- 357 - SECTION 514 -- MICROSURFACING
514.01 Description
1.This work shall consist of an app lication of microsurfacing material to an existing surface. The microsurfacing material shall be a mixture of polymer-modified emulsified asphalt, aggregate, mineral filler, water, and other additives properly proportioned, mixed, and spread.
514.02 Material Requirements
1.The asphalt emulsion for use in this work shall be CQS-1H polymer modified material and shall conform to the requirements of Section 1032.
2.a. Crushed mineral aggregate fo r use in this work shall be gravel conforming to the gradation requirements in Table 514.01.
b.Chat aggregate shall conf orm to the gradation requirements shown in Table 514.01.
c.Quartzite or granite sha ll conform to either gradation. Table 514.01 Microsurfacing Gradations Chat Gradation Sieve Size Percent Passing 3/8 inch (9.50 mm) 99 - 100 No. 4 (4.75 mm) 86 - 94 No. 10 (2.00 mm) 40 - 60 No. 50 (300 mm) 10 - 25 No. 200 (75 m) 5 - 15 Crushed Mineral Aggregate Gradation * Sieve Size Percent Passing 3/8 inch (9.50 mm) 100 No. 4 (4.75 mm) 84 - 100 No. 10 (2.00 mm) 50 - 64 No. 50 (300 m) 13 - 29 No. 200 (75 m) 5 - 15
3.Aggregate shall have a minimum fine aggregate angularity of 45% in accordance with AASHTO T 304 Method A.
4.Los Angeles Abrasion loss percentage shall not exceed 40. 5. Aggregates shall have a soundness loss of not more than 12% by weight at the end of 5 cycles using sodium sulfate solution.
6.A sand equivalent value of 60 or higher shall be required for any of the aggregates specified. The sand equivalent shall be tested according to AASHTO T 176.
7.The Contractor must pass t he aggregate over a 1/2 inch (13 mm) screen to remove any oversize material before the aggregate enters the mixing unit.
8.Mineral filler for use in this work shall be Portland cement, Type I or Type IP, that is free from lumps. Acceptance will be based on visual inspection. The amount of mineral filler needed shall be determined by the laboratory mix design and will be considered as part of the material
514.02 Microsurfacing
- 358 - gradation requirement. An increase or decrease of less than 1% by weight may be allowed when the microsurfacing is being placed if it is found necessary for better consistency or set times.
9.Water shall be potable. 10. Other additives may be allowed in the mixture or any of the component mixtures to provide the spec ified properties. Set retarding agents may also be included.
11.a. The Contractor shall be responsible for the design and proportioning of the microsurfacing mixture.
b.The contractor shall submit a tentative design to the Engineer for approval, in writing, ten working days prior to beginning microsurfacing production. The design shall list a ll the ingredients of the mixture.
c.Mix Design Requirements are shown in Table 514.02. Table 514.02 Microsurfacing Mix Design Requirements Property Test Requirements Wear Loss (Wet Test Track) ASTM D6372 (1 hour soak) (6 day soak) 50 g/ft2, maximum 75 g/ft2, maximum Wet Cohesion ASTM D6372 @30 minutes @60 minutes 10 in-lbs, minimum 17 in-lbs, minimum Wet Stripping ISSA TB-114 90%, minimum Mix Time @ 77°F ISSA TB-113 Controllable to 120 seconds, minimum
d.The Mix Design shall include all test results from Table 514.02.
e.The design shall list all the ingredient proportions and the gradation of the pr oposed aggregate.
f.Based on the dry weight of the aggregate, the microsurfacing mixture shall contain:
1.6% to 11% of residual asphalt. (2) 0.5% to 3.0% of mineral filler.
3.A sufficient quantity of water to produce a mixture having the proper consistency.
12.a. In the event a combination of aggregates is used, the aggregates shall be mechanically blended before loading the materials into the mixing machine.
b.Blending by loading alternate buckets will not be allowed.
514.03 Equipment
1.a. The material shall be mixed by a self-propelled continuous-flow mixing unit able to accurately deliver and proportion the aggregate, emulsified asphalt, mineral filler, and water to a revolving multi-blade mixer and discharge the thoroughly-mixed pr oduct on a continuous flow basis. Microsurfacing 514.04 - 359 - b. The machine shall have sufficient storage capacity for aggregate, emulsified asphalt, mineral filler, and water to maintain an adequate supply to the proportioning controls.
c.The machine shall be capable of loading all materials while continuing to apply the microsurfacing.
