UNITED STATES DEPARTMENT OF AGRICULTURE 
% BULLETIN No. 532 
i?/" Contribution from the Office of Public Roads and Rural •\J» 
Engineering 
LOGAN WALLER PAGE, Director 
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. 
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. Improperh 7 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 
overstressecl, 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- 
