Cement Energy and Environment

enhancement of the global temperature and climate change, on which, considerable data are reported. The emission of carbon dioxide (C0 2 ) due to industrial processes have increased from about 10 billion tonnes in 1960 to about 37 billion tonnes in 2004. The cause - effect relationship of release of greenhouse gases and the global temperature is now well accepted. A recent estimate by Inter-Governmental Panel on Climate Change {IPCC) indicates that the rise in global temperature, which was of the order of 0. 76°C in the twentieth century, can range from 1.4°C to 4°C during this century. The involvement of cement and concrete constructions in the campaign for sustainable societal development arises from the following; • Cement concrete is the most widely used material of construction the world over, • Manufacture of cement involves exploitation of vast raw material resources, thermal and electrical energy, and can give rise to particulate and gaseous emissions, which, unless controlled, can pollute the environment, • Both cement and concrete have affinity to various industrial wastes, which can be incorporated in them as substitute raw materials, fuels and ingredients. Cement and concrete can help in valorization of toxic elements from hazardous wastes of other industries, • Notwithstanding the fond belief that concrete is a durable material, there are instances galore to the contrary. Poor service record of concrete structures in many countries has brought durability of concrete and construction.s into sharp focus. Collapse of structures exposed to calamities like hurricanes, cyclones and floods bring about the importance of adequate serviceability of concrete structures. • Reduced service life of structures necessitates more constructions, greater deployment of materials and energy resources, and greater wastes to dispose. Hence, concrete structures must have long service life as designed, in order to be sustainable. Features of sustainable concrete • By juxtaposing the requirements of sustainable development, as enumerated above, one may classify concrete being sustainable on the basis of the following criteria; • Whether it uses minimum amount of cement per unit volume, consistent with the requirements of performance. • Whether concrete incorporates industrial wastes, thereby reducing environmental pollution • Whether the concrete is durable and results in satisfactory service life. Testing and Performance Monitoring It is said that if something can be measured, it can be improved. Testing forms an important part of Quality control. As a part QAJQC, Codes and specifications of concrete construction lay down that; • A control system shall be operated to provide assurance that materials used in the structure • conform to the relevant BIS Standards. This may include checks, sampling testing, certification material suppliers relevant information. visual and from and • Batches of materials like cement, mineral admixtures and chemical admixtures should be tested when first received at the site of production of concrete . Certification form the producers shall be obtained for tests on physical properties and chemical characteristics, as well as uniformity between consignments. • Water and aggregates should be tested at more frequent intervals. In practice, ingredient materials of concrete may or may not be tested; it depends on how intensive is the Quality practice in the project. Many times, the only tests carried out are for slum and 28 days cube test for compressive strength. Whatever tests as carried out, they should be reliable and accurate. Proper testing facilities are requi red. Tests for durability Durability and assured service life of the structure as designed are important components of quality. If the structure is not durable and the intended service life is not fulfilled , the quality can not be rated as satisfactory. At present, there are no reliable , quick tests for durability of concrete in the structure. Codes of Practices recognize a number of mechanisms for the deterioration of concrete during service, but the prescriptions are essentially geared against corrosion of 9