* Treat porous pavers and open-graded aggregate
, which mitigate the heat island effect, separately from other paving materials
On a road of open-graded aggregate
(stone), much of that material would seep down into the pavement and soil, and the community of microorganisms living there would begin a rapid breakdown process.
The alternative surface program is an environmentally friendly surface treatment consisting of an open-graded aggregate
(#57 stone), bound by an asphalt emulsion.
The joints allow water from storms to flow freely into an open-graded aggregate base or subbase reservoir that stores the water before it is released to aquifers, streams, and lakes.
The contractor also should complete placement and compaction of the open-graded aggregate base and subbase as close together in time as possible to minimize the risk of sedimentation from construction vehicles or nearby erosion.
Compaction of the open-graded aggregate is required for all applications.
Openings between the pavers are filled with an open-graded aggregate, usually a 0.25-inch (0.6-centimeter) crushed and washed stone, to allow water to infiltrate into the setting bed and soil below The green alley pilots used 3.15-inch (8-centimeter)-deep L-shaped pavers, 10.24 inches (26 centimeters) by 10.24 inches (26 centimeters) wide, with 0.47-inch (12-millimeter) open joints.
All the alleys had 12 inches (30.5 centimeters) of class A, washed, open-graded aggregate (both crushed and uncrushed were tested) beneath them, except for the alley with the center trench, which had 5 feet (1.5 meters) of aggregate below the trench, with the sides lined in a waterproof membrane.
Due to the contamination, 26,000 square feet (2,415 square meters) of the approximately 1-acre (0.4-hectare) site had to be remediated to a depth of 2 to 3 feet (0.6 to 0.9 meter).Taking these conditions into account, CDOT decided to replace the remediated soil with open-graded aggregate, pave the surface with porous pavers, and install an adjacent bioswale (a concave landscaping feature that reduces the volume and rate of surface runoff and improves water quality).
Open-graded aggregates are compacted aggregates with relatively large void spaces not filled with intermediate-sized particles.
State and local transportation agencies frequently use crushed, manufactured open-graded aggregates as structural backfill material for retaining walls, bridge foundations, and other ground improvement applications.
Strength Characterization of Open-Graded Aggregates
for Structural Backfills (Report)