The City of New Haven has recently instituted a pavement preservation program. Pavement preservation is a planned system of treating pavements at the optimum time to maximize their useful life, thus enhancing pavement longevity at the lowest cost.
Pavements perform well under loads until a particular point in their life spans, at which time they deteriorate precipitously and rapidly to failure. Experience shows that spending $1 on pavement preservation before that point eliminates or delays spending $6 to $10 dollars on future rehabilitation or reconstruction costs.
Ideally, pavement preservation can mean maintenance of a pavement even when there is nothing apparently wrong with it. Successful pavement preservation requires a pavement in good condition to start. With good pavement, water can be kept out of the pavement, prevent oxidation of the asphalt, and maintain good skid resistance. Pavement preservation techniques will improve performance and extend life.
This approach is directly opposed to the typical road management method of "worst-first," in which scarce maintenance dollars are used to provide band-aid repairs to pavements which have gone too far and are failing. Soon after repairs are made, base or pavement failures are reflected through to the surface and the effort has been wasted.
In May 2005, the FHWA came out strongly in support of pavement preservation. "Each highway agency faces different challenges in applying pavement preservation treatments and establishing an effective preservation program," said David R. Geiger, P.E., director, FHWA Office of Asset Management. "Preservation involves a paradigm shift from worst-first to optimum timing. Preservation programs must focus on demonstrating benefit, securing commitment of top agency management, convincing the public, and selecting the right treatment for the right pavement at the right time."
Pavement preservation is inherently green based on its focus on keeping good roads in a condition where they do not need to consume more energy and raw materials to restore their serviceability.
Microsurfacing is a cold mix paving system formulated to remedy a broad range of problems on today's streets, highways and bridges. Advancements in materials and technology have made this one of the most cost effective road resurfacing products available. All ingredients must pass stringent laboratory tests to conform exactly to the engineered mix design and job mix formula.
Microsurfacing creates a new, stable surface that is resistant to rutting and shoving. Because Microsurfacing can be applied effectively at an average thickness of 3/8", more area per ton of mix is covered, resulting in cost effective road resurfacing. Microsurfacing provides texture corrections where the road surface is too rough or too smooth, eliminating hydroplaning and increasing skid resistance. Ruts up to 1.5" can be filled with Microsurfacing without milling.
Advantages: Environmentally safe - 90% reduction in CO2 and energy consumption versus traditional Hot-Mix Asphalt. Life expectancy of ten years; No loss of curb reveal, does not
alter drainage; Eliminates hydroplaning, increase skid resistance; Resistant to rutting and shoving; Applied with continuous load pavers to minimize traffic delays; Fills ruts up to 1.5" - special application available for profile correction of uneven and rutted surfaces.
Microsurfacing has been used on some of the heaviest traveled roadways in the country, including the Brooklyn Bridge, Manhattan Bridge, Long Island Expressway and Interstate 285 in Atlanta, Georgia. Continuous load pavers utilize support units which bring materials to the job site and load the machine while working, thus maximizing production and minimizing transverse joints. These pavers can lay three miles per day with no long traffic delays.
Microsurfacing is being used successfully on a routine basis across North America. It found that agencies were consistently satisfied with its performance and that it is effective in a pavement preservation role if the underlying pavement is structurally sound. Microsurfacing works well to address rutting, raveling, oxidation, bleeding, and loss of surface friction. If it is applied to the right road at the right time, most agencies expect an effective service life
extension of six to seven years.
Asphalt-Rubber is a blend of asphalt cement, reclaimed tire rubber, and certain additives in which the rubber component is at least 15%, by weight, of the total blend. It is mixed at a temperature of 250'F to react the rubber and cause swelling of the rubber particles.
Stress Absorbing Membrane (SAM)
Surface treatment. Asphalt-Rubber is spray applied to pavement surfaces at 0.5 to 0.7 gallons per square yard (gpsy) and then covered with clean, nominal 3/8" single-sized chips. The A-R application rate is adjusted for the existing road surface characteristics, and the aggregate is sized according to the membrane thickness. A tack coat of emulsified asphalt, diluted 1:1 with water, may be used on oxidized existing pavement surface. A 0. 1 to 0. 15 gpsy fog seal application is recommended to maximize chip retention The fog seal should also consist of emulsified asphalt,
diluted 1:1 with water.
Provides a lasting waterproof, skid resistant and durable surface which resists oxidation and cracking, and flexes to conform with movements of the underlying pavement surface.
Asphalt-Rubber SAM improves and extends the serviceability of asphalt concrete pavements which are experiencing distresses, such as alligator and block cracking. The pavement life is extended by (a) decreasing the amount of surface water intrusion into the base and subgrade by providing a waterproof membrane to obtain maximum stability of the structure, (b) reducing the oxidation of the existing surface, (c) binding the existing surface together, and (d) reducing the spalling around reflective cracks.
4. Appropriate Uses:
There are a variety of situations where Asphalt-Rubber SAMs provide highly effective alternates to existing conventional strategies, methods, and/or materia
The following list identifies some of the appropriate uses.
For rehabilitation / maintenance:
· over a pavement with fatigue cracking.
· over a pavement with oxidative or block cracking.
· over pavements with raveling.
· surface treatment for low volume roads.
