from anywhere you buy the CRUSH sand it all same. ensure it manufactured through vertical shaft impactor.do the sieve analysis as per is 10262. the site engineer ha to take a call on the quality after checking all parameters
Contains harmful Impurities like mud, soil, silt, salt, alkalies, mica, organic matter etc.
No consistency in particle size due to different sources and its natural properties and can harm mix design due to variability.
irregular size can lead to wastage of sand (unintended in terms of cost) due to oversize called shingles.
Supply of material not available all time and fluctuations in cost can hamper Project Cost.
Extraction of sand from river bed is environmental hazard and ban in many places.
Advantages of Manufactured Sand over River Sand
Contains no organic, harmful impurities, hence significant improvement in strength of concrete at same cement content.
Gradation of particles can be controlled during production.
As Gradation is controlled there is no wastage due to oversize materials.
Consistency in supply and also price is almost stable so does not affect the Project Cost.
Disadvantagesof Manufactured Sand
As such there are no disadvantages in manufactured sand but if the production control is loose or manufacturer wont care of production quality as long as his material gets accepted at construction projects. It will have following disadvantages. Quality of Rock used to produce sand
If you had ever visited a quarry, then you must have seen, its either a mountain or a normal ground which is cut / blast / break to get the rock, which is further broken into boulder sizes.
The quarry contains the following
Then Basalt or any other hard rock (It depends on the properties on strata in that area, it may have soil and then beneath a hard rock)
One should check the quarry of supplier to get an idea at what level it is.
If boulder transported to jaw crusher contains hard or soft murrum boulder, its likely to get crush into more finer size due to law strength and all this goes into production of manufactured sand. This have law strength and more water absorption.
It affects the water demand in concrete and setting properties of concrete.
By seeing the color of sand, you can judge its contains such materials or not, If its Basalt rock then the sand look blackish and if it contains murum then color goes towards brownish. Such sand are really bad for concrete and can affect almost all properties of concrete
Setup at Manufacturing Unit
As rightly said by Mr. @K Kiran, Their is possibility of higher finer particles than 150 micron either due to quality of rock or if dust collector or separator are not used. The problem why Dust collector or separator not used even though they are install to show clients, in my previous projects where i used to do a very high strength concrete, we did a study on it and we selected some suppliers after doing visits to their Quarry and plant set up and given order to them, You will not believe they provided such a great quality of sand, you cant even make difference, is it river sand or manufactured. They did all control for rounding of particle separation of dust etc.
After few months they called me to visit their plant and showed me a layer of dust deposited on all ground which is almost a feet high and the big hips of fine particles and asked me to provide solution for it as to where use that material, its like clay when water is added and crumble down like black cotton soil when water evaporates from it. (I did some experiment but not succeeded at that time to utilize it and later i changed job so never get a chance to experiment again)
As per IS 383 a Manufacture sand is allowed to have 150 micron passing up to 20% in all zones.
But i prefer we should not cross 10% as when we say 10% it might be less or more again its a subject of how sampling done, testing procedure etc.
During Rainy Season
During rainy season, contamination in boulders happens if its deep cut in earth, the material surrounding the area tends to fall into it and also the pits get flooded.
It is very difficult to get quality sand, if there is no Quality Control on material received at site.
Apart from above, if you ask me about Robo Silicon plants, then i frankly tell you, those people does not supply good quality materials. i am telling you base on what i know 6 years back. Do not know Today's condition.
Best answer is Visit their plant and Quarry. Take the sample of material they showed you (this is what they will show you a good production)
If you get inferior quality of material than that reject it. here you can compare apple to apple from both materials made at there plant (Kindly collect big sample of at least 4 bags of 50 kg, this gives a better idea)
Crushed sand call it has in many names m sand robo sand ,
Generally sand is used in making concrete and in ceiling ,internal and external wall plaster
Sand used for concreting it confirms to IS 383-2016
Sand used for masonry mortar which confirms to IS 2116-1980
Sand used for plaster which confirms to IS 1542-1992.
Now days river sand scarcity ,river sand is available in river banks actually river sand is good for construction its having excellent properties to bind with cement .
Manufacture sand is also good but excess finess cracks will appear on walls and it shrinks fastly so well graded and mixed with the admixture increases its strength and water tightness...