Question 1

What does concrete grade M20 mean?

Accepted Answer

M stands for 'Mix' and 20 represents the characteristic compressive strength of 20 MPa (N/mm²) at 28 days when tested with 150mm cube specimens. M20 is the minimum grade recommended for reinforced concrete work by most building codes.

Question 2

Why is the water-cement ratio so important?

Accepted Answer

The water-cement ratio directly controls strength and durability. Too much water creates pores as excess water evaporates, reducing strength and increasing permeability. Too little water makes the concrete unworkable. Every 0.01 increase in w/c ratio reduces strength by approximately 1-2 MPa.