures and in the presence of moisture to form compounds possessing binding properties. Pozzolanas when added to lime make it hydraulic. The resulting mortar will be stronger than the ordinary lime mortar. Pozzolanas are divided into : (a) Natural Pozzolanas. (b) Artificial Pozzolanas. (a) Natural Pozzolanas. These are natural clay or siliceous volcanic materials having Pozzolanic properties. These occur in Pozzuoli near Vesuvins, south east France; the Azores; Canary islands; Germany, Grecian islands etc. (b) Artificial Pozzolana. There include powdered bricks, tiles, burnt clay (surkhi) and fly ash. Clay pozzolana have the folliwing advantages : Clay pozzolana replace cement to the extent of 20…
Learn : Testing portland cement,Consistency of standard cement paste with the help of Vicat's apparatus ,Soundness.with the help of "Le Chatelier's apparatus" TESTING PORTLAND CEMENT In this article learn 9 tests 1.samples for testing 2.Chemical composition 3.Fineness 4.Temperature for testing 5.Consistency of standard cement paste with the help of Vicat's apparatus 6.Soundness.with the help of "Le Chatelier's apparatus"7.Setting time.with the help of Vicat's apparatus 8.compressive strength 9.Tensile strength with the help of briquette testing machine. The Indian Standards Institution, New Delhi, has prescribed the following tests so as to control the quality of Portland cement. Samples for testing. Each sample for testing shall consist of an intimate mixture or approximately equal portions selected from at least 12 different bags or packages when the cement is not loose or 12 different positions in the heap or heaps when the cement is loose. Selection of samples shall be done in such a…
Manufacturing Of Cement. Manufacturing Of Cement. by any one of the two methods : (i) Dry process, and (ii) Wet process. In both these processes the three distinct operations of (a) Mixing, Ball mill (b) Burning, Rotary kiln and (c) Grinding are carried out. 1. Dry process. In this process lime stone and clay are ground separately to tine powders and are then mixed together in the desired proportions. Water is then added to it so as to get a thick paste of which cakes are then made, dried and burnt in kilns. To the clinker obtained after burning, is added three to four per cent of gypsum and ground to very fine powder. This powder is cement ready for use. This process is slow and costly. Also it is difficult to have the correct proportion of constituents and to do so is a cumbersome operation. The quality of…
Ordinary portland cement and its composition Cement, commonly used for normal construction work, is known as Ordinary Portland Cement. However, for use under specific conditions a variety of Ordinary portland cement and its composition are available these days. Its quick setting property, strength and case with which it can be used under variety of conditions has revolutionized the concept of construction and made it the most popular cementing material. It was first of all introduced in 1824 by Joseph Aspdin, a brick layer of Leeds, England. On setting, the colour of cement resembles the colour of rocks near Portland in England and hence the name of this cement. Below are discussed the composition, manufacture and tests etc. of Ordinary Portland Cement. 2. COMPOSITION Approximate composition of raw materials used for manufacturing Ordinary Portland Cement is : Calcium Oxide (CaO) = 60 to 65% Silica (S1O2) = 20 to 25% Aluminium…