Manufactured Sand an Answer to Ban on River Sand Mining in India

MAAD Minerals & Mines have recently introduced a new washing plant from CDE which is producing manufactured sands from basalt.

Located near Mumbai, MAAD Realtors and Infra Ltd is one of the leading construction and property development companies in the region. Mumbai has recently seen the government introducing a ban on the mining of natural sand from rivers in an effort to protect the natural environment. This initial decision was challenged in the Mumbai High Court where the Government's decision was upheld which has had a significant impact on the construction industry in the region.

After the ban many construction companies started looking for alternative ways and started importing sand from neighboring states but it is not a permanent solution and also transportation cost putting extra financial burden.

Faced with this changing situation, MAAD Mines & Minerals began looking at alternatives which would allow them to continue to produce the construction sands they require for the commercial building activities conducted through their Real Estate division.

They zero down to Crushed sand which is a proven alternative to natural sand. It can be artificially produced by crushing rocks, applying different sizing and washing technologies and can be used to produce sands for concrete, plastering and other construction works. It has been established throughout the globe, that manufactured sand is a better substitute to river/natural sand. Apart from better control on shape and grading than the river sand, crushed sand is free of coal, bones, shells, mica, silt and other organic impurities.

After careful study of various sand washing, systems available worldwide MAAD mines and minerals selected CDE Asia's combo DBS sand washing systems.

Introduction of CDE the Integrated Sand Washing plant – Combo DSB, helped by adding quality and value to the crushed sand produced by MAAD Mines & Minerals and ensured that the sand produced was one of the finest manufactured sand quality available in the region.

The washing system was installed after the Vertical Shaft Impactor (VSI) and the fine aggregate produced by the VSI was fed directly into the washing station for graded sand production.

Unwashed Sand	Final Product - Masonry Sand with -3mm feed	Final Product - Masonry Sand with < 5mm feed

The main objective of the CDE washing system was to remove the excess –150 micron material to achieve a final grade with no more than 10% –150 micron remaining in product. Also even more critical was the need to restrict the loss of ultrafines (i.e. particles below 75 micron) to absolute optimum levels as losing good sand with the waste would translate into heavy commercial losses for the plant owners. Achieving the proper cut-point efficiency was the key to success of the project as any residual ultrafine below 75 micron will give the sand a dirty appearance. At the same time CDE system must recover the maximum level of permissible fines in accordance with preferred specification to optimize commercial output.

A further key feature of the CDE system was that the washed sand is much drier than the conventional systems so that the sand is ready to dispatch immediately upon production. In normal operating conditions consistent moisture content (by weight) of 8-12% was generally expected.

COMBO DSB is a Dual Sand Washing system, capable of producing both Coarse & Fine sand material. Depending upon the feed charactertics, the plant can be made to produce one or two sands. The Plant's feed capacity is 70 tons per hour (considering a bulk density of 1.6 tons/m3), with a possibility of feeding a maximum size of 10mm. The system can easily remove upto 15% of ultrafines/silt from the material, although option to process dirtier material is also available.

A total of 87kW (143hp) power is being consumed during operation of this COMBO DSB plant (where 440V 3 Phase 50Hz Power is supplied as standard in India). Top–up water (Estimated amount of fresh water that is needed to be added each hour for smooth running of the plant) requirement amounts to ~22M3/hr. This unique modular design ensures smallest plant foot-prints. Therefore, it has a land utilization of about 35m x 45m including the stockpile.

Though, the standard cut-off point is set at 75 micron, smaller cutpoints can be achieved if required. A moisture content of around 10–12% is being attained and the sand produced by the system is visually dry and being directly dispatched.

The Combo DSB Washing plant is designed to produce both coarse and fine sand but is flexible to also operate as a single sand plant producing only the Plastering sand which fetches a much higher market value or coarse sand for concreting application. Accordingly, the aperture on the vibrating screen (customer scope) segregating the VSI product is adjusted, and fed to CDE system. The product grade of both Concrete and Plastering sand matched the criteria as per IS Specification of IS 383.

Combo Sand washing plant efficiently removes ultra Fines (-75 micron) thus reduces and controls amount of material below -150 micron size in the product resulting in improved sand quality, with consistent grade & quality when compared with natural sand that contributes towards saving cement consumption during the production of concrete. The washed sand produced through the CDE Sand washing plant is being supplied to many major building and RMC companies including customer's own captive consumption for highrise construction.

The ban on river sand mining in the Mumbai region is indicative of a wider trend throughout India .This presents a big opportunity for systems which can deliver high quality washed manufactured sands as a natural sand substitute. Whether the natural sand shortage comes from a ban on river sand mining or a shortage of natural sand within a particular area due to its geology, these systems offer operators a proven mechanism to increase the efficiency of their operations while at the same time maintaining the highest levels of product quality.