MANUFACTURED SAND
INTRODUCTION: WHAT IS M-SAND?
M-sand is crushed aggregates produced from hard granite stone which is cubically shaped with grounded edges, washed and graded with consistency to be used as a substitute of river sand. Manufactured sand is a term used for aggregate ag gregate materials less than 4.75mm and which are processed from crushed rock or gravel. WHY M-SAND?
Due to booming of construction activities in our country, natural sand resources are increasingly depleted and its cost is becoming increasingly high. The main natural and cheapest che apest sources of sand are riverbeds and these natural resources are depleting very fast. Due to various v arious reasons good sand is not necessarily readily available and it should be transported from long distances. Transportation is a major factor in the delivered price of construction sand. Moving construction sand to the market increases the sale price of the market significantly, due to the high cost of transportation. The use of specific deposits of sand depends on the performance of these materials in standardized engineering tests, including, but not limited to, grain size distribution, shape and percentage of silt or clay. It is agreed that natural sand, which is available today, is deficient in many aspects to be used directly for concrete production. Some of the factors include: • 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. 1
From the environmental point of view, the following are areas of problems in the future. • Digging of the sand from riverbeds reduces the water head, so less percolation of rainwater in ground resulting in lower ground water level. • In the absence of sand, more water gets evaporated due to direct sunlight. • If there is no sand in riverbeds, water will not be filtered. In the future aggregate prices are expected to rise due to decrease in sand deposits, quality and more environmental and land use regulations, which are associated with the rapid urban expansion that contributes to these shortages. Therefore, the importance of finding substitute sources of fine aggregate for concrete production that can be used in place of natural river sand cannot be overemphasized.
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M-Sand is manufactured sand, obtained from specific hard rock (granite) using the stateof-the-art International technology. 2
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Its numerous advantages over river sand have made it a favorite and a "Must-to-Use" with quality conscious builders. M-Sand is cubical in shape and is manufactured using international technology like High Carbon steel hit rock and then ROCK ON ROCK process which is synonymous to that of natural process undergoing in river sand information. Modern and imported machines VSI(Vertical Shaft Impact) are used by Poabs to produce M-Sand, ensuring to IS 383 ZONEII . For quality control, Poabs has engaged in a scientific tie-up with the RND lab and department heads of Trivandrum Engineering College who rigorously and constantly monitor our production at every stage. This exceptional kind of technical support always assures us to maintain consistency in quality as well as to upgrade our technology from time to time. The particle shape of the aggregates is very important for making concretes. It is a well known fact that the sand having cubical particles with grounded edges gives higher tensile strength and compression strength to the concrete. The grains should be of durable material and the size of the grains must be such that it should give minimum voids. The presence of clay and slit is avoided since it retards the setting of the cement and making mortar. Experiments shown that considerable variations in strength of mortar may occu r owing to form and variety of the sand particle. The strength of mortar may differ by about 50% of average. It is not possible in river sand that all particles should be of higher strength.This can be achieved only by making sand with the help of machines. In machine-made sand, we can use the raw material of higher strength. The manufactured sand produced by proper machines can be better substitute to river sand. There is discrepancy in the river sand for two loads lifted from same source. Hence to achieve consistent quality, each truck of sand should be tested. Moreover the sand has to be sieved to remove stones, slit and clay. In routine average wastage of sieving are about 35% and extra labour cost involved. Whereas Poabs M-Sand is ready-to-use-sand with no wastage since it do not have organic impurities. The superior shape and gradation of Poabs M-Sand ensures high strength concrete with significant savings in cement.
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QUALITY TESTS •
Poabs M-Sand Quality strength : M-Sand adheres to the highest standards and undergoing the following quality tests done by the College of Engineering, Trivandrum. 1. Sieve analysis. 2. Optical Microscopic Study to check the particle shape. 3. Workability (slump test by slump cone method). 4. Cube test for compressive strength. 5. No fear of adulteration with sea sand or muddy soil.
OBSERVED PROPERTIES OF M-SAND •
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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 exce llent 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 and used, which gives superior strength and its cubical shape ensures significant reduction in the cement used in the concrete 4
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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. Vasthu Shastra Says Building material must be from traces of human body or animal. M-sand is free of such material and is produced by crushing hard granite stone when compared to river sand that is produced naturally from weathered rock.
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: •
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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: •
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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 makes the sand useless for concrete work.
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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.
