Masonry Magazine April 1993 Page. 32
Semi-Rigid Base System
Only mortarless brick paving should be placed over a semi-rigid asphalt base. Typically, an asphalt base is supported by an aggregate subbase. Each material layer is compacted as placed. An asphalt or bituminous setting bed is placed over the base. Usually delivered hot from the plant, the asphalt setting bed is rolled to a 3/4 in. (19 mm) depth. A tack coat of 2% neoprene-modified asphalt adhesive should be applied by a mop, squeegee or trowel on top of the asphalt setting bed. This tack coat should be very thin, not exceeding 1/16 in. (2 mm), to avoid pumping of the material between the pavers and onto the surface when hot. When the tack coat is dry to the touch, paving units may be laid in the desired bond pattern. After brick placement, sand should be swept into the joints.
Rigid Base Systems
Both mortarless and mortared brick paving systems may be laid over a rigid concrete base. Concrete bases may or may not be laid over an aggregate subbase depending upon the application and traffic. Typically, the concrete base should cure a minimum of seven days before installation of the setting bed and pavers.
In mortarless applications, a sand or asphalt setting bed is laid directly on top of the concrete base. A 1/2 in. (13 mm) sand setting bed or 3/4 in. (19 mm) asphalt setting bed is used. A thin tack coat is applied to the asphalt setting bed. Membranes can be laid directly on the concrete base, but only after the base has cured properly. The pavers are laid and jointing sand is swept into the joints.
When pavers are installed with mortar, standard bricklaying or tile setting procedures should be followed. The preferred method of mortar placement is with a trowel. The concrete base should be clean and slightly dampened, but be surface dry immediately prior to placing the mortar setting bed. The setting bed is laid in the desired thickness, no more than 2 ft (0.6 m) ahead of the laying of the paving units. Brick pavers should be buttered with mortar on the bottom and edges and shoved into the mortar setting bed. The joints between the units should be completely filled to minimize moisture penetration. Joints should be tooled with a concave jointer when the mortar becomes thumbprint hard.
When installing thin pavers, a thin mortar bed is used. As with full pavers, the concrete base is cleaned and dampened. However, a bond coat is applied to the concrete base prior to installation of the setting bed. The mortar setting bed and thin pavers are immediately installed on top of the bond coat.
If care is exercised during mortar installation, cleaning can be avoided or kept to a minimum. Burlap bags rubbed over the surface or wet sand swept over the surface may remove some mortar droppings which are still soft. If cleaning is necessary, use procedures and cleaning solutions recommended in Technical Notes 20 Revised. Avoid the use of acid solutions when possible.
An alternate method of installation of full or thin pavers involves placing pavers on a mortar setting bed and leaving a space the size of a mortar joint between the units for a grout mixture. A grout mixture with proportions of cement, lime and sand the same as the appropriate mortar but with greater flow is used. The grout is poured, injected or squeegeed into the joints after the pavers have set in the mortar. The joints are tooled to a concave finish when the grout is thumbprint hard. When grout is placed in the joints in this manner, special care must be taken to protect the units from grout stains. Pavers may have their top surface coated with paraffin or wax before they are laid. Failure to coat the pavers will result in stains on pavers that are difficult to remove. Coated pavers may be special ordered from the brick manufacturer, or the coating may be applied at the jobsite. The paraffin or wax should have a melting point between 150 and 170°F (66 and 77°C). Experience has shown that materials with lower melting points are often affected by hot sunlight, while those with higher melting points are difficult to remove. While applying the coating, care must be taken to prevent the edges or joint surfaces of the pavers from becoming coated since the edges must be clean for proper bond. The pavement should be steam cleaned soon after the mortar in the joints has cured.
Pavement Tolerances
The maximum variation from plane of the pavement surface should be ±1/4 in. in 10 ft (± 10 mm in 300 mm). The edges of any two adjacent pavers should not differ by more than 1/16 in. (2 mm) in height for mortarless brick paving or 1/8 in. (3 mm) for mortared brick paving. Pavers adjacent to drainage inlets and channels should not be lower than the top of the drain and not be more than 3/16 in. (5 mm) above it.
MAINTENANCE
Although brick paving surfaces are very durable, some routine maintenance may be necessary.
Snow Removal
Snow removal from brick pavements should not present any particular problem. It can be removed by plowing, blowing or brushing away the snow. When using plows or shovels there are precautionary measures that can be taken to preserve the surface character of the brick. Metal blades should be rubber tipped or mounted on small rollers. The blade edge should be adjusted to a clearance height suitable for the pavement surface. Avoid the use of any chemicals containing rock salt to aid in melting ice. Use of these materials may cause efflorescence. A product called urea is used to melt ice at many airports without causing efflorescence. Otherwise, remove snow before it can be compacted or turn to ice. To render icy surfaces passable, use clean sand on the icy areas.