With the way real estate outfits are springing up and growing stronger in Nigeria, there is no doubt that the sector has carved a niche for itself in terms of employment and provision of housing for many Nigerians; an area where the Federal and many state governments have failed over the years. One major product that plays a vital role for the real estate business is cement. Of course, everybody knows that there can be no construction without cement. When mention is made of cement in the country today, the biggest brands in that sector come to mind and they are Dangote, Lafarge and BUA cements.
In March 2019, Africa’s richest man, AlikoDangote disclosed that his Dangote Cement’s exports to other countries are targeted to rise to $600m annually, with the management intensifying efforts at actualizing the planned increase.
Declaring that his massive investments in Nigeria’s economy is borne out of his firm belief in her vast economic potential, Dangote said “by next year we will be the largest exporter of cement in sub-Saharan Africa with about $600 million worth of cement export to other African countries with limited access to limestone. In addition, we also have new terminals coming up at Onne and in Lagos and we are hopeful the congestion at Apapa will soon be behind us helping us meet our export targets.” That is just to show how fast growing the sector is and how important the product is to the everyday life of a developing nation like Nigeria.
Cement is a prominent construction material. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete. Cement is the most widely used material in existence and is only behind water as the world’s most-consumed resource. Builders say that apart from the beauty cement add to construction, it is majorly used in bonding different materials together. As important and widely consumed this product is, it will be a big surprise to discover that there are different types of cement manufactured to meet different physical and chemical requirements for specific construction projects.
Many collapsed buildings in the country according to Builders have been linked to the usage of substandard cement or usage of wrong type of cement simply because some of the employed builders do not know the difference in the types of cement in the market and their specific usage.
City People’s Brands & Product recently conducted construction site survey and realized that not many builders are aware of the different types of cement used in construction and their different uses. Hence, a need to sensitize builders and clients on the different types of cement and their usage.
Ordinary Portland Cementis the most common type of cement is manufactured and widely used worldwide. It is used for all ordinary purposes such as making concrete, mortar, plaster etc. OPC is available in three different grades namely grade 33, 43 and 53.Ordinary Portland Cementis mixed with aggregates, and water to make concrete, which is an essential modern building material. It is also used to make mortar for joining masonry and plaster to give perfectly finished walls. OPC has many applications such as in the manufacturing of grout, wall putty, solid concrete blocks, AAC blocks, and other types of cement.
Portland Pozzolana Cement (PPC) is a variation of ordinary Portland Cement (OPC), which includes a mixture of pozzolanic materials, OPC and gypsum. The different pozzolanic materials used are fly ash, rice husk ash, volcanic tuffs, etc. Fly ash is most commonly used pozzolanic material. The heat of hydration rate is lower in this type of cement. There are many advantages of PPC over PPC, which has made it prominent in the construction industry. Nowadays, some manufacturers are only manufacturing PPC. Portland pozzolanic cement is now used as a replacement of OPC. Apart from common applications, it is used in mass concrete constructions like high-rise buildings, underwater concrete structures such as bridges, piers, dams etc.
RAPID HARDENING CEMENT
Rapid Hardening Cement attains high strength in early days as compared to OPC. It has other properties quite similar to that of Ordinary Portland cement, but it is a bit finer than OPC. It has more lime and C3S than OPC which helps in gaining strength early. Rapid hardening cement is used when there is a need to remove formwork at an early stage for saving the cost of construction. It is also used in prefabricated concrete construction.
EXTRA RAPID HARDENING CEMENT
Extra Rapid Hardening Cementis obtained by addition of calcium chloride to rapid hardening cement. Calcium chloride added helps in accelerating the hardening and setting processes. The compressive strength of Extra Rapid Hardening Cementis about 25% higher than that of Rapid Hardening Cement at one or two days. Extra rapid hardening cement is used in cold weather concreting, to set the cement fast. It is also used in situations when formwork is to be removed early.
QUICK SETTING CEMENT
Quick Setting Cementsets faster as compared to OPC, but the rate of gain of strength remains the same. In these types of cement, the quantity of gypsum, which acts as a retarder is reduced. It has an initial setting time of 5 minutes and a final setting time of 30 minutes. This types of cement is used where a quick setting is needed in a very short period like underwater structures, cold and rainy weather conditions etc. Quick setting cement is also used in structural repairs where the setting is an important criterion.