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COMPARISON OF M-SAND AND CRUSHER DUST: S.NO
PROPERTY
M-SAND
CRUSHER DUST
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Color
Grey
Grey
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Particle Shape
Cubically Shaped
Flaky , Elongated (Shapeless)
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Product
Manufactured as per IS, BS, ASTM Standards
a) It is fractured dust of jaw crusher b) A waste product in production process of stone crusher
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Manufacturing Process
International technology controlled manufacturing process through imported machines
No controlled manufacturing process as it is the by-product of stone crusher
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Gradation
As per IS 383 - 1970 Zone-II
Does not adhere to IS 383 - 1970 or any other standards
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Suitability for concreting
Recommended for usage in concrete & masonry works worldwide by the concrete technologists. Confirms international 6
Not recommended for use in concrete or masonry works. Does not have quality.
standards
COMPARISON OF M-SAND AND NATURAL SAND:
BLENDING: •
Blending is effective in reducing the level of micro fines in the fine aggregate used in the concrete mix compared with the micro fines in the manufactured sand. Blending is in fact the simplest and probably the most cost effective means of minimizing any adverse 7
properties arising from the typical 10 to 20% passing 75-micron fraction present in most manufactured sands. •
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The micro fines are the proportion of the grading most likely to include mineralogy that will increase water demand in the concrete mix. Blending has been shown to reduce and control this trend. In addition, CCAA research has demonstrated that high levels of micro fines correlate with lowered bleed. Where this situation is not desirable, blending with natural sand will reduce the micro fines in the blended fine aggregate, increasing the bleed.
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CONCLUSIONS:
The use of manufactured sand in producing concrete for normal strength, intermediate strength and high strength were studied and after the research work is done, the following conclusions are made and recommendations are forwarded. 1. The results of the hardened properties of the mix have shown that the concrete mixfor ISC and HSC with proportion of manufactured and natural sand achieved a higher compressive strength almost at all tested age of concrete. 2. A mean compressive strength of 93MPa, which is about C-75 concrete were produced using a 50% proportion of both natural and manufactured sand whereas with the same proportion of constituent material, a mean compressive strength of 88MPa was achieved on 100%NS and 100%MS indicating that the suitable proportion of NS and MS would result in improved compressive strength. 3. Manufactured sands are made by crushing aggregate to sizes appropriate for use as a fine aggregate. During the crushing process the manufactured sand have irregular shapes and more fine particles contributing to improved compressive strength compared to natural sand control mix. 4. Due to the irregular particle shape of the manufactured sand, in addition to the reduced amount of water cement ratio, manufactured sand is more important for high strength concrete mixes. 5. Analysis made on the influence of manufactured sand in the cost of the concrete revealed that no significant cost variation is observed for mixes with full or partial replacement of the manufactured sand with natural one. 6. Manufactured sand offers important economic advan tages in regions where the availability of natural sand is scarce or in cities where transportation cost is high as in the case of Addis Ababa and Jimma. 7. The use of manufactured sand in the construction industry helps to prevent unnecessary damages to the environment and provide optimum exploitation of the resources. 8. Manufactured sand offers a viable alternative to the natural sand if the problems associated with the workability of the concrete mix can be resolved by using super plasticizer. The a ddition of super plasticizer to a concrete mix with manufactured sand allows the mix to have a better workability.
RECOMMENDATIONS: 14
1. To minimize cost of manufactured sand transportation more advanced mobile plants might be a solution. 2. In order for a manufactured sand mix containing super plasticizer to be more economical, the maximum dosage of the super plasticizer should be made optimum by reducing the volume of admixture and to get the required consistency. 3. As the amounts of fines depend on the characteristics and on the strength of individual minerals, control over the selection of the raw material has to be made. 4. The manufacturing process of manufactured sand requires active production control of all processes, storage should be dry and transportation has to be minimized to prevent segregation and cost too. 5. Concerned authorities have up-to-date information about the locations and details of existing quarries in addition with the potential of available quarries. 6. Designers, specifiers, contractors and material suppliers need to understand the effects of manufactured sand angularity as well as fines content on concrete water demand and concrete durability. Further research is proposed in the following areas:
1. The effects that have on digging for natural sand on environment shall be studied. 2. More research and investigations need to be carried out to assess the scope for saving through optimization of both natural and manufactured sand. 3. Guide lines, mix design proposals and specifications shall be prepared using manufactured sand to establish acceptable mixes for concrete producers, contractors and their clients.
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