402.04 Method of Measurement.
2.Longitudinal Joints . Longitudinal joints shall be constructed when the slurry is completel y uncured or when it is totally cured. Should the slurry be completely cured, the cured slurry at the joint area shall be wetted by the spray bar. Should the slurry be completely uncured, the slurry shall not be wetted. A burlap drag, or other suitable dev ice, that will cause the fresh slurry coming from the spreader box to distribute itself evenly over the joint, shall be pulled along the joint seam.
h.Curing . Treated areas shall be allowed to cure until such time as the Engineer or inspector -in-charge s hall permit their opening to traffic. All traffic shall be diverted up to a maximum of 24 hours to permit undisturbed curing of the slurry or until such time as curing has taken place and rolling has been completed.
i.Rolling . Any rolling required for th e slurry seal shall be done with a pneumatic roller. The roller shall be capable of exerting a contact pressure during rolling of 350 to 450 kPa. Rolling shall consist of not less than four complete coverages over the specified areas.
j.Tack Coat . When s pecified, a tack coat shall be placed in accordance with Section 405.
402.04 Method of Measurement.
The amount of slurry seal coat, applied as directed and accepted, will be measured in square yards {square meters}. The length will be the actual length mea sured along the surface. The width will be the actual width sealed as shown on the plans or directed.
402.05 Basis of Payment.
a.Unit Price Coverage . The number of square yards {square meters}, measured as provided above, will be paid for at the contract unit price for the item of Slurry Seal Coat of the type specified on the plans, complete in place, which price shall be payment in full for furnishing all materials and constructing the Slurry Seal Coat, and for all equipment, tools, labor, and in cidentals necessary to complete the work.
b.Payment will be made under Item No .: 402-A Slurry Seal Coat, Type * - per square yard {square meter} * Indicate I or II MICRO -SURFACING SEAL COAT
403.01 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 shall be a mixture of a poly mer modified asphalt emulsion, 100 percent crushed mineral aggregate, mineral filler, water, and other additives for control of set time in the field. All ingredients shall be properly proportioned, mixed, and spread on the paved surface in accordance with the Specification and as directed by the Engineer.
403.02 Materials.
All materials shall comply with the requirements of Division 800, Materials, except as noted herein. Special reference is made to the following:
a.Aggregate.
1.Coarse aggregates for m icrosurfacing seal coat shall be crushed aggregate meeting the requirements of Section 801. The kind of aggregate materials used shall be at the Contractor's option within the following limits.
2.The use of carbonate stone such as limestone, dolomite, or aggregate tending to polish under traffic shall be restricted as follows, based on the average daily traffic (ADT) count in both directions: 500 vehicles per day or less - No restrictions apply.
403.03 Composition of Mixture.
501 to 5,000 vehicles per day - Carbonate stone shall be limited to a maximum of 30% of the blended gradation. Over 5,000 vehicles per day - Carbonate stone shall not be used in any application. Aggregates shall be limited to siliceous aggregates such as granite, quartzite, blast furnace slag or lightweight aggregates (expanded clays or shales produced by the Rotary Kiln Method). Crushed gravel shall have a bulk specific gravity greater than 2.550 (AASHTO T 85). The aggregate shall meet the appropriate requirements of Sections 801 and 802, and the following: Test Property Test Method Specification Sand Equivalent on material passing No. 4 Sieve AASHTO T 176 65 Min LA Abrasion AASHTO T 96 36% Max Sodium Sulfate Soundness AASHTO T 104 10% Max
3.Aggregates shipped to the project shall be uniform and shall not require blending or pre -mixing at the storage area before use and shall meet the appropriate gradation as shown in Table No. 1 in Article 403.03. All aggregates shall be thoroughly screened directly into the support vehicles prior to the application of any mixture to eliminate the potential of oversized and deleterious materials.
b.Mineral Filler. The mineral filler may be any recognized brand of non -air entrained Portland cement or hydrated lime that is free of lumps, or any other mineral additive approved by the Engineer. It shall be accepted upon visual inspection. The amount of mineral filler needed shall be determined by the laboratory mix design and shall be considered as part of the m aterial gradation requirement. The mineral filler shall not exceed 3% of the weight of the aggregate, and shall have a mixture control tolerance of ±0.25%.
c.Asphalt Emulsion. The emulsified asphalt shall be either a cationic type CQS -1hp meeting the req uirements of Section 804 or a cationic type CSS -1h meeting the requirements of Section 804. The CSS -1h shall also be polymer modified containing a minimum of 3.0% polymer by volume. The polymer shall conform to the requirements given in Section 811.
d.Water. The water for the Micro -Surfacing mixture shall be potable and free from any contaminants detrimental to the mixture.
e.Other Additives. The emulsion manufacturer shall provide other additives as required to control the set time of the mixture in the field.
