Part 1 — General
1.1 Section Includes
A.Products and procedures for mixing and spreading a properly proportioned homogeneous mixture of aggregate, mineral filler, additives, polymer -modified asphalt emulsion and water to an existing pavement providing a firm surface adhesion and smooth, stable , and skid-resistant texture.
1.2 Related Sections
A.Section 02701: Pavement Smoothness
B.Section 02742S: Project Specific Surfacing Requirements
C.Section 02746: Hydrated Lime
1.3 References
A.AASHTO M 17: Mineral Filler for Bituminous Paving Mixtures
B.AASHTO M 85: Portland Cement
C.AASHTO T 11: Materials Finer Than 75 µm (No. 200) Sieve in Mineral Aggregate by Washing
D.AASHTO T 27: Sieve Analysis of Fine and Coarse Aggregates
E.AASHTO T 49: Penetration of Bituminous Materials
F.AASHTO T 53: Softening Point of Bitumen (Ring -and-Ball Apparatus)
G.AASHTO T 59: Emulsified Asphalts
H.AASHTO T 96: Resistance to Degradation of Small -Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine
I.AASHTO T 104: Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate
J.AASHTO T 112: Clay Lumps and Friable Particles in Aggregate
K.AASHTO T 176: Plastic Fines in Graded Aggregates and Soils by Use of the Sand Equivalent Test
L.AASHTO T 278: Surface Frictional Properties Using the British Pendulum Tester
M.AASHTO T 279: Accelerated Polishing of Aggregates Using the British Wheel
N.ASTM D 6372: Design, Testing , and Construction of Microsurfacing
O.International Slurry Seal Association (ISSA ) Specifications and Guidelines
P.UDOT Minimum Sampling and Testing Requirements
Q.UDOT Quality Management Plans
1.4 Definitions
A.Emulsified A sphalt - The emulsion.
B.Emulsified Asphalt Residue - The residue of the emulsion.
C.Residual A sphalt - The residue of the mixture.
D.Lot – One day’s production.
1.5 Submittals
A.Provide the mix design for approval before beginning construction.
1.Refer to this Section, A rticle 2.6.
2.The m ix design must be performed by an AASHTO R esource accredited laboratory experienced in the design of micro surfacing systems.
3.Provide the Engineer with the following for polymer -modified asphalt emulsion with job -mix design.
a.Test report that meets the requirements of this Section, Article 2.1.
b.Target gradation for combined aggregate, and for mineral filler.
c.Name of the asphalt emulsion supplier .
d.Verification that the emulsion supplier adheres to UDOT Quality Management Plan Section 508, Asphalt Emulsion.
B.Provide test reports for mineral aggregate for information.
1.Refer to this Section, A rticle 2.2.
C.Provide a Manufacturer’s Certificate of Compliance for the Mineral Filler for information.
1.Refer to this Section, A rticle 2.3 .
D.Provide calibration documentation for each mixing unit , including an individual calibration for each material at various settings that corresponds to the mixing unit metering device for information.
E.Changes in the job- mix gradation for approval .
1.Submit a written request for a ny change in the job- mix gradation.
2.Submit a new job -mix design if changes in gradation are outside the gradation band allowed by the stockpile tolerance in Table 4 .
F.Provide a daily report and log sheet for information that that contains:
1.Calculations of the residual asphalt content of the mixture from the equipment computer display at least three times daily.
2.The aggregate application rate from the equipment computer display at least three times daily.
3.Aggregate used, ton (dry) .
4.Daily tickets from the screening unit.
5.Micro surfacing emulsion used, ton.
6.Bituminous materials for tack coat used, if specified, ton.
7.Mineral filler used, lbs .
8.Water used in mixture, gallons .
9.Additive used in mixture, gallons .
10.Surface area completed, square yards .
11.Surface area application rate (dry lbs aggregate per square yard) .
12.Percentage of asphalt residue based on dry aggregate.
1.6 Acceptance
A.The Department perform s acceptance sampling and testing of material according to UDOT Minimum Sampling and Testing Requirements.