· to extend the life of severely distressed pavements (basket cases) that require reconstruction for which funds are not yet available.
· to improve fractional characteristics (skid resistance)
Stress Absorbing Membrane Interlayer (SAMI)
A SAM followed by the placement of one or more courses of asphalt concrete or Asphalt-Rubber concrete (ARC).
The use of Asphalt-Rubber SAMIs extends the serviceable life of overlays by significantly retarding the rate of reflective crack formation. The SAMI also waterproofs the underlying pavement and
significantly retards age hardening of underlying asphalt concrete.
Many pavements that are in need of rehabilitation because of extensive cracking also require improvement of rideability and/or structure. A SAMI placed as an interlayer is more effective than as a surface course in reducing reflective cracking. It also provides significant reduction in tensile stresses transmitted to layers above.
4. Appropriate Uses:
Appropriate uses for SAMIs include most of those previously listed for SAMs. SAMIs can be effectively used in cases where it is necessary to improve ride quality or structural capacity by constructing an overlay. An additional function for which SAMIs are appropriate is to control reflective cracking over cement-treated and lime-stabilized bases.
Because the low-modules SAMI significantly improves resistance to reflective cracking, asphalt concrete overlay thickness can be generally reduced. Use of a SAMI also reduces the amount of surface preparation, particularly crack sealing, required prior to overlaying. These factors reduce the cost of the overlay.
Benefits of Asphalt Rubber SAMIs
· Retards reflective cracking
· Waterproofs and seals cracks and imperfections on the old pavement surface
· Flexes with the pavement even at temperature extremes
· Uses recycled material
· Quick construction and traffic return with minimal user delays
· With the right hot mix overlay, adds structure, improves rideability and smoothness, allows thinner lifts
· Long lasting corrective maintenance for improving rideability and extending the life of your pavements
Benefits of Asphalt Rubber SAMs
· Waterproofs and seals small cracks and imperfections on the existing pavement surface
· Minimizes loss of curb reveal and alignment; thinner than hot mix overlays
· Uses recycled material, reduces scrap tire inventories
· More durable than conventional asphalt
· Developed for high traffic volume roads
· Quick construction and traffic return with minimal user delays
· Long lasting preventive maintenance preserves the value of your structurally sound pavements with distressed surfaces
NovaChip is a high performance surface treatment which uses an award-winning technology that seals the existing road surface and provides a new, skid-resistant, smooth & ultrathin (5/8” to 3/4”) HMA wearing course in one simultaneous operation. The process consists of polymer modified asphalt emulsion spray applied (at a rate of approximately 0.2 gallons per yd2) immediately ahead of an overlay of gap-graded hot mix asphalt (HMA).
The thick polymer asphalt membrane seals and protects the surface and provides superior bonding of the ultrathin mix to the pavement. The high quality gap-graded HMA is designed for a durable, skid resistant surface. The ultrathin mat optimizes the use of high quality aggregates and improves smoothness by correcting minor deficiencies in the existing pavement layer while maintaining overhead clearances and curb reveal. The one-pass construction process moves quickly, allowing for rapid construction and traffic return, significantly lowering user costs. The durable NovaChip surface can last ten years or longer.
Seals and waterproofs existing surface
Resists raveling and delamination with superior bonding of the open, ultrathin overlay, over asphalt or concrete
Restores durable skid resistance while conserving high quality aggregates
A proven durable wearing coarse in demanding high traffic/high speed applications
Reduces user delays with quick, one-pass construction and no tracking
Immediate traffic return and convenient night construction
Retains curb reveal and clearances under bridges and overpasses
Reduces tire noise, especially on concrete pavements
Reduces tire spray, preventing hydroplaning and improving visibility in wet weather
Long lasting, effective preventive maintenance treatment that extends and preserves the value of your pavement, yielding lower life cycle costs
Hot in-place recycling is an on-site, in-place method that rehabilitates deteriorated bituminous pavements and thereby minimizes the use of new materials. This process may be performed
as either a single pass (one phase) operation that monolithically recombines the restored pavement with virgin material, or as a two pass procedure, wherein the restored material is recompacted and the application of the new wearing surface then follows a prescribed interim period that separates the process into two distinct phases.
Hot in-place recycling provides a very low cost maintenance strategy that enables the public works official to effectively re-use existing materials. This process demonstrates that asphalt is a rather unique construction material in that it can be effectively and economically restored. Rather than bury the deteriorated pavement with inordinate depths of new material conventionally applied, or lose it to the grinder, proponents of Hot In-Place Recycling encourage restoration.
Hot in-place recycling effectively addresses the classic symptoms of deteriorated pavement:
Cracks are interrupted and filled. Aggregate stripped of the bitumen is remixed and recoated. Ruts and holes are filled, shoves and bumps are leveled, drainage and crowns are re-established. Flexibility is restored by chemically rejuvenating the aged and brittle pavement. Aggregate gradation and asphalt content may be modified by some variations of this process.Highway safety is enhanced through improved skid resistance.
In a period of rapidly increasing costs and limited funding, Hot in-place recycling presents the opportunity to spread available dollars over a much greater area. Roadway deterioration can be suspended, pavements preserved and upgraded, and costly reconstruction avoided.