5-36 Section 504. Micro-Surfacing
504.01. Description This work consists of the surface preparation and application of a single course micro -surfacing or multiple course micro -surfacing. 504.02. Materials Provide materials in accordance with the following sections : Portland Cement, Type I ....................................................................... 901 Fine Aggregates, 2FA, 3FA ................................................................... 902 Asphalt Emulsion , CSS -1hM, CSS -1mM .............................................. 904 Water ..................................................................................................... 911
A.Aggregate . Provide aggregates complying with gradation and physical requirements in Tabl es 902-7 and 902- 8. Use 3FA fine aggregate in micro-surfacing mixture for rut filling. Use 3FA or 2FA fine aggregates in micro-surfacing mixtures for micro -surfacing and longitudinal micro-surfacing. Use 2FA fine aggregate in micro-surfacing mixture for single -course applications. Aggregate used for micro-surfacing must be screened at the project site to ensure that aggregate being introduced into the micro-surface mixture is not larger than the top size aggregate allowed in the mix design. The aggregate must be screened directly into the material transport units or micro -surface machine(s). The aggregate screening unit must be capable of producing adequate tonnage to maintain project production.
B.Mix Design . Provide micro -surfacing mixtures consisting of a blend of polymerized asphalt emulsion, fine aggregate, portland cement, water, and other additives. The mixture must be designed by a laboratory that participates in AASHTO re :source ’s Proficiency Sample Program. Submit the mix design to the Engineer at l east 7 days before beginning construction. Provide a JMF meeting the criteria shown in Table 504-1 and limits shown in Table 504-2 to the Engineer at the pre-production meeting. Submit a new mix design for changes in aggregate or asphalt emulsion sources. MDOT Standard Specifications for Construction Section 504
5-37 Table 504- 1:
Micro -Surfacing Performance Design Criteria Test Method Parameter Specification ISSA TB -114 Wet stripping ≥90% ISSA TB -100 Wet track abrasion loss — 1-hour soak ≤50 g/ft² 6-day soak ≤75 g/ft² ISSA TB -144 Saturated abrasion compatibility ≤3 g loss ISSA TB -113 Mix time at 77°F Controllable to ≥120 s Mix time at 100°F Controllable to ≥35 s Table 504- 2: JMF Limits Test Method Specification Asphalt binder content (residual) 7.5%–9.0%, dry weight, 2FA aggregate 7.0%–8.5%, dry weight, 3FA aggregate Mineral filler 0.25%–3.0%, dry weight aggregate
C.Mix Design Documentation. Provide the following information in the final mix design:
1.Proportion of each material ;
2.Sources of each material , including:
a.Aggregate;
b.Name and pit number ;
c.Gradation;
d.Sand equivalence; and
e.Angularity index ;
3.Field simulation tests , including:
a.Wet stripping tests ;
b.Wet track abrasion loss ;
c.Saturated abrasion compatibility ; and
d.Trial mix time at 77°F and 100°F ;
4.Interpretation of results and t he determination of a JMF , including:
a.Mineral filler, percent (minimum and maximum) ; MDOT Standard Specifications for Construction Section 504
5-38 b. Water, including aggregate moisture, percent (minimum and
maximum);
c.Mix set additive, percent ;
d.Modified emulsion in mix, percent ;
e.Residual asphalt content of modified emulsion, percent ; and
f.Residual asphalt content in mix, percent ;
5.Average daily traffic ( ADT) for the pavement sections where placing mix; and
6.Mix designer ’s signature and date.
D.Bond Coat. Use the same emulsion for bond coat as used in production of the mixture. 504.03. Construction
A.Equipment. Provide equipment that can produce a specification product.
1.Mixing Machine . Provide at least one self -propelled, front -feed, continuous -loading mixing machine equipped and operated as follows:
a.A positive-connection co nveyer belt aggregate delivery system and an interconnected positive displacement, water -jacketed gear pump to proportion aggregate and asphalt emulsion;
b.Continuous -flow, twin -shaft, multi -blade type pugmill at least 50 inches long;
c.Mineral filler feed that drops mineral filler on the aggregate before discharging into the pugmill ;
d.Asphalt emulsion introduced within the first one-third of the mixer length to ensure mixing of materials before exiting the pugmi ll;
e.Rate indicators for proportioning each material, readily accessible and positioned to allow determination of the quantity of each material. Calibrate and test each material rate indicator to ensure proper operation before production;
f.A water pressure system and nozzle type spray bar to provide water s pray in front of and outside the spreader box. Apply water to dampen the existing pavement surface without causing free-flowing water in front of the spreader box ;
g.Opposite-side driving stations on the front to optimize longitudinal alignment during placement ; and MDOT Standard Specifications for Construction Section 504
5-39 h. Remote forward-speed control at the rear -mixing platform for the
back operator to control forward speed and level of mixture in the spreader box . Provide enough transports to ensure continuous operation during mix production and application. Use transport units with belt -type aggregate delivery systems, emulsion storage tanks, and water storage tanks to proportionally mix aggregate delivered by each transport . The Contractor may use truck -mounted batch-type machines on projects or sections of projects smaller than 15,000 square yards. Provide at least two truck -mounted batch-type machines. Stop mix production if delays exceed 15 minutes . Calibrate mixing machines before use. Maintain documentation of the calibrations of each material -metering device at various settings. Supply materials and equipment, including scales and containers, for calibration. Recalibrate mixing machines after changes in aggregate or asphalt emulsion sources.