B.The Department will assess price adjustments based on the average daily application rate of aggregate and residual asphalt per lot , using the Contractor’s daily report, as verified by the Engineer. See this Section, Article 1.5 F .
1.Calculate the p ay factor and apply it to the square yard micro surfacing item.
a.Pay Factor = PF rate (Table 1) x PF residue (Table 2) ,.
C.The aggregate application rate pay factor ( PFrate) is based on the application rate of dry aggregate.
1.The aggregate application target rate is 25 lbs/yd2 Table 1 Aggregate Application Rate Pay Factor Average Application Rate (lbs/yd2) PFrate
25.0 or Greater 1.0
20.0 to 24.9 (Avg. Rate ÷ 25)
Less than 20.0 Reapplication with option to remove
D.The residual asphalt pay factor (PF residue ) is based on the emulsified asphalt residue and content placed for each lot.
1.The Target Value is the Residual asphalt target value for emulsion, based on the mix design.
2.The emulsified a sphalt residue is provided on the Certificate of Compliance from the Emulsion Supplier . Table 2 Residual Asphalt Pay Factor Residual Asphalt , Daily Average (%) PFresidue (Target Value - 0.50) ≤ Daily Average ≤ (Target Value + 0.50) 1.0 (Target Value - 1.00) ≤ Daily Average < (Target Value - 0.50) or (Target Value + 0.50) < Daily Average ≤ (Target Value + 1.00) 0.8 Daily Average < (Target Value – 1.00) or Daily Average > (Target Value + 1.00) Reapplication with option to remove and replace
E.Smoothness
1.Refer to Section 02701 for smoothness requirements.
Part 2 — Products
2.1 Emulsified Asphalt
A . Use a polymer -modified asphalt emulsion manufactured specifically for micro surfacing.
1.Refer to Table 3.
2.The supplier must be on the approved list adhering to the UDOT Quality Management Plan 508 Asphalt Emulsion. Table 3 Polymer -Modified Asphalt Emulsion Test Method Description Micro CQS -1P(NLR) Or Micro CQS -1P(SLR) Micro CQS -1hP(NLR) Or Micro CQS -1hP(SLR) (a) AASHTO T59 Viscosity, 25o C, SFS 20 Min; 100 Max 20 Min; 100 Max AASHTO T59 Particle Charge Test Positive Positive AASHTO T59 Sieve Test, % 0.1 Max 0.1 Max AASHTO T59 -modified ( b) Residue by distillation , % 65 Min 65 Min Emulsion Residue Testing AASHTO T49 Penetration, 25°C, dmm 70 – 120 40 – 70 AASHTO T53 Softening point , °C 55 Min 57 Min AASHTO T301 (Modified) (c), (d) Elastic Recovery , 5 cm per min., 25°C, % 60 Min 60 Min (a) Generally used for Washington County (b) Modified distillation procedure – Heat emulsion residue to 177 ± 5° C and maintain that temperature for 20 min. Perform the distillation within 60 ± 15 min. (c) Modify paragraph 4.5 as follows: Stop the ductilometer after 20 cm has been reached and within 2 seconds , sever the specimen at its center with a pair of scissors. (d) The polymer -modified asphalt emulsion residue is obtained from the distillation process.
B.Mill or blend the polymer material into the asphalt or emulsifier solution before the emulsification process.
1.Obtain certification from the asphalt emulsion manufacturer that the emulsion contains at least 3.0 percent polymer solids of natural latex rubber (NLR) or synthetic latex rubber (SLR) based on the weight of asphalt (asphalt residual).
2.Latex rubber must be 100 percent natural latex rubber (NLR) or synthetic latex rubber (SLR) as specified in Section 02742S .
C.The Department reserves the right to test the emulsion and also look at bills of lading to verify the polymer or modifier types used.
D.Formulate the polymer -modified asphalt emulsio n so the paving mixture will sufficiently cure to allow a return to traffic in one hour under application conditions .
2.2 Mineral Aggregate
A.Use 100 percent crushed mineral aggregates , clean and free from organic matter or other detrimental substances that meet the following requirements:
1.Maximum clay lumps and friable particles of 2 percent for coarse and fine aggregates. Refer to AASHTO T 112.
