for Highway Construction Page 273 of 71 5 SECTION 415 – MICROSURFACING
415.01 Description.
Microsurface as specified. Provide a microsurfacing mix placed with a properly proportioned blend of fine graded aggregate, liquid admixture, polymer -modifie d emulsified asphalt , and water. Use the mixture to fill ruts and as an evenly spread surface treatment. Ensure the cured slurry is homogeneous, fills cracks, and adheres firmly to the surface wi th a skid resistant texture.
415.02 Materials.
Provide materials as specified in: Asphalt ......................................................................................................................................... 702 Aggregate ................................................................................................................................ 703.03
415.03 Construction Requirements.
Determine when microsurfacing is to be mixed and spread after the emulsified asphalt arrives on the project site. Shotting. While some shotting (small beads of asphalt in suspension in the emulsion) is normal for the emulsion, an excessive amount of shotting is an indication that the emulsion is ready to break and should not be used.
A.Mix Design . The mix design is the Contractor’s responsibility. At least 2 weeks before microsurfacing, submit a complete mix design that meets the specification. Use the same component materials, aggregate and gradation in the mix design as will be provided on the project site. Submit a new mix design to the Engineer if aggregate source, aggregate blend, gradation, or asphalt emulsion source is changed. Provide the component materials within the following limits: Residual asphalt ............................................................... 5.5% to 10.8% by dry weight of aggregate Mineral filler ........................................................................ 0.0% to 3.0% by dry weight of aggregate Polymer -based modifier .............................. Minimum of 3% solids based on bitumen weight content Provide a mix design that meets the following International Slurry Seal Association (ISSA) test requirements: ISSA Test No. Description Specification ISSA TB- 100 (a) Wet Track Abrasion Loss 1-hour soak 6-day soak 50 g/ft2 maximum 75 g/ft2 maximum ISSA TB- 113 Mix Time @ 77 °F Controllable to 120 seconds minimum ISSA TB- 147 Lateral Displacement (Loaded Wheel Test, Method A) 5% maximum for Highway Construction Page 274 of 71 5 Specific Gravity after 1,000 cyc les of 125 lb 2.10 maximum ISSA TB- 114 Wet Stripping Pass (90% m inimum) ISSA TB- 109 Excess Asphalt by Loaded Wheel Tester and Sand Adhesion 50 g/ft2 maximum ISSA TB- 139 Wet Cohesion @ 30 Minutes Minimum (Set) @ 60 Minutes Minimum (Traffic) 12 kg- cm minimum 20 kg- cm minimum or n ear spin minimum
a.Perform the wet track abrasion loss test under laboratory conditions as a component of the mix design process. Ensure the ISSA test results are signed and sealed by a professional engineer licensed in the state where the tests were performed. A list of laboratories experienced in microsurfacing mix designs may be obtained from the ISSA. Provide an optimized emulsion content for the microsurfacing mix design, using no less than 3 emulsion contents spread over a range not to exceed 2.0 percent residual.
B.Mixing Equipment. Provide a machine specifically designed and equipped to allow for the application of the microsurfacing material. Mix the material by an automatic sequenced, self -propelled microsurfacing mixing machine. Use a continuous flow mixing unit, able to accurately deliver and proportion the aggregate, emulsified asphalt , mineral filler, control setting additive, and water in a revolving multi -blade double- shafted mixer capable of discharging the mixed product on a continuous flow basis. Provide sufficient storage capacity to maintain an adequate supply to the proportioning controls. Use of tr uck-mounted units is not allowed. The microsurfacing equipment will use a computerized material monitoring system with integrated material control devices such that the amount of each material can be determined at any time. The monitoring system will be ca librated as specified in 415.03.G. The monitoring system will be capable of recording, displaying, and printing the following information:
1.Individual sensor counts for emulsion, aggregate, mineral filler, water, and additive.
2.Aggregate , emulsion, and mineral filler output in pounds per minute.
3.Percentages of emulsion, mineral filler, water, and additive.