2.Spreader Box. Provide a mechanical -type spreader box, attached to the mixer and equipped with paddles mounted on adjustable shafts , to continually agitate and distribute the mixture. Equip spreader boxes with the following:
a.Front and rear flexible seals capable of maintaining direct contact with the road;
b.A secondary strike -off, attached to the spreader box , capable of providing a finished smooth surface texture on the final or surface pass ; and
c.A drag capable of producing a uniform finish. Replace the drag if mixture builds up.
3.Rut Box . Use an Engineer -approved steel V -configuration screed rut box designed and manufactured to fill ruts to perform micro- surface rut filling applications. Ensure a mixture spread width from 5 to 6 feet and use a secondary strike -off to control crown on the rut box. A third strike -off may be used to control texture.
4.Longitudinal Box . Provide a steel screed box designed and manufactured to distribute the mixture to perform micro-surface longitudinal application. The device must be capable of spreading mixture 2 to 4 feet wide and use a secondary strike-off to control crown on the box. MDOT Standard Specifications for Construction Section 504
5-40 5. Miscellaneous Equipment . Provide hand squeegees, shovels, and
other equipment to perform the work. Provide cleaning equipment for surface preparation, including power brooms, air compressors , water -flushing equipment, and hand brooms.
6.Lights on Equipment . Equip power brooms, distributors, and truck mount spreaders with at least one Department -approved, flashing, rotating, or oscillating amber light, visible in every direction. Equip continuous spreader units with one light on each side of the spreader.
B.Pre-Production Meeting . Before beginning work, conduct an on-site pre-production meeting with the Engineer to discuss the following:
1.Detailed work schedule;
2.Traffic control plan;
3.Plan for fillin g corrugations ;
4.Equipment calibration;
5.Equipment calibration calculations ;
6.Equipment inspection, including transport units ;
7.Test strips to check the material and demonstrate placement procedures ;
8.JMF; and
9.Availability of materials . If using multiple machines, lay a test strip with each machine at the time of the pre-production meeting. Immediately upon completion of the test section the Engineer will evaluate the test area to determine if the application rates are acceptable. Full production work may only begin after the Engineer accepts the test section.
C.Surface Preparation . Immediately before surfacing operations, remove pavement markings using an abrasion method. Clean existing surface of loose materials, vegetation, dirt, dust, mud, and other deleterious materials. Remove animal remains before placing the mixture. Protect drainage structures, monument boxes, water shut -offs, and other existing structures during bond coat and mix application. Apply bond coat on concrete surfaces. Mix bond coat with one part emulsion to two parts water. Apply the bond coat at a rate from 0.035 gallon per square yard to 0.070 gallon per square yard, without excessive runoff. Allow the bond coat to cure before placing mixture. MDOT Standard Specifications for Construction Section 504
5-41 Before placing the mixture, establish, identify, and maintain 1, 000-foot
intervals until project completion.
D.Application Methods and Rates. Apply micro -surface mixtures to fill minor cracks and ruts in the roadbed, to construct a uniform surface with straight longitudinal joints, transverse joi nts, and edges.
1.Rutfilling . Fill ruts if the rut is at least ½ -inch deep and the contract includes the pay items for either standard micro-surfacing or rut filling. Use a 3FA mixture for rut filling and apply using a rut box for each wheel track. Maintain a clean overlap and straight edges between wheel tracks. Limit each pass of rut filling to no deeper than 1 inch. For each 1 inch of mix, provide an additional ⅛ -inch crown.
2.Micro -Surface Longitudinal . Fill centerline corrugations or longitudinal joints. When filling corrugations, fill the corrugations to allow new corrugations to be established. Apply at least one course of 2FA mix at the needed application rate.
