10 
BULLETIN 373, U. S. DEPARTMENT OF AGRICULTURE. 
structecl of Portland cement concrete may frequently be advan- 
tageously used. Concrete curbs may be constructed alone or in com- 
bination with either a concrete gutter or a concrete foundation. 
When constructed alone they should have approximately the same 
cross-sectional dimensions as stone curbs and should be constructed 
in sections about 8 to 10 feet in length. Figures 2, 3, and 1 show the 
three common types of concrete curbs. 
Vitrified clay curbing should be set in much the same manner as 
that described for stone curbing. The principal additional require- 
ment is that, since vitrified clay is a lighter material than stone and 
the curb sections are ordinarily shorter, the bedding must be made 
correspondingly more secure in order to prevent displacement. 
y/r/?/F/£0 3/r/c/r-) 
Fig. 1. — Proper method of constructing stone curb. 
OPRRE 8994 
Several sections of brick pavement in which curbs were altogether 
omitted were constructed during 1915 in the State of Illinois. The 
methods employed in constructing these pavements, which are desig- 
nated " monolithic," are described on page 21. 
THE FOUNDATION OR BASE. 
A firm, unyielding foundation is one of the most essential features 
of a brick pavement. This fact can be more readily appreciated 
when it is considered that the surface of a brick pavement is made up 
of small individual blocks, any one of which might be easihy forced 
down, causing unevenness in the surface, if the foundation were poor ; 
and since the ability of the pavement to resist wear depends very 
largely on the smoothness of the surface, every reasonable precaution 
should be taken to prevent any unevenness from developing. The 