2.The controls for proportioning each material shall be accessible for ready calibration. The controls shal l be calibrated, properly marked, and located so that the Engineer may determine the amount of each material used at any time.
3.The aggregate feeder to the mixi ng unit shall be equipped with a revolution counter or similar device.
4.The emulsion pump shall be of the positive displacement type and shall be equipped with a revolution counter or similar device.
5.The mixing unit shall be equipped with an approved fine aggregate feeder that shall deliver a uniform, accurately metered flow of mineral filler. The delivery of mineral filler shall be coordinated with the aggregate feeder flow such that a properly propo rtioned mixture can be produced.
6.The mixing unit shall be equipped with a water pressure system and nozzle type spray bar to provide a water spray to the roadway surface immediately ahead of the microsurfacing spreading equipment. The pump for dispensing water to the mixing unit shall be equipped with a meter that will register directly in gallons (liters). The pump shall have a minimum of two valves, one of which shall establish t he required flow. The other valve shall be the quick acting type and shall be used to start and stop the water flow.
7.A rigid rear screed shall be us ed on the rut box, and it shall be adjusted to strike off the application of microsurfacing mixture flush with the edges of the rut depressions to the ex tent possible and within the limits imposed by the maximum aggregate particle size.
8.The laydown box shall use either a rigid metal primary strike off or a flexible rubber strike off. This strike off sha ll have three elevation adjustments to provide for quarter poin t elevation adjustments. Behind the primary strike off shall be a secondary st rike off which is cantilevered to the laydown box. The secondary strike off shall have a flexible rubber squeegee and be equipped with elevat ion adjustments matching the primary strike off. The secondary strike off shall have a pi vot point where it can be tilted for texturing or raised off the surface.
9.An inside skid shall be attached to the laydown box approximately 1 foot (300 mm) inside both ends of the box and running parallel to the outside skid. The inside skid shall be adjustable in height, allowing the weight of the laydown box to be carried on the inside skid while making adjacent passes.
10.Attached to each end of the dist ributor box shall be a "drip system" capable of adding a small amount of d iluted set-retarding agent into both rear corners. This will help ensure that material being deposited at the longitudinal joint edges has not set before being placed.
514.04 Calibration Methods
1.The laydown machine/mixing unit shall be calibrated before placement begins. The Contractor sha ll furnish the necessary accessories,
514.04 Microsurfacing
- 360 - materials, personnel and shall perform the tests and calibrations on the equipment under the obser vation of the Engineer.
2.The aggregate feeder and emulsi on pump shall be calibrated using the Calibration Computat ion Spreadsheet included in the Microsurfacing Workbook provided by the Department.
3.Emulsion pump calibration shall be based on the average of three calibration tests. The emulsion pump calibration tests shall be performed at pump rates that encompass those emul sion pump rates that will be used during production, or at a fixed pr oduction pump rate if the rate of microsurfacing (in pounds per revolution) will remain fixed throughout production. The individual test results shall not vary more than 0.5% from the average of the three tests.
4.The aggregate feed rate calib ration shall consist of the development of a graphical relationship of the gate setting (opening size in inches) versus aggregate feed rate (pounds of dry aggregate per count). This relationship will be used by the Contractor to select the aggregate gate height that will produce microsurfacing that conforms to the Contractor's mix design. The aggregate feed rate calibrati on shall consist of the following:
a.If an aggregate feed system is used that can be set to automatically provide an aggregat e feed rate that is uniform and proportioned to the emulsion feed rate to provide a mix that is consistent with the Contractor’s approved mix design, then the gate setting requirements in b. below are unnecessary.
b.The production aggregate-gate-height setting shall be selected based on the following:
1.The three various gate settings shall be selected to provide a production setting that is encompassed by the calibration gate settings. The calibration gate setting values shall plot equidistant along the aggregate gate height axis of the graphical relationship chart.
2.The feed-rate tests shall be performed at a consistent aggregate belt speed (aggregate count ra te) that is consistent with the aggregate belt speed that will be used during production. The aggregate feed-rate calibration tests shall have a minimum duration of feed-rate counts to produce a minimum of 1,000 lbs of wet aggregate per test.
