Why in News?
Waste Foundry Sand (WFS) is in the news because of a major initiative to integrate this industrial byproduct into India's infrastructure under a "waste-to-wealth" model. On March 26, 2026, the CSIR-Central Road Research Institute (CSIR-CRRI) signed a landmark agreement with the Institute of Indian Foundrymen (IIF) and private partners to standardize the use of WFS in road construction.
Origin
- WFS is a byproduct of the metal casting industry (both ferrous and non-ferrous), consisting of high-quality silica sand that has been recycled multiple times until it loses its molding properties.
Classification
It is generally categorized into two types based on the binders used:
- Clay-bonded (Green Sand): Contains 85–95% silica sand and 4–10% bentonite clay.
- Chemically Bonded Sand: Uses resins or chemical additives (like sodium silicates or phenolic urethanes) for higher heat resistance.
Physical Properties
- High Thermal Conductivity: Originally chosen for molds because of its ability to withstand molten metal heat.
- Texture: Ranges from sub-angular to rounded; often appears black (green sand) or off-white (chemically bonded).
Applications in Construction
- Roads: Used for road bases, subgrades, and hot mix asphalt.
- Concrete: Can replace up to 20–30% of natural river sand in concrete without compromising structural integrity.
- Bricks/Tiles: Recent CSIR-NIIST technology allows for the production of up to 5,000 bricks per day using 30 tonnes of waste sand.
Benefits
- Cost Savings: Its use can reduce material costs by approximately 7.5–10% in construction projects.
- Eco-Friendly: Prevents illegal sand mining of riverbeds and lowers the carbon footprint of infrastructure projects.
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