221 SECTION 420 SINGLE / MULTIPLE COURSE MICRO SURFACING
420.1 -DESCRIPTION : This section covers the materials, equipment, construction and application procedures for placing Micro Surfacing material for filling ruts and for surfacing existing paved surfaces. The Micro Surfacing is a mixture of a latex -modified asphalt emulsion, crushed mineral aggregate screenings, mineral filler, water and other additives for control of set time in the field. All ingredients are to be properly proportioned, mixed and spread on the paved surface in accordance with this Specification and as directed by Engineer.
420.2 -MATERIALS : Furnish a Micro Surfacing mixture consisting of a properly designed and proportioned blend of polymerized asphalt emulsion, fine aggregate, Portland cement, water and other additives. All materials must be from a WVDOH approved source. Use materials meeting the following:
420.2.1 -Mineral Filler: Portland cement, hydrated lime, limestone d ust, fly ash, or other approved filler meeting the requirements of ASTM D242 shall be used if required by the mix design.
420.2.2 -Fine Aggregates, 2FA and 3FA: The fine aggregate used shall be suitable for the particular application and shall be a crus hed stone such as granite, slag, limestone, chat, or other high -quality aggregate, or combination thereof. Additionally, on projects with an ADT greater than 3000, the fine aggregate used in the surface course shall also meet the requirements of the WVDOH commercial source list for potential anti -skid aggregate quality specifications. The aggregate shall be passed over a scalping screen immediately (not prescreened) prior to transfer to the micro surfacing mixing machine to remove oversized material.
Tests Requirements Sand Equivalent Value of Soils and Fine Aggregate AASHTO T 176 65 minimum Soundness of Aggregates by Use of Sodium Sulfate MP 703.00.22 15% max. w/ NA2SO4
Material Percent Passing ⅜ in No. 4 No. 8 No. 16 No. 30 No. 50 No. 100 No. 200 2FA(a) 100 90-100 65-90 45-70 30-50 18-30 10-21 5-15 3FA(a) 100 70-95 45-70 28-50 19-34 12-25 7-18 5-15
420.2.3 -Asphalt Emulsion -CSS-1hM or CQS -1hM: Polymer Modified Asphalt Emulsion shall be a CQS -1P or CQS -1hP in accordance with AASHTO M 316 with the following exceptions: the distillation procedure shall be conducted at 175°C with a 20 minute hold perio d. The polymer material shall be processed into the asphalt cement or milled into the asphalt emulsion. Post adding to the asphalt emulsion is not permitted. The minimum polymer solids content will be 3.0% based on the residual of the emulsion.
222 420.2.4 -Water: Water shall be potable and free of harmful salts and contaminants.
420.2.5 -Additives: Chemical additives may be used to accelerate or retard the break/set of the Micro Surfacing mixture. Appropriate additives, and their applicable use r ange, should be approved by the laboratory as part of the mix design.
420.3 -MIXTURE REQUIREMENTS : 420.3.1-Mix Design: Submit to the Engineer, at least fourteen calendar days be fore the start of production, a complete mix design prepared and certified by an experienced laboratory. The source for all materials must be shown. Provide a job mix formula (JMF) to the Engineer at the pre -paving meeting showing individual proportions of each material, that when combined, shall meet the requirements of AASHTO PP 83, with the exception that the Saturated Abrasion Loss by ISSA TB -144 shall be 2.0g max. A new mix design is required for any change in aggregate or asphalt emulsion source.
The JMF must be within the following limits:
Asphalt Binder Content (Residual) 7.0% -8.5%, dry weight, 2FA aggregate 6.5% -8.0%, dry weight, 3FA aggregate
Mineral Filler 0.25% -3.0%, dry weight, of aggregate
420.3.2 -Mix Design Format: Provide the following information in the final mix design:
420.4 -CONSTRUCTION : 420.4.1 -Equipment: Provide safe, environmentally acceptable equipment that can produce a specification product.
223 420.4.1.1 -Mixing Machine: Provide one or more self -propelled, front feed, continuous loading mixing machines equipped and operated as follows:
interconnected positive displacement, water -jacketed gear pump to accurately proportion aggregate and asphalt emulsio n.
fifty (50) inches long.
recommendation.
on the aggregate before discharging into the pugmill.
proper mixing of all materials before they exit from the pugmill.
that are readily accessible and positioned so the amount of each material used can be determined at any time. The mixer shall be equipped with a back -up electronic materials counter that is capable of recording ru nning count totals for each material being monitored. The mixer shall be equipped with a radar ground measuring device. Each material control device shall be calibrated prior to each mix application and as often thereafter as deemed necessary by the Engi neer. The computer system shall have the capability to record, display and print the following information:
metering device
spray ahead of and outside the spreader box when required. Apply water to dampen the surface without resulting in free flowing water ahead of the spreader box.
during placement. Remote forward speed control at the back mixing platform so that the back operator can control forward speed and level of mixture in the spreader box.
