M-Sand

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Context:

• Northern Coalfields Limited (NCL), the Miniratna coal-producing company is all set to start production of ‘M-Sand’-the core material used in construction in civil works in its Amlohri Project.

M Sand

• M Sand is artificial sand made from the crushing of rock or granite for construction purposes in cement or concrete.
• It is used as a substitute for river sand.
• M sand differs from natural river sand in its physical and mineralogical properties.

Manufacturing

M-Sand is manufactured in a three-stage process:

Crushing:

Quarry and rock stones are crushed at jaw crushers, cone crushers, and vertical shaft impact crushers, respectively leading to the formation of angular and cubical fine aggregate particles.

Screening:

Screening ensures this material is properly graded that’s similar to river sand.

Washing:

Washing removes all the micro-fine particles. Also, fine aggregates for concrete and plaster sand are also formed.

M Sand (Manufactured Sand)	River Sand
Made of on factories under the supervision	Available naturally at river beds.
Moisture is only available in water-washed M sand.	Moisture is trapped between the fine particles for concrete purposes
High concrete strength compared to river sand	Low concrete strength compared to M sand
The sand particles of M sand are in cubic form. This makes the bond stronger.	Bonding is weak because of its Excessive presence of flaky, sharp and angular grains
zero slit content	3-20% silt content
0% of marine products	2-4% Marine Products (shells, etc)
No oversized products as they are well standardized and manufactured under control.	6-10% enlarged material (stones) should be sieved
Better quality control from being manufactured in a controlled environment	There is no restriction on quality as it occurs naturally. There may be differences in silt contents in the same riverbed sand.
An eco-friendly product, which causes less damage to the environment compared to river sand.	Harmful to the environment. Environmental imbalances reduce groundwater levels and river water dries up.
M-sand dry density of 1750 kg/m3	Naturally Sand dry the density of 1600 kg/m3
M-sand specific gravity is approximately 2.73 (Depend on the parent rock.)	River sand specific gravity is approximately 2.65 (Depending on rocks in the catchment area.)
Made of on factories under the supervision	Available naturally at river beds.
Moisture is only available in water-washed M sand.	Moisture is trapped between the fine particles for concrete purposes
High concrete strength compared to river sand	Low concrete strength compared to M sand
The sand particles of M sand are in cubic form. This makes the bond stronger.	Bonding is weak because of its Excessive presence of flaky, sharp and angular grains
zero slit content	3-20% silt content
0% of marine products	2-4% Marine Products (shells, etc)

Advantages of M Sand:

• It is highly cohesive and compressive in strength.
• It does not have the presence of impurities such as clay, dust, and silt coatings. This helps in producing better quality concrete.
• M-sand produced under strict industrial control and manufactured to meet BIS standards has proven to produce stronger concrete compared to river sand.
• A nearly 30 %(percent) increase in masonry strength is obtained with the use of manufactured sand.
• It requires a lower water-cement ratio if the mortar is mixed with manufactured sand, which also results in better characteristics in the hardened state.
• It does not contain an organic and soluble compound that affects the setting time and properties of cement, thus the required strength of concrete can be maintained.
• Manufacturing sand also eliminates the environmental impact that occurred due to the lifting of natural sand from the river bed.

Disadvantages of M-sand:

• Improper crushing of manufacturing sand may lead to angular and flaky particles that are not suitable for concrete production, both technically and economically.
• Also, an adequate set up of crusher may not be available in some parts of the county like West Bengal, as it costs higher than river sand.
• For high-grade pumpable concrete in high-rise buildings, the requirement of cement is higher than the river sand, which may not be cost-effective.

M Sand in India:

• All the four southern states Andhra Pradesh, Tamil Nadu, Telangana, Karnataka have recognized it as a substitute for river sand, and have been promoting its use over the years. Gujarat also manufactures M-sand.
• Karnataka has been the most proactive of the lot. In fact, the 2011 sand policy encourages the establishment of M-sand units by giving it a top priority while allotting quarries. The State has 164 M-sand manufacturing units that produce 20 million tonnes of M sand per annum.

Hurdles in Using Alternative Sands:

Manufactured sand is being used in India, but is still not popular due to the following reasons:

• Lack of standard: In India too there are no details and specifications, especially regarding gradation, properties like void content, sand equivalent, limits of deleterious materials, and on proper mix proportions.
• No government support: Besides the lack of government support, there are malpractices in every stage of construction, and lack of an appropriate policy to formulate and implement proper management of waste and use of alternatives. This is because even the government buildings are being built with river sand. Although there are guidelines for sustainable mining, illegal sand mining continues to be prevalent.
• Limited awareness: Lack of awareness of the possibilities of production and use of alternative sand in construction is a major barrier. There is a need to generate experimental data on different types of alternative sands and on their properties so that they can be recognized by the government and private construction sectors.
• Absence of suitable technology: Very few commercially viable and accepted technologies for the production of alternative sands are present. Knowledge to tackle feedstock storage and transportation for proper quality of the sands is still lacking. There are no proper testing equipment and lab facilities to ensure the quality of alternative sands. Also, the presence of quarry dust and inspection of production units is not undertaken.
• Hesitancy of people: Limited knowledge has made people reluctant towards using alternative sands. This reluctance is more amongst the government officials and builders regarding the sands’ effect on quality.

Recommendations:

Generating Awareness

• There is a pressing need to create awareness of the problems related to environmental degradation and promote the use of alternative sands.
• This can be brought about through the media, encouragement from different organizations, through seminars and conferences.

Government Initiative

• Engagement of organizations could generate extensive experimental data. This data in turn would help in creating guidelines and codes.
• Government organizations should set an example of using alternative sand in buildings, bridges, highways, skyscrapers, etc. to bring confidence in the public at large.

Initiative by Construction Industry

• The construction industry can articulate guidelines to inspire the use of alternative sand in projects and create a market mandate.
• An association of builders in consultation with experts and scientists can start work to promote its usage. Likewise, contractors and builders can endorse the sands in their client buildings.

Initiative by Research institutions

• Research and academic institutions can play a vital role in the development of evaluation methods and specifications for use of alternative sands in construction.

Media

• The media can sensitize the public by highlighting the importance of conserving our natural resources.

 

https://www.pib.gov.in/PressReleasePage.aspx?PRID=1889973