civil engineer

civil engineer: 8 FACTORS AFFECTING SETTING & HARDENING OF CEMENT : 8 FACTORS AFFECTING SETTING & HARDENING OF CEMENT:- THE IMPACT OF CEMENT’S COMPOSITION:- The mineral composition of cement and the...

The various types of cement available in the market are as follows:- 1. Ordinary Portland Cement (OPC):-  Ordinary Portland cement is the most widely used type of cement which is suitable for all general concrete construction. It is most widely produced and used type of cement around the world with annual global production of around 3.8 million cubic meters per year.  This cement is suitable for all type of concrete construction. It   should not   be used   for construction work exposed to sulphates in the soil. Applications of 33 Grade Ordinary Portland Cement (OPC) :- ·          It is used for normal grade of concrete upto M-20, plastering, flooring, grouting of cable ducts in PSC works etc. The fineness should be between 225 and 280. Application of 43 Grade Ordinary Portland Cement (OPC) :- ·          It is the most widely used general purpose cement. F...

8 FACTORS AFFECTING SETTING & HARDENING OF CEMENT:- THE IMPACT OF CEMENT’S COMPOSITION:- The mineral composition of cement and their ratios are the main factors affecting the setting and hardening of cement. As mentioned above, various mineral components will reveal different characteristics when reacting with water. For example, the increase of C3A can speed up the setting and hardening rate of cement, and the heat of hydration is high at the same time.Generally speaking, if mixed materials are added into the cement clinker, the anti-erosion will increase, and the heat of hydration and the early strength will decrease. THE MIXING AMOUNT OF GYPSUM:-Gypsum is called the retarding agent of cement which is mainly used for regulating the setting time of cement and is an indispensable component. Without gypsum, cement clinker can condense immediately by mixing with water and release heat. The major reason is that C3A in the clinker can dissolve in water qu...

 These compounds contribute to the properties of cement in different ways     Tricalcium aluminate, C3A:-It liberates a lot of heat during the early stages of hydration, but has little strength contribution. Gypsum slows down the hydration rate of C3A. Cement low in C3A is sulfate resistant.  Tricalcium silicate, C3S:-This compound hydrates and hardens rapidly. It is largely responsible for portland cement’s initial set and early strength gain.    Dicalcium silicate, C2S: C2S hydrates and hardens slowly. It is largely responsible for strength gain after one week.   Ferrite, C4AF:This is a fluxing agent which reduces the melting temperature of the raw materials in the kiln (from 3,000o F to 2,600o F). It hydrates rapidly, but does not contribute much to strength of the cement paste. By mixing these compounds appropriately, manufacturers can produce different types of cement to suit several construction environments. Settin...

          The various constituents combine in burning and form cement clinker. The compounds formed in the burning process have the properties of setting and hardening in the presence of water. They are known as Bogue compounds after the name of Bogue who identified them. Le-Chatelier and Tornebohm have referred these compounds as Alite (C3S), Belite (C2S), Celite (C3A) and Felite (C4AF). The following Bogue compounds are formed during clinkering process. The properties of Portland cement varies markedly with the proportions of the above four compounds, reflecting substantial difference between their individual behaviour. Tricalcium Silicate :- It is supposed to be the best cementing material and is well burnt cement. It is about 25-50% (normally about 40 per cent) of cement. It renders the clinker easier to grind, increases resistance to freezing and thawing, hydrates rapidly generating high heat and develops an early ha...

: T he function of various ingredients of an ordinary Portland cement, as mentioned above, are as follows :--          1)   Lime (CaO):       This is the important ingredient of cement and I s proportion is to be carefully maintained. The lime in excess makes the cement unsound and causes the cement to expand and disintegrate. On the other hand, if lime is in deficiency, the strength of cement decreases and it causes cement to set quickly. Functions of Lime:- ·          Presence of lime in a sufficient quantity is required to form silicates          and aluminates of calcium. ·          Deficiency in lime reduces the strength of property to the cement. ·          Deficiency in lime causes cement to set quickly. ·          Excess lime mak...