403.03 Composition of Mixture.
a.Constituents The Micro -Surfacing material shall be a uniform mixture of aggregate, polymer modified emulsified asphalt, mineral filler, water and other additives as required to control set time in th e field. The Engineer will require immediate adjustments or replacement of any constituent as needed to produce an acceptable mixture. The constituents shall be proportioned to produce a uniform mixture meeting the requirements of Table No. 1.
403.03 Composition of Mixture.
TABLE NO. 1 MICRO -SURFACING DESIGN LIMITS GRADATION REQUIREMENTS Mixture Control Tolerances Sieve Size Percent Passing Type II Type III ± 0 % 3/8 inch 100 100 ± 5 % No. 4 90 – 100 70 – 90 ± 5 % No. 8 65 – 90 45 – 70 ± 5 % No. 16 45 – 70 28 – 50 ± 5 % No. 30 30 – 50 19 – 34 ± 5 % No. 50 18 – 30 12 – 25 ± 3 % No. 100 10 – 21 7 – 18 ± 2 % No. 200 5 – 15 5 – 15 DESIGN REQUIREMENTS ± 0.75 % Range for Residual Asphalt 6.0 – 10.0 5.0 – 9.0 Specification Test Method Mixing Time Test, secs @ 77° F (25° C), 120 minimum ISSA TB 102 Mix Time @ 50 and 100° F (10° C and 37.7° C) (informational) ISSA TB 102 Set Time Tests: 30 minutes 12 kg -cm minimum ISSA TB 139 Early Rolling Traffic Time: 60 minutes, 20 kg -cm minimum ISSA TB 139 Wet Stripping Test, % coating 90% minimum ISSA TB 114 Wet Track Abrasion Test, loss in g/ft2 (g/m2) 75 (800) max 6 days 50 (538) max. 1 hour ISSA TB 100 Measurement of Excess Asphalt Max. 50 grams/ft2 (540 grams/m2) Sand Adhesion, 1,000 Cycles @ 125lbs. (57 kgs) ISSA TB 109 Classification Compatibility 11 pt. minimum ISSA TB 144 Note 1: Percent residual asphalt based on weight of dry aggregate. Note 2: Type II for spread rates of 10 - 20* pounds per square yard based on dry aggregate weight. Note 3: Type III for spread rates of 15 – 30* pounds per square yard based on dry aggregate weight. Note 4: If more than 30 pounds per square yard of mixture is required, additional lifts shall be applied. Note 5: The gradation and percent residual asphalt as shown on the Micro- Surfacing design or as established by the Engineer shall be maintained with the listed Mixture Control Tolerances. * The Micro -surfacing type and target spread rate will be as shown in the plans and shall be controlled to within plus or minus 2 pounds per square yard except in no case shall a spread rate be less than the minimum be allowed. Scratch courses and rut filling applications are exempt from this specifications as rates will vary based upon the depth of the ruts and shall be spread as separate lifts.
b.Mixture Design. At least three weeks prior to beginning work, the Contractor shall submit to the Materials and Tests Engin eer a mix design with certified test results along with representative samples of each ingredient to be used in the Micro -Surfacing mixture. The sample shall include information relative to sources, type of materials, and project number. The job mix formul a shall be designed in accordance with the International Slurry Surfacing Association (ISSA) recommended guidelines and technical bulletins. Mixing tests shall pass at the maximum expected air temperature in accordance with ISSA T 113. If aggregate proportions are changed, a new job mix formula shall be submitted for approval. No Micro -Surfacing work shall begin nor shall any mixture be accepted unless the Bureau of Materials and Tests has evaluated the Micro- Surfacing design.