LOW HEAT CEMENT
Low Heat Cementis obtained by reducing the content ofTricalcium aluminate (C3A)which is mostly related to the heat of hydration and increasing the content of C2A. The name itself indicates this type of cement will release low heat of hydration. Low heat cement has more initial setting time as compared to OPC.It is used in massive concrete construction like large footings, large raft slabs, gravity dams, thick pavements etc. Low heat cement is also used in the construction of hydraulic structures and retaining walls.
SULPHATE RESISTING CEMENT
SulphateResisting Cementis beneficial in the area where the concrete is vulnerable to Sulphatesattack. This type of has less contents of C3S and C4AF. SulphateResisting Cementis used where concrete has exposure to sea coast or soil or saline groundwater.
PORTLAND SLAG CEMENT
It is special blended cement with low heat of hydration. The by-product from a blast furnace, i.e. slag is used in the manufacturing of Portland Slag Cement. It is less expensive as compared to OPC. Portland slag cement has less heat of hydration as compared to OPC. It is used in mass concrete structures like dams, water treatment plants, marine and off-shore structures.
HIGH ALUMINA CEMENT
High Alumina Cementis obtained by melting bauxite during the manufacturing process of OPC. It has a high compressive strength and is more workable as compared to OPC. It attains high strength in less time and has initial and final setting time of 3.5 hours and 5 hours respectively. This type of cement is used where concrete structures are subjected to high temperatures like workshop, refractory, foundries etc. Also, it can be used where concrete is subjected to frost action and acidic action.
White Cementis obtained by using raw materials which are free from iron oxide in the manufacturing of cement. Lime and china clay are used in more amounts in its manufacturing. White cement has all other properties similar to an OrdinaryPortland Cement. It is expensive as compared to OPC. White cement is used for architectural purposes such as pre-cast curtain wall and facing panels etc. It is also used in making wall putty, tile grout, tile adhesive, etc. White cement is also used for external rendering as it provides a smooth and pleasing finish. It is also preferred for terrazzo flooring works.
ColouredCementis obtained by mixing Ordinary PortlandCementwith 5 – 10% mineral pigments. The pigments impart colours to the cement.This types of cement is widely used for decorative works in floors and ceiling. Coloured cement is commonly used in grouting of tiles.The cement is selected such that the colour of the grout and colour of tiles match perfectly for finishing the flooring.
AIR ENTRAINING CEMENT
Various Air Entraining agents such as resins, glues, sodium sulphate, etc. are added along with the clinker to produce air entraining cement. For the same water-cement ratio, air entraining cement has more workability as compared to OPC. This type of cement has more resistance to frost. But as it contains voids, it has less durability. Air Entraining Cementis used to fill up the gaps in concrete which are produced by the excessive amount of water during the casting of concrete members. It also used in cold weather when frost resistance in concrete is an important criterion.
Hydrophobic Cementis made by adding admixtures such as naphthalene soap, acidol, oxidised petroleum, etc. in the Ordinary Portland Cement. A water-repellent layer around the cement particles is formed, which would facilitate its storage for longer periods in extremely wet climatic conditions. In Nigeria, this cement is useful in certain places such as Lagos,Ondo, Plateau,etc., which get plenty of rainfall in the rainy season have high humidity in other seasons. Hydrophobic cement is used in the construction of dams, spillways, underwater constructions. It can also be used in cold and rainy weather conditions.
This type of cement is obtained by added plasticising materials such as limestone, hydrated lime, etc. in the clinker during manufacturing of OPC. It remains in the plastic state for a longer time so that the masonry units can be placed properly. The masonry cement is often used in brick, concrete block and stone masonry construction; also used to produce plaster.
OPC shrinks after setting, due to which shrinkage cracks are formed. Expansive cement is used to avoid formation of shrinkage cracks. Expansive cement expands as it starts setting, and does not shrink during and after hardening. The purpose of this type of cement is to reduce the size and amount of shrinkage cracks.
This type of cement is increasingly used for the repair of concrete structures. Expansive cement is used in grouting anchor bolts and pre-stressed concrete ducts.
OIL WELL CEMENT
Oil Well Cementis manufactured by adding retarders to Ordinary Portland Cement. There is no chemical effect of oils on oil well cement. This cement can be used under high temperature and high-pressure conditions. It is costly, when compared with OPC. Oil well cement is used in the petroleum industry for cementing work during the drilling of gas and oil well. It is also used in filling up the gaps between rocks and steel casing of the oil wells.
OIL WELL CEMENT
The aforementioned different types of cement are used in different circumstances. Conclusively, for general construction Portland pozzolana cement is mostly used, as it is an eco-friendly option of Ordinary Portland Cement.