Manufactured sand is angular while most river sand is smooth. Crushed rock and crushed sand interlock and help form stable bases. In our area, crushed sand is a byproduct of making crushed stone (gravels). It should be even better in concrete than river sand.Bloody marvellous, excellent video to watch, and very therapeutic I must say.River sand is best for wall plaster and floor plaster/ceiling plaster ...but this video is excellent when river is full of water in rainy season we can use this manufacturing sand for emergency needs.