Understanding Concrete Calculations
Accurate concrete volume calculations ensure proper material ordering and project planning.
- Mix Proportions 1:2:3 ratio (cement:sand:stone). Water ratio: 0.45-0.50. Air: 4-6%. Slump: 3-5". Yield: 27 ft³/yd³. Add 10% waste factor.
- Strength Requirements Residential: 2500-3000 psi. Commercial: 3500-4500 psi. Industrial: 4000-6000 psi. Test age: 28 days. Early strength: 70% at 7 days.
- Volume Calculations Slab: L×W×D. Footings: L×W×D + 10%. Walls: L×H×W + 5%. Columns: π×r²×h. Stairs: (R×T×W×N)/27 + 15% waste.
- Material Quantities 1 yd³ = 27 ft³. Cement: 6 bags/yd³. Sand: 1 ton = 20 ft³. Stone: 1 ton = 15 ft³. Water: 30-33 gal/yd³. Fiber: 1.5 lbs/yd³.
Placement Guide
Site Preparation
Subgrade: 95% compaction. Base: 4-6" gravel. Forms: brace 4ft O.C. Vapor barrier: 6 mil poly. Reinforcement: centered. Joints: 24-36× thickness.
Weather Considerations
Cold: <40°F use blankets. Hot: >90°F use ice. Wind: <20mph. Rain: protect surface. Cure: 7 days minimum. Moisture: maintain 100% RH.
Cost Factors
Ready-mix: $120-150/yd³. Pump: $150-200/hr. Forms: $2-4/ft². Labor: $4-8/ft². Finish: $0.50-2/ft². Testing: $75-150/set.
Quality Control
Test every 50yd³. Slump tolerance: ±1". Air: ±1.5%. Temperature: 50-90°F. Strength: ±500 psi. Thickness: ±1/4". Flatness: FF25/FL20.