PORTLAND CEMENT CONCRETE ROADS. 31 
chased. If the pavement is to be machine-finished, heavy forms 
are desirable and usually are more economical than light ones, as 
they hold their shape much better under the vibrations set up by the 
finishing machine. The forms should always be set true to line 
and grade before the subgrade is finished, in order to serve as a guide 
for the finishing. It is very essential that the forms be firmly sup- 
ported and bear uniformly upon the subgrade, as any sag produces 
an irregular surface in the pavement. The ends of the different 
sections of forms should be fastened together so that no relative dis- 
placement occurs. The joints between the sections on the two sides 
of the road should not be opposite each other, but should be stag- 
gered. The height of the forms should preferably be equal to the 
thickness of the pavement at the edge. Forms 1 inch less in height 
than the edge of the pavement can be used satisfactorily, however, 
by bolting under them a 1-inch strip of wood. These wood strips 
should be somewhat wider than the base of the forms, so that addi- 
tional bearing can be secured. In States that use a variable thick- 
ness of pavement at the edge this arrangement reduces the amount 
of forms required for different classes of work. 
Forms for concrete pavements should always be oiled before the 
concrete is placed against them. This oiling prevents the concrete 
from sticking to them, makes cleaning easy, and prolongs the life 
of the forms. Any crude oil can be used for this purpose and 
approximately 1 barrel per mile will be required. 
The use of bent forms should be prohibited. It is usually specified 
that variations in the surface of the pavement of over one- fourth 
of an inch in 10 feet will not be permitted. These variations in the 
surface of the pavement are caused to a large extent by the forms, 
so it would appear that no greater variation should be permitted in 
the forms than is permitted in the pavement. Forms, therefore, 
should not be used if their top surfaces vary more than one-fourth 
inch when tested with a 10-foot straightedge. A sufficient number of 
forms should be provided so that it will not be necessary to remove 
them within 12 hours after the concrete is placed. 
HANDLING AND HAULING MATERIALS. 
For handling and hauling the materials used in concrete pave- 
ment construction a number of different methods may be used. The 
most economical method to employ will, of course, depend upon the 
particular problems of the work in question. The discussion of 
this subject will be confined to the general methods which may be 
employed and the advantages and disadvantages of each. 
Nearly all of the materials used in concrete pavements are shipped 
by rail. The method of unloading the materials from railroad cars 
will depend to a large extent upon the method of handling the re- 
