Micro-Surfacing_Specifications.docx

Micro-Surfacing (Conventional and HiMA) Specifications

Description Micro-Surfacing is a tough and durable thin overlay material which can restore the original service properties to worn but structurally sound pavements. Its properties are based on a blend of select crushed aggregate and a sophisticated chemical formulation of asphalt cement, cationic emulsifiers, additives, and polymers. This specification covers all materials, equipment, construction and application procedures for rut filling and/or surfacing of existing paved surfaces. The Micro-Surfacing shall be a mixture of cationic, polymer-modified asphalt emulsion, mineral aggregate, mineral and field control additives, and water, properly proportioned, mixed and spread on the paved surface in accordance with this specification and as directed by the Engineer.

Where required by the Engineer, additional Micro-Surfacing mixture additives shall be utilized for the purpose of improving performance and durability. These mixture additives shall include heavy polymer dosages in the emulsion (6% SBS polymer and referred to as “HiMA”, or “Highly Modified Asphalt”), as determined by the Engineer, and all additives shall be homogenously blended with the other Micro-Surfacing components.

Materials

1. Emulsified Asphalt: The emulsified asphalt shall be a quick-set, polymer-modified cationic type CSS-1H emulsion, and shall conform to the requirements specified in AASHTO M208 and ASTM 2397. It shall pass all applicable storage and settlement tests. The polymer shall be milled into the emulsion, or in the case of the HiMA (6% SBS) emulsion, may be blended into the unmodified base asphalt. The cement mixing test shall be waived for this emulsion.

a. Conventional Micro-Surfacing Residue Properties: Distillation of residue will be at a temperature of 350° F for 20 minutes. Softening Point (ASTM D36 or AASHTO T53) of the residue shall be not less than 140° F.

b. HiMA (6% SBS) Micro-Surfacing Residue Properties: For HiMA mixtures, emulsion testing by distillation method (ASTM D5 or AASHTO T49) shall yield a Softening Point (ASTM D36 or AASHTO T53) not less than 170° F.

2. Aggregate

a. General: The mineral aggregate used shall be of the type and grade specified for Micro-Surfacing. The aggregate shall be manufactured crushed stone such as granite, slag, limestone, chat, or other high-quality aggregate or combination thereof.

b. Aggregate Physical Requirements

i. Grading: The aggregate including natural fines when tested by AASHTO methods T11 or T27 or ASTM C117 or C136 should meet the reference gradation requirements.

ii. Deleterious Substances: To limit the permissible amount of clay-like fines in an aggregate, a sand equivalency value of 65 or higher is required when tested by ASTM 2419.

iii. Soundness: The aggregate shall have a weighted loss of not more than 15% when the sodium sulfate test is used, or 20% when the magnesium sulfate test is used.

iv. Hardness: The aggregate wear, from resistance to abrasion, shall be a maximum of 35% when using AASTHO T96 or ASTM C131 test methods.

3. Water: The water shall be potable and shall b free of harmful soluble salts.

4. Modifier: Special quick-setting emulsifier agents shall be milled into the asphalt emulsion. The emulsified asphalt shall be so formulated that when the paving mixture is applied at a thickness of one inch with the relative humidity at not more than 50% and an ambient air temperature of at least 75° F, the material will cure sufficiently so that rolling traffic can be allowed in one hour with no damage to the surface, as verified by the Engineer.

5. Additives: A mineral additive shall be introduced to the aggregate and may be any recognize brand of non-air entrained Portland cement or hydrated lime that is free of lumps, or other approved mineral additive. It may be accepted upon visual inspection. The amount of mineral additive needed shall be determined by the laboratory mix design and will be considered as part of the material gradation requirement.

A liquid field control additive may be introduced and blended with water to provide effective control of the required quick-set properties. This additive shall be made available by the chemical supplier or emulsion manufacture and certified to be compatible with the mixture.

