Masonry Magazine April 1993 Page. 29
Brick pavers, especially heavy vehicular pavements, may be made with lugs or spacers. These lugs, usually % in. (3 mm) in size, space the pavers apart and provide a controlled gap for jointing sand. Lugs also keep the paver edges from touching to reduce the amount of chippage during compaction and use. Lugs should be included when measuring the specified dimensions and when laying out a paving pattern.
The dimensional tolerances for pavers from ASTM C 902 are listed in Table 4. Dimensional tolerances are more critical in mortarless brick paving applications than in mortared brick paving applications since thin sand joints cannot accommodate paver dimensional variation as easily as thicker mortar joints. Brick with larger dimensional variation will shift the alignment of the pattern, making installation difficult in mortarless herringbone and basketweave applications.
TABLE 4
Dimensional Tolerances of Brick Pavers
| | Minimum Permissible Variation ±, in. (mm) |
| --- | --- |
| | Dimension, in. (mm) |
| Application | 3 (76) and Under | Over 3 to 4 (76 to 102) incl. | Over 5 to 8 (127 to 203) incl. |
| PS | %(3.2) | (1.6) | no limit |
| PX | (4.7) | %(4.7) | no limit |
| PA | %(6.4) | %(3.2) | no limit |
Salvaged Brick. The use of salvaged brick is generally not recommended for paving applications. This is obviously true for used building or facing brick. The durability of brick depends upon the properties of the units. Generally speaking, salvaged brick will not be uniformly durable when used in a pavement which is exposed to weathering. Some older "vitrified brick pavers" are extremely durable, but are often difficult to distinguish from poor pavers. Only a paver's past performance can be used for comparison.
Setting Bed Materials
The setting bed, placed between the base and the paving surface, functions as a leveling course to help refine the finished grade due to slight irregularities in the base or the units. Setting bed materials may be sand, building felt, asphalt or mortar.
Sand. Sand used as the setting bed should be a washed, well-graded angular sand with a maximum particle size of about 3/16 in. (4.8 mm). Sand should conform to either ASTM C 33 Specification for Concrete Aggregates or ASTM C 144 Specification for Aggregate for Masonry Mortar. In setting beds thinner than 1 in. (25 mm), smaller sand particles such as sands conforming to ASTM C 144 should be used. In setting beds thicker than 1 in. (25 mm) and all vehicular applications, sand conforming to ASTM C 33 should be used. Naturally occurring silica sand should be used in vehicular pavements.
The sand should be free of salts and other deleterious materials to avoid efflorescence or staining. The use of dry sand-cement mixtures should be avoided. Although cement may tend to keep the sand in place initially, the mixture will likely break up in a short time due to flexing of the paving system and weathering. In addition, use of a sand-cement mixture makes removal and reuse of the paving units more difficult.
Materials not suitable for use as the setting bed include sands with clay or dust in excess of that permitted in ASTM C 33 or C 144. Also, fine limestone screenings must not be used, since this material is normally too soft and may cause staining.
Building Felt. In residential pedestrian applications, brick may be placed directly on an asphalt or concrete base. In these applications, building felt may serve as a cushion between the brick pavers and the base, and compensate for minor dimensional variations in the base or brick. Generally, two layers of No. 15 building felt or one layer of No. 30 building felt is appropriate. Building felt should conform to ASTM D 226 or D 227.
Asphalt. Asphalt setting beds composed of aggregate and asphaltic cement may be used. Proportions of these materials are generally determined by specialty contractors or the asphalt plant and are beyond the scope of this Technical Notes; however, an asphalt setting bed generally consists of 7% asphalt and 93% sand. This mix is typically prepared and heated at an asphalt plant before being delivered to the job. A tack coat of neoprene modified asphalt should be placed on top of the asphalt setting bed to help adhere the pavers to the setting bed.
Mortar. Mortar setting beds are used in mortared brick paving applications. Mortar should conform to the proportion specifications of ASTM C 270 Specification for Mortar for Unit Masonry or ANSI A118.4 Specification for Latex-Portland Cement Mortar when a latex additive is used.
For exterior mortared brick paving on grade, Type M mortar is preferred. Type M mortar consists of 1 part portland cement, ½ part hydrated lime and 3% parts sand; or 1 part Type M masonry cement and 3 parts sand. Type S mortar may be used for exterior applications when the pavement is not in contact with the earth, such as suspended diaphragms or in interior applications. Type S mortar consists of 1 part portland cement, part hydrated lime and 4% parts sand; or 1 part Type S masonry cement and 3 parts sand. Portland cement should conform to ASTM C 150, Types I, II or III. Masonry cement should conform to ASTM C 91, Type M or S. Hydrated lime should conform to ASTM C 207, Type S, and sand should conform to ASTM C 144. The thickness of the mortar setting bed may vary from % in. to 1 in. (10 mm to 25 mm).