An early version of interlocking concrete pavement dates back to the Roman Empire in 312 BC. Interlocking concrete pavement (ICP) consists of solid concrete paving units called pavers with openings that allow water to infiltrate. The pavers are placed on an open-graded aggregate base and subbase to store and infiltrate water. ICP provides benefits like permeability for stormwater management, durability lasting over 30 years, and easy repair of individual units.

1. INTERLOCKING PAVEMENT
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2. CONTENT
• HISTORY
• INTRODUCTION
• CLASSIFICATION
• METHODOLOGY
• SPECIFICATIONS
• BENEFITS
• LIMITATION
• APPLICATION
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3. HISTORY
• An early version of interlocking concrete pavement dates back
to the Roman Empire when The Appian Way was built from
stone paving on an aggregate base in 312 B.C.
• Used as a main route for military
supplies, it connected Rome to
Brindisi, Apulia, in southeast Italy.
• The road is 350 miles long about
20 feet wide and has held up for
more than 2,000 years.
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Figure 1: The Appian Way

4. Contd.
• As City Engineer with the City of Ripon, Matt Machado
developed interlocking concrete pavement as a roadway
standard, adopted by City Council.
• With the standard in place the
City constructed more than 1.3
million square feet between
2005 and 2008.
• This included the high-profile
Main Street in historic downtown
Ripon with 50,000 sf of
interlocking concrete pavement.
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Figure 2: Main Street in historic
downtown Ripon, California

5. Contd.
• Located in Westley, California at exit 441 on I-5, Howard Road
handles a tremendous amount of heavy truck traffic.
• Asphalt pavement had failed, the County looked at
interlocking concrete pavers as the innovative solution.
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Figure 3: Failed Asphalt on Howard
Road
Figure 4: New Howard Road

6. INTRODUCTION
• Permeable interlocking concrete pavement, also referred to
as PICP, consists solid concrete paving units called ‘pavers’
with joints that create openings in the pavement surface
when assembled into a pattern.
• The joints are filled with permeable aggregates that allow
water to freely enter the surface.
• The permeable surface allows flow rates as high as 1,000
in./hr (2,540 cm/hr).
• The paving units are placed on a bedding layer of permeable
aggregates which rests over a base and subbase of open-
graded aggregates.
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7. Contd.
• The base and subbase store water and allow it to infiltrate
into the soil subgrade.
• Perforated underdrains in the base or subbase are used to
remove water that does not infiltrate within a given design
period, typically 48 to 72 hours.
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8. Pavers
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Figure 5: Common types of pavers

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Figure 6: Cross-section of interlocking pavement

10. Classification
• A partial infiltration design is providing drainage to
accommodate some water that does on enter low infiltration
soils.
• PICP over high infiltration subgrade soils may not require an
underdrain(s) and these are called are called full infiltration
designs.
• The use of a geo-membrane to restrict infiltration into the soil
subgrade is often called a no infiltration design.
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11. METHODOLOGY
Design
• Consideration is given to hydrologic design for storm water
management and to structural design to support anticipated
vehicle axle loads.
• The thicker of the two bases from structural and hydrologic
designs is selected.
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12. Pre-construction meeting
• Walk through the site with builder/contractor/ subcontractor
to review erosion and sediment control plan/storm water
pollution prevention plan.
• Determine when PICP is built in project construction
sequence and confirm specified measures for PICP protection
and surface cleaning
• Aggregate material storage locations identified (hard surface
or on geotextile)
• Sediment management
• Access routes for delivery and construction vehicles identified
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13. Excavation
• Utilities located and marked by local service
• Excavated area marked with paint and/or stakes
• Excavation size and location conforms to plan
• The stakes should be marked to
establish grades, or have string
lines pulled and tied to them.
• Slopes should be a minimum of
1.5%.
• Protect temporary soil stockpiles
from erosion from water and wind
13Figure 7: Excavation of the soil subgrade.

14. Soil Subgrade
• Rocks and roots removed, voids refilled with open-graded
aggregate
• Soil compacted to specifications and field tested with density
measurements per specifications
• No groundwater seepage or
standing water
• Low, wet areas can be stabilized
with a layer of crushed stone.
• The surface of the stone is even
with the top of the compacted
soil subgrade.
14Figure 8: Compacting the soil subgrade.