2.Maximum weighted sodium sulfate soundness loss of 15 percent. Refer to AASHTO T 104 .
3.Maximum loss by abrasion of 30 percent. Refer to AASHTO T 96 .
4.Sand equivalent of 65 or greater . Refer to AASHTO T 176 , alternate method 2, pre-wet method (test the sample in the wet condition).
5.Minimum polishing value of 31. Refer to AASHTO T 278 and T 279.
a.Do not use predominantly limestone or dolomite aggregates.
B.Establish a job mix or target gradation within the gradation band as specified in Table 4 .
1.Base the mix design on the target gradation.
2.Verify that the percent passing each sieve does not vary by more than the stockpile tolerance from the target. Refer to AASHTO T 11 and AASHTO T 27 . Table 4 Gradation Limits Sieve Size Job Mix Gradation Target Band Percent Passing Stockpile Tolerances ⅜ 100 0 #4 75-85 ±5 #8 50-65 ±5 #16 33-45 ±5 #30 24-29 ±5 #50 16-21 ±4 #100 10-15 ±3 #200 7-13 ±2 The p ercent passing is based on total aggregate (dry weight) and fine and coarse aggregate with approximately the same bulk specific gravities.
2.3 Mineral Filler
A.Use one of the following for Mineral Filler . Refer to AASHTO M 17 .
1.Non-air entrained Type I/II Portland cement. Refer to AASHTO M 85.
2.Hydrated lime, free from lumps or foreign matter. Refer to Section 02746.
B.Determine the amount of mineral filler needed through the laboratory mix design.
1.The amount of mineral filler used must be between 0.5 percent and
2.0 percent by the weight of dry aggregate.
2.Adjust the percentage of mineral filler ± 0.5 percent as necessary for better consistency or to optimize set times with Engineer’s approval.
3.Mineral filler is considered separately from the aggregate gradation.
2.4 Water
A.Use potable water free from harmful salts , reactive chemicals, and any other contaminants.
2.5 Additives
A.Use additives as required to accelerate or retard the break -set of the micro surfac ing mix, to improve the resulting finished surface, or to increase adhesion.
1.Determine the initial additive quantities from the mix design for the micro surfac ing mix or individual materials.
2.Use additives compatible with the other components of the mix.
2.6 Job-Mix Design
A.Design according to the specifications listed in Table 5.
1.Show each ingredient amount meets the following requirements :
a.The m inimum residual asphalt content is at least 7.5 percent by dry total weight of aggregate. The design residual asphalt content and allowable tolerances must fall at or above the
7.5 percent minimum . Determine the o ptimum residual
asphalt content according to the requirements in Table 5.
b.The aggregate gradation target is within the job- mix gradation design limits in Table 4 .
c.Mineral filler, percentage by total dry weight of aggregate.
d.The asphalt emulsion contains at least 3.0 percent polymer solids , based on the residual asphalt content certified by emulsion supplier.
2.Identify the optimum residual asphalt as a percent age of the dry weight of aggregate to meet Table 5 requirements. The job mix formula tolerance is +/ - 0.5% residual asphalt .
3.Identify any additives included to control mix times and cohesion .
a.Provide acceptable limits for additives.
4.Use the same materials and aggregate gradation to be used on the project.
5.Provide a micro surfacing mixture that can be spread in variable thickness cross- sections , ruts, scratch courses, and s urfaces .
6.Changes in aggregate source, emulsion, or mineral filler will require a new mix design submitted for approval by the engineer and a new test strip as outlined in Section 3.5. Table 5 Mix Design Requirements ISSA T est No. Description Specification ISSA TB- 139 Wet Cohesion @ 30 Minutes Minimum (Set) @ 60 Minutes Minimum (Traffic) 12 kg- cm Minimum 20 kg- cm Minimum or Near Spin ISSA TB- 109 Excess Asphalt by LWT Sand Adhesion 50 g/ft2 Maximum (538 g/m2 Maximum) ISSA TB -114 Wet Stripping Pass (90% Minimum) *ISSA TB- 100 Wet-Track Abrasion Loss One -hour Soak Six -day Soak 50 g/ft2 (538 g/m2) Maximum 75 g/ft2 (807 g/m2) Maximum ISSA TB -147 Lateral Displacement 5% Maximum ISSA TB- 144 Classification Compatibility 11 Grade Points Minimum (AAA, BAA) ISSA TB- 113 Mix Time @ 77 ° F (25° C) Controllable to 120 Seconds Minimum * Perform the wet track abrasion test under labor atory conditions as a component of the mix design process.
