M-Sand

ABSTRACT

Scarcity of good quality Natural River sand due to depletion of resources and restriction due to environmental consideration has made concrete manufactures to look for suitable alternative fine aggregate. One such alternative is “Manufactured sand”. Though manufactured sand has been in use in concrete manufacturing in India, the percentage of its contribution is still very negligible in many parts of the country. Except in Kerala and in some pockets in Southern and Western India, real processed manufacture sand is not available and this makes manufacturing of good quality of concrete very difficult. The application of concrete meeting the specification is of paramount importance, to ensure construction of durable R.C.C. structure. Hence durable concrete covers and bears the responsibility of sustaining the entire R.C.C. structure throughout it service life. A well processed manufactured sand as partial or full replacement to river sand is the need of the hour as a long term solution in Indian concrete industry until other suitable alternative fine aggregate are developed.

About M-Sand

Manufactured sand is a term used for aggregate materials less than 4.75mm and which are processed from crushed rock or gravel. Due to booming of construction activities in our country, natural sand resources are increasingly depleted and its cost is becoming increasingly high.

Natural or River sand are weathered and worn out particles of rocks and are of various grades or sizes depending upon the amount of wearing. Now-a-days good sand is not readily available; it is transported from a long distance. Those resources are also exhausting very rapidly. So it is a need of the time to find some substitute to natural river sand.

The artificial sand produced by proper machines can be a better substitute to river sand. The sand must be of proper gradation (it should have particles from 150 microns to 4.75 mm in proper proportion).

When fine particles are in proper proportion, the sand will have fewer voids. The cement quantity required will be less. Such sand will be more economical. Demand for manufactured fine aggregates for making concrete is increasing day by day as river sand cannot meet the rising demand of construction sector. Natural river sand takes millions of years to form and is not replenishable.

Because of its limited supply, the cost of Natural River sand has sky rocketed and its consistent supply cannot be guaranteed. Under this circumstances use of manufactured sand becomes inevitable.

River sand in many parts of the country is not graded properly and has excessive silt and organic impurities and these can be detrimental to durability of steel in concrete whereas manufactured sand has no silt or organic impurities.

However, many people in India have doubts about quality of concrete / mortars when manufactured or artificial sand are used. Manufactured sand has been regularly used to make quality concrete for decades in India and abroad.



Issues with River Sand

  • It doesn’t contain fine particles, in the required proportion.
  • Contains an organic and soluble compound that affects the setting time and properties of cement.
  • The presence of impurities such as clay, dust and silt coatings, increase water requirement and impair bond between cement paste and aggregate.
  • The presence of organic materials affects durability of the concrete therefore it shortens the life of the concrete product.

General Requirements of Manufactured Sand

  • All the sand particles should have higher crushing strength.
  • The surface texture of the particles should be smooth.
  • The edges of the particles should be grounded.
  • The ratio of fines below 600 microns in sand should not be less than 30%.
  • There should not be any organic impurities.
  • Silt in sand should not be more than 2%, for crushed sand.
  • In manufactured sand the permissible limit of fines below 75 microns shall not exceed 15%.

The following factors contribute to the production of good quality concrete

  • Knowledge of the properties and fundamental characteristics of concrete making materials and the principles of design,
  • Reliable estimates of site conditions and costs,
  • Quality of component materials,
  • A careful measurement of weigh-batching of cement, water and aggregate,
  • Propertransport, placement and compaction of the concrete,
  • Early and thorough curing,
  • Competent direction and supervision

Crushing, Screening, and Washing

Manufacturing of M Sand process involves three stages, crushing of stones in to aggregates by VSI, then fed to Rotopactorto crush aggregates into sand to required grain sizes (as fines). Screening is done to eliminate dust particles and Washing of sand eliminates very fine particles present within. The end product will satisfy all the requirements of IS:383 and can be used in Concrete & construction. The VSI Plants are available capacity up-to 400Ton Per Hour(TPH).

Manufactured Sand (M Sand)

Only, sand manufactured by VSI crusher/Rotopactor is cubical and angular in shape. M Sand made by other types of machines is flaky, which is troublesome in working. The Jaw crushers, are generally used for crushing stones in to metal/aggregates. Manufactured sand from jaw crusher, cone crusher, roll crusher often contain higher percentage of dust and have flaky particle.