15. Applying Geotextiles (Optional)
• Geotextile fabric(impermeable membrane) may be used in
areas where soil remains saturated part of the year
• As a separation layer, they prevent
soil from being pressed into the
aggregate base under loads
• When geotextiles are used they
preserve the load bearing capacity
of the base over a greater length of
time than placement without them
• Protect the foundation of
near by structure
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Figure 9: Application of the geotextile under
aggregate base.

16. Spreading and Compacting the Sub-
base and/or Base Aggregates
• Spread and compact the base in 4 to 6 in. (l00 to 150 mm)
lifts.
• Non freeze-thaw areas with well-drained soils should have at
least a 6 in. (150 mm) thick base.
• When spread and compacted, the aggregate base should be
at its optimum moisture.
• If the surface allow ingress of
bedding sand, a choke course
of fine material is spread and
compacted into the surface, or a
bitumen tack coat can be applied.
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Figure 10: Base compaction with a vibratory
roller.

17. Placing and Screeding
the Bedding Sand
• Masonry sand for mortar should never be used for bedding,
nor should limestone screenings or stone dust.
• The bedding sand should have symmetrical particles,
generally sharp, washed, with no foreign material.
• Bedding sand should be
spread and screeded to
a nominal 1 in. (25 mm)
thickness
• The sand is screeded
with a true strike board.
17Figure 11: Screeding the bedding sand.

18. Placing the Concrete Pavers
• Concrete pavers can be placed in many patterns.
• Joint widths between the pavers should be consistent and be
between 1/16 and 3/16 in. (2 and 5 mm).
• Cut pavers should be used to fill gaps along the edge of the
pavement. Pavers are cut with a double bladed splitter.
• After an area of pavers is placed, it should be compacted with
a vibrating plate compactor
• Dry joint sand is swept into the joints and the pavers
compacted again until the joints are full.
• Excess sand is then removed.
• A small amount of settling is typical of all flexible pavements.
• Optional sealers or joint sand stabilizers may be applied.
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Figure 12: Placing the
concrete pavers.
Figure 13: Saw cutting
pavers.
Figure 14: Excess sand swept
from the finished surface
Figure 15: Compacting Figure 16: Spreading and
sweeping joint sand.
Figure 17: Vibrating sand
into the joints.

20. Specifications
• Foundation Walls: At least 10 ft (3 m) from foundations with
no waterproofing or drainage
• Water Supply: At least 100 ft (30 m) from municipal water
supply wells
• Concrete sand conforming to CSA A23.1 is recommended - it's
the same sand mixed into concrete pavers and poured, cast-
in-place concrete.
• The ICPI only recommends the use of base material meeting
gradation requirements of ASTM-D2940 with 6 to 12% passing
the no. 200 (80 micron) sieve.
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21. Contd.
• ICPI recommends a minimum base thickness of 4 inches (100
mm) for residential patios and walkways and 6 inches (150
mm) for driveways in non freeze thaw areas.
• In colder climates these base thicknesses are increased and
most contractors will use 6 and 10 inches (150 mm and 250
mm) respectively.
• For non-vehicular uses such as embankment stabilization, the
maximum slope is determined by the angle of repose of the
bedding sand, typically around 35 to 38 degrees.
• For vehicular traffic, the highest slope in use is about 10
degrees.
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22. What are the benefits of concrete pavers?
• Concrete pavers do not crack like asphalt or poured-in-place
concrete - each unit has joints that allow for a small amount
of movement without cracking.
• Concrete pavers are easy to repair and/or replace, especially
when repairs are being done to the base or underground
utilities. Asphalt, concrete, and stamped concrete can't make
this claim.
• Resists deterioration from freeze-thaw cycles.
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23. • Concrete pavers come in many shapes and colours.
• Paving stones should last over 30 years, which is much longer
than alternative pavements under normal residential use.
• Capable of wet weather (light rain) installation
• Immediately ready for traffic upon completion, no time
needed for curing
• Upto 100% infiltration depending on the design
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24. LIMITATION
• PICP should not be used in areas subject to loading/unloading
or storage of hazardous materials.
• It is generally not placed in areas with high depth to seasonal
water tables.
• It should not be used in very cold areas, where temperature
drops below freezing point of water.
• When load is eccentric pavers may come out or shift from
their position.
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25. Application
PICP is used for:
• Walkways
• Driveways
• Parking lots
• Alleys
• Low-speed roads
• Road shoulders etc.
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