2.7 Equipment
A.Use mixing equipment specifically designed and manufactured to mix and place micro surfacing.
1.Mix the material by an automatically -sequenced, self -propelled micro surfac ing mixing machine with a continuous -flow revolving multi- blade double - shafted mixing unit that :
a.Accurately deliver s and proportions the aggregate, emulsified asphalt, mineral filler, control additives, and water .
b.Discharg es the mixed product on a c ontinuous flow basis.
2.Use a machine with sufficient storage capacity for aggregate, emulsified asphalt, mineral filler, control additive, and water to maintain an adequate supply to the proportioning controls.
3.Use a machine capable of self -loading materials while continuing to place micro surfacing.
4.Verify that the operator has full control of the forward and reverse speed during applications of the micro- surfacing material.
a.Use original manufacturer design ed equipment for the self - loading device, opposite side driver stations, and forward and reverse speed controls.
B.Use a machine with a hydraulically adjustable (while applying mixture) spreader box with a screed adjustment for yield control and a n adjustment for the joint matcher.
C.Equip the micro surfacing spreader box with the following:
1.Ribbon flights mounted on an adjustable shaft to continually agitate and distribute the materials throughout the box.
2.Curb bumpers and replaceable runners with at least 5 ft long end runners.
3.A sufficient walkway to provide access to either side of the spreader box so the operator can avoid walking through the freshly placed material .
4.Verify that t he equipment provides sufficient turbulence to prevent the mix from setting in the box or causing excessive side buildup or lumps.
5.Flexible seals in contact with the road, front and rear, t o prevent the loss of the mixture from the box .
6.A secondary strike -off located approximately 2 to 3 ft behind the primary strike -off to minimize transverse corrugations and to improve surface texture.
a.Verify that the secondary strike -off has elevation and width adjustments similar to the primary strike- off and a pivot point that can be tilted for texturing or raised completely off the surface.
b.Verify that the secondary strike -off has the same adjustments as the spreader box.
7.The ability to side -shift the box to compensate for variations in the pavement geometry.
8.The Capability of applying micro surfacing mixture in variable widths up to 15 f t.
D.Use a rut -filling spreader box specifically designed to fill ruts with an average depth greater than ½ inch. Ruts greater than ½-inch deep require multiple passes to restore the cross section.
E.Use a computerized material monitoring system with integrate d material control devices s uch that the amount of each material can be determined at any time.
1.Calibrate each material control device before each mix application and as often thereafter as deemed necessary by the Engineer.
2.Use a monitoring system c apable of record ing, display ing, and printing the following information:
a.Individual sensor counts for emulsion, aggregate, mineral filler, water , and additive.
b.Aggregate, emulsion, and mineral filler output in pounds per minute.
c.Percentages of emulsion, mineral filler , water , and additive.
d.Cumulative totals of aggregate, emulsion, mineral filler , water , and additive.
e.Scale factor for all materials .
F.Verify the daily totals from the computerized monitoring system for the aggregate and the daily total from the scalping -screen weighing system are within 2 percent.
G.Calibrate each mixing unit in the presence of the Engineer before construction.
1.Do not use any machine until calibration has been completed.
2.During the project construction, any mechanical change to the equipment components that deliver micro surfacing materials to the pug mill mixer will require new calibration.
Part 3 — Execution
3.1 Limitations
A.Do not apply micro surfac ing during rain or other adverse weather conditions within 48 hours after a rain event . Allow pavements and cracks to dry thoroughly after significant rain events before applying micro surfacing, to avoid trapping moisture in the underlying pavement layer .
B.Do not apply micro surfac ing if either the pavement or air temperature is below 50 degrees F.