IS Code Provisions

BIS Guidelines IS : 383-1970 for selection and testing of Coarse and Fine aggregates available. Generally, Sand is classified as Zone I, Zone II, Zone III and Zone IV (i.e. Coarser to Finer). There is sieve designation for each zone. Gradation is made in accord with the usage of the sand. There are testing sieves, consists of 4.75mm, 2.36mm, 1.183mm, 600microns, 300 microns, 150 microns and a pan.

Comparison of River & Manufactured Sand

IS Sieve % of passing
(RiverSand)
% of passing
(Manufactured Sand)
Zone II
(As per IS:383)
4.75mm 100 100 90-100
2.36mm 99.7 99.7 75-100
1.18mm 89 66.2 55-90
600micron 60.9 39.8 35-59
300micron 17.7 25.5 8-30
4150micron 3.1 9.9 0-20
75micron Max 3 Max 15 Max 15
Zone II Zone II

comparison between Manufactured and River sand

SI.No Property River sand Manufactured sand Remarks
1 Shape Spherical particle Cubical particle Good
2 Gradation Cannot be controlled Can be controlled
3 Particle passing 75micron Presence of silt shall be less than 3% (IS:383-1970) Presence of dust particle shall be less than 15% Limit 3% for uncrushed & limit 15% for crushed sand
4 Silt and Organic impurities Present (Retard the setting & Compressive Strength) Absent Limit of 5% for Uncrushed & 2% for Crushed sand
5 Specific gravity 2.3-2.7 2.5-2.9 May vary
6 Water absorption 1.5 - 3% 2 - 4% Limit 2%
7 Ability to hold surface moisture Up-to 7% Up-to 10%
8 Grading zone(FM) Zone II and III FM 2.2-2.8 Zone II FM 2.6-3.0 Recommends Zone II for Mass Concrete
9 Soundness(Sodium sulphate-ss & Magnesium sulphate -ms) (5 cycles) Relatively less sound (Ex. >5) Relatively sound (Ex. <5) Limit 10% ss and 15% ms
10 Alkali Silica Reactivity 0.002- 0.01 0.001- 0.008 Limit 0.1 %expansio

SI.No Property River sand Manufactured sand Remarks
1 Workability & its retention Good & Good retention Less & Less retention Control of fines & apply water absorption correction, use of plasticisers
2 Setting Normal Comparatively faster Apply water absorption correction, use retarders
3 Compressive strength Normal Marginally higher As shown above
4 Permeability Poor Very poor
5 Cracks Nil Tend to surface crack Early curing & protection of fresh


SI. No. Description 100% River Mix 100% M Sand Mix
1 Grade of Concrete M20 M20
2 Cement (Kg/Cum) 210 210
3 Fly Ash (Kg/Cum) 90 90
4 20mm (Kg/Cum) 771 779
5 12.5mm (Kg/Cum) 419 423
6 River Sand (Kg/Cum) 835 0
7 M Sand (Kg/Cum) 0 849
8 Water (Kg/Cum) 183 186
9 Chemical Admixture (Kg/Cum) 1.2 1.4
10 W/C 0.55 0.55
11 Compressive strength @ 7 days (Mpa) 15.11 16.44
12 Compressive strength @ 28 days (Mpa) 26.22 28.44

Vastu Aspects of River sand

Now-a-days, Vastu Shastra is more popular, consults Vastu by many people while constructing a house. As per Vastu Shastra, the building material must be free from traces of human or animal body. The river sand contains bones of human beings and animals. The shells are also a kind of bone. It is not easy to take out all such things present in the river sand. Hence, the best solution for this is to use artificial/crushed sand of good quality for human well being.

COMPARISON BETWEEN M SAND AND RIVER SAND

The natural river sand was the cheapest resources of sand. However the excessive mining of river bed to meet the increasing demand for sand in construction industry has lead to the ecological imbalance in the state. Now the sand available in the riverbed is very coarse and contains very high percentage of silt and clay.

The silt and the clay presence in the sand reduce the strength of the concrete and holds dampness. The natural river sand is the product of sedimentation, mica, coal, fossils and other organic impurities are present in the river sand above certain percentage which make the sand useless for concrete work.