Engineering

1. General: Before work commences, the contractor shall submit a signed and certified mix design covering the specific materials to be used on the project. This design shall be performed by an AASTHO res:ource accredited facility specifically accredited for Pavement Preservation and micro-surfacing mix designs. Proof of such AASHTO accreditation shall be submitted with the mix design. Once the materials are approved, no substitution will be permitted unless first tested and approved by the laboratory preparing the mix design.

2. Mix Design: The AASHTO re:source accredited laboratory shall develop the job mix design and present certified test results for the contractor’s approval. Compatibility of the aggregate and emulsion shall be verified by the mix design. The job mix formula shall meet standard ISSA A143 micro-surfacing mix design requirements. All component material used in the mix design shall be representative of the material proposed by the contractor for use on the project.

3. Specifications: The Engineer shall approve the design mix and all Micro-Surfacing materials and methods prior to use. The component materials shall be within the following limits:

Residual Asphalt – 5% to 9% by dry weight of aggregate Mineral Additive – 0.5% to 3% by dry weight of aggregate Polymer Modified & Field Control Additive – As required to provide specified properties Water – As required to produce consistency Aggregate – Recommended Gradations:

Suggested Application Rates Type II – Primary and Residual Streets and Airport Runways:

Type III – Interstate Routes:

Double Course = 30-36 lbs/sy Wheel Ruts = as required Note: All application rates above are dry aggregate weights exclusive of emulsion and all other additives.

Equipment

1. General: All equipment, tools, and machines used in the performance of this work shall be maintained in satisfactory working condition at all times to ensure a high-quality product.

2. Mixing Equipment: The material shall be mixed by a self-propelled Micro-Surfacing mixing machine which shall be a continuous flow, continuous run mixing unit able to accurately deliver and proportion the aggregate, emulsified asphalt, mineral and field control additives, and water to a revolving multi-blade twin shafted mixer and discharge the mixed product on a continuous flow basis. The Contractor shall own and have available two (2) continuous flow, continuous run mixing machines to ensure highest quality, and to mitigate the effect of equipment breakdowns. The machines shall have sufficient storage capacity for aggregate, emulsified asphalt, mineral and field control additives, and water to maintain an adequate supply to the proportioning controls. The machines shall be equipped with self-loading devices which provide for the loading of materials while continuing to lay Micro-Surfacing, thereby minimizing construction joints.

3. Proportioning Devices: Individual volume or weight controls for proportioning each material to be added to the mix, i.e., aggregate, emulsified asphalt, mineral and field control additives, and water shall be provided and properly marked. These proportioning devices are usually revolution counters or similar devices and are used in material calibration and determining the materials output at any time.

4. Emulsion Pump: The emulsion pump shall be a heated, positive displacement type pump.

5. Spreading Equipment: The surfacing mixture shall be spread uniformly by means of a mechanical type spreader box attached to the mixer, equipped with paddles to agitate and spread the materials throughout the box. The spreader box width shall be capable of adjustment while paving in order to accommodate the changing width of some roadways without excessive overlaps. A front seal shall be provided to ensure no loss of the mixture at the road contact point. The rear seal and secondary strike-off shall act as the final strike-off, and both shall be adjustable. The mixture shall be spread to fill cracks and minor surface irregularities and leave a uniform skid resistant application of material on the surface. The spreader box and rear strike-off shall be so designed and operated that a uniform consistency is achieved to produce a free flow of material to the rear strike-off. The longitudinal joint where two passes join shall be neat in appearance, uniform and lapped. All excess material shall be removed from the jobsite prior to opening the road. The spreader box shall have suitable means provided to side-shift the box to compensate for variations in pavement width and longitudinal alignment. A rut box shall be available to pre-fill wheel ruts when necessary prior to overlay to eliminate puddles or runoff interruption. The rut box shall be no less than 4’ wide and no more than 6’ wide.

6. Auxiliary Equipment: Suitable surface cleaning equipment, traffic control equipment, hand tools and any support equipment shall be provided as necessary to perform the work.

