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Using Slag as Fine Aggregate in Concrete

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Disposal of waste slag is a major concern and is perceived as an environmental hazard across the steel industry. Nagesh Veeturi, Executive Director – Civil, and Sumanta Sahu, DGM – Quality, KEC International, investigate the possibility of utilising slag as a fine aggregate and its effect on the strength and workability parameters of concrete.

Concrete is one of the major construction materials in civil construction. It is a composite material with cement, aggregate, sand, admixture and water as ingredients. River sand and Manufactured Sand are mostly used as fine aggregate in concrete. River sand is formed by the natural weathering of rocks over many years and is preferred to be used as fine aggregate. Manufactured Sand is produced by crushing hard rocks into smaller sizes using a crusher followed by washing to use in concrete. The growth of infrastructure and building projects demand the use of huge quantities of sand in concrete.
The mining of sand from riverbeds is posing a serious threat to the environment causing the erosion of riverbeds and banks, triggering landslides, inducing loss of vegetation on the riverbanks, lowering the underground water table, etc. Hence, sand mining from riverbeds and rock is being restricted or banned by the authorities nowadays. To nullify the above concerns, concrete mix trials were conducted in our quality laboratory by using LD slag and blast furnace slag as fine aggregate.

LD Slag
LD slag is a byproduct of the steel industry. It is produced from impurities during the steel-making process. LD Slag consists of calcium, magnesium, iron, silicon and aluminium oxides minerals. During the production of steel, the slag is separated from steel in the furnace, and steel slag fine aggregate is formed after quenching the molten slag with water. There are many grades of steel produced and properties of steel slag vary depending on raw materials used for steel production. LD slag is typically granulated and used as a fine aggregate. Normally it is heavier than sand and its specific gravity is observed to be 3.2 to 3.6 with water absorption around 3 per cent.

Production process of LD Slag.
Due to its high density, segregation is observed as a fine aggregate in concrete. Materials can be used as partial replacement of fine aggregate.

Blast furnace slag
Blast furnace slag is a byproduct produced during the iron making process in blast furnaces. During the smelting process, iron ores are fed into the furnace at high temperature. The process leads to the production of molten iron and waste materials. Slag, which is a waste material, is separated and quenched with water. This rapid cooling process solidifies the slag into granular particles. Blast furnace slag is observed to be lighter than sand, specific gravity of sand is found to be 2.01.

Concrete mixes with slag as fine aggregate
Concrete mix trials were conducted with LD slag, BF slag as fine aggregate. Due to the high density of LD slag, segregation was noticed on concrete mixes. The same segregation is observed in concrete mix by using BF slag due to its lightweight. Further concrete mix trials were conducted by mixing LD slag and BF slag with different proportions – this is done to study the initial properties of concrete such as cohesiveness and workability retention.
The concrete mix is observed to be cohesive
with good workability retention by using LD slag and BF slag as fine aggregate with the same
proportions. Other properties of concrete such as setting, and strength were observed complying to specification requirements.

Benefits of using LD slag and BF slag as fine aggregate
Durability:
Calcium oxide and silicon oxide are prime chemicals used in the composition of LD slag and BF slag, and both possess pozzolanic properties. calcium oxide and silicon oxide react with calcium hydroxide produced during hydration of cement and increases strength and permeability properties
of concrete.
Sustainable approach: LD slag and BF slag are the by-products from the iron industry which makes it an industrial waste product. Using materials as fine aggregate helps to conserve natural resources. Storage of this material is a major concern in industry. Utilisation of LD slag and BF slag as fine aggregate minimise storage area, air pollution.
Reduction in carbon footprint and heat of hydration: The use of LD slag and BF slag as a fine aggregate leads to reduction in cement content in concrete mixes. Cement is a major source of rise in temperature in concrete mixes that leads to increase in carbon emission during its production process. Reduction in cement content minimises the heat of hydration and prevents thermal cracks in concrete.
Enhance workability in concrete mixes: Workability in concrete is increased due to the even surface of LD slag and BF slag. This makes the concrete easier to place during the construction process.
Cost optimisation: LD slag and BF slag are industrial waste products and are cheaper than manufactured sand and river sand. Also due to the pozzolanic properties of slag, cement content in concrete can be minimised. Overall concrete cost is reduced with improved performance.
Due to the vast growth of construction sectors, the demand for concrete has increased as a fine aggregate. Thus, it is essential to find suitable alternatives to sand such as slag materials.
It is observed that the combined use of LD slag and BF slag as fine aggregates leads to cohesive mix with desired workability and strength. The PC base chemical admixture was added to reduce the water content and maintain workability of the mix. Finally, it is concluded that slag can be used as an alternative of sand in concrete. As both types of slags are by-products from the steel industry, their long-term performance is vital, and further studies in this direction are still in progress.