3.Adjustment for the mois ture content of the aggregate to convert to a dry weight of aggregate shall be made.
c.The results of the three calibration tests shall be provided to the Engineer and plotted. The fixed aggregate-gate-height setting (production gate height setting) shall be selected by the Contractor. This setting shall produce a uniform proporti on of aggregate and emulsion that conforms to the Contractor's mix desig n. The Engineer shall be notified of any changes to the aggregate/emulsion pr oportion or to the aggregate gate height.
d.The aggregate feed rate shall be calibrated based on the average of three calibration tests. Thes e calibration tests shall be performed at the fixed aggregate-gate-height setting (production gate height setting). These calibration tests shall be performe d at aggregate feeder rates that encompass those aggregate feeder rates that will be used during production Microsurfacing 514.05 - 361 - or at the fixed aggregate feeder rate if the rate of microsurfacing (in pounds per revolution) will remain fixed throughout production. The individual test results shall not vary more than 0.5% from the average of the three tests.
5.The calibration results shall be approved by the Engineer prior to placement of microsurfacing.
6.The Contractor shall notify the Engineer of all feed rate adjustments. A lock shall be placed on the aggregate feeder gate and the emulsion pump shall be mechanically linked to the aggregate feeder to insure that the fixed aggregate/emulsion proportion is not altered without the Engineer's approval.
514.05 Construction Methods
1.The Contractor shall furnish and apply the microsurfacing materials. The Contractor shall construct the micr osurfacing as shown in the contract or as directed by the Engineer.
2.Immediately before applying the microsurfacing, the Contractor shall clean the surface of all vegetation, loose materials, excess joint material, excess oil, dirt, mud, and other objectionable materials.
3.The Contractor shall water the surface before the application of the microsurfacing. The water shall be applied at a rate such that the entire surface will be damp.
4.When ruts occur, regardless of the rut depth, the microsurfacing shall be placed in two separate applications.
a.The first pass will bring the ruts up to a minimum level of the existing pavement profile, and shall be performed using a scratch course. A scratch course does not r equire the use of a secondary strike off behind the rigid metal primary strike off plate. The first pass will not be subject to the repairs required in Subsection 514.05, Paragraph 15.
b.The second pass shall place microsurfacing material over the entire lane.
5.Areas that cannot be reached with the mixing machine shall be surfaced using hand tools to provide complete and uniform coverage. Such handwork and the machine application shall be completed simultaneously.
6.A sufficient amount of microsurfacing shall always be carried in all parts of the distributor box so t hat complete coverage is obtained.
7.No lumping, balling, or unmix ed aggregate will be allowed. Any oversized aggregate or foreign materials shall be screened from the aggregate before delivery to the microsur facing mixing machine. No streaks or slick spots shall be left in the finished surface.
8.a. Water used to produce the proper consistency shall be metered.
b.The use of water to routinely clean the box during placement will not be allowed.
9.Microsurfacing mixture shall be placed only when:
a.The atmospheric temperature is 50°F (10 C) or greater.
514.05 Microsurfacing
- 362 - b. The temperature is expected to be above 32°F (0 C) for 24 hours after placement.
c.It is not foggy or rainy. 10. Longitudinal joints shall be placed on lane lines where possible. Joints shall overlap and shall not ex ceed 3 inches (75 mm). Care shall be taken to ensure straight lines along the roadway centerline, lane lines, and shoulder or curb lines. Lines at intersec tions shall be kept straight to provide a good appearance as determined by the Engineer.
11.At driveways, intersections, and other locations where sharp turning movements or vehicle accelerations may occur, additional time may be required for adequate curing before allowing traffic on the newly placed material.
12.On the first production day, a 1, 000 foot test strip shall be placed and approved before full production begi ns. The Contractor shall construct the test strip using the approved job mix design, laydown procedures and equipment that will be used on the project.
a.Full production shall not begin until the Engineer has determined that:
1.The material is curing properly to allow normal traffic on the surfaced roadway within 1 hour.
i.Proper curing will be determined by the Engineer testing the section by driving their inspection vehicle on the material after 1 hour of curing, and the surface does not display tearing, marking, or any permanent deformation under the load of the vehicle in straight forward driving operations and in slig ht turn radius situations.
2.The mix is in conforma nce with the mix design criteria.
3.The edge lines are placed straight and remain straight. (4) No lumping, balling or unmixed aggregate exist. (5) The surface texture is uni form and free of streaks, slick spots or excessive drag marks.
b.When a test strip produces a mixture or surfac e that does not meet the specifications, the test st rip shall be rejected and will not be measured as part of completed work. The Contractor shall remove and replace the test strip at no additional cost or overlay the test strip with microsurfacing that conforms to the pr oject specifications, at the Engineer's discretion. The edges and ends of over laid material shall be feathered to conform to the longitudinal and transverse joint requirements in Subsection 514.05, Paragraphs 16 and 17.
c.Accepted test strips, when placed in areas that are to be microsurfaced, will remain in place and be measured as part of the completed work.
d.A new test strip will be performed when there is field evidence that the system is not performing as spec ified, is out of control, or when a new mix design is required.