Acute shortage and high price for river sand has lead to the adulteration of sand with salty sea sand which has raised serious concern among builders.

Environmental Impact

The River sand lifting from river bed, impact the environment in many ways :

  • Due to digging of the sand from river bed reduces the water head, so less percolation of rain water in ground, which result in lower ground water level.
  • The roots of the tree may not be able to get water.
  • The rainwater flowing in the river contents more impurities.
  • Erosion of nearby land due to excess sand lifting
  • Disturbance due to digging for sand & lifting, Destroys the flora & fauna in surrounding areas
  • The connecting village roads will get badly damaged due to over- loading of trucks, hence, roads become problem to road users and also become accidents prone
  • Diminishing of Natural Rivers or river beds, not available for future generations.
SI. No. PROPERTY M-SAND CRUSHER DUST
1 Colour Grey Grey
2 Particle Shape Cubically Shaped Flaky
3 Product Manufactured as per IS, BS, ASTM Standards Elongated (Shapeless)
a) It is fractured dust of jaw crusher
b) A waste product in production process of stone crusher
4 Manufacturing Process Internation technology controlled manufacturing process through imported machines No controlled manufacturing process as it is the by-product of stone crusher
5 Gradation As perlS 383 - 1970 Zone-ll Does not adhere to IS 383 - 1970 or any other standards
6 Suitability for concreting Recommended for usage in concrete & masonry works worldwide by the concrete technologists. Confirms international standards Not recommended for use in concrete or masonry works. Does not have quality.

High Strength

The superior shape, proper gradation of fines, smooth surface texture and consistency in production parameter of chemically stable sands provide greater durability and higher strength to concrete by overcoming the deficiencies like segregation, bleeding, honey combing, voids and capillary.

Greater workability

The crusher dust is flaky and angular in shape which is troublesome in working. There is no plasticity in the mortar which makes yet difficult for the mason to work. Whereas the cubical shape with grounded edge and superior gradation gives good plasticity to mortar providing excellent workability.

Comparison of Impurities - River Sand Vs M-Sand

SI. No. RIVER SAND M-SAND
1 Marine Products 2 - 4 % Nil
2 Oversized Materials 6-10% Nil
3 Clay & Silt 5 - 20 % Nil

ADVANTAGES OF M SAND :

  • M-Sand Quality strength
  • M-Sand adheres to the highest standards and undergoing the following quality tests.
  • Sieve analysis
  • Optical Microscopic Study to check the particle shape.
  • Workability (slump test by slump cone method).
  • Cube test for compressive strength.
  • No fear of adulteration with sea sand or muddy soil.

Greater Durability

M-Sand has balanced physical and chemical properties that can withstand any aggressive environmental and climatic conditions as it has enhanced durability, greater strength and overall economy. Usage of M-Sand can overcome the defects occurring in concrete such as honey combing, segregation, voids, capillary etc.

High Strength

The superior shape, proper gradation of fines, smooth surface texture and consistency in production parameter of chemically stable sands provides greater durability and higher strength to concrete by overcoming deficiencies like segregation, bleeding, honey combing, voids and capillary.

Greater Workability

The crusher dust is flaky and angular in shape which is troublesome in working. There is no plasticity in the mortar which makes it even difficult for the mason to work, whereas the cubical shape with grounded edge and superior gradation gives good plasticity to mortar providing excellent workability.

Offsets Construction Defects

M-Sand has optimum initial and final setting time as well as excellent fineness which will help to overcome the deficiencies of concrete such as segregation, bleeding, honeycombing, voids and capillary

Economy

Usage of M-Sand can drastically reduce the cost since like river sand, it does not contain impurities and wastage is NIL. In International Construction Scenario, no river sand is used at all, only sand is manufactured, which gives superior strength and its cubical shape ensures significant reduction in the cement used in the concrete.

Eco-Friendly

M-Sand is the only alternative to river sand. Dredging of river beds to get river sand will lead to environmental disaster like ground water depletion, water scarcity, threat to the safety of bridges, dams etc.
Beside with the Government contemplating ban on dredging of River beds to quarry river sand, as part of the growing concern for environment protection, M-Sand will be the only available option.

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