Masonry Magazine January 1973 Page.20
Concrete Masonry
Slope Paving
When depressed highway construction is used for noise abatement, or for other reasons, bridges will be required for cross-traffic grade separation. Earth slopes directly underneath bridges must be paved to accommodate drainage when the bridges are located at the low points of long grades. Other reasons for using slope paving under bridges include vegetation and erosion control. Concrete masonry units have been successfully employed for slope paving under many bridges at highway grade intersections. A million concrete masonry units were used for the slope paving along the Massachusetts turnpike alone.
A typical slope paving design is shown in Figure 4. Slope base preparation consists of compaction and shaping to grades and details on the plans. The slope is often designed so as not to exceed the natural angle of repose of the soil. A compacted sand or gravel bed from 2 to 6 inches thick is then placed on the slope to form a sand bed base for the concrete block. The granular base minimizes frost heave in cold climates. Beginning at the bottom of the slope, the concrete masonry units are laid up in running bond with the long axis parallel to the edge of the pavement. Some installations must be built with a type of support at the base of the slope in order to prevent sliding of the block.
Hoists or conveyors may be used to lift the block up the incline of the paving as the work progresses. As the block are laid up, they are firmly embedded in the sand layer so that the completed surface is uniformly placed at the correct grade. Ungrouted units are laid up tightly against adjacent units. In the case of units to be grouted, wood spacers are generally set to maintain uniform joints. Joints are usually at least 3/4 inch wide to facilitate placement of grout. Grout mixtures of 1 part portland cement to 2 1/4 to 3 parts of sand by volume are combined with sufficient water to achieve a flowable consistency.
At the edges of the slope paving, a header of reinforced masonry or concrete may be installed to insure pavement integrity, and a drainage trough added to carry off water.
Figure 4- TYPICAL SLOPE PAVING DETAILS
Grout
Curb or retaining wall
Ground line
NATIONAL CONCRETE MASONRY ASSOCIATION
P.O. Box 9185, Rosslyn Station, Arlington, Virginia 22209