13.Microsurfacing shall cure to allow turning truck traffic within 3 hours. Adequate cure shall be verified by having truck operations with no Microsurfacing 514.06 - 363 - displacement. Microsurfacing that exhibits aggregate displacement or deformation shall be removed and replaced at no cost to the Department.
14.The transverse pavement cro ss section as measured using a 10 foot straight edge shall not have dev iations that exceed 3/8 inch. This shall not apply to any area within 12 inches of the edge line, lane line, or center line.
15.The Contractor shall construct the surface course without excessive scratch marks, tears, rippling, or other surface irregularities. Repair tear marks greater than 1/2 inch wide and 4 inches long and marks greater than 1 inch wide and 1 inch long. Repair transverse ripples or streaks greater than 1/4 inch in depth as measured by a 4 foot straight edge. All repairs shall be either hand repairs made immediately after placement and before the microsurfacing material has broken, full-width repairs that shall require removing the full width of microsurfaci ng and replacing with microsurfacing that conforms to the proj ect specifications, or ov erlay the defective areas with microsurfacing that conforms to the project specific ations. Hand repairs shall have a finished surface texture and color that matches the adjacent microsurfacing. The edges and ends of overlaid material shall be feathered to conform to the longitudinal and transverse joint requirements in Paragraphs 16, 17 and 18 of this section.
16.Constructed longitudinal joints, with no more than 1/2 inch overlap thickness as measured with a 4 foot straight edge, and less than a 3 inch overlap on adjacent passes. Longitudinal construction joints and lane edges shall coincide with the proposed pa inted lane lines. Place overlapping passes, on the uphill side, to prevent ponding of water.
17.Construct transverse joints, with no more than 1/4 inch difference in elevation across the joint as meas ured with a 4 foot straight edge.
18.Construct edge lines along curbs, shoulders, lane lines and centerline with no more than 2 inches of horizontal variance in any 100 foot location. No runoff in these areas will be permitted.
19.The Contractor may restrict traffic to one lane while applying the microsurfacing. The Contractor shall take whatever other means necessary to protect the microsurfacing from damage by traffic. Any damage done by traffic shall be repaired by the Contra ctor at no cost to the State.
514.06 Method of Measurement
1.a. "Aggregate for Microsurfaci ng" shall be measured by the ton (Megagram). The weight shall be determined on approved scales under the observation of the Engineer. Deductions will be made for the moisture in the aggregate at the time it is weighed. Moisture determinations will be made for each of the first 5 loads and as often a fter that as is necessary to describe the fluctuations in the moisture content.
b.The weight of "Aggregate for Microsurfacing" may be determined using the aggregate feeder count er, as an alternative to using an approved scale, provided the aggregate fe eder counter is calibrated. Lading certificates for the aggr egate shall be provided to the Engineer. This payment alternative must be requested by the Contractor prior to the placing of microsurfacing and approved by the Engineer.
514.06 Microsurfacing
- 364 - 2. The "Emulsified Asphalt for Microsurfacing" is measured by the gallon (kiloliter). The volume of "Emulsifi ed Asphalt for Microsurfacing" will be determined using the emulsion pump revolution counter, as an alternative to using refinery certified volumes, provided the emulsion pump revolution counter is calibrated. Refinery certific ates with certified volumes shall be provided to the Engineer.
3."Mineral Filler for Microsurfa cing" shall be measured by the ton (megagram) of Portland cement. If furnished in bags, the weight shall be determined by converting the bag count to tons (megagrams).
4.The "Microsurfacing Placement" shall be measured by the station along the project centerline without regard for width or depth of the work and without regard for the number of passes needed to complete the work. The work of placing the Microsurfacing in all ruts is included in this measurement. When lug-outs, driveways and intersections will be microsurfaced as shown on the contract, they shall be considered subsidiary. Microsurfacing of driveways or intersections that extends past the end of the radius, in excess of 50 feet will be included in the pay length. Measurement of these segments will begin at the end of the radius.
514.07 Basis of Payment
1.P a y I t e m P a y U n i t Aggregate for Microsurfacing Ton (Tn) [Megagram (Mg)] Emulsified Asphalt for Microsurfacing Gallon (Gal) [ K i l o l i t e r ( k L ) ] Mineral Filler for Microsurfacing Ton (Tn) [Megagram (Mg)] Microsurfacing Placement Station
2.The approved polymer-based modifier, other additives, and any additional emulsifying agents will not be measured for payment but shall be considered subsidiary to the item "Emulsified Asphalt for Microsurfacing".