4.Cumulative totals of aggregate, emulsion, mineral filler, water, and additive.
5.Scale factor for all materials.
C.Proportioning Device. Provide properly marked individual volume or weight controls for proportioning material to be added to the mix (e.g., aggregate, mineral filler, emulsified asphalt , additive, and water). These proportioning devices are usually revolution counters or similar devices that are used i n material calibration and in determining the material output at any time. These devices will require approval before use. for Highway Construction Page 275 of 71 5 D. Spreading Equipment. Spread the mixture uniformly by means of a conventional augured surfacing spreader box attached to the mixer and equipped with paddles to agitate and spread the material throughout the box. Provide a front seal to prevent loss of mixture at the road contact point. Provide an adjustable rear seal to act as final strike- off. Provide a spreader box that is able to side shift the box to compensate for variations in the pavement geometry.
E.Rut-filling Equipment. Where shown, microsurfacing will be used to fill ruts, utility cuts, an d other depressions. When rutting or deformations allow a full width scratch course may be applied with the spreader box using a metal or stiff rubber strike- off; otherwise ruts will be filled independently with a rut box of 5 or 6 feet in w idth. All rut -filling material will cure under traffic for at least 24 hours before an additional course is placed.
F.Auxiliary Equipment. Provide suitable surface preparation, equipment, hand tools, and other support equipment as necessary to perform the work. Screen the aggr egate when loading units going from the stockpile area to the lay down operation.
G.Calibration. Before construction, calibrate each mixing unit used to perform the work in the Engineer’s presence. Notify the Engineer at least 2 working day s in advance when calibration will be performed. The Engineer may accept previous calibration documentation covering the exact materials to be used, provided they were performed in the current calendar year. Ensure the documentation includes an individual calibration of each material at various settings, that can be related to the machine's metering devices. A machine is not allowed to be used until the cali bration has been completed or documentation accepted. In the Engineer’s or their representative’s presence, demonstrate that the calibration data has been entered into the computerized control unit used to print the pay ticket.
H.Weather Limitations . Apply microsurfacing if the air temperature is less than 100°F, and when both pavement and air temperature are above 60°F and rising. Apply microsurfacing when there is no danger the finished product will freeze or be rained on within 24 hours. Do not apply microsurfacing during rain, when road surface moisture is present, or during other adverse weather conditions. Do not apply microsurfacing when the temperature is expected to drop below 37°F within 48 hours of pl acing microsu rfacing. Stop microsurfacing operations when the weather or other conditions prolong opening road surface to traffic beyond one hour.
I.Surface Preparation . Clear vegetation, loose material, dirt, mud, and other extraneous materials from the surface immediately before applying the microsurfacing. If water is used, allow cracks to dry thoroughly. Obtain approval of the surface preparation before microsurfacing. An approved fabric material will be used to protect utility covers and street monuments before microsurfacing. Alternate methods may be used to protect utility covers and street monuments if approved.
J.Mix Stability. Prevent premature breaking of the emulsion in the spreader box. Ensure the mixture is homogeneous during and following mixing and spreading. Do not allow excess water or emulsion or segregation of the emulsion and aggregate fines from the c oarser aggregate. for Highway Construction Page 276 of 71 5 K. Water Application. Pre-wet all dry, locations by fogging ahead of the spreader box. Adjust the rate of application of the fog spray during the day to suit temperatures, surface texture, humidity, and dryness of the pavement . Water used in pre-wetting is an incidental cost to microsurfacing.
L.Appearance of the Mix. The microsurfacing will be of the desired consistency upon leaving the mixer. Carry a sufficient volume of material in the spreader box so a complete coverage is obtained. Maintain a coverage thickness be between 3/8 inch and 5/8 inch, except in ruts. Avoid overloading the spreader. Remove lumps, balls, or unmixed aggregate. Do not leave streaks, such as those caused by oversized aggregate, in the finished surface. If streaking develops, the Engineer will stop the work until the situation has been corrected. Excessive streaking is defined as more than 4 drag marks greater than 0.5 inch wide and 4.0 inch es long or 1.0 inch wide and 3.0 inches long in any 30 square yard area. No transverse ripples or longitudinal streaks of 0.25 inch in depth or greater will be allowed , when measured by placing a 10 -foot straightedge over the sur face.
