Old macadam roads are sometimes utilized for the foundation for the brick surface, but the instances where this is permissible are comparatively few in number. When an old macadam is to be used it is reshaped to the proper cross section and re-rolled and bonded so as to afford a stable foundation of the proper cross slope. BEDDING COURSE FOR BRICK SURFACES In order to equalize the variations in size and shape of the brick, they are laid on a bedding course composed of material into which the brick may be forced by rolling. In this 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.