Use a sufficient number of transports to assure a continuous operation during mix production and application. Use transport units with belt type aggregate delivery systems, emulsion and water storage tanks of adequate size to proportionally mix aggregate delive red by each transport. Unless otherwise noted in the plans or as approved by the Engineer, truck -mounted batch type machines will only be allowed on small projects (15,000 square yards or less). Provide a minimum of two units at all times. Schedule thes e truck -mounted machines so that mixture production is never delayed more than 15 minutes. Stop production anytime there is noncompliance with this requirement.
224 Calibrate the mixing machines before use. Maintain documentation of calibration of each ma terial metering device at various settings. Supply all materials and equipment, including scales and containers, necessary for calibration. Recalibrate after all changes in aggregate or asphalt emulsion sources. Calibrations shall be done a minimum of o nce per job.
420.4.1.2 -Spreader Box: Attached to the machine shall be hydraulically adjustable (adjustable while applying mixture) type spreader box with a positive screed adjustment for yield control and a positive adjustment for the joint matcher. Equipped with paddles or augers mounted on adjustable shafts to continually agitate and distribute the mixture to prevent stagnation, excessive build -up, or lumps. Equip spreader boxes with front and rear flexible seals to maintain direct contact with the r oad. Use a secondary strike off attached to the spreader box to provide a finished smooth surface texture on the final pass or surface pass. Use a drag that produces a uniform finish.
420.4.1.3 -Rut Box: Use a steel V configuration screed rut box speci fically designed and commercially manufactured to fill ruts to perform all Micro Surface, rut -filling applications. Ensure a mixture spread width of five ( 5) to six (6) feet and use a secondary strike off to control crown on the rut box. The rutbox must be equipped with a third strike off that may be used to control texture.
420.4.1.4 -Miscellaneous Equipment: Provide hand squeegees, shovels and other equipment as necessary to perform the work. Provide cleaning equipment such as power brooms, air compr essors, water flushing equipment, and hand brooms for surface preparation.
420.4.1.5 -Lights on Equipment: Equip power brooms, distributors and truck mount spreaders with at least one approved, flashing, rotating or oscillating amber light that is visibl e in all directions. Equip continuous spreader units with one such light on each side.
420.4.2 -Application: Micro Surfacing mixtures shall be applied in a manner to fill ruts, minor cracks and leave a uniform surface with straight longitudinal joints, transverse joints and edges. When performing multiple course Micro Surfacing, the total application rate shall be a minimum of thirty ( 30) pounds per square yard by weight of dry aggregate with the final surface course not less than sixteen ( 16) pounds per square yard by weight of dry aggregate.
Multiple Course will restore the cross section of the driving lane within ¼ inch as measured transversely across the pavement with a seven ( 7) foot straight edge. The prece ding will not apply to any pavement segment that is designed with a quarter crown cross slope or any area of the segment within six (6) inches of the edge line, lane line, or centerline.
item is Micro Surface. Rutfilling shall use a Micro Surfacing mix with fine aggregate 3FA applied with an approved rut box for each designated wheel track. A clean overlap and straight edges shall be required between wheel tracks. Eac h pass of rutfilling shall be limited to a maximum depth of one ( 1) inch. For each one ( 1) inch of applied mix, an additional ⅛ inch crown is required for traffic consolidation. All rutfilling material
225 should cure under traffic for at least twenty four (2 4) hours before additional material is placed.
Micro Surface, Single Course: A single course shall be applied full lane width in one course to the entire pavement surface including the shoulder if indicated in the contract documents. Application rate shall be a minimum of 20 pounds per square yard by weight of dry aggregate for a 3FA mix and 16 pounds per square yard by weight of dry aggregate for a 2FA mix.
420.4.3-Temporary Pavement Marking: Shall be in accordance with Section 636.
420.4.4 -Pre-paving Meeting: Hold an on -site pre -paving meeting with the Engineer before beginning work to review and discuss the following.
420.4.5 -Test strip: Test Strip(s) to demonstrate the mixing of materials and placement procedures of each mixing machine to be used on the project. Test strip shall be performed at the beginning of the first day production and on the roadway to be treated. The completed test strip (minimum 500 feet length) shall be reviewed to detect and correct any variances in surface texture, material ratio(s) and finished surface appearance. Additionally, the test strip will be used to establish the target job application rate. The test strip shall be placed in conditions similar to those expected to be encountered during the project. If conditions change (e.g., roadway surface, environmental conditions, day/night) then another test strip shall be performed.