403.04 Equipment.
403.04 Equipment.
a.Gener al. All equipment, tools, and machines used in the performance of this work shall be approved by the Engineer. No work shall be attempted with equipment that is malfunctioning. The Engineer may order that the work be discontinued if sufficient equipment an d tools are not in use to place the materials satisfactorily.
b.Mixing Equipment. The paving mixture shall be mixed by a self -propelled Micro -Surfacing mixing machine which shall be a front feed continuous flow mixing unit able to accurately deliver and proportion the aggregate, emulsified asphalt, mineral filler, field control additives and water to a revolving multi- blade, twin shafted mixer and discharge the mixed product uniformly on a continuous flow basis. Additionally the mixing machine shall be equipped with dual side driving stations of original equipment manufacturers design that will assist in proper alignment when applying mixture. A spray bar shall be provided to completely wet the aggregate entering the pugmill with additive (if used) and water. The Contractor shall provide a computerized material monitoring system with integrated materials control devices that are readily accessible and positioned so the amount of each material used can be determined at any time. Each material control device shall be clearly marked and calibrated prior to mix application. The mixer shall be equipped with a back -up electronic materials counter that is capable of recording running count totals for each material being monitored. . The mixer shall have the capability to record and display the following information: • Individual sensor counts for emulsion, aggregate, mineral filler, water and additive; • Aggregate, emulsion, and mineral filler output in lbs. per minute; • Ground travel distance; • Spread reate in lbs. per square yard; • Percentages of emulsion, mineral filler, water, and additive; • Cumulative totals of aggregate, emulsion, mineral filler, water, and additive; • Scale factor for all materials. The Contractor shall calibrate the mixing machine for eac h material type with a minimum of 3 tests. The mixing machine shall be calibrated every time a material component is changes. Additional calibrations may be required during production as directed by the Engineer.
1.Water Pressure System. The mixing mach ine shall be equipped with a water pressure system and nozzle type spray bar to provide a water spray ahead of and outside the spreader box when required.
2.Proportioning Devices. Individual volume or weight controls for proportioning each material to be added to the mix shall be provided and properly marked. These proportioning devices shall be used in materials calibration and for determination of materials output at any time. Each mixing unit shall be calibrated prior to commencement of the work.
3.Emu lsion Pump. The emulsion pump shall be a heated, positive displacement type pump.
c.Spreading Equipment. The Micro -Surfacing mixture shall be spread uniformly by means of a hydraulically adjustable type spreader box with a positive screed adjustment and equipped to expand as necessary for varying pavement widths attached to the mixer, equipped with ribbon flighted augers to agitate and spread the materials throughout the box. These augers shall be designed to maintain sufficient turbulence in the mixture to prevent the material from setting -up in the box or causing buildup and lumps. A front seal shall be provided to ensure no loss of the mixture at the road contact surface. The rear seal shall act as a final strike -off and shall be adjustable. The spreade r shall be maintained to prevent the loss of the paving mixture in surfacing super -elevated curves. The spreader box and rear strike -off shall be designed and operated so that a uniform consistency is achieved to produce a free flow of material to the rear strike- off without causing skips, lumps, or tears in the finished surface.
d.Rut -Filling Equipment. Microsurfacing materials may be used to fill ruts, utility cuts, depressions in the existing surface, and minor surface blemishes. Ruts less than 0.5 i nches in depth shall be filled with a leveling course
403.05 Construction.
pulled full width with the spreader box. Ruts equal to or greater than 0.5 inches in depth shall be filled independently with a rut -filling box. Ruts greater than 1.5 inches in depth may require multi ple applications with the rut -filling box to restore the cross -section. The rut -filling box shall be either 5 foot or 6 foot in width. All rut -filling material shall be allowed to cure under traffic for at least 24 hours before any additional material is placed.
e.Auxiliary Equipment. Suitable crack and surface cleaning equipment, barricading equipment, hand tools and other support equipment shall be provided by the Contractor as necessary to perform the work.
f.Equipment Calibration Each mixing unit shall be calibrated in the presence of the engineer prior to the start of the project. Any component replacement affecting material proportioning requires that the machine be recalibrated. No machine will be allowed to work on the project until the calibration has been completed and/or accepted. Additional calibrations may be required during production as directed by the Engineer. Calibrations shall be performed in accordance with ALDOT procedure 454, “Calibration of Microsurfacing Equipment”. The Contrac tor shall provide a copy of the of the calibration worksheets to the Engineer.