C.Do not apply micro surfacing when the temperature is projected below 37 degrees F within 48 hours of placing micro surfacing.
D.Cease micro surfacing operations when the weather or other conditions prolong opening road surface to traffic beyond two hours.
E.Remove and replace the micro surfac ing if any of the following occurs:
1.Lumping, balling, or unmixed aggregates.
2.Separation of the coarse aggregate from the emulsion and fines.
3.Excessive breaking of emulsion inside the spreader box.
4.Streaking caused by oversized aggregate.
5.Flushing or excessively rich areas appearing in the micro surfacing after two hours from the time of placement.
6.Any measurable rutting, shoving, or other evidence of premature deformation when exposed to traffic .
F.Keep traffic off the roadway surface until the micro surfac ing has cured.
1.Allow for additional curing time at locations such as driveways, intersections , and where sharp turning movements may take place or where vehicles may accelerate quickly.
3.2 Stockpil E
A.Construct individual 500- ton stockpiles of micro surfacing aggregates.
1.Engineer will test stockpiles at least one, and at most seven days , before use.
2.Combining, altering, or moving 500- ton stockpiles may require retesting by the Engineer before use.
B.Notify the Engineer at least seven calendar days before micro surfacing placement in order for the initial stockpiles to be sampled and tested for acceptance.
C.Obtain the Engineer’s written acceptance of a stockpile before its use for micro surfacing.
D.Provide stockpile Quality Control information to the Engineer for every 500 tons of aggregates to include the following:
1.Aggregate gradation meeting job- mix formula tolerances according to Table 4.
2.Sand Equivalency . Refer to AASHTO T 176 .
E.Be capable of determining aggregate moisture within 10 minutes at all times.
F.Rework or r emove material not meeting specifications from the stockpile area. Identify stockpiles that will be reworked.
G.The Department will retest corrected material for acceptance.
3.3 Preparation
A.Clean the pavement surface of all dirt, sand, dust, oil, and other objectionable material immediately before applying micro surfacing.
B.Allow unsealed cracks to dry thoroughly before applying micro surfacing when using water to clean the road surface.
C.Cover manholes, valve boxes, drop inlets , and other service utility entrances before surfacing.
D.Protect all structures, including items such as guardrail, guideposts, concrete barriers, drains, and parapet walls.
3.4 Application
A.Pre-wet the pavement surface as required due to local conditions by fogging ahead of the micro surfacing box.
1.Do not create standing water on the pavement in front of the micro surfacing box.
B.Place micro surfacing mix that meets the job- mix design.
1.Control the ingredient proportions with metering or measuring devices on the micro surfacing equipment.
a.Use readings from the metering or measuring devices to determine compliance with limits stated in the approved job- mix design.
2.Limit any increase or decrease in the amount of mineral filler added to the mix during production as per Section 2.3. Mineral Filler, B.1 and B.2.
3.Limit the set -control agent to ± 1 percent of the job- mix design quantity .
4.Verify that the emulsion submitted with the job- mix design is the same emulsion used throughout the project.
5.Verify that the emulsion residue is ± 0.5 percent of the job- mix design.
a.Engineer may require a new job- mix design for review if large disparities occur.
b.Calculate the percent emulsion on the daily electronic printout from the calibrated paver for emulsion and aggregate quantities.
C.Produce a mixture according to the mix design and the quality control tolerances.
1.Maintain quality control documentation and make it available to the Engineer upon request or at completion of daily work. Refer to this Section, Article 1.5 F.
D.Pass the mineral aggregate over a vibratory scalping screen before transfer to the micro surfacing mixing machine to remove oversize material.
1.Verify that the screening unit is capable of providing weigh tickets for each load of material.
E.Carry a sufficient amount of micro surfac ing in all parts of the spreader box so that full width and complete coverage is obtained with no streaks or narrow spots.
1.Avoid overloading the spreader box.
2.Do not spray water directly into the spreader box during the application of micro surfacing under any circumstances .
F.Apply micro surfac ing of proper consistency at a minimum rate of 2 5 lbs/yd2 based on the dry weight of aggregate for each lot.
G.Apply micro surfac ing for rut filling .
