UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 532 



Contribution from the Office of Public Roads and Rural *\Jv 



Engineering *^Ly 



LOGAN WALLER PAGE, Director JVTWt 



Washington, D. C. 



PROFESSIONAL PAPER. 



October 13, 1917 



THE EXPANSION AND CONTRACTION OF CON- 

 CRETE AND CONCRETE ROADS. 



By A. T. Goldbeck, Engineer of Tests, and F. H. Jackson, Jr., Assistant Test- 

 ing Engineer. 



CONTENTS. 



Page. 



Laboratory measurements of expansion and 

 contraction 2 



Results of expansion and contraction meas- 

 urements 5 



Measuring the expansion and contraction of 

 concrete roads 12 



Results of test measurements at Chevy Chase, 



Md 15 



Expansion and contraction of Ohio post road . 20 



General discussion 27 



Conclusions 30 



Observation of concrete roads shows that most of the irregularities 

 of wear make their initial appearance at expansion joints and at 

 transverse and longitudinal cracks. Soon after a crack is formed 

 traffic begins to batter down the edges, and unless immediate and 

 effective maintenance measures are adopted, each succeeding vehicle 

 will act with greater destructive effect. Under such conditions and 

 without proper maintenance, little time elapses before depressions 

 are formed in the road surface, which lessen the life of the road and 

 render it decidedly unpleasant to the fast-moving traffic generally 

 carried by concrete roads. Improperly maintained expansion joints 

 wear in a manner similar to cracks, and the cost of their maintenance 

 is dependent upon their frequence. 



Cracks result when the tensile strength of the concrete has been 

 exceeded, or compression cracks may be caused in rare instances by 

 excessive expansion without proper provision for such a movement. 

 Tension may occur in a concrete pavement as the result of settlement 

 or upheaval, in which case the pavement is stressed as a slab, and, if 

 overstressed, will crack on the tension side. Most transverse cracks, 

 however, are caused by contraction due to two principal phenomena : 

 1, decrease in temperature ; 2, drying out of water from the concrete. 



80045°— 17— Bull. 532 1 



