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 due 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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