M.Joints . Prevent excess buildup, uncovered areas, or unsightly appearance on joints. Provide a 10- foot straightedge and ensure the surface does not vary more than 1/4 inch from the lower edge when the straightedge is laid flat on the pavement in a direction parallel to centerline or normal to centerline.
N.Hand Work. Hand work surface areas that cannot be reached with the mixing machine using squeegees to provide complete and uniform coverage. If necessary, before mix placement , lightly dampen the area to be hand- worked to provide a uniform appearance. Produce the same type of finish as applied by the spreader box. Complete handwork during the machine application process. Repair irregularities at the locations of temporary traffic control markers.
O.Traffic and Curing. Protect the microsurfacing from traffic damage until the mixture cures and wil l not be damaged by vehicle tires. Repair any traffic damage at no cost to the Depar tment. Allow microsurfacing applied for rut filling to cure at least 24 hours before being covered by the full lane width placement . Traffic may be allowed on the rut filling material during this period under the same requirements for protection, surface preparation, and repair as for other placements.
P.Clean up. Remove debris daily.
Q.Test Strip. Construct a test strip at least 1,000 feet in length before production placement. Initial set must be achieved within 30 minutes and must show no signs of distress when exposed to traffic action after curing for 1 hour. If the microsurfacing does not meet these conditions, remove and replace the microsurfacing at no additional cost to the Department. for Highway Construction Page 277 of 71 5 Make necessary adjustments if the test strip does not perform as required. Obtain the Engineer’s approval before repeating the test strip. The Engineer may require a new job- mix design and test strip if failures show an ingredient problem. Acceptable test strips within the project site will be paid at contract unit prices.
R.Production Microsurfacing. The Contractor will place microsurfacing mix that meets the job- mix design and the following:
1.Control the ingredient proportions with metering or measuring devices on the microsurfacing equipment. Use readings from the metering or measuring devices to determine compliance with limits stated in the approved job- mix design and specifications.
2.Limit any increase or decrease in the amount of mineral filler added to the mix during production to within 1 percent of the job- mix design, not to exceed specifications.
3.Limit the set -control agent to within 1 percent of the job -mix design.
4.Verify that the emulsion submitted with the job- mix design is the same emulsion used throughout the work.
5.Limit the emulsion content to within 1.0 percent of the job -mix design, not to exceed specifications. The Engineer may require a new job- mix design and re- approval of the microsurfacing if large disparities occur between the approved mix design and production applic ation.
S.Reporting.
1.Maintain quality control documentation and make available to the Engineer upon request or at completion of dail y work. This includes machine counts for aggregate, emulsion, and water.
2.Randomly calculate the percent asphalt content of the mixture from the equipment computer display readings at least three times daily.
3.Randomly calculate the yield of the aggregate being placed from the equipment computer display readings at least three times daily.
4.Provide printouts from the computerized control unit and maintain a daily report and log sheet containing the f ollowing information:
a.Aggregate used, ton (dry).
b.Microsurfacing emulsion used, ton.
c.Mineral filler used, pounds.
d.Water used in mixture, gallons.
e.Additive used in mixture, gallons.
f.Surface area completed, square yards.
g.Surface area application rate, dry pounds aggregate per square yard.
h.Percentage of emulsified asphalt based on dry aggregate.
