Avoiding thermal contraction cracks
In terms of avoiding thermal contraction cracks, experience has shown that by limiting temperature differentials to 20°C in gravel aggregate concrete, cracking can be avoided.
CIRIA Report Early thermal cracks control in concrete C660 (2007) gives limiting differential temperatures for different aggreagte types.
Table: Limiting temperature changes to avoid cracking
for internal restraint R = 0.42 (from C660)
||Limiting differential temperature, oC|
|Lightweight aggregate concrete, with natural sand
If these temperatures are exceeded, cracks are likely to form and sufficient reinforcement should be provided to control their widths (see Controlling thermal contraction cracks).