3.Micro -Surfacing . Select one of the following application methods for micro -surfacing:
a.Apply at least one course of 3FA mix to the pavement surface, as indicated in the plans, at an average application rate of at least 35 pounds per square yard, by weight of dry aggregate. Apply 3FA mix to pavement surface, as indicated in t he plans, at a rate of at least 22 pounds per square yard, by weight of dry aggregate.
b.Apply at least two courses of 2FA mix to the pavement surface, as indicated in the plans, at an average combined application rate of at least 30 pounds per square yard, by weight of dry aggregate. Apply 2FA mix to pavement surface, as indicated in the plans, at a rate of at least 17 pounds per square yard, by weight of dry aggregate.
c.If using to fill shoulder corrugations, fill the corrugation area with a separate pass of micro -surfacing material prior to application of the top course. When a chip seal is applied to the shoulder as part of the project, a separate pass of micro-surfacing will not be required prior to application of the top course. Fill the corrugations to allow new corrugations to be established. Only a single course of micro- surfacing is required to fill shoulder corrugations.
4.Single Course Micro -Surfacing . Apply a single course using 2FA mix at an average minimum application rate of 24 pounds per square yard, MDOT Standard Specifications for Construction Section 504
5-42 by weight of dry aggregate, to the pavement surface, as indicated in
the plans.
E.Surface Quality
1.Joint Construction . Place longitudinal construction joints and lane edges to coincide with the planned painted lane lines. Construct longitudinal joints with less than 3 inches overlap on adjacent passes and no more than ⅜ -inch-thick overlap as measured with a 10-foot straightedge. To prevent water from collecting on the pavement surface, place successive passes on the upslope side of the overlap. Construct neat and uniform transverse joints with less than a ⅛ -inch difference in elevation across the joint as measured with a 10-foot straightedge. Provide neat and uniform lane edges with no greater than 2 inches of horizontal variance over 10 0 feet. Immediately stop work to correct defective joints or edges and obtain the Engineer ’s approval before resuming work.
2.Cross Section . Restore the driving lane cross section to within ¼ inch of the planned elevation, measured transversely across the pavement with a 10-foot straight edge or areas of the segment within 6 inches of the edge line, lane line, or centerline.
F.Cure Time and Repair. Do not allow traffic on the mixture until it cures. Ensure the new surface can carry normal traffic without damage within 1 hour of application. Protect the new surface from damage at intersections and driveways. Repair damage to the mixture caused by traffic at no additional cost to the Department.
G.Weather and Seasonal Limitations
1.Weather Limitations. Place the mixture when the air and pavement temperatures reach at least 45°F. Do not place mixture in rain, inclement weather, or when the air temperature is forecast to be below 32°F within 24 hours of work completion.
2.Seasonal Limitations. Place mixture from June 1 to September 15 in the Upper Peninsula and from May 1 to October 15 in the Lower Peninsula.
H.Quality Control . Provide a finished surface free of excessive scratch marks, tears, rippling, and other surface irregularities, as determined by the Engineer. Do not leave ripples greater than ⅛ inch as measured by a 10-foot straight edge in accordance with MTM 722. Do not leave tear marks greater than ½ inch wide and 4 inches long, or other marks greater than 1 inch wide and 1 inch long. If the finished surface exceeds the MDOT Standard Specifications for Construction Section 504
5-43 specified tolerances, stop work immediately and correct irregularities.
Review corrective action with the Engineer before resuming production. Produce a mixture that will meet the JMF and the QC tolerances specified in Tables 504-3 and 504-4 . Notify the Engineer immediately if QC test results exceed the tolerances specified in Tables 504-3 and 504-4 and stop mix production. Identify the cause of the deviation and determine the corrective action necessary to bring the mixture into compliance. Obtain the Engineer ’s approval before resuming work. The Engineer reserves the right to verify QC test accuracy and production controls. If the Engineer identifies a condition that causes an unsatisfactory micro -surfacing treatment, immediately stop production work and correct the defect at no additional cost to the Department. Table 504- 3: Micro -Surfacing Quality Control Aggregate Gradation Tolerance s Sieve Size Tolerance No. 4 ±5.0% No. 8 ±5.0% No. 16 ±5.0% No. 30 ±5.0% No. 50 ±4.0% No. 100 ±3.0% No. 200 ±2.0% Table 504- 4: Micro -Surfacing General Quality Control Tolerances Parameter Tolerance Aspha lt cement c ontent s ingle test ±0.5% from JMF Aspha lt cement c ontent daily average ±0.2% from JMF Application rate (as determined by 1000 -foot yield checks) ±2 pounds per square yard Sand equivalent test (ASTM D2419) ±7% from JMF
1.QC Plan Contents . Provide and follow a QC plan, in accordance with requirements of section 501, that will maintain QC for production and construction processes. Provide the Engineer with a copy of the QC plan for review and approval before the pre-production meeting. Include, at a minimum, the following items:
a.The source of materials used on the project ; MDOT Standard Specifications for Construction Section 504
5-44 b. The s ampling and tes ting methods used to determine compliance
with material specifications ;
c.A detailed description of how field crews will determine pavement rut depths and locations ; detail each section of multiple pavement sections separately ;
d.The equipment to be used on the project ;
e.The c alibration method used to determine compliance with the mix design (JMF) ;
f.The pavement cleaning and preparation procedure;
g.A plan for protecting micro-surfacing mixture from damage by traffic ;
h.A procedure for monitoring initial acceptance r equirements ; and
i.An action plan demonstrating adjustments of the micro-surfacing operation for adverse environmental conditions .
