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Types of Brick Paving Surfaces The two types of brick paving surfaces are mortarless and mortared. Mortarless brick paving contains sand between the units which are laid on a variety of materials. Conversely, mortared brick paving consists of units with mortar between the units and always laid in a mortar setting bed. Types of Bases Flexible Base. A flexible base consists of compacted crushed stone, gravel or coarse sand. Only mortarless brick paving is suitable for this type of base. Semi-Rigid Base. This type of base consists of asphalt concrete, commonly referred to as asphalt. Only mortarless brick paving is suitable over this type of base. Rigid Base. A rigid base is defined as a reinforced or unreinforced concrete slab on grade. Mortarless or mortared brick paving may be placed over this type of base. EXAMPLES OF BRICK PAVING ASSEMBLIES Flexible Base Pavements Only mortarless brick paving can be laid over a flexible base. Flexible bases include crushed stone, gravel or coarse sand. 
Applications for flexible bases range from residential patios to
city streets.
Flexible paving systems are typically the most
economical to install since less labor and fewer materials
are involved. Figure 1 is a typical section through a flexible
brick pavement. Brick pavers are set in a 1 in. to 1 1/2 in.
sand setting bed over a compacted base, subbase
(if necessary) and compacted subgrade.
Drainage Adequate drainage of flexible and rigid paving systems is an extremely important design consideration for successful performance and durability. Ponding water can cause deterioration of the paving in areas of repeated freeze/thaw and cause slippery conditions. The best way to obtain drainage of the pavement is to slope the paving surface to provide as much surface drainage as possible. 
A slope of 1/8 in. to 1/4 in. per ft (1 to 2 mm per 100 mm) is suggested.
Large paved areas and vehicular traffic areas may require a slope greater than 1/4 in. per ft (2 mm per 100 mm). The paving system should be sloped away from buildings, retaining walls and other elements capable of collecting or restricting surface runoff. To improve surface drainage, the direction of continuous mortar joints should run parallel to the desired direction of surface runoff. Mortarless paving requires both surface and subsurface drainage. The majority of drainage should occur on the surface. However, some water will penetrate downward until it reaches an impervious layer. This layer may be a concrete or asphalt base, a flexible base compacted to high density, an impervious soil such as clay or an impervious membrane used to separate pavement layers. Water not drained off the pavement surface will percolate to the top of this impervious layer, possibly causing pending of the water. Due to these conditions, subsurface drainage is required.
Mortarless brick paving constructed over a porous base such as gravel may permit drainage through the entire system to the subgrade. The use of a geotextile between the sand setting bed and the base will permit drainage without allowing migration of the sand setting bed into the base.
Figure 2 shows drainage in a flexible paving system. Edge Restraints Many different types of edge restraint materials exist, Including brick, rigid plastic, wood, stone, steel, aluminum and concrete. Existing walls or structures may also be used as an edge restraint. The particular application and site conditions determine which material to use. Any of the materials previously listed can be used in light traffic applications. Only concrete, brick or stone embedded in concrete, some varieties of rigid plastic, or metal should be used in areas subjected to light or medium traffic. Heavy traffic applications require cast-in-place concrete, granite or curbs of equal strength. Asphalt or an asphalt pavement does not provide adequate edge restraint for paving subjected to vehicular traffic. Edge restraints are necessary in mortarless brick pavements as they hold the pavers together and prevent spreading and movement of pavers due to horizontal traffic loads. Intermediate restraints may be used within the pavement when there is an interruption in the paving surface or on sloped or curved areas. Intermediate restraints will provide additional thrust resistance to traffic loads and pavement creep. Edge restraints are not necessary in mortared brick paving but may be used for aesthetic reasons, to reduce chipping of perimeter brick or to control landscaping. Any of the edge restraint materials mentioned may be used. INSTALLATION One factor which has a great impact on the performance of brick pavements is workmanship. Proper preparation and compaction of the base is absolutely critical. There are numerous ways to install brick pavements which vary by region. The recommendations in this Technical Notes are based on experience and provide a minimum level of workmanship necessary for satisfactory performance. Subgrade Preparation One element common to all paving assemblies is the soil or subgrade. In preparation for the base or subbase, the subgrade should be excavated to the proper elevation, deleterious materials removed, and the subgrade compacted. If subsurface drainage is required, drain pipes should be installed and be properly backfilled. The entire subgrade should be compacted to 90-95% maximum density. Flexible Base Systems Only mortarless brick paving should be placed over flexible bases. Generally, flexible bases are the most economical type of base to install. Proper construction of the subbase, sand setting bed and brick pavers is necessary to ensure good performance. Subbase and Base Preparation The subbase and base materials should be spread and compacted in layers. The thickness of these layers must be consistent with the capabilities of the compaction equipment. Heavy compaction equipment such as vibratory rollers may be necessary when constructing a street with crushed stone, whereas a plate vibrator may be used when constructing a sand base for a residential patio. Each material should be placed and compacted in layers no greater than 4 in. (100 mm). It is essential that the intended surface profile of the pavement is formed by the base so the pavers can be placed on a uniform thickness of bedding sand. If a geotextile is used, it should be placed after compaction of the subgrade or base. The geotextile should be placed smooth and be overlapped a minimum of 12 in. (300 mm) at its ends. The geotextile should be lapped further in conditions such as poor soils. The geotextile should be placed so that the material entirely covers the base and extends up the side of the excavated area to contain the setting bed material. Construction equipment should be kept off of the geotextile. Check the geotextile manufacturer's literature for further installation recommendations. Edge restraints should be placed before base installation if the restraint is anchored below the base. The edge restraint should be installed after base compaction if it is intended to be anchored into the base. In the latter case, the base should extend at least 6 in. (150 mm) past the end of brick paving above. Setting Bed Preparation. The setting bed material should be spread over the base in a uniform thickness. A screed board is often used to spread the sand. The setting bed is not meant to and should not be used to fill in low spots nor its thickness adjusted to bring the pavement to the correct grade. Any changes in thickness or undulations in the sand will reflect on the pavement surface. To prevent disturbance of the sand it should not be spread too far in front of the laying face of the pavers. Prepared setting bed materials left overnight should be properly protected from disturbance and moisture. The moisture content of the sand during installation should be as uniform as possible, with the material moist but not saturated. Stockpiled sand should be kept covered to prevent contamination. Paver Installation. Pavers should be laid in the desired bond pattern with a 1/16 to 1/8 in. (2 to 3 mm) average joint width. The term "handtight" is a misnomer since sand between the pavers is desired. The joint width should not exceed 1/4 in. (6 mm). String lines or chalk lines may be used to keep the pattern aligned. Whole pavers should be laid first, followed by pavers cut to size. All pavers should be cut with a masonry saw to produce an accurate, clean, straight cut. A trial area may be laid out in advance of work to determine paver positions and minimize the amount of cutting required. In pedestrian paving applications, jointing sand may be swept into the joints. In some pedestrian and all vehicular paving applications, the brick should be vibrated into place using a mechanical plate vibrator/compactor. Compaction of the brick forms a more stable surface and promotes interlock between the sand and pavers. If a vibrator is used, the first pass of the vibrator should be prior to the spreading of jointing sand to force bedding sand into the joints from below. On subsequent vibrator passes, jointing sand is spread across the surface before compaction. Several passes of the vibrator may be necessary to fill the joints. Compaction should not occur within 3 ft (0.9 m) of any unrestrained edge. 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 ± 3/8 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. For more information visit: http://www.brickinfo.org |