Concrete strength can be specified by using either cube strength or cylinder strength.
The
characteristics strength of concrete usually represents its crushing strength
at the 28th day after casting. However, it is also essential to know
the concrete strength at any time.
The rate of
concrete strength gain is important as it governs the time to apply prestress.
Concrete with high early strength is necessary for precast segmental construction
to allow daily casting cycle for the segment production cell.
Typically, 12MPa
of strength should be achieved within 10 hours to allow stripping of the
shutter. 25MPa should be achieved after 36 hours to allow the transportation of
segment to storage yards.
Modulus of
elasticity of concrete is dependent of the concrete strength and aggregate
properties.
To minimize the
creep and shrinkage losses, the cement content and water/cement ratio should be
maintained at minimum.
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