403.05 Construction.
a.Weather Limitations. The Micro -Surfacing mixture shall be spread only when the ambient temperature for the 48 hours prior to placement is at least 50 ° F. The current pavement surface and ambient temperature is at least 50° F and rising. The weather is not foggy or rainy and there is no forecast of temperatures below 32 ° F within 48 hours from the time of placement. The Micro -Surfacing mixture shall be sp read at the discretion of the Engineer if the relative humidity exceeds 80 percent or the weather is overcast.
b.Surface Preparation. The area to be surfaced shall be thoroughly cleaned of vegetation, loose aggregate, and soil. All cracks shall be cleaned to the satisfaction of the Engineer prior to overlay. Traffic markings and stripe shall be removed flush with the pavement surface. Whenever conditions are such as to require pre - wetting the surface, the water shall be sprayed ahead of and outside of the spreader box at a rate sufficient to dampen the surface without any free flowing water ahead of the spreader box.
c.Application. The paving mixture shall be spread on the prepared surface in such a way as to leave a uniform finished surface. Care shall be taken when filling ruts to restore the designed profile of the pavement cross section. Excess crowning or overfilling of the rut area will not be permitted. The Contractor shall use squeegees and lutes to spread the mixture in areas inaccessible t o the spreader box and areas requiring hand spreading. A sufficient amount of material shall be carried at all times in all parts of the spreader box to ensure complete coverage. No lumping, balling or unmixed aggregate shall be permitted. No segregation of the emulsion and aggregate fines from the coarse aggregate will be permitted. If the coarse aggregate settles to the bottom of the mix, the mix will be removed from the pavement. The paving mixture shall have proper consistency so that excessive spla ttering and excessive free water is avoided. The paving mixture shall be applied based on dry aggregate weight as specified on the plans. Adjustments to the additive will be permitted if necessary to provide a slower setting time when hand spreading is needed. If hand spreading is necessary, the mixture shall be poured in a small windrow along one edge of the surface to be covered and then spread uniformly by a hand squeegee or lute. A smooth, neat seam shall be provided where two passes meet. Excess material shall immediately be removed from ends of each run.
d.Joints Longitudinal joints and transverse joints shall have no more than ¼ inch vertical space over the joint when measured with a 10 ft. straightedge placed perpendicular to the joint. A maximum of 3 inches shall be allowed for overlap of the longitudinal lane line joints. The edge lines shall be repaired if the edges vary more than 3 inches from a 100 foot straight line or from a 100 foot arc on a curved section.
403.06 Method of Measurement.
e.Traffic Control. Traffic sh all not be allowed on the Micro -Surfacing mixture until it has cured sufficiently to prevent pick up and/or marring of the surface. Curing of the Micro -Surfacing with the ability to carry rolling traffic shall be within 60 minutes of placement. The Contrac tor shall maintain traffic control as necessary to prevent damage to the mixture. Any such damage done by traffic to the mixture shall be repaired by the Contractor at no additional cost to the Department. Application of the surfacing mixture shall be sus pended early enough each day to permit traffic to safety travel over the completed work before sunset. Work required or materials used in controlling of traffic will not be paid for directly but shall be considered subsidiary obligations of the item of Mic ro- Surfacing seal coat.
f.Quality Control The Contractor shall produce a mixture in compliance with the mix design, mixture control tolerances and spread rate placement tolerances. The Contractor shall maintain all quality control documentation. Qualit y control documentation shall be made available to the Engineer upon request or at the completion of work.
1.Asphalt Cement The Contractor shall calculate the % asphalt content of the mixture from the equipment computer display readings, a minimum of 3 t imes a day.
2.Application Rate The Contractor shall calculate the yield of the course being placed from the equipment computer display readings, a minimum of 3 times a day.