7. Screening Plant: All aggregate shall be rescreened immediately prior to being loaded onto Micro-Surfacing equipment. The screening plant shall be equipped with a 3/8” screen to remove all oversize aggregate and shall be capable of discharging screened aggregate directly onto the support equipment. Any material discharged onto the ground must be rescreened prior to use.

Machine Calibration Each mixing unit to be used in the performance of the work shall be calibrated in the presence of the Engineer prior to construction, or previous calibration documentation covering the exact materials to be used may be acceptable provided they were made during the same calendar year. The documentation shall include the individual calibration of each material at various settings, which can be related to the machine metering devices.

Weather Limitations The materials shall be spread only when the road surface and atmospheric temperatures are at least 45° F and rising, the weather is not rainy, and there is no forecast of temperatures below 32° F within 48 hours from the time of placement of the mixture.

Surface Preparation

1. General: The area to be resurfaced shall be thoroughly cleaned of vegetation, loose aggregate and soil, particularly soil that is bound to the surface. Manholes, valve boxes, and other service entrance will be protected from the surfacing material with polyethylene sheeting. All services will be uncovered upon completion of work.

2. Cracks in Surface: If required by the Engineer, pre-treat the cracks in the surface with a fiberized crack sealer prior to the application of the Micro-Surfacing. Crack sealer shall be a polymer and crumb rubber modified asphalt cement including not fibers (PCRM + fibers). The modified asphalt cement incorporated in the PCRM +fibers material must meet PG 64-28E MSCR testing requirements. If crack sealing pre-treatment is required by the Engineer, a separate pay item will be included in the bid proposal form.

3. Tack Coat: The Contractor may be required to apply a tack coat on any heavily oxidized pavements, or on high traffic roadways as directed by the Engineer. The tack coat shall consist of one part emulsified asphalt (CSS-1H) and three parts water, and be applied with a distributor at a rate of 0.05-0.10 gallons per square yard. If tack coat is required by the Engineer, a separate pay item will be included in the bid proposal form.

Stockpile Precautions shall be taken to ensure that aggregate stockpiles do not become contaminated. The mineral aggregate shall be re-screened prior to being directly loaded onto Micro-Surfacing equipment. Participant shall provide suitable stockpile and staging area to winning vendor.

Application

1. General: The surface should be pre-wetted by fogging ahead of the spreader box when required by surface and ambient conditions. The rate of application of the fog spray shall be adjusted during the day to suit temperatures, surface texture, humidity, and dryness of the pavement surface.

The Micro-Surfacing mixture shall be of the desired consistency upon leaving the mixer and no additional materials should be added. A sufficient amount of material shall be carried in all parts of the spreader at all times so that a complete coverage is obtained. Overloading the spreader shall be avoided. No lumping, balling, or unmixed aggregate shall be permitted.

No streaks, such as those caused by oversized aggregate, will be left in the finished surface. If excessive amounts of oversized aggregate appear in the mix, the job will be stopped until the winning bidder proves to the Engineer that the situation has been corrected.

2. Joints: No excessive buildup, uncovered areas, or unsightly appearances shall be permitted on longitudinal or transverse joints. The winning bidder shall provide suitable width spreading equipment to produce a minimum number of longitudinal joints throughout the project. When possible, longitudinal joints shall be placed on lane lines. Half passes and odd width passes will be used only in minimum amounts. If half passes are used, they shall not be the last pass of any paved areas.

3. Mix Stability: The Micro-Surfacing mixtures shall possess sufficient stability so that premature breaking of the material in the spreader box does not occur. The mixture shall be homogenous during and following mixing and spreading. It shall be free of excess water or emulsion, and free of segregation of the emulsion and aggregate fines from the coarser aggregate.

4. Hand Work: Areas which cannot be reached with the mixing machine shall be surfaced using hand squeegees to provide complete and uniform coverage. The areas to be hand-worked shall be lightly dampened prior to mix placement. Care shall be exercised to leave no unsightly appearance from handwork. The same type finish as applied by the spreader box shall be required. Handwork shall be completed immediately after the Micro-Surfacing mixture is discharged from the spreader box.

