The proper use of waste materials fundamentally affects our economy and environment. Over a period of time waste management has become one of the most complex and challenging problems in India affecting the environment. The rapid growth of industrialization gave birth to numerous kinds of waste byproducts which are environmentally hazard and create problems of storage. The construction industry has always been at forefront in consuming these waste products. The consumption of Slag which is waste generated by steel industry, in concrete not only helps in reducing green house gases but also helps in making environmentally friendly material. During the production of iron and steel, fluxes (limestone and/or dolomite) are charged into blast furnace along with coke for fuel. The coke is combusted to produce carbon monoxide, which reduces iron ore into molten iron product. Fluxing agents separate impurities and slag is produced during separation of molten steel. Slag is a nonmetallic inert byproduct primarily consists of silicates, aluminosilicates, and calcium-alumina-silicates. The molten slag which absorbs much of the sulfur from the charge comprises about 20 percent by mass of iron production. The schematic production details of Slag are shown in Figure 1.

The availability of good quality aggregates is depleting day by day due to tremendous growth in Indian construction industry. Aggregates are the main ingredient of concrete occupying approximately 75% of its volume and directly affecting the fresh & hardened properties. Concrete being the largest man made material used on earth is continuously requiring good quality of aggregates in large volumes. A need was felt to identify potential alternative source of aggregate to fulfill the future growth aspiration of Indian construction industry. Use of slag as aggregates provides great opportunity to utilize this waste material as an alternative to normally available aggregates. The total steel production in India is about

72.20 Million Tones and the waste generated annually is around 18 Million Tones (considerably higher than the world average) but hardly 25% are being used mostly in cement production (information source, Source, world steel association 2011 data, J. P. Morgan Ernst & Young analysis).

Reviews of literature survey are presented as below, Chen Meizhu, Zhou Mingkai, Wu Shaopeng, 2007 [1] worked on mortar made up of ground granulated blast furnace, gypsum, clinker and steel slag sand. The experimental results show the application of steel slag sand may reduce the dosage of cement clinker and increase the content of industrial waste product using steel slag sand.

Isa Yuksel, Omer Ozkan, Turhan Bilir, 2006 [2] experimented use of non ground granulated blast furnace slag as fine aggregate in concrete. The study concluded that the ratio of GGBs/sand is governing criteria for the effects on the strength and durability characteristics.

Juan M. Manso, et al., 2004 [3] carried out work in laboratory to produce concrete with good properties using oxidizing EAF slag as fine and coarse aggregate. The concrete was tested for durability characteristics like soundness, leaching test, accelerated ageing test etc. The durability of the EAF slag concrete was found to be acceptable, especially in the geographical region for which its use was proposed, where the winter temperature hardly ever falls below 32˚F (0˚C).

Keun Hyeok Yang, Jin Kyu Song, Jae-Sam Lee, 2010 [4] studied alkali activated mortars and concrete using light weight aggregates. Test results showed that the compressive strength of alkali activated mortar decreased linearly with the increase of replacement level of light weight fine aggregate regardless of the water binder ratio.

Li Yun-feng, Yao Yan, Wang Liang, 2009 [5] investtigated effects of steel slag powder on the workability and mechanical properties of concrete. Experimental results show that mechanical properties can be improved further due to the synergistic effect and mutual activation when compound mineral admixtures with steel slag powder and blast furnace slag powder mixed in concrete.

Lun Yunxia, Zhou Mingkai, Cai Xiao, Xu Fang, 2008 [6] used steel slag as fine aggregate for enhancing the volume stability of mortar. Experimental results indicated that powder ratio, content of free lime and rate of linear expansion can express the improvement in volume stability of different treated methods. Autoclave treatment process is found more effective steam treatment process on enhancement of volume stability of steel slag.

L. Zeghichi, 2006 [7] experimented on substitution of sand by GBF crystallized slag. Tests carried out on cubes of concrete showed the effect of the substituting part of sand by granulated slag (30%, 50%) and the total substitution on the development of compressive strength. Compressive strength test results at 3, 7, 28, 60 days and 5 months of hardening concluded that the total substitution of natural coarse aggregate with crystallized slag affects positively on tensile, flexural and compressive strength of concrete. The partial substitution of natural aggregate with slag aggregates permits a gain of strength at long term but entire substitution of natural aggregates affects negatively the strength (a loss in strength of 38%).

Saud Al-Otaibi, 2008 [8] studied use of recycling steel mill as fine aggregate in cement mortars. The replacement of 40% steel mill scale with that of fine aggregate increased compressive strength by 40%, drying shrinkage was lower when using steel mill scale.

Sean Monkman, Yixin Shao, Caijun Shi, 2009 [9] investigated the possibility of using a carbonated LF slag as a fine aggregate in concrete. The slag was treated with CO₂ to reduce the free lime content while binding gaseous CO₂ into solid carbonates. The carbonated LF slag was used as a fine aggregate in zero-slump press-formed compact mortar samples and compare to similar samples containing control river sand. The 28-day strengths of the mortars made with the carbonated slag sand were comparable to the strengths of the normal river sand mortars. The carbonation of LF slag was found to be suitable for use as a fine aggregate. Significant amounts of carbon sequestration could be realized in a potentially useful form that further utilizes a waste slag material. Carbonated mortars that used LF slag sand offer the largest gains in terms of CO₂uptake.

Tarun R Naik, Shiw S Singh, Mathew P Tharaniyil, Robert B Wendfort, 1996 [10] investigated application of foundry by-product materials in manufacture of concrete and masonry products. Compressive strength of concrete decreased slightly due to the replacement of regular coarse aggregate with foundry slag however strengths were appropriate for structural concrete.

In this study, concrete of M20, M30 & M40 grades were considered for a W/C ratio of 0.55, 0.45 & 0.40 respectively with the targeted slump of 4 ± 1 in. (100 ± 25 mm) for the replacement of 0%, 30%, 50%, 70% & 100% of aggregates (fine & coarse) with that of slag aggregate. These concrete mixes were studied for the properties like compressive, split tensile and flexure strengths.