Question 1

How do I calculate concrete volume for a rectangular slab?

Accepted Answer

Volume = Length × Width × Thickness. All measurements should be in the same unit. For a 5m × 4m × 0.15m slab: Volume = 5 × 4 × 0.15 = 3 cubic meters. Add 5–10% extra for wastage.

Question 2

What is a standard concrete mix ratio?

Accepted Answer

Common mix ratios are 1:2:4 (cement:sand:aggregate) for general use, 1:1.5:3 for stronger structural concrete, and M25 grade (1:1:2) for high-strength applications. The ratio affects strength and cost.

Question 3

How many bags of cement are needed per cubic meter?

Accepted Answer

Approximately 7–8 bags (50kg each) of cement per cubic meter for M20 grade concrete. The exact amount depends on the mix ratio, water-cement ratio, and aggregate type.

Question 4

Should I add extra concrete for wastage?

Accepted Answer

Yes, always add 5–10% extra to account for spillage, over-excavation, and uneven surfaces. For critical structural elements, 10% extra is recommended to avoid running short mid-pour.

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