3.Water used in the preparation of the microsurfacing mixture and for prewetting the surface of the roadway will not be measured for payment but shall be considered subsidiary to other items for which payment is made.
4.Any amount of microsurfacing emulsified asphalt which is outside the specified property ranges of T able 514.03, shall be paid for at the contract unit price multiplied by the pay factor determined in Table 514.03. If the resultant Pay Factor for the material indicates rejection as an option, the Engineer will determine if the non-compliant material will be removed. Microsurfacing 514.07 - 365 - Table 514.03 Tolerances and Pay Factors Specified Property Tolerance Pay Factor AASHTO T 59, Residue after Distillation ≥ 61.0% 1.00 59.0% - 60.9% 57.0% - 58.9% 0.85 0.70 < 57.0% 0.40 or Reject AASHTO T 53, Softening Point > 131.5°F 1.00 < 131.5°F 0.75 or Reject Pay Factors for Tests for ALL other Properties Specified* 1.00 for deviation of ± less than or equal to 10% 0.75 for a deviation of ± greater than 10% to less than or equal to 25% 0.40 or Reject for deviation of ± greater than 25% * When the specification requirement is stated as a percentage, the test result deviation from the s pecification will be divided by the specification value. The result ing deviation percentage is then applied to the listed criteria. Note : When more than one specified property exceeds specification tolerances, t he single largest Pay Factor Reduction will be the one applied.
5.When disputes arise in test resu lts, the Department will select an independent laboratory for referee test ing on the remainder of the sample. The identity of the independent labo ratory will not be revealed until the selected laboratory has completed the referee testing.
a.Only the Contractor can init iate dispute resolution, and request referee testing. Should the Contractor request referee testing, it shall be submitted in writing to the Departmen t within 4 days of receiving the notification of deficienc y. This written request is also affirmation and agreement that the testing may occur beyond the 14 day testing timeframe of the asphaltic emulsion specifications.
b.If the independent lab’s tests indicate failing results and pay deductions equal to or greater than the Department’s, the Contractor will reimburse the Department for the cost of testing. If the independent lab’s tests indicate that the material meets s pecifications or is at a pay deduction less than the Department’s, the Department will assume the cost of testing. When the independent lab’s tests indica te a pay deduction, the lesser of the Department’s and the independent la b’s deductions will be applied.
6.Payment is full compensation for all work described in this Section. - 366 - SECTION 515 -- ARMOR COAT OR CHIP SEAL
515.01 Description
1.Armor Coat and Chip Seal is the sprayed application of emulsified asphaltic material with a covering of aggregate at the locations shown in the contract or as directed by the Engineer.
515.02 Material Requirements
1.Armor Coat and Chip Seal emulsified asphaltic material shall be the type and grade shown in the contract and shall conform to the requirements of Sections 1031 or 1032.
2.Aggregate for Armor Coat and Chip Seal shall conform to the requirements of Subsection 1033.02 , Paragraphs 1. and 2. The aggregates shall have a Los Angeles Abrasion loss percentage of not more than 40.
3.Aggregate for Armor Coat sha ll have a soundness loss of not more than 5% by mass at the end of 5 cycles using sodium sulfate solution. The aggregate shall also conform to the grad ation requirements of Table 515.01. Table 515.01 Armor Coat Aggregate Gradation Limits Sieve Size Percent Passing 3/8 inch (9.5 mm) 99 to 100 No. 4 (4.75 mm) 60 to 85 No. 10 (2.0 mm) 0 to 15 No. 50 (300 m) 0 to 10 No. 200 (75 m) 0 to 3
4.Aggregate for Chip Seal s hall be limestone, expanded shale, granite, or quartzite. The aggregate shall have a soundness loss of not more than 7% by mass at the end of 5 cycles using sodium sulfate solution.
a.The limestone, granite, and quartzite chip seal aggregates shall conform to the gradation requirements of Table 515.02. Table 515.02 Limestone, Granite, and Qua rtzite Chip Seal Aggregate Gradation Limits Sieve Size Percent Passing 3/8 inch (9.5 mm) 99 to 100 No. 4 (4.75 mm) 0 to 70 No. 10 (2.0 mm) 0 to 10 No. 50 (300 m) 0 to 5 No. 200 (75 m) 0 to 3
b.The expanded shale chip seal aggregate shall conform to the gradation requirements of Table 515.03.
Source: Nebraska Standard Specifications for Highway Construction, 2017 Edition. Pages 391–399 of 1,048.