The material. Concrete is a composite, and a complex one. The matrix is cement; the reinforcement, a mixture of sand and gravel ("aggregate") occupying 60-80% of the volume. The aggregate increases the stiffness and strength and reduces the cost (aggregate is cheap). Concrete is strong in compression but cracks easily in tension. This is countered by adding steel reinforcement in the form of wire, mesh, or bars ("rebar"), often with surface contours to key it into the concrete; reinforced concrete can carry useful loads even when the concrete is cracked. Still higher performance is gained by using steel wire reinforcement that is pretensioned before the concrete sets. On relaxing the tension, the wires pull the concrete into compression.
6:1:2:4 Water:Portland cement:Fine aggregate:Coarse aggregate
Electrical conductor or insulator? Electrical resistivity Dielectric constant Dissipation factor Dielectric strength
1.8 X 1012 – 1.8 X 1013 pohm. cm
*8 – 12
*0.001 – 0.01
0.8 – 1.8 106 V/m
Reinforced concrete enables large structures and complex shapes.
Annual world production Reserves
Embodied energy, primary production CO2 footprint, primary production Water usage Eco-indicator
Construction energy Construction CO2
Embodied energy, recycling CO2 footprint, recycling Recycle fraction in current supply
Typical uses. General civil engineering construction and building.