1.Apply micro surfac ing as a scratch -coat pass using a steel or high density rubber strike -off when required to fill ruts less than ½ inch deep or as directed by the Engineer.
2.Make multiple passes with the rut filling spreader box for ruts greater than ½ inch deep or as directed by the Engineer.
3.Allow 24-hour cure time after filling ruts , before placing an additional micro surfac ing layer.
H.Do not apply water to freshly placed micro surfacing.
3.5 Test Strip
A.Construct a test strip at least 500 ft long on the roadway before initial placement.
1.Arrange for the test strip to be constructed on the project site under anticipated placement conditions (intersections, travel lanes, approaches, time of day, temperature, and humidity) in coordination with the Engineer .
2.Construct the test strip with the job mix proportions, materials, and equipment to be used on the project.
3.Adjustments to the mixture formula will be permitted provided they do not exceed the values stated in the mix design.
a.Prepare a new mix design and construct another test strip i f modifications to the mixture formula are in excess of the values in the mix design.
4.The Engineer will evaluate the test strip to determine if the mixture set and cure properties as well as the equipment and placement techniques are acceptable.
a.Verify that the initial set is achieved within 30 minutes and the surface show s no signs of distress when exposed to traffic after curing for 1 hour .
5.Remove and replace or repair the test strip placement, with the Engineer’s approval and at no cost to the Department , if the test strip does not meet the conditions stated above.
B.Make necessary adjustments if test strip does not perform as required.
1.Repeat the test strip process.
2.The Engineer may require a new job- mix design if failures indicate an ingredient problem.
3.6 Finishing Details
A.Verify that t he depth of each micro surfac ing course does not exceed twice the maximum aggregate size.
1.Not required when using a rut filling spreader box.
B.Verify that the finished l ongitudinal and transverse joints are neat and uniform.
1.Construct l ongitudinal joints within 6 inches of the lane lines where possible.
2.Verify that the overlap of micro surfacing at any joint does not exceed 6 inches.
3.Repair the joints if any of the following conditions exist:
a.Build -up of material at the joints .
b.Uncovered areas at the joints .
c.Longitudinal and transverse joints with more than ¼ inch vertical space between the surface and a 4 ft straightedge placed perpendicular to the joint .
4.Verify that t he edges of the micro surfacing follow the centerline, lane lines, shoulder lines, and curb lines.
5.Repair the edges if they vary more than 6 inches .
6.Use methods approved by the Engineer to correct deficiencies.
a.Verify that the repaired surfaces are dense with a uniform texture.
b.Repair sections with surface irregularities the same width as the existing pass of micro- surfacing.
c.Small areas of patching are not permitted.
C.Verify that t he finished micro surfacing has a uniform texture free of scratches, tears, and other surface irregularities.
1.Repair the surface, at Contractor’s expense, if any of the following conditions exist:
a.More than one surface irregularity ¼ inch or wider and 10 ft or longer in any 100 ft section.
b.More than three surface irregularities ½ inch or wider and more than 6 inches long in any 100 ft section.
c.Any surface irregularity 1 inch or wider and more than 4 inches long.
d.Any tire track damage to the fresh micro surfacing .
e.Slick spots or any area of bleeding (surface flushing) .
D.Place the micro surfac ing adjacent to concrete pavements or concrete curb and gutter with a straight longi tudinal edge.
1.Do not allow over -lap in these areas.
E.Maintain neat construction lines at all locations.
F.Place the micro surfac ing at side streets and intersections out to right -of- way line including around radii where applicable.
G.Use hand squeegees to spread the micro surfac ing in areas where micro surfac ing machine cannot operate.
1.Lightly dampen areas before mix placement.
2.Provide complete and uniform coverage.
3.Avoid unsightly appearance from handwork.
4.Use the same type of finish in hand worked areas as applied by the spreader box.
H.Use construction paper or comparable products so that beginning and ending joint lines from each construction pass are straight and neat .
I.Use construction paper or comparable products to protect all roadway utilities.
Source: Utah Standard Specifications for Road and Bridge Construction, 2026 Edition. Pages 439–453 of 1,331.