Selection of Water Cement Ratio for M30 Grade of Concrete Mix design. Maximum Water Cement Ratio Permitted As per MORTH Clause – 1715.2: 0.40. W/c Ratio Selected As 0.39. Selection of Water for M30 Grade of Concrete Mix Design Water Content as per Table 2, of IS: 10262:2009 for 20 mm maximum size of aggregate IS: 186 litres.