T.Acceptance. Acceptance of the asphalt emulsion and aggregate will be based on the following: for Highway Construction Page 278 of 71 5 1. Polymer modified Emulsified Asphalt . The Engineer will accept polymer modified emulsified asphalt, including the viscosity and residue percent obtained at the plant, by manufacturer’s certification and the verification testing performed by the Department. The Engineer will sample asphalt twice a day from a random truck or trailer onsite in accordance with AASHTO T 40 and deliver to the Central Materials Laboratory within 3 calendar days for viscosity and evaporation residue laboratory verification tes ting. The Department will assess a price adjustment in accordance with the Department’s Laboratory Operations Manual Section
350.02.03 when test results show the asphalt does not meet the specifications.
Perform f ield testing to ensure the asphalt emulsion has not broken excessively during transportation to the project site. Before introduction to the microsurfacing machine, check each load of emulsion for shotting by sieving in accordance with AASHTO T 59 (sodium oleate solution is not required). Submit results.
2.Aggregate. Stockpile aggregate 10 calendar days before placement operations begin in an approved location. Obtain approval before using stockpile locations within the right of way. Notify the Department when production stockpiles are in place. The Engineer will sample and test the aggregate stockpile for acceptance. The Engineer will reject aggregate material not meeting the JMF gradation tolerances or other material requirements specified above.
415.04 Method of Measurement.
The Engineer will measure acceptably completed work as follows: The printouts from the calibrated computerized control unit will be used to measure the pay items . Microsurfacing aggregate will be measured by the ton (dry weight basis). Polymer -modified emulsified asphalt will be measured by the ton, as delivered to the project site. Submit printouts daily. Make daily machine counts available for verification of Contractor supplied printouts.
415.05 Basis for Payment .
The Department will pay for accepted quantities as follows: Pay Item Pay Unit Microsurfacing Aggregate ....................................................................... Ton Polymer Modified Emulsified Asphalt ...................................................... Ton Water , cleaning the surface, mineral filler, additives , and protecting the microsurfacing (until it has set sufficiently to allow traffic to run on the new surface without displacing the new material) are included in the microsurfacing unit price. 416-419 for Highway Construction Page 279 of 715 SECTIONS 416 -419 - RESERVED for Highway Construction Page 280 of 715 SECTION 420 – CONCRETE PAVEMENT REHABILITATION
420.01 Description .
Perform concrete pavement rehabilitation as follows:
1.Repair the roadway 1 lane at a time with traffic being maintained on the remaining lane. Limit the work areas to 2 miles in length, with only the active work area closed within the 2- mile limit. Obtain approval for night work. Open lanes to traffic at night, except for those areas that are in the curing process. Separate work areas by at least 3 miles.
2.Schedule concrete slab replacement operations to ensure removal and replacement are completed during 1 working day. If unforeseen circumstances prevent concrete placing, temporarily fil l the cavity with crushed base before leaving the project site. Crushed base used to temporarily fill cavities is considered incidental work.
3.Compl ete the work in the following order:
a.A - Slab Replacement (full or part ial).
b.B - Repairing Spalls.
c.C - Subsealing – Grout Method.
d.D - Grinding.
e.E - Repairing Cracks and H – Resealing Joints .
f.F - Reconstruction of Plant Mix Shoulders and 606.
g.G - Sealing Edge Joints . NOTE: C will not precede D by more than 30 calendar days and E /C by 60 calendar days. Grind subsealed pavement and seal crack joints the same construction season.
4.Rehabilitation work is specified in 409.
A.Slab Replacement. Remove and replace concrete pavement in failing areas
B.Repairing Spalls. Core or saw around the perimeter of the specified area, chip or sandblast the spall repair area, and patch the cavity with rapid- hardening concrete or epoxy mortar.
C.Subsealing. Provide pavement subsealing by determining a gro ut hole pattern, dril ling holes through the portland cement concrete pavement , pumping grout through the holes into the voids, and patching the drilled holes with mortar.
D.Grinding. Grind the portland cement concrete pavement surface to eliminate joint faulting, restore proper drainage, and provide riding characteristics and skid resistance or any combination as specified.
Source: Idaho Standard Specifications for Highway Construction, 2023 Edition. Pages 309–315 of 768.