EXPANSION AND CONTRACTION OF CONCRETE. 31 
tion due to fall in temperature. A shrinkage of 0.04 per cent (one- 
quarter inch in 50 feet) is. a safe allowance clue to drying. 
10. Temperature at time of construction of road should be con- 
sidered in designing joints. Cold- weather construction requires a full 
allowance for temperature expansion and, on wet sub-bases, for mois- 
ture expansion also. Hot-weather construction theoretically requires 
no joints at all, even in wet sub-bases, as the temperature contraction 
exceeds the moisture expansion. However, the difficulty of keeping 
the cracks clear probably renders joints imperative. 
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