3.Daily Report The daily report shall include aggregate used in tons, asphalt emu lsion used in tons, mineral filler used in tons, water used in mixture in gallons, and additive used in mixture in gallons.
g.Test Strip Prior to production application, the Contractor shall place a 1,000 foot test section to verify the mix design and th e ability to carry rolling traffic within 60 minutes. If rolling traffic cannot be carried within 60 minutes, the emulsion or mixture must be adjusted and another test strip shall be required. The test section shall be placed at the same time as the pavi ng is to take place, night or day, and under the same ambient conditions.
h.Testing and Lots. The Engineer will take samples of the aggregate and liquid asphalt emulsion for every 1000 tons of aggregate used in production and as otherwise deemed appropri ate. A BMT -91 is required for all aggregates shipped for use on the project. Aggregates will be sampled in accordance with AASHTO R 90. If tests on either component material or the mixture fails, the operation shall cease. It will be the responsibility o f the Contractor to prove that the problems have been corrected and that a satisfactory operation can be accomplished before work can be started again. A LOT is normally defined as 10,000square yards. For each LOT the Contractor shall provide a lot sheet c ontaining the following information: • Lot Number, Job Number, Route, Inspector; • Date, Air Temperature; • Control settings, calibration Values, Unit Weight of emulsion in lbs. per gallon, Percent residue in emulsion; • Beginning and Ending Intervals • Computer display readings for materials usage (Beginning, and Ending, and Total) • Length, Width, Total Area in square yards of aggregate, pounds of Emulsion, and pounds of cement; • Percent of each material, percent of asphalt cement, application rate, and combined application rate in lbs./sy.; • Mix design percentages of materials required; • Calibration forms; • Contractor’s authorized signature
403.06 Method of Measurement.
The quantity of Micro -Surfacing mixture, of the type specified, used and accepted will be measured in tons. A means, suitable to the Engineer, for confirmation of the weights of the materials shall be
403.07 Basis of Payment.
furnished by the Contractor. The weight of the dry aggregate, asphalt emulsion, and the cement used in the mixture shall be calculated and included in the total weight measured for payment. Additional materials such as mineral fillers, water, and chemical additives shall be included in the contract price for micro -surfacing seal coat and will not be measured separately for payment. Deductions in measurement will be made for all material wasted or lost or applied beyond the limits of the work.
403.07 Basis of Payment.
a.Unit Price Coverage. Compensation for the Micro -Surfacing material, measured as provided above, will be made on a tonnage basis and the contract unit price per ton shall be full compensation for construction of the Micro -Surfacing complete in place as shown on the plans or directed. This price shall include all materials, procurement, handling, hauling, and processing and includes all equipment, tools, labor, and incidentals required to complete the work, with the following exception: Tonnage placed in excess of the amount shown on the plans or directed in writing, plus two pounds per square yard, will be paid for at eighty percent of the contract unit price bid. No payment will be made for unacceptable material; for material furnished or used in excess of the amount indicated or directed, except as provided above; for material used in replacing defective or condemned work; for mater ial wasted in handling, hauling, or otherwise; or for maintaining the work.
b.Payment will be made under Item No.: 403-B Micro -Surfacing Seal Coat, Type * - per ton * Specify Type “II” or “III”. SECTION 405 TACK COAT
405.01 Description.
The work under this Section shall cover the furnishing and placing of a bituminous tack coat on a surface which is to be covered by a bituminous plant mix material in accordance with these specifications and in reasonably close conformity with the lines shown on the plans or directed by the Engineer. The work shall include cleaning the surface prior to application of the tack coat. The area of treatment and the rate of application of a tack coat shall be based on the plans and specifications after evaluating the actual surface condition on which the plant mix overlay is to be placed.
405.02 Materials.
a.Tack Coat Bituminous material for tack coat shall be Emulsified Asphalt or one of the Performance Graded (PG) Asphalt Binders shown in Article 804.07. Emulsified Asphalt s shall not be diluted prior to application. The Contractor shall have the option of using the following materials for the tack coat: • PG 58 -22 performance graded asphalt binder • PG 64 -22 performance graded asphalt binder • PG 67 -22 performance graded asphalt binder • PG 76 -22 performance graded asphalt binder • CRS-1H emulsified asphalt • CRS-2 emulsified a sphalt • CRS-2H emulsified asphalt • CMS-1HP emulsified asphalt • CSS-1 emulsified asphalt • CSS-1H emulsified asphalt • CQS-1H emulsified asphalt • CQS-1HP emulsified asphalt • CRS-2P emulsified asphalt • CRS-2L emulsified asphalt
Source: Alabama Standard Specifications for Highway Construction, 2022 Edition. Pages 191–196 of 934.