Dec 24, 2017. #3. Concrete mix Design for M30 Grade concrete with GGBS is as follows; OPC Cement 53 Grade – 280 Kg. GGBS – 100 Kg. Water Cement ratio (w/c) – 0.4. Free Water – 152 liters. 20mm Metal / Aggregates – 772 Kg. 10mm Metal / Aggregates – 343 Kg.