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| Granite Pavers The Perfect Way to Pave |
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LAYING COURSE AND SUB-BASE
The laying course consists of clean, sharp sand placed to a
thickness such that when the blocks are vibrated into place the
resulting thickness of the laying course is about ¾" to 1¼"
thick. Many opinions exist concerning the maximum size,
gradation, and moisture content of the sand used for the laying
course. This suggests that the performance of the block
pavement is not sensitive to these variables over a fairly wide
range. To achieve uniformity, however, the sand should be
obtained from one source and before use protected so as to
maintain uniform moisture content.
As with any pavement, the sub-base for paving block is of
primary importance. Inasmuch as the block pavement can be
considered as a flexible pavement, the sub-base should be that
required for conventional asphalt pavements; it could consist of
old pavements, unjointed concrete slabs or most any old road.
They are all suitable sub-bases. The require4d thickness of a
sub-base will depend upon both the expected service loads and
the soil conditions; the need for a substantial sub-base is
greater in low, wet areas. Table 1. Also, sub-base materials and
standards must comply with the requirements of the local road
authority.
| Table 1. Suggested Sub-Base Thickness |
| Application |
Thickness of Sub-Base, Inches |
| Well-Drained Dry Areas |
Low Wet Areas |
LIGHT DUTY:
Residential:
Patios
Pool Decks
Walkways
Parking
Bicycle Path
|
2 to 4 inches |
4 to 8 inches |
MEDIUM DUTY:
Driveways
Shopping Malls
Residential Streets
Public Parking
Service Roads
Parking Lots
|
4-6 inches |
8 inches |
HEAVY DUTY:
Bus Stops
City Streets
Intersections
Gas Stations
Loading Docks
Loading Ramps
Loading Floors
Stables
|
8 inches |
10 inches |
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For light duty usage in residential construction, a sub-base
from 3" to 5" is recommended, i.e. patios, pool decks, walkways.
For driveway use, one would be well advised to place a
compacted sub-base of from 4" to 8", depending upon how well
the driveway area drains after a rain. The material used for the
sub-base should be a well graded gravel (Class11) having a
maximum topside of about 1½" and containing about 10% sand
sizes. A thick sub-base should be placed in layers of about four
inches, each layer leveled and compacted or vibrated, prior to
placing the next layer. Having the sub-base well compacted is
important to the durability of the finished construction.
CONSTRUCTION
After the sub-base is in place at the correct surface level and
is free of debris and mud, the sand laying course is spread
evenly between curbs. This is followed by screeding the sand to
the desired level. For roads up to about 16 feet wide the sand
course is usually screeded from the curb as shown in Fig.1; but
for wide areas, temporary screed rails should be used. As the
final road surface is largely governed by the uniformity of
screeding. It is important that the care is taken during the
screeding operation. A cambered screed board is used for
pavements with a cambered cross-section. To avoid unevenness
caused by pre-compaction, the sand must not be walked on or
disturbed once it has been screeded.
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Figure 1. |
Figure 2. |
Figure 2 shows a typical cross-section, consisting of the subbase,
the laying course of sand and the pavers themselves.
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