Masonry Magazine April 1993 Page. 28
TABLE 1
Physical Property Requirements of Pedestrian and Light Traffic Paving Brick
| Paver Class | Minimum Compressive Strength, psi (MPa) | Maximum 24 Hr Cold Water Absorption, % | Maximum Saturation Coefficient |
|---|---|---|---|
| | Avg. of 5 Brick | Individual | Avg. of 5 Brick | Individual | Avg. of 5 Brick | Individual |
| SX | 8000 (56.2) | 7000 (48.3) | 8 | 11 | 0.78 | 0.80 |
| | 4000 (27.6)¹ | 3500 (24.1)¹ | 16¹ | 18¹ | 0.78¹ | 0.80¹ |
| MX | 3000 (20.7) | 2500 (17.2) | 14 | 17 | no limit | no limit |
| NX | 3000 (20.7) | 2500 (17.2) | no limit | no limit | no limit | no limit |
| ¹Requirements for molded brick
Abrasion Resistance
Paving brick are exposed to the continual abrasive effect of pedestrian and vehicular traffic. Of these two types of traffic, pedestrian traffic can cause the most wear of the pavement surface. The impact force of high-heeled shoes causes the highest degree of abrasion. Tires, without studs, do not have such a drastic effect, although brick streets will polish over time with repeated tire traffic.
Abrasion resistance is a measure of the resistance of paving brick to the wearing action due to traffic. ASTM C 902 lists two ways in which the abrasion resistance of brick pavers can be determined: 1) an abrasion index calculated by dividing the 24 hr cold water absorption by the compressive strength (units of psi) and then multiplying by 100, or 2) by the volume abrasion loss in accordance with ASTM C 418 Test Method for Abrasion Resistance of Concrete by Sandblasting. The abrasion requirements for pavers by traffic type are shown in Table 2.
TABLE 2
Abrasion Requirements of Pedestrian and Light Traffic Paving Brick
| Traffic Type | Maximum Abrasion Index | Maximum Volume Abrasion Loss, cm³/cm² |
|---|---|---|
| I | 0.11 | 1.7 |
| II | 0.25 | 2.7 |
| III | 0.50 | 4.0 |
Slip and Skid Resistance
The slip resistance of a paving surface is related to pedestrian traffic, while skid resistance is related to vehicular traffic. Slip resistance and skid resistance are measures of the slipperiness of a paving surface. Slip resistance and skid resistance are adversely affected by the accumulation of water on the pavement surface. Over time, the skid resistance of all paving surfaces decreases because of the polishing effect of traffic. The skid resistance of most brick is initially very high and decreases while in use, approaching an equilibrium condition within one year after placement. Since both slip and skid resistance rely on the microtexture of the paving brick, a brick with a rougher texture such as a wire cut paver will provide a higher slip and skid resistance.
There are no requirements for testing slip and skid resistance in ASTM C 902, although there are methods for testing skid resistance in the proposed ASTM Specification for Heavy Vehicular Paving Brick. The latter specification references ASTM E 303 Method for Measuring Surface Frictional Properties using the British Pendulum Tester (BPT). Skid resistance values of new brick pavers vary between 51 and 87 which fall within the range of concrete and asphalt pavements. [4]
Dimensions
Brick pavers are available in a wide range of sizes. The most commonly available sizes of pavers are listed in Table 3. Some pavers used in mortarless applications may have a small chamfer not exceeding % in. (5 mm) in depth or width, or rounded edges with a radius less than % in. (5 mm). Chamfers provide a better path for surface drainage along the pavement surface, better slip and skid resistance and reduce the amount of chippage along the top edges of the brick during installation and use. The chamfer dimension is subtracted from the specified height when determining the thickness of the pavement surface layer for design. Pavers used in mortarless applications,
TABLE 3
Typical Specified Sizes or Brick Pavers
| Width, in. (mm) | Height, in. (mm) | Length, in. (mm) |
|---|---|---|
| 4 (100) | 1% (38) | 8 (200) |
| 4 (100) | 2% (57) | 8 (200) |
| 4 (100) | 2% (70) | 8 (200) |
| 3% (92) | 1% (32) | 7% (194) |
| 3% (92) | 2% (57) | 7% (194) |
| 3% (95) | 2% (57) | 7% (191) |
| 7% (194) | 2% (57) | 7% (194) |
| 8 (200) | 2% (57) | 8 (200) |