2.Minimum QC Sampling and Testing Frequency . Include the following minimum QC sampling and testing frequencies in the QC Plan:
a.Fine Aggregate Gradation . Sample fine aggregate from the project stockpile and test for gradation. Perform one test per 500 tons of fine aggregate or one test per day of mixture production, whichever is less.
b.Sand Equivalent Test (ASTM D2419) . Perform at least one sand equivalency test for each mixture design.
c.Asphalt Content . Calculate the percent asphalt content of the mixture at least three times per day, on a random basis, using the equipment counter readings.
d.Application Rate. Calculate the yield of t he course placed at least three times per day, on a random basis, using the equipment counter readings.
3.Documentation . Complete a daily report that includes the following information:
a.Control section ;
b.Job number ;
c.Route;
d.Engineer ; MDOT Standard Specifications for Construction Section 504
5-45 e. Date;
f.Air temperature;
g.Control settings ;
h.Calibration values ;
i.Unit weight of emulsion (pounds per gallon) ;
j.Percent residue in emulsion;
k.Beginning and ending intervals ;
l.Counter readings (beginning, ending, and total difference) ;
m.Length and width;
n.Total area (square yards);
o.Aggregate weight ;
p.Gallons of emulsion;
q.Percent of each material including asphalt cement ;
r.Application rate (pounds per square yard) ;
s.Combined application rate (pounds per square yard) ;
t.JMF (percent portland cement, percent emulsion, gradations, perce nt asphalt cement) ;
u.Contractor ’s authorized signature;
v.Calibration forms ;
w.QC aggregate gradations ;
x.Materials acceptance documentation;
y.Asphalt emulsion bill of lading ; and
z.QC and equivalent test result(s) . If truck -mounted machines are used, complete a separate daily report for each machine.
4.Field Tests. Before opening micro-surfacing to traffic, perform both of the following field tests:
a.Probe the entire depth of the micro-surfacing to verify no free emulsion exists in the mixture ; and MDOT Standard Specifications for Construction Section 504
5-46 b. Place a white absorbent paper blotter on the micro-surfacing to
confirm the presence of clear water without brown staining from unbroken emulsion.
I.Acceptance. Allow the Engineer access to in-progress work for QA review and testing.
1.Field Inspection Acceptance. Upon completion of work, schedule an inspection with the Engineer. The Engineer will note deficiencies, including areas exhibiting adhesion or cohesion failure. Reconstruct work identified by the Engineer as unacceptable. 504.04. Measurement and Paymen t Pay Item Pay Unit Micro -Surface, Rutfilling ...................................................................... Ton Micro -Surface ........................................................................ Square Yard Micro -Surface, Single Cse .................................................... Square Yard Micro -Surface, Longit ........................................................................ Foot
A.General . The unit prices for Micro -Surface, regardless of the type required, include cleaning existing pavement , applying a bond coat , placing temporary pavement markings , stationing, corrective action, and traffic control to complete corrective action.
B.Micro -Surface Rutfilling. The Engineer will measure Micro -Surface, Rutfilling based on the dry weight of fine aggregate in the mix. The unit price for Micro -Surface, Rutfilling includes placing mix over each wheel rut to create full -lane coverage.
C.Micro -Surface. The unit price for Micro -Surface includes all material, equipment, and labor for preparing the surface, placing temporary pavement markings, placing the micro-surfacing mixture, and applying a leveling course , a surface course filling shoulder , or centerline corrugations, or all, for full -width coverage as specified in the contract.
D.Micro -Surface, Single Course. The unit price for Micro Surface, Single Cse includes all material, equipment, and labor for preparing the surface, placing temporary pavement markings, placing the micro-surfacing mix, filling shoulder or centerline corrugations, and applying a si ngle course of mixture for full -width coverage as specified in the contract.
E.Micro -Surface, Longitudinal. The unit price for Micro -Surface, Longit includes all material, equipment, and labor for preparing the surface and placing the micro-surfacing mixture at the width specified in the contract.
F.Pavement Marking Removal. The Department will pay separately for removing pavement markings in accordance with subsection 812.04.
Source: Michigan Standard Specifications for Construction, 2020 Edition. Pages 295–305 of 1,146.