ABOUT THE AUTHOR:
Nagesh Veeturi, Executive Director – Civil, KEC International
is a seasoned professional having entrepreneurial and leadership skills with key focus on strategy and business transformation.

Sumata Sahu, DGM – Quality, KEC International has 32 years of rich experience in the construction industry mainly as QA/QC and project management professional.

Concrete

Cement Makers Reaffirm Commitment to Sustainable Growth

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World Environment Day spotlight on innovation and circularity

On World Environment Day, the Indian cement industry reiterated its commitment to supporting India’s climate ambitions through sustainable manufacturing, resource efficiency and the adoption of cleaner technologies.

The Cement Manufacturers’ Association (CMA) said the sector remains aligned with the Government of India’s Net Zero commitments and is accelerating efforts to reduce its environmental footprint while supporting the country’s infrastructure and development agenda.

Parth Jindal, President, CMA and Managing Director, JSW Cement, said the industry is increasingly adopting cleaner technologies, improving energy efficiency and expanding the use of alternative fuels and raw materials. He also highlighted the growing importance of circular economy practices, where industrial by-products and waste streams from one sector are utilised as resources in another.

“The Indian Cement Industry is aligned to the Government’s commitments on carbon mitigation and is accelerating the adoption of cleaner technologies, resource efficiency and circular economy practices while actively exploring the potential of Carbon Capture, Utilisation and Storage (CCUS) as a critical pathway for deep decarbonisation,” said Jindal.

He added that coprocessing industrial waste and by-products helps conserve natural resources, reduce disposal requirements and lower the environmental footprint across multiple sectors.

According to Jindal, sustainability is no longer limited to manufacturing processes but is increasingly influencing investment decisions, innovation strategies and long-term growth plans within the industry.

Echoing similar views, Dr Raghavpat Singhania, Vice President, CMA and Managing Director, JK Cement, said sustainable development extends beyond emissions reduction and must also focus on responsible resource utilisation and waste minimisation.

“Sustainability in the built environment cannot be measured by emissions alone. It is equally about how efficiently we use resources, how effectively we minimise waste and how responsibly we create the infrastructure that will serve future generations,” said Singhania.

He noted that the cement industry is advancing its sustainability agenda through greater resource efficiency, increased circularity, technological innovation and continuous improvements in manufacturing practices. As a key contributor to India’s infrastructure development, the sector has a critical role to play in balancing economic growth with environmental responsibility.

On the occasion of World Environment Day, industry leaders reaffirmed their commitment to supporting India’s climate goals while delivering the materials required for resilient, durable and sustainable infrastructure.

 

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Concrete

Building a Greener Future Together

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Environmental sustainability requires immediate action, not just long-term commitments and discussions. Recycling, circular economy practices, and technology-driven waste management can help industries reduce environmental impact while supporting sustainable growth.

Author: Jignesh Kundaria, Director and CEO, Fornnax Technology

World Environment Day serves as an important reminder that environmental sustainability can no longer remain confined to discussions, reports, or long-term commitments. The environmental challenges facing the world today demand immediate, measurable, and collective action. Across industries and communities, waste generation continues to outpace our ability to process it responsibly, placing increasing pressure on ecosystems, natural resources, public health, and the well-being of future generations.

