Cement is an adhesive material & binder, that sets and hardens independently, and can bind other materials together. Cement is a hydraulic binder, i.e. it hardens when water is added.
Cement is a mixture of compounds, consisting mainly of silicates and aluminates of calcium, formed out of calcium oxide, silica, aluminum oxide and iron oxide. Cement is manufactured by burning a mixture of Calcareous (limestone) and argillaceous (clay) material at high temperatures in a kiln, and then finely grinding the resulting clinker along with gypsum.
The Varieties of Cements manufactured by Binani Cement Limited are:
Depending upon the strength requirement OPC is classified in three different grades as per the requirements of Bureau of Indian Standards (BIS). The classification is mainly based on the minimum compressive strength of cement sand mortar cube in N/mm2 at 28 days. The grades are:
Blended cements are Portland-based cements that include supplementary cementitious materials (SCMs), such as ground granulated blast-furnace slag, fly ash or other pozzolanas, such as silica fume or metakaolin. Two types of blended cements are popularly manufactured in India – Portland Pozzolona Cement (PPC) and Portland Slag Cement (PSC).
PPC is manufactured either by intergrinding Portland Cement Clinker, flyash and gypsum to the required fineness or by blending ground pozzolana with Portland cement. Fly ash is a byproduct in coal based thermal plants, which is processed and used in manufacturing of PPC.
Binani Cement is manufactured from high grade & quality lime-stone which is available in our thandi beri & amli mines. The main advantage of Binani cement is its stringent Quality Control & superior Raw material which in turns produce better quality of cement which having high compressive strength, Better particle size distribution & anti corrosive properties.
A pozzolana is a siliceous or aluminosiliceous material that, in finely divided form and in the presence of moisture, chemically reacts with the calcium hydroxide released by the hydration of portland cement to form calcium silicate hydrate and other cementitious compounds. Pozzolans and slags are generally categorized as supplementary cementitious materials or mineral admixtures.
The Portland Pozzolana Cement makes concrete more impermeable and denser as compared to Ordinary Portland Cement. The long-term strength (90 days and above) of Pozzolana cement is better compared to OPC. The pozzolanic material reacts with calcium hydroxide liberated by the hydrating Portland Cement and forms cementitious compounds generally known as C-S-H gel. The reaction can be given as under:
The flyash converts Ca(OH)2 in to useful cementitious compound (C3S2H3) thereby increasing the properties of hardened concrete.
The Portland Pozzolana Cement produces less heat of hydration thereby controlling temperature differentials, which reduces thermal strain and resultant cracking in mass concrete structures like dams. It also conserves mineral resources in the sense that lesser amount of limestone is used. Moreover, it is eco-friendly as it helps in disposing fly ash which otherwise creates havoc in the environment. The carbon-di-oxide emission, which contributes to global warming, is also reduced due to lower consumption of clinker. Normally one tone of carbon-di-oxide is released into the atmosphere for every tone of clinker produced.
As per the above stated answer of question no.9, Blended cement (PPC or PSC) is the best cement in terms of durability & strength. However, house builder can also go for OPC 43 or OPC 53 grade cement for their construction.
The term setting implies solidification of the plastic cement paste to hardened state or stiffening of cement paste. The paste does not solidify suddenly; it requires considerable time to become fully rigid. The time taken to solidify completely marks the final set, which should not be too long.
Gypsum is a retarder & retards the chemical reactions i.e. controls the flash setting.
“Soundness” refers to the ability of a hardened cement paste to retain its volume after setting without delayed destructive expansion. This destructive expansion is caused by excessive amounts of free lime (CaO) or magnesia (MgO). If free lime is within the prescribed limits then cement is said to be sound.
The colour of the cement depends on the raw materials used. If the raw materials contain more iron resulting cements will be darker. Colour has no significance on any properties of cement. The strength of the cement is dependent on the correct proportion of raw material mix