420.4.6 -Surface Preparation: Remove all plastic pavement markings using an abrasion method. Remove markings just before the surfacing operation. Work and payment for removal of pavement markings shall follow Section 6 36.7 of the Specifications. Micro Surfacing shall not be placed on top of patches, crack seal, Base Repairs, Edge Repairs, or any other asphalt pavement repairs for at least 30 calendar days. Work and payment for these items shall follow their appropria te sections. Thoroughly clean the existing surface of all loose materials, vegetation, dirt, dust, mud and other objectionable materials at the time of placing the mixture. Remove animal remains and thoroughly wash the surface before placing the mixture. The project plans will dictate whether to remove or temporarily cover existing RPMs prior to placement of micro surfacing; payment for removal or covering shall be incidental. When removal is required, the Contractor shall remove RPMs with minimal dama ge to the pavement surface. Payment for new RPMs shall be in accordance with Section 663. Protect drainage structures, monument boxes, water shut -offs, etc., during application of tack coat and mixture. Apply tack coat according to section 408, except for the following. Mix tack coat with one part emulsion to three parts water. Use the same emulsion as used in the production mixture. Apply the tack coat uniformly, at an application rate of 0.05 -0.12 ga llons per square yard and without excessive run off. Allow the tack coat to cure before placement of mixture.
226 Establish 1,000 -foot intervals for the entire project, before placing the mixture. Clearly identify and maintain these intervals until projec t completion .
420.4.7 -Surface Quality: Provide a finished surface free from excessive scratch marks, tears, rippling, and other surface irregularities. Do not leave ripples greater than 1⁄8 inch measured by a ten (10) foot straight edge. Do not leave tear marks greater than 1⁄2 inch wide and four ( 4) inches long, or other marks greater than one ( 1) inch wide and one ( 1) inch long. If the finished surface exceeds the described tolerance, stop work immediately and deter mine appropriate correct action. Review corrective action with the Engineer before resuming production. Place longitudinal construction joints and lane edges to coincide with the proposed painted lane lines. Construct longitudinal joints with less tha n three ( 3) inches overlap on adjacent passes and no more than 3⁄8 inch overlap thickness as measured with a ten (10) foot straight edge. Place successive passes to prevent ponding of water on the up -slope side of the overlap. Construct neat and uniform transverse joints with less than a 1⁄8 inch difference in elevation across the joint as measured with a ten (10) foot straight edge. Provide neat and uniform lane edges with no more than two ( 2) inches of horizontal variance in 100 feet. If defective joi nts or edges are placed, stop work and take corrective action and reviewed by the Engineer.
420.4.8 -Traffic Control: Do not allow traffic on the mixture until it has cured sufficiently to prevent pickup by vehicle tires. The new surface must be able t o carry normal traffic without damage within one hour of application. Protect the new surface from damage at intersections and driveways. Repair all damage to the mixture caused by traffic. All costs associated with this repair work will be borne by the Contractor. Otherwise Traffic Control will be in accordance with Section 636, and the Manual on Temporary Traffic Control for Streets and Highways, latest version , or as directed by the Engineer.
420.4.9 -Weather and Seasonal Limitations:
be below 32 °F within 24 hours of completion of the work.
420.4.10 -Quality Control: The con tractor shall have at least one employee on the job site who is certified in Slurry Systems through AASHTO’s Transportation System Preservation Technical Services Program (TSP2), or through another reputable certification program approved by the Engineer. The contractor shall submit a Quality Control Plan prior to beginning work. Produce a mixture that will meet the JMF and the quality control tolerances. Notify the Engineer immediately if the quality control test results exceed any of the tolerances and stop mixture production. Identify the cause of the excess deviation and determine the corrective action necessary to bring the mixture into compliance. Secure the Engineer’s approval before resuming work.
227 Micro Surfacing Quality Control Tolerances Aggregate Gradation Tolerances (±) from JMF Sieve Size # 4 # 8 # 16 # 30 # 50 # 100 # 200 Tolerance 5.0% 5.0% 5.0% 5.0% 4.0% 3.0% 2.0%
General Quality Control Tolerances (±) Asphalt Cement Content Single Test 0.5 % from JMF Asphalt Cement Content Daily Average 0.2 % from JMF Application Rate: 2 lb/sq yd (as determined by 1,000 ft yield checks)
Verify and document quality control with the following minimum measures:
test per 500 tons of aggregate or one test per day of mixture production, whichever is greater.
emulsion once per production lot, according to the emulsion supplier. This sample shall be sent to MCS&T Division’s Emulsions Lab for testing.
percent asphalt content of the mixture using the equipment counter readings.
yield of the course being placed using the equipment counter readings.
Complete a separate d aily report for each truck mounted machine:
For Quality Assurance purposes, samples for gradation wi ll be taken from aggregate stockpiles designated by the Contractor for use. The frequency of sampling and testing will be established by the Engineer based upon the Division’s current acceptance program and local conditions encountered.