Polymer Modified Asphalt Rubber Modified Slurry Seal
Slurry Seal shall consist of mixing asphalt emulsion, aggregate, and water and spreading the mixture on a surface or pavement where shown on the plans, as specified in these specifications and the special provisions, and as directed by the Engineer.
The materials for slurry seal immediately prior to mixing shall conform to the following requirements:
2.02 (a) POLYMER MODIFIED ASPHALT EMULSION WITH CARBON BLACK DISPERSION AND DISPERSED ASPHALT RUBBER
The base polymer emulsified asphalt shall be a quick traffic, quick cure (QT-QC) type, shall be a homogeneous brown color throughout and show no separation after thorough mixing, shall break and set on the aggregate within five (5) minutes and shall be ready for cross-traffic within fifteen (15) to forty five (45) minutes. The polymer asphalt emulsion, upon standing undisturbed for a period of twenty-four (24) hours, shall show no white or milky colored substance on its surface and conform to the requirements in Table I.
|Tests on Emulsion|
|Viscosity, SSF, @ 77 degrees F, sec||ASTM D244||15 - 90 sec|
|pH||1 to 3|
|Distillation Residue %, Minimum||60|
|Test on Residue from Distillation Test|
|Penetration, 77 degrees F., 100g, 5s||ASTM D5||40-80|
|Softening Point (Ring & Ball), degrees F||ASTM||130+|
|Ductility, 77 degrees. F
(25C, 5 cm/Min., Minimum)
|Fraass-Breaking Point (degrees C.) min.||DIN 52012||-18|
Carbon black dispersion compatible with the emulsion shall be added by suitable blending ( in line or propeller mixing) to the emulsion at the plant before use. The carbon black at 30% solids by weight shall be added at 2-5 % on emulsion total weight.
A dispersion of asphalt rubber - RG-1 or equivalent - shall be blended in line with the emulsion at the plant and the emulsion remixed before use.
This shall be added at 5-8% based on emulsion total weight.
The emulsion shall be mixed by circulation or other method before pumping into the slurry truck.
2.02 (b) WATER
Water shall be potable, free of harmful soluble salts and shall be of such quality that the asphalt will not separate from the emulsion before the slurry seal is in place in the work.
2.02 (c) AGGREGATE
Aggregate shall consist of sound, durable, crushed stone or crushed gravel and approved mineral filler. The material shall be free from vegetable matter and other deleterious substances. Aggregates shall be 100% crushed with no rounded particles. The percentage composition by weight of the aggregate shall conform to the following grading:
|Sieve Sizes||Type II|
|No. 4(4.75- mm)||90-100|
|No. 8(2.36- mm)||65-90|
|No. 16(1.18- mm)||40-70|
|No. 30(600- um)||25-50|
|No. 200 (75- um)||5-15|
|Theoretical asphalt content
% based on dry aggregate
|Approximate application rate
The aggregate shall also conform to the following quality requirements:
|Test||Method of Test||Requirement|
or ASTM D2419
|California Method 217||60 Min.|
|Durability Index||California Method 229||55 Min.|
2.02 (d) POLYMER
Styrene Butadiene Rubber latex polymer shall be added to the water/soap phase by injection prior to the mill manufacture of the asphalt emulsion by the emulsion producer. The polymer shall be BASF NX 1118 or approved equal. The amount of polymer solids shall be between 3 and 4 percent of the asphalt residual content and shall be certified by the emulsion producer on each load of emulsion delivered to the job site. No post or field addition of polymer will be allowed. Samples of polymer shall be provided and shall conform to the following requirements.
|Total Solids, min %||60|
|Bound Styrene %||24 - 60|
|pH at 25 Degrees C||4.2 - 5.2|
|Brookfield Viscosity RVT||1000 - 4000|
|Residual Monomer %||0.08 max.|
2.02 (e) MINERAL FILLER
The mineral filler shall be either Portland Cement or other approved mineral fillers, if required. Portland Cement if used, shall be commercially available Type I-II and shall be free of lumps and clods.
2.03 MIX DESIGN
At least 7 working day before slurry seal placement commences, the Contractor shall submit to the Engineer for approval a laboratory report of tests and proposed mix design covering the specific materials to be used on the project. The percentage of asphalt emulsion proposed in the mix design shall be within the percentage range specified in Section 2.04 "Proportioning."
The tests and mix design shall be performed by a laboratory capable of performing the applicable International Slurry Seal Association (ISSA) tests. The proposed slurry seal mixture shall conform to the requirements specified when tested in accordance with the following tests:
|Test||ISSA Test Method||Requirement|
|Slurry Seal Consistency, cm||T106||3 max.|
|Cohesion Test, kg - cm
within 1 hour
|T139||20 min. (b)|
|Wet Track Abrasion, g/sq ft.||T100||75 max.|
|(a) Mixing test must pass at the maximum expected air temperature at the project site during application.|
|(b) Using project source aggregate asphalt emulsion and set-control agents if used.|
The laboratory report shall be signed by the laboratory that performed the tests and mix design and shall show the results of the tests on individual materials, comparing the test results to those required by the specifications. The report shall clearly show the proportions of aggregate, filler (as determined from the tests, minimum and maximum), water (minimum and maximum), asphalt solids content based on the dry weight of aggregate and set-control agent usage. Previous laboratory reports covering the same materials may be accepted provided they are made during the same calendar year.
Asphalt emulsion shall be added at a rate determined by the mix design and in the range of the table above. A job mix design shall be submitted by the Contractor for approval by the Engineer that conforms to the specification limits, and that is suitable for the traffic, climate conditions, curing conditions and final use. This will include recommended application rate of slurry to suit the job conditions.
The Slurry Seal mixture shall be proportioned by the operation of a single start/stop switch or lever which automatically sequences the introduction of aggregate, emulsified asphalt, admixtures, if used, and water to the pug mill.
Calibrated flow meters shall be provided to measure both the addition of water and liquid additives to the pug mill. If necessary for workability, a retarding agent, that will not adversely affect the seal, may be used.
Water, and retarder if used, shall be added to ensure proper workability and (a) permit uncontrolled traffic on the slurry seal no more than three (3) hours after placement without the occurrence of bleeding, raveling, separation or other distress; and (b) prevent development of bleeding, raveling, separation or other distress within fifteen (15) days after placing the slurry seal.
2.05 MIXING AND SPREADING EQUIPMENT
The Slurry Seal shall be mixed in a self-propelled mixing machine equipped with a continuous flow pug mill capable of accurately delivering and automatically proportioning the aggregate, emulsified asphalt, water and additives to a double shafted, multi-blade pug mill mixer capable of minimum speeds of 200 revolutions per minute.
A minimum of two operational mixing machines of 12 cubic yard capacity, or larger, shall be maintained on the project. The mixed slurry seal retention time in the pug mill shall be less than three seconds. No retention of mixed slurry seal shall be allowed within the pug mill by gate shut-off or other mechanical means. Any machines with pugmill retention or shut-off gates shall have them removed prior to being used on this project. The mixing machine shall have sufficient storage capacity of aggregate, emulsified asphalt, and water to maintain an adequate supply to the proportioning controls.
The mixing machine shall be equipped with hydraulic controls for proportioning the material by volume to the mix. Each material control device shall be calibrated, properly marked, preset and lockable at