Cement IS 269
cement is used to bind the materials in concrete The manufacturing process includes Proportioning of raw materials like chalk or limestone,Grinding and burning at 1400-1450OC in rotatory kiln. Due to intense heat the material becomes like spherical balls called clinkers. Gypsum is then added in 3-4%. Cement is formed by grinding the clinkers to required fineness.
Tricalcium Silicate (C3S) hardens rapidly and is largely responsible for initial set and early strength. In general, the early strength of portland cement concrete is higher with increased percentages of C3S. Dicalcium Silicate (C2S) hardens slowly and contributes largely to strength increases at ages beyond 7 days. Tricalcium Aluminate (C3A) liberates a large amount of heat during the first few days of hardening and, together with C3S and C2S may somewhat increase the early strength of the hardening cement (this effect being due to the considerable heat of hydration that this compound evolves). It does affect set times. Tetracalcium Aluminoferrite (C4AF) contributes very slightly to strength gain. However, acts as a flux during manufacturing. Contributes to the color effects that makes cement gray.
1. the bright grey colour indicates fresh cement. 2. The greasy touch when cement is rubbed in hand with fingers indicates pure cement.3. Shake small quantity of cement and water in a jar and allow it to settle. The foregin particles will float on surface. 4 Prepare a cement paste with 0.3 w/c and allow it to settle for 24 hours. The good quality of cement will resist pressure of a thumb.
Tricalcium Silicate (C3S) hardens rapidly and is largely responsible for initial set and early strength. In general, the early strength of portland cement concrete is higher with increased percentages of C3S. Dicalcium Silicate (C2S) hardens slowly and contributes largely to strength increases at ages beyond 7 days. Tricalcium Aluminate (C3A) liberates a large amount of heat during the first few days of hardening and, together with C3S and C2S may somewhat increase the early strength of the hardening cement (this effect being due to the considerable heat of hydration that this compound evolves). It does affect set times. Tetracalcium Aluminoferrite (C4AF) contributes very slightly to strength gain. However, acts as a flux during manufacturing. Contributes to the color effects that makes cement gray.
1. the bright grey colour indicates fresh cement. 2. The greasy touch when cement is rubbed in hand with fingers indicates pure cement.3. Shake small quantity of cement and water in a jar and allow it to settle. The foregin particles will float on surface. 4 Prepare a cement paste with 0.3 w/c and allow it to settle for 24 hours. The good quality of cement will resist pressure of a thumb.
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