Which one is the best for RCC concrete, M-sand or river sand?

At this point, the debate is evenly poised with the freshers supporting “M.Sand” and the experienced professing “River Sand”. I just felt like putting a little of my perspectives. The reason the freshers are supporting “M.Sand” is based on the Technical Literature available and the reason the experienced supporting “River Sand” is experience. Anyhow

1. In some of the states like Maharashtra, Goa etc. mining of river sand is illegal for environmental reasons. So, the only choice you have is “Manufactured Sand” or better we call it “Crushed Sand”
2. Considering river sand to be legal. Still, the gradation of the same is very much dependent on the seasonal variation, mining technique, washing and screening after mining etc. The river sand of Ganga or Brahmaputra is to fine to be used. Sand from Son river is very good. It depletes. However, all said and done. The spherical shape of river sand gives it the advantage of higher workability for same water content. Say, the use of M.Sand results in increase of water demand by 20 litres. It means increase in cement by 50 kg or admixture dosage by 0.5% bwc. The increase in strength due to angularity will only happen when water cement ratio is kept nearly constant.
3. Just the way “River Sand” has certain lacunae like excess silt, coarser gradation, organic deleterious materials etc.. “M.Sand” also has it’s share. First of all, all sands marketed as “M.Sand” is not “M.Sand” but most of them are Crusher Dust, merely a by product of Crushing Plant. It generally contains huge fines along with. High Fines means High water demand ….
4. Production of High Quality of “Crushed Sand” requires very high end crusher which should be tailor made for the parent rock type. The general convention being “Jaw Crusher” as primary crusher – followed by “Cone Crusher” as secondary crusher and finally “Vertical Shaft Impactor” as tertiary crusher. However, this doesn’t work always. VSI is not very effective for rocks like sandstone wherein the tertiary crusher is also preferred to be a cone crusher.
5. Sometimes. the production cost of M.Sand exceeds procurement cost of R.Sand.
6. Sometimes it is wiser to blend both of them together.