CostBuildrConcrete Mix Ratio Guide – M10 to M25
Concrete grades (M10, M15, M20, M25) specify the compressive strength the mix must achieve after 28 days of curing. Each grade corresponds to a specific cement:sand:aggregate ratio. Choosing the right grade ensures your structure is strong enough without wasting cement on unnecessarily rich mixes.
Grades, Ratios, and When to Use Each
M10 (1:3:6) achieves 10 MPa—used for leveling courses and non-structural PCC bedding. M15 (1:2:4) achieves 15 MPa—the standard for residential slabs and lintels. M20 (1:1.5:3) achieves 20 MPa—used for columns, beams, and structural members. M25 (1:1:2) achieves 25 MPa—used for high-load areas, water tanks, and post-tensioned slabs.
Never use M10 for any reinforced concrete work. M15 is the minimum grade for reinforced slabs per most building codes. M20 is required for multi-story buildings, all columns and beams, and water-retaining structures. M25 is for pre-stressed elements, heavy industrial floors, and high-rise structures.
Material Quantities per Cubic Meter
Per cubic meter of concrete: M10 needs 210 kg cement, 0.45 m³ sand, 0.89 m³ crush. M15 needs 310 kg cement, 0.44 m³ sand, 0.88 m³ crush. M20 needs 395 kg cement, 0.42 m³ sand, 0.84 m³ crush. M25 needs 530 kg cement, 0.38 m³ sand, 0.76 m³ crush.
These are nominal mix proportions; design mixes based on actual material testing may differ slightly. Higher grades use more cement but slightly less aggregate due to the richer paste content filling voids more effectively.
Quality Control on Site
Always use clean, well-graded aggregate—dirty sand with clay or silt reduces strength by up to 25%. Maintain a water-to-cement ratio of 0.45–0.50; excess water is the most common cause of weak concrete on residential sites.
Mix for at least 2 minutes in a mixer or 4 minutes by hand. Take cube samples (150 mm) during every major pour and test at 7 and 28 days. If results fall below the specified grade, the structural engineer may require load testing or demolition of the affected element.
Questions fréquentes
What is the most common concrete grade for houses?
M15 (1:2:4) for residential roof slabs and lintels, and M20 (1:1.5:3) for columns and beams. Most residential construction uses a combination of both grades.
Can I use M10 concrete for a roof slab?
No. M10 is too weak for any reinforced concrete work. The minimum grade for reinforced slabs is M15 (1:2:4). M10 is only suitable for plain concrete bedding under foundations.
How is concrete grade tested?
Cube samples (150×150×150 mm) are cast during the pour and cured in water for 28 days, then crushed in a compression testing machine. The result in MPa must meet or exceed the specified grade (e.g., ≥20 MPa for M20).