In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word “cement” traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick additives that were added to the burnt lime to obtain a hydraulic binder were later referred to as cementum, cimentum, cäment and cement.
Cement used in construction is characterized as hydraulic or non-hydraulic. Hydraulic cements (e.g., Portland cement) harden because of hydration, chemical reactions that occur independently of the mixture’s water content; they can harden even underwater or when constantly exposed to wet weather. The chemical reaction that results when the anhydrous cement powder is mixed with water produces hydrates that are not water-soluble. Non-hydraulic cements (e.g., lime and gypsum plaster) must be kept dry in order to retain their strength.
The most important use of cement is the production of mortar and concrete—the bonding of natural or artificial aggregates to form a strong building material that is durable in the face of normal environmental effects.
Concrete should not be confused with cement, because the term cement refers to the material used to bind the aggregate materials of concrete. Concrete is a combination of a cement and aggregate.
Portland cement
Cement is made by heating limestone (calcium carbonate), with small quantities of other materials (such as clay) to 1450 °C in a kiln, in a process known as calcination, whereby a molecule of carbon dioxide is liberated from the calcium carbonate to form calcium oxide, or quicklime, which is then blended with the other materials that have been included in the mix . The resulting hard substance, called ‘clinker’, is then ground with a small amount of gypsum into a powder to make ‘Ordinary Portland Cement’, the most commonly used type of cement (often referred to as OPC).
Portland cement is a basic ingredient of concrete, mortar and most non-speciality grout. The most common use for Portland cement is in the production of concrete. Concrete is a composite material consisting of aggregate (gravel and sand), cement, and water. As a construction material, concrete can be cast in almost any shape desired, and once hardened, can become a structural (load bearing) element. Portland cement may be grey or white.
SPECIFICATIONS
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ORDINARY PORTLAND CEMENT 42.5 R/N ACCORDING TO BRITISH STANDARDS 12/1996 OR ASTM C-150 |
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| SPECIFICATION CHEMICAL COMPOSITION: | |||
| CHEMICAL ANALYSIS | UNIT | CONTROL RANGE | TYPICAL |
| SILICON DIOXIDE (SiO2) | % | 20.80 – 23 | 21 |
| ALUMINIUM AXIDE (Al2O2) | % | 4.50 – 6.00 | 5.30 |
| FERRIC OXIDE (Fe2O3) | % | 3.10 – 6.00 | 3.30 |
| CALCIUM OXIDE (CaO) | % | 64 – 68 | 65.60 |
| MAGNESIUM OXIDE (MgO) | % | 1.70 – 3.00 | |
| SULPHUR TRIOXIDE (SO3) | % | 2.70 – 3.00 | 2.70 |
| LOS OF IGNITION (Loi) | % | 1.00 – 3.00 | 1.90 |
| INSOLUBLE RESIDUE | % | 0.10 – 0.70 | 0.40 |
| TRICALCIUM SILICATE (C3S) | % | 50.00 – 64.40 | 60 |
| DICALCIUM SILICATE (C2S) | % | 14.20 – 18.20 | 15 |
| TRICALCIUM ALUMINATE (C3A) | % | 6.00 – 9.50 | 8.05 |
| TRICALCIUM ALUMINO FERRICE (C4AF) | % | 10.50 – 12.00 | 9.76 |
| CHROMINUS ES (CR6) AT LEST FOR A 6 MONTHS
PERIOD |
<2ppm |
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| PHISICAL AND MECHANICAL PROPERTIES: | |||
| PHISICAL ANALYSIS | UNIT | CONTROL RANGE | |
| BLAIN | CM2/GR | 3.25 | |
| AUTOCLAVE EXPANSION | MM | 0.02 | |
| NORMAL CONSISTENCY | % | 27.50 | |
| INITIAL SETTING TIME | Hours : Mins | 3:25 – 4:50 | |
| FINAL SETTING TIME | Hours : Mins | 4:54 – 6:00 | |
| FINTES INDEX | CM2/GR | 2800 – 3040 | |
| COMPRENSIVE STRENGTH ISO/EN 19/200 | BS 4550 MORTAR | ||
| @ 03 DAYS | KG/CM2 | 26.50 – 34.20 | |
| @ 07 DAYS | KG/CM2 | 37.30 – 42.50 | |
| @ 28 DAYS | KG/CM2 | 52.80 – 54.60 | |
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