Environmentally safe for sustainable development, foundry sand is used in embankments, barrier layer construction, flowable fills, roads construction, Portland cement concrete, and more.
Foundries for the metal-casting industry generate by-products such as used foundry sand. In fact, foundries successfully recycle and reuse sand many a times, and the remaining sand, which is foundry sand, is removed from the foundry. This sand is uniformly sized, high-quality silica sand combined with a binder and used to form moulds for ferrous and non-ferrous castings.
The properties of used foundry-sand properties vary owing to the type of equipment used for foundry processing, types of additives, number of times the sand is reused, and the type and amount of binder. Within the concrete industry, the most successful examples have been using coal fly-ash to make high-quality, durable concrete and recycling old, demolished concrete as aggregate for new concrete.
Dr Jayeshkumar Pitroda, Assistant Professor-Civil Engineering Department, BVM Engineering College, shares more on the applications of foundry sand, which is technically sound and environmentally safe for sustainable development.
The Indian foundry industry: India ranks second in the world based on the number of foundry units that exist (4,550 units) and fourth in terms of total production (7.8 million tonne), according to the 42nd Census of World Casting Production, 2007. Apart from the registered 4,550 units, there are several unregistered units, which according to sources range from 1,500 to 5,000 units. Today, India ranks 10th among casting exporters. Foundries produce a wide variety of castings such as manhole covers, pipe and pipe fittings, sanitary items, tube-well bodies, metric weights, automobile components, railway parts, electric motors, fan bodies, etc; 90 per cent of the castings produced are from the SSI sector. Most of these units are situated in clusters, with cluster size ranging from 30 to 500 units.
The applications: Foundry sand is a by-product of ferrous and non-ferrous metal casting industries, where sand has been used for centuries as a moulding material because of its thermal conductivity. Foundry sand consists primarily of high-quality silica sand with uniform physical characteristics, coated with a thin film of burnt carbon, residue and dust. It can be used in concrete to improve its strength and other durability factors. It can be used as a partial replacement of cement or as a partial replacement of fine aggregates or total replacement of fine aggregate and as supplementary addition to achieve different properties of concrete.
Foundry sand can be used in embankments, barrier layers construction, flowable fills, roads construction, as soil reinforcement, in hot mix asphalt and Portland cement concrete. Further, engineering applications include Portland cement manufacturing, mortars, agriculture or soil amendments, verification of hazardous materials, smelting, rockwool and fibreglass manufacturing and landfill covers or hydraulic barriers. However, limitations include the ability to meet the quantity requirements of precast manufacturers and reduction in workability of concrete.
That said, it can be suitable for a variety of reuses such as:
- Flowable fill: Flowable fill is a liquid-like material that self-compacts and is used as a substitute for conventional soil backfill. The product is easily transported and can be readily re-excavated. The typical mixture contains sand, fly-ash, Portland cement and water. Foundry sand can readily be substituted for virgin sand in flowable fill mixtures.
- Cement and concrete: Sand is a component of Portland cement and concrete. Portland cement requires sand with a silica content of at least 80 per cent, which most foundry sands meet. It also requires certain minerals such as iron and aluminium oxides, which are found in many foundry sands. Cement and additional sand or gravel are components of concrete, allowing further reuse of foundry sand.
Types and physical characteristics: Two general types of binder systems are used in metal casting:
In conclusion: Concerning the compressive strength and flexural strength test of concrete (M20 Grade) for rigid pavement, here are some observations: The maximum compressive strength, flexural strength is achieved at 50 per cent replacement of natural fine aggregate with used foundry sand, which is 40.89 N per sq mm and 8.45 N per sq mm respectively; California Bearing Ratio (CBR) value 4 per cent, Dry Lean Concrete (DLC) = 100 mm thick, so cost of rigid pavement decreases from Rs 757.04 to Rs 632.17. Hence, the use of foundry sand in concrete can save the ferrous and non-ferrous metal industries disposal, cost and produce a ´greener´ concrete for construction. Further, environmental effects from wastes and disposal problems of waste can be reduced. Indeed, used foundry sand can be an innovative construction material if judicious decisions are taken by engineers.
A mix M20 grade was designed as per Indian Standard method (IS: 10262-1982) and the same was used to prepare the test samples. The design mix proportion is done in Table 1.
DESIGN OF A ROAD PAVEMENT (IRC: 58-2002)
A cement concrete pavement is to be designed for a two-lane two-way National Highway in Gujarat. The total two-way traffic is 3,000 commercial vehicles per day (cvpd) at the end of the construction period.
- Seraphina D´Souza