One of the most significant shifts required today is a change in how society perceives waste. Rather than being viewed as a material to be discarded, waste must be recognised as a valuable resource that can contribute to both economic growth and environmental protection when managed through the right technologies and systems. This mindset forms the foundation of the circular economy model that countries across the world are increasingly adopting to reduce landfill dependence, recover valuable materials, and create more sustainable industrial ecosystems.

India has made meaningful progress in strengthening awareness around sustainability, recycling, and environmental responsibility over the past decade. Significant efforts are being made to formalise the recycling sector through improved infrastructure, technology adoption, policy implementation, and broader stakeholder participation. These developments are creating a stronger foundation for responsible waste management and resource recovery across the country.

However, achieving long-term environmental impact requires collaboration from all stakeholders. Industries, policymakers, technology providers, and communities must work together with greater accountability to strengthen recycling ecosystems, encourage responsible waste management practices, and create sustainable outcomes through consistent execution rather than temporary interventions.

As someone closely associated with the recycling industry, I firmly believe that technology will play a decisive role in addressing future environmental challenges. Advanced recycling systems have the potential to recover valuable resources, reduce pollution, minimise landfill burdens, and conserve energy, creating a more sustainable future for generations to come. This belief is deeply reflected in Fornnax’s motto, “Committed to Create a Green Future,” which embodies our commitment to building long-term environmental value through innovation and responsible action.

At the same time, technology alone cannot deliver meaningful change. Real progress requires intent, awareness, participation, and a shared sense of responsibility. Sustainable development can only be achieved when innovation is supported by collective action and a genuine commitment to environmental stewardship.

On this World Environment Day, let us move beyond conversations and take meaningful steps towards creating a cleaner, greener, and more sustainable planet. By embracing innovation, strengthening recycling ecosystems, and acting responsibly today, we can create lasting environmental impact and secure a better future for generations to come.

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Concrete

JK Lakshmi Advances LC3 Cement Expansion

Company highlights commercial production and research partnerships

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The meeting reviewed progress in limestone calcined clay cement (LC3) technology and its commercial adoption in India’s cement sector, focusing on low-carbon alternatives to conventional binders. JK Lakshmi Cement noted that limestone calcined clay cement can reduce carbon dioxide emissions by up to 40 per cent compared with conventional cement and said this reduction supports industry decarbonisation. The company highlighted that it was among the first two cement manufacturers in India to move LC3 into commercial production after the Bureau of Indian Standards approved the technology as a cement standard.

Vinita Singhania said the transition of LC3 from research to commercial production reflected collaboration between industry, academia and international institutions. Maya Tissafi acknowledged JK Lakshmi Cement’s role in advancing LC3 adoption in India and its contribution in taking the technology from laboratory trials to commercial implementation. Both representatives underlined the growing relevance of sustainable construction materials as India expands infrastructure and urban development.

The meeting explored continued collaboration with Swiss research institutions such as EPFL, EMPA and ETH Zurich alongside Indian academic partners and development organisations. JK Lakshmi Cement has been associated with the LC3 initiative since 2014 and worked with EPFL, IIT Delhi, IIT Madras, Development Alternatives and Technology and Action for Rural Advancement. The company conducted one of the earliest industrial trials of LC3 and recently announced commercial production of Green Pro LC3 cement from its Jaykaypuram plant in Rajasthan.

India remains the world’s second-largest cement producer and expansion of infrastructure, urbanisation and housing demand continue to support long-term sector growth, increasing interest in low-carbon technologies. The company reported an annual turnover of more than Rupees (Rs) 60 bn and current cement capacity of about 18 million (mn) tonnes (t) per annum, with a target of reaching 30 million (mn) tonnes (t) by 2030. Apart from grey cement, the company also makes ready-mix concrete, gypsum plaster, wall putty, primers, adhesives and fly ash blocks, and both sides concluded on the need for continued collaboration to develop sustainable construction solutions.

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