Commonly available Portland cements such as OPC, PPC and PSC do not always meet every need of the construction industry. Other specialty cements have therefore, been developed to meet such special needs. These specialty cements are nothing but modified Portland cement wherein certain components are added to Portland cement to impart the desired qualities. In these cements, the calcium silicates continue to provide the strength but changes are made to Aluminate and ferrite phases. Specialty cements are characterized by smaller quantum of production, limited availability and increased costs.
Some of the specialty cements which are in the product range of DCL and produced against specific customer requirements are described below:53-S Grade OPC:
It is a specialty cement manufactured as per specifications originally formulated by the Indian Railways vide their specification No.IRS T-40 for manufacturing concrete sleepers. However, there was an amendment (No.6) to IS 12269, IRS T-40 cement and then, this was brought under the ambit of BIS. It is now designated as 53-S Ordinary Portland Cement and conforms to BIS specification IS:12269-1987. 53-S OPC's negligible chloride content protects it against corrosion. High fineness enhances workability and high early strength enables improved mass production cycle of Railway Sleepers. Apart from its main usage in the manufacture of concrete sleepers, it can also be put to use in pretest concrete elements or high rise buildings where high early strength is required.
Deccan Cements is one of the few manufacturers approved by the Research Designs and Standards Organisation (RDSO) of Indian Railways to manufacture and supply this special grade of superfine cement having enhanced quality and performance characteristics required in the production of Railway Sleepers.
This type of specialty cement is manufactured according to BIS specifications IS-8041:1990. The name by itself is an explanation of the nature of the cement i.e. it gets hardened at a very rapid pace. Apart from rapid hardening, it also develops high strength at an early stage than even OPC 53. It is used in pre-fabricated concrete construction work or in situations where Form Work has to be removed for reuse at a fast rate or some times in road repair works too.Sulphate Resistant Cement:
This type of specialty cement has to conform to BIS specifications IS:12330:1988. As the name indicates it resists sulphate attacks to which Ordinary Portland Cement is highly vulnerable. Being specially formulated cement with low C3A content, it can withstand sulphate attack.
This cement is found to be beneficial in areas where concrete has an exposure to sea-coast or sea water. Under any such instances, the concrete is vulnerable to sulphates attack and can cause damage to the structure. By using this specialty cement, one can reduce the impact of the chemical attack and consequent damage to the structure. It is also used in underground structures in sulphate salts rich environment, effluent treatment plant, sugar and other chemical industries, where civil works are likely to be subject to sulphate attack.High Alumina Cement:
This is manufactured as per BIS specifications IS 6452:1989. It is a cement with very high content of alumina and has the unique property of extensively high rate of strength development, gaining its ultimate strength within 24 hours and has a high resistance to chemical attack. It also has good refractory properties, enabling its usage in high temperature conditions such as furnace lining.Oil Well Cement:
This is manufactured as per BIS specifications IS 8229:1986 for use in oil wells, using special set of admixtures to contain C3A component in cement. It can withstand high temperature and pressure inside the oil wells, even while maintaining its mobility. This product is used by the petroleum industry for cementing the steel casting to the walls of the oil wells.
The cement is required to withstand the extreme conditions wherein cement slurry must be flowable for hours and then set rapidly. The slurry may be pumped thousands of meters below the surface and exposed to high temperature of up to 300oC and high pressure of greater than 20000 psi.