is way the upper surfaces of all
brick can be brought to the proper elevation to insure smoothness and
easy riding qualities. Several kinds of bedding course are now
employed.

=Sand Bedding Course.=--The sand bedding course has been referred to
as a sand cushion, but as a matter of experience the cushion effect is
slight, although sometimes pavements have become uneven because the
brick have pushed down into the sand after the pavement was used for a
time. The sand for the bedding course should preferably be fine
grained, all particles passing the eight mesh sieve, but ordinary
concrete sand is satisfactory. The sand need not be clean, as a
comparatively large percentage of silt or clay does not impair the
usefulness of the material.

[Illustration: Fig. 19.--Cross Sections for Brick Highways]

=Sand Mortar Bedding Course.=--In order to eliminate the tendency for
the straight sand bedding course to shift because of the impact of
traffic on the brick, a lean cement mortar is sometimes employed
rather than the straight sand. Sand and cement in the ratio of one
part cement to four or five parts of sand are mixed dry, and after the
brick have been rolled, is moistened to furnish water to hydrate the
cement. The sand employed is ordinary clean concrete sand.

=Green Concrete Bedding Course.=--In the monolithic type of brick
road construction, the brick are laid directly on the green concrete
base before the concrete has taken a set and the irregularities of the
brick are taken up by rolling them until bedded in concrete.

FILLERS FOR BRICK SURFACES

The spaces between the brick are filled with some material that will
prevent the brick from being displaced and prevent water getting to
the bedding course. A suitable filler must adhere to the brick and
fill completely the spaces between them. It must withstand traffic so
as to remain intact in the joints and when in place it must be rigid
enough to prevent displacement of the brick.

=Cement Grout Filler.=--One of the most commonly used fillers for
brick pavements consists of a grout composed of Portland cement and
fine sand. When properly mixed and applied the grout filler meets all
requirements for a filler except that it is non-elastic and some means
must be adopted for caring for pavement expansion.

=Bituminous Fillers.=--Asphaltic materials and tars are widely used as
fillers for brick pavements. Such fillers are of high melting point
and consequently solid a