5. Lines: Care shall be taken to ensure straight lines along curbs and shoulders. No runoff on these areas will be permitted. Lines at intersections will be kept straight to provide a neat workmanship appearance.

6. Rolling: If required by the Engineer, specified areas shall be rolled by a self-propelled, 5 to 10 ton pneumatic roller with a tire pressure of 50 PSI and equipped with a water spray system. If rolling is required by the Engineer, a separate pay item will be included in the bid proposal form.

Quality Control

1. Materials: The winning bidder will permit the Engineer to take samples of the aggregate and asphalt emulsion to be used in the project at the Engineer’s discretion. Gradation and sand equivalency tests may be run on the aggregate, and residual asphalt content test run on the emulsion. Test results will be compared to specifications. Tests will be run by a qualified laboratory at the expense of the participant. The participant must notify the winning bidder immediately if any test fails to meet the specifications.

2. Micro-Surfacing Mixture: Samples of the mixtures should be taken daily and many be taken directly from the mixing unit(s). Consistency and residual asphalt content test may be made on the samples and compared to the specifications. Test will be run by a qualified laboratory at the expense of the participant. The participant must notify the winning bidder immediately if any test fails to meet specifications. The Engineer may use the recorder and measuring facilities of the unit to determine application rates, asphalt emulsion content, mineral and field control additives, and water.

3. Non-Compliance: If any two successive tests fail on the stockpile material, the job shall be stopped. It is the responsibility of the winning bidder, at his own expense, to prove to the Engineer that the conditions have been corrected. If any two successive tests on the mix from the same machine fail, the use of the machine shall be suspended. It will be the responsibility of the winning bidder, at his own expense, to prove to the Engineer that the problems have been corrected and that the machine is working properly.

Performance It is the intention of the participant not to award a contract for Micro-Surfacing work under this or any other proposal if the winning bidder cannot furnish satisfactory evidence that he has the ability and experience to perform this class of work, and that he has sufficient capital and equipment to enable him to prosecute the work successfully, and to complete it within the time named in the contract. The participant also reserves the right to reject this or any other proposal, or to award the contract as is deemed in the best interest of said participant.

Experience To ensure contractor’s capabilities, the bidder shall provide with his bid evidence that at least two (2) of the company’s Micro-Surfacing field supervisory personnel have completed AASHTO TSP2 training, and successfully passed the Slurry Systems certification exam administered by the National Center for Pavement Preservation (NCPP). During completion of the work, contractor will be required to have at least two (2) AASHTO TSP2 Slurry Systems certified employees including the crew foreman assigned to the job and present at all times when Micro-Surfacing work is being performed.

Performance Warranty The winning bidder must furnish the following warranty after completion of the work and prior to final payment: The winning bidder hereby warrants that all workmanship and all materials furnished under this contract comply fully with requirements of these Micro-Surfacing Specifications. If at any time within two years after the date of the final inspection, any unfaithful or defective work should appear which, in the opinion of the participant, is due to inferior materials or workmanship, the winning bidder warrants to do whatever is necessary to remedy the defects immediately without the cost to the participant. The participant will notify the winning bidder in writing of the defects and the repairs to be made, and the winning bidder will begin repairs within a mutually agreed time frame.

Notification All homeowners and businesses affected by the construction shall be notified a minimum of one day in advance of the surfacing by the participant.

Traffic Control Suitable methods shall be used by the winning bidder to protect the Micro-Surface from traffic until the new surface will support traffic without damage. All traffic control methods used shall be in accordance with the Engineer’s specifications and shall be employed in a safe manner. The cost of flags and any police details, if required, will be paid or reimbursed by the participant. The participant will coordinate detail assignments which will be billed to the contractor directly based on the hourly cost. The winning bidder will not be reimbursed for police detail expenses incurred due to failure to cancel or cancelling without required notice.