How much water to use to make concrete

1. common to use 0.4-0.6 water / cement ratio
2. olny 0.23 is required for hydration
3. Extra water required for hydration and compaction
4. If not enough water , compaction not done properly , result in high porosity

Maximum permitted concentration of various harmful element As suggested by 1.s.1

1. Organic solid 0.02%
2. Inoganic solid 0.03%
3. Sulphates 0.05%
4. Alkali chloride 0.10%