Green Concrete Using GGBS, River Pebbles and CRF as Partial Replacement to Cement and Aggregates

Concrete is the most commonly and widely used building material applied in all forms of construction, with an annual production exceeding 2 billion metric tons per year, it is the single most widely used manufactured substance on earth owing to its remarkable versatility as a building material. But the production of raw materials of concrete has certain detrimental effects on environment, mostly the production of cement and coarse aggregated obtained from crushing plants and continuous mining of river beds for getting the natural sand. Eight to 10 percent of the world's total CO2 emissions come from manufacturing cement. The global warming gas is released when limestone and clays are crushed and heated to high temperatures. Whereas production of granitic coarse aggregates on large scales and indiscriminate mining of river beds for sand, to overcome the demand of concrete raw materials has resulted in serious environmental and social problems. Therefore there is an urgent need to find alternative or green materials of concrete to preserve and protect our natural resources for future, by replacing them partially or fully to achieve sustainable development in construction industry. Green concrete is defined as a concrete which uses waste material as at least one of its components, or its production process does not lead to environmental destruction, or it has high performance and life cycle sustainability This paper mainly discusses the potential use of ground granulated blast furnace slag (GGBS), naturally available river pebbles, crushed rock fines (CRF) as partial replacements to cement, sand and coarse aggregates for making green concrete. This research evaluates the strength of hardened concrete, by partially replacing cement by various percentages of ground granulated blast furnace slag, natural sand by CRF and coarse aggregates by river pebbles for M40 grade of concrete at different ages. From this study, it can be concluded that, since the grain size of GGBS is less than that of ordinary Portland cement, its strength at early ages is low, but it continues to gain strength over a long period. The optimum use of green materials as replacement to cement, sand and coarse aggregates is characterized by high compressive strength and good workability.