Environmentalism has undoubtedly

Environmentalism has undoubtedly

No matter what are the causes but the environmentalism has undoubtedly increased in the whole world. In 2010, there may not be any one who does not have knowledge about pollutants, pollution, global warming and their causes. If we start discussion on pollution with a primary student; along with many other important points he or she will definitely give his or her opinion about industrial waste as “it should be minimized”.

To minimize industrial waste does not mean to lock the factories and sit inside the homes, but to design the process so gently and minimize the consumption and release of harmful materials, use it again and again with is the factory or send it to any other factory to be used as raw material. Cost of manufacturing process and final product can be decreased by reusing and recycling of waste materials.

Among many industrial waste products foundry sand can be considered as one of the most important because it is being produced in immense volume in foundries.

Foundry is a place where metals are shaped by a process in which metals are melted and poured into moulds/dies, this process (casting) has many types and among all the types sand casting is most widely used. In which the liquid metal is poured into sand mould (a mould which is made up of sand), as it is clear from its name. When moulds/dies are made with sand, sand particles are bonded together by using binders, which may be a clay or a chemical, clay bonded sand is known as green sand whereas chemically bonded is called resin-bonded sand. Although these two types have different properties but both are being used beneficially.

Green Sand Composition

Silica sand


Bentonite clay


Carbonaceous additive




Green sand is being used to produce about 90 percent castings in the whole world. It is prepared by blending high quality silica sand, bentonite clay, carbonaceous additive and water together. Green sand is black in colour due to carbon content, and adhere together due to clay and water.

Resin Sand Composition

Silica sand


Chemical Binder


Resin sands which are light in colour and coarser in texture are also used where high strength, ability to withstand high temperature of the molten metal and collapsibility are required.

Foundries purchase new sand to make casting molds, and the sand is reused numerous times within the foundry. However, heat and mechanical abrasion eventually make the sand unsuitable for use in casting molds, and a portion of the sand is continuously removed and replaced with virgin sand. This removed sand is called foundry sand. Take a look of flow chart and see how sand becomes foundry sand.

As I said foundry sand is being produced in immense volume therefore it is not a good idea to dispose it safely because of two reasons. Land fill cost has greatly increased and in US where 2 million ton of sand were disposed of it was 25$ per ton in 2006. Another disadvantage of the foundry sand disposal is the possible contamination of under ground water because of the presence of metal and phenolic resins.

In order to get rid of the harmful affects related to disposal of foundry sand one should try to make it raw material for some other industry means one should recycle it. The recycling of foundry sand can save energy, reduce the need to mine virgin material and may reduce the cost for both producers and users.

Grain Size Distribution of Foundry Sand


Particle Size

Sieve No.



30 and 100




Before start recycling one should be familiar with the properties of foundry sand. Foundry sand has many advantageous properties which make its recycling beneficial. Foundries spend significant resources in monitoring and testing sand systems so that the engineering properties remain the same day after day. Its consistent properties make it superior than other types of granular materials and in some cases it provides comparable performance at lower cost.


ASTM Standard

Foundry Sand with Clay ( 5%)

Foundry Sand Without Clay

Bulk Density(pcf)




Moisture content(%)




Specific gravity




Dry density (pcf)

D698 Standard Proctor



Optimum moisture content(%)




Permeability coefficient(cm/s)




There are various applications in which foundry sand can be used successfully.

According to a research which was done in the Ceramic Materials Laboratory, Brazil it was observed that foundry sand can replace the conventional material used in the production of triaxial ceramics which are ceramic products composed of kaolin (a clay mineral), feldspar( a tectosilicate mineral) and silica( SiO2). In this research the quality of pressed ceramic bodies containing foundry sand was found good and there was no significant change in their densities.

Another research work which was also done in Brazil, tells us that foundry sand can be employed to make trough of the blast furnace. The material which is used to cover the trough of the blast furnace should have high refractoriness (ability to withstand high temperature), ability to avoid the adherence of the pig iron and compactability. All these properties were found in the blend of foundry sand and clay, in a 2:1 volume ration. Although there were some deficiencies regarding adherence and fluidity of the blend which were easily overcome.

Foundry sand can be used safely in concrete for durability and strength purpose. It was proved by an Indian student who made his thesis of master of engineering in Thapar Institute of Engg. & Tech, Patiala, India. In his experimental work he replaced fine aggregates with three percentages of foundry sand. The percentages of replacements were 10, 20 and 30 % by weight of fine aggregates. Then he observed the behavior of the concrete on the application of load and tested mechanical properties for all replacement of foundry sand. The results showed improvement in the properties of concrete in which fine aggregates were replaced with foundry sand. The black colour of foundry sand should be kept in mind, because it can make final concrete of gray or black colour which may not be desirable. A 15% replacement of fine aggregate with foundry sand may cause a minimal change.

Portland cement is manufactured by using calcium oxide, silica, alumina and iron oxide as a raw material. While silica is the main constituent of the foundry sand therefore foundry sand can easily be used in the manufacturing of Portland cement.

Another engineering material in which foundry sand can be used is mortar. Mortar consists of sand, cement and other additives. It is used to joint masonry units, to strength masonry structures by bonding with steel reinforcing and to provide architectural quality, almost one cubic foot of sand is used to make one cubic foot of mortar.

Sand Gradation for Mortar

Sieve No.

Sieve Size (mm)

Percent Passing by Weight






















Although the particle size of foundry sand is less than the particle size distribution which is required in mortar but it can be used by mixing with some amount of coarse particles.

Environmental Protection Agency of US also says that foundry sand can be used to encapsulate the hazardous materials because of its high silica content.

Fiber Glass is very famous engineering material and at present it is playing its role in numerous composite materials. Fiberglass is produced by melting silica sand and straining it through a platinum sieve with microscopic holes, thereby forming the desired glass fibers. Manufacturers of fiberglass have specifications for silica content and particle size distribution, so to be used in this application, the foundry sand has to have the needed properties.

In developed countries foundry sand is successfully recycled, but this is not the situation in under developed countries like Pakistan. There is a need to educate foundries and possible recyclers about environmental and economical aspects of foundry sand recycle. This recycling will also solve the problem of sand disposal.

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