An initiative by the country's leading steel producer is leading the way to convert the waste generated in the steelmaking process into eco-friendly construction material as an alternative to bricks, which industry insiders say will greatly help reduce stress on the environment.
Steelmaking involves melting scraps into billets. During the process, a soil-like but solid waste called steel slag (induction furnace slag) is generated. This waste, when dumped in the environment, threatens biodiversity and reduces land fertility.
However, Bangladesh Steel Re-Rolling Mills (BSRM) has turned this slag into a commercial product after nearly a decade of effort.
A research conducted by the Islamic University of Technology found that a 35% reduction in the CO2 footprint of concrete can be achieved by fully replacing brick with slag, with at least a 30% reduction in cost.
"Replacement of brick aggregate (chips) by IFS (steel slag) enhances concrete mechanical performance and workability compared to 100% brick aggregate concrete," the research report said.
According to BSRM, a crusher machine breaks slags into various sizes. Currently, the company is producing at least three types of slag gravel which are being used as an alternative to brick and stone chips.
The company used pavement blocks made of slags as an alternative to crushed bricks in road construction in its factory complexes and hollow blocks made from slag were used for building walls.
Besides, a fine sand-like material that comes out during slag crushing has been used in road dividers instead of sand, the company said.
Besides, it can be used as railway stones, BSRM said.
The initiative is more pertinent today as Bangladesh will be observing World Environment Day on Monday amid ever-increasing industrial pollution and environmental catastrophes in the country.
BSRM's steel slag history
In 2012, BSRM took the initiative to work with slags. Also, Buet's Civil Engineering Department was engaged to look into the utility of the material. In 2016, work on slags officially began.
In 2017, BSRM's two factories installed crusher machines to break down slags and pavement and hollow blocks were successfully produced in 2018.
In 2020, the government gave permission to use the material for road construction.
Currently, BSRM processes slag at four plants including two at Nasirabad Industrial Area, and two at Bhatiari and Mirsharai.
Among these, two crusher machines have been installed in two factories to break the slag at the cost of about Tk6 crore.
BSRM now produces around 1.20 lakh tonnes of slag each year, 100% of which is used as construction material.
BSRM received the "SDG Brand Champion Awards 2023"' for their initiative.
Slag gravel in Manikganj road
BSRM jointly undertook a pilot project with Bangladesh Road Research Laboratory to use steel slag instead of concrete in road construction in 2021.
Under the project, slag gravel was used for constructing a 100-metre section of Golora-Saturia road in Manikganj.
The research agency's Director Ahsan Habib told The Business Standard that they found the road in good condition during an inspection after one year of construction.
"We are planning to use the material on a large scale and it is being added to the list as an alternative to other construction materials," Ahsan Habib added.
Environment and affordability
To meet the growing demand, a total of 5,000 brick kilns across the country produce 12 billion clay-burnt bricks annually.
In contrast, slags are generated during steel production. Then it is broken by crusher machines only.
According to BSRM, steel slag is better as construction materials because its water absorption capacity is 2% against 13% for brick aggregate.
The average price per cubic foot of brick aggregate is Tk120, stone aggregate Tk200 and slag aggregate Tk70 in the current market.
BSRM Deputy Managing Director Tapan Sengupta told TBS, "Our steel slag is being recycled 100%. Slag is used in our own factory basement and factory road in Mirshrai."
Steelmakers in Bangladesh produce 7.5 million tonnes of steel annually, according to industry insiders.
About 40kg-70kg of slag is produced against each tonne of steel. As such, about 4.50 lakh tonnes of steel slag is produced in this sector.
Only BSRM converts this waste into usable materials while the rest dumps it as waste.
The selling price of BSRM's slag Tk1,700 to Tk1,750 per tonne.
With this, if the entire sector recycles slag, the initial market will stand at around Tk80 crore.
Hussaini T Fakhri, managing director of Fakhris Green Building Resource Limited told TBS, "As we produce environment-friendly building products, we use steel slag as an aggregate instead of stones to reduce the carbon footprint."
"It is also cost-effective for us and steel slag does not negatively impact the quality of the finished product," he added.