Interlocking concrete pavements (ICP) are flexible pavements. Flexible pavements are designed to spread loads imposed on a small area of the pavement surface through a base layer (or series of layers or sub-bases) to a large enough area of the soil sub-grade that the soil sub-grade can support the load without rutting. A 1,000 lb. wheel with a footprint of 40 sq. in. exerts a load on the pavement surface of 3,600 lbs./sq. ft. With proper design and construction, a flexible pavement can expand the footprint to 8 sq. ft. on the soil sub-grade, thus reducing the load on the subgrade to only 125 lbs./sq. ft. In a flexible pavement, the pavement surface and base have the ability to move slightly or flex under load then recover when the load is removed.The unique aspect of interlocking concrete pavements is that the pavers interlock to help spread the imposed loads. There are three kinds of interlock: vertical, rotational and horizontal.
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| Kind of Interlocking block |
VERTICAL INTERLOCK
This is achieved by the shear transfer of loads to surrounding units through the sand joints. This shear transfer also prevents one paver from
in the moving vertically in relationship to its neighbor(s).
ROTATIONAL INTERLOCK
This is achieved through use of the proper paver thickness in relationship to load and use and by a perimeter edge restraint. A slight crown constructed into the pavement will increase rotational interlock and the load bearing capacity of the pavement.
HORIZONTAL INTERLOCK
This is achieved through the use of laying patterns that minimize the length of uninterrupted joint lines and disperse forces from braking, turning and accelerating vehicles. Certain geometrically interlocking paver shapes enhance horizontal interlock.
The components of an ICP are:
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Subgrade • Geotextile (if needed) • Sub-base (if needed) • Base • Bedding Sand • Edge Restraint
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Interlocking Concrete
Pavers • Joint Sand
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| Section Details |
CONSTRUCTING THE ICP
UTILITY LOCATION
Before beginning any phase of the construction process, make sure that all underground utilities,services and structures have been located and clearly marked on the ground surface in all areas involved in the construction process including access lanes. In many areas, a single number such as Miss Utilities may be called.
Items to be located are:
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Electrical • Sanitary sewer •
Gas • Septic tank • Water supply
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Telephone • Storm sewer • Cable TV • Drainfield • Irrigation piping
SITE ACCESS
Before any demolition, delivery or construction equipment is allowed on site, make sure that there are no hazardous conditions such as overhead electric lines in the way. Plan all activities so that no damage will occur to existing pavements, structures, trees, shrubbery, gardens or other site amenities.
LAYOUT
Identify the area to be excavated and mark it on the ground with spray paint. Make sure the area to be excavated is at least 12 in. wider on all outside edges than the size of the pavement. Place grade stakes with string lines just outside the area to be excavated, making sure that the excavation is at least 12 in. wider than the edge of pavement. Mark the elevations on the stakes so that the depth of excavation can be checked as it progresses. Use nylon mason’s line and set it at the finished elevation of the pavement. Measure all excavations and base thickness from these lines. Set the initial elevations and check them at the beginning of each day with a builders level. The stakes can be moved at night by mischievous persons.
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| Site layout |
• Base must be
12 in. wider than pavement on all sides.
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Use proper
base material.
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Place and compact base in layers.
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Fully compact.
EDGE RESTRAINT
SAND SETTING BED
PAVERS
In most ICP projects, the pavers, regardless of paver shape, are laid in patterns where two sets of joints run perpendicular to each other. Radii or curves are cut into the pavement after the field pavers have been laid but not compacted. Straight joint lines not only make the finished pavement look clean and sharp but make installation much easier. If pavers shaped to geometrically interlock with each other are not laid in straight lines,they will not fit together.To keep joint lines straight, parallel string lines or chalk lines snapped on the sand setting bed should be used. The lines should be spaced five to ten feet apart with the spacing equal to the laying modulus of the paver shape being installed. This can be determined by laying a course of pavers in the proper pattern with 3mm ( 1/8 in.) joints and measuring the distance between at the desired line separation distance.
Procedure:
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Snap a string line on the screeded sand in the center of the area(s)
to be placed.
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The line should
be perpendicular to the laying face.
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Place pavers in
the given laying
pattern on both sides of the line.
If additional lines are snapped, they should be parallel to each other. Check this by measuring the distances at the opposite ends of each line. They should be equal.
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If they are not parallel, they can be erased and snapped again.
Parallel string lines are also used to pave around openings in the pavement such as manholes or swimming pools.
Procedure:
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Pull perpendicular string or snap chalk lines
on all four sides of the opening.
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Lay pavers
on one side, then the other.
Count the courses needed to surround the openings on each side. They should be equal in number on both sides.
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Then fill around the remaining side of the opening.
• Cut pavers to fit and fill against the edge restraint around the opening.
CUTTING PAVERS
Pavers may be cut with any one of three basic pieces of equipment. They are:
1. Mechanical or guillotine splitter
1. Masonry saw
1. Hand held cut-off saw
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