IMPACT OF ECO FRIENDLY BLAST FURNACE SLAG ON PRODUCTION OF BUILDING BLOCKS

Solid waste management is one of the prime concerns in the world due to ever increasing proportion of non-biodegradable industrial waste product. Blast Furnace Slag (BFS) is one of the largest by products of steel and iron industries which creates scarcity of land filling area due to ineffective reuse and recycle. The use of such substance to create building blocks not most effective makes it economical, however it also enables in decreasing disposal concern. Clay bricks are the oldest walling material of construction industries. Due to preferable mechanical properties bricks are considered as prime source of masonry units that is used as walling material. Conventional clay bricks required burning process known as kiln firing which emits huge amount of CO2 into the atmosphere. World is facing same problem with the production of cement too. The major reasons behind pollution and environment depletion are due to unremitting decay in natural resources caused form deriving of raw materials such as sand, clay and dirt and also from huge amount of hazardous and nonhazardous wastes produced by the industries. Reuse of industrial waste such as BFS instead of naturally occurring raw material leads to contribute towards green environment. Present study intended toward use of steel and iron industry waste for manufacturing of building blocks to promote low cost housing along with mitigation of environmental violation. Based on the results, BFS may effectively replace with naturally occurring fine aggregates due to favourable physical properties. Durability aspects in terms of water absorption and compressive strength also found adequate as per the requirement of IS codes. An amount of partial to full replacement of BFS may allow as per required weathering conditions.


INTRODUCTION
Approximately 500 kg per tonne waste materials are generated from crude steel by steel plants. Out of these wastes, around 400 kg per tonne is only BFS [1]. India's crude steel production for 2018 was 106.5 Mt, up by 4.9% in 2017, meaning India has replaced Japan as the world's second largest steel producing country [1].
The most widely recognized walling material utilized in structure development is bricks. Bricks are the simplest and oldest building blocks used in construction. Annual production of bricks is currently 1391 billion units worldwide and the demand expected to be rising [3]. In India the annual demand is 200 billion bricks, producing around 250 billion bricks from 1, 50,000 kilns [2,4]. The main ingredients used for bricks are derived from natural resources occupies more than 80% by volume. The traditional method consumes 350 million tonnes of fertile soil and 25 million tonnes of coal annually [2]. On the other hand manufacturing of cement along with its use also tends to increase the amount of CO2. The huge consumption of naturally occurring materials and energy eventually lead to exhaustion of environment.
In both developed and developing countries, the problem of waste management has already become an issue to be addressed immediately. This problem is compounded by the rapidly increasing amounts of industrial wastes of a complex nature and composition.
As per the review of previous research works, various variety of wastes have been utilized by the researchers in terms of developing building blocks. Table 1 shows a summary of research work done for production of building blocks/bricks from various industrial wastes. But the effective percentage of industrial waste utilization was quite inadequate due to unfavourable mechanical and chemical properties.  Waste marble powder 0% to 80% by weight Found relative water absorption and mechanical properties up to 10% replacement. [9] Keeping the views of previous research works, present study makes an effort to extricate the problem of managing steel industrial waste like BFS by its effective utilization to turn it into valuable building blocks as per required durability and mechanical properties ultimately leads to promote sustainable and low cost development and also to mitigate the depletion of natural resources.

MATERIALS AND METHOD
BFS was collected from the furnace workshop of Iron Industry located near Gadbadi Puliya, AB Road, Indore, M.P., India. More than 20 steel and iron industries are working at present in Indore and also producing a huge amount of wastes every day. Characteristics of raw materials have been carried out considering procedure and requirements as described in IS Codes. In order to determine specific gravity, water absorption, silt content and unit weight of BFS and river sand, 1.18mm passing and 150μm retained particles were selected. The properties of BFS and river sand are showed in Table 2 and Table 3 respectively. Similarly, to determine properties of PPC cement the particle size were chosen it was finer than 90μm. Table 4 shows the properties of PPC cement.

Procedure for BFS based building block production
Crushed sample of BFS was replaced in different amount (10%, 20%, ---, 100%) by volume of sand and a standard amount of 10% cement was added. The control building block specimens were also prepared (0% BFS) to set the benchmark for results. 40-45% of water was added to dry mix to convert it into the shape of building blocks. Brick hand moulds of size 19cmX9cmX9cm were used for casting building blocks. For initial removal of moisture brick specimens were air-dried at room temperature for 24 h and then placed into curing tank after stripping. The building block samples were designated as B represented the identity of BFS. Table 5 shows the composition of different mixes for preparing building blocks. Total 60 numbers of moulds were prepared to ensure the properties of building blocks.

Determination of properties of building blocks
Water absorption of prepared building blocks was determined as per the procedure described in IS-3495 (Part-III):1992 [15]. Compressive strength of building blocks was determined with digital compression testing machine (CTM 2000kN capacity) as per IS-3495 (Part-I):1992 [16]. Both tests were performed after 28 days curing. (Figure 1) shows BFS based building blocks after 28 days curing.

METHODOLOGY
The purpose of this research is to develop building blocks using BFS and to conduct experimental investigations demonstrating efficacy of the product. Method implying experimental work followed in this research is showed in (Figure 2).

Determination of compressive strength
Compression test was carried out when building blocks acquired the necessary curing condition i.e., after 28 days curing and in wet condition. Table 6 shows the observations found during experimental investigation.

Determination of water absorption
Water absorption test was carried out on completely dried samples. Initially blocks were dried using ventilated oven by maintaining temperature to 110 o C. After drying, the blocks were immersed in clean water at a room temperature of 27 ± 2 °C for 24 hours. After 24 hours immersion the blocks were removed and wipe out using damp cloth. Table 7 shows the observation to demonstrate the results of water absorption of building blocks.

Characterization of Building Blocks
Experimental investigations for compressive strength and water absorption capacity were performed to insure the durability of BFS based building block samples as per IS code specifications. Building blocks found free from defects like bloating, cracks and efflorescence as examined on all types of samples from B0 to B10.
Water absorption is an important parameter to indicate open porosity. To ensure external weather resistance, the lower percentage of water absorption is always better. As per IS 12894-2002 [17], the average water absorption not more than 20 percent demonstrates a good quality of building block. (Figure 3) shows water absorption for BFS based building blocks. Maximum percentage of water absorption was found 11.0% proven the requirements as per IS code recommendations.

-Compressive strength of BFS based building blocks
Compressive strength is the most critical index of building blocks and is shown in ( Figure  4). Figure shows, as the percentage of BFS increase from 10% to 40%, compressive strength also increases. Replacements of BFS by more than 50% by volume exhibits decrement in the value of compressive strength. As per IS 1905-1987 [18], minimum compressive strength required by the building block after 28 days curing should not be less than 0.7 MPa for 1:8 mortar mix. Minimum compressive strength achieved by BFS based building blocks was found 4.50 MPa shows good quality requirements. Correlation was developed considering 10 observations. The details of selected experimental data to develop correlation are showed in Table 8. The actual and predicted productivity has been carried out for developed regression model and their accuracy was determined through formulations as listed below. Equation (1) shows the formula for Mean Absolute Percentage Error (MAPE) whereas Average Accuracy Percentage (AA%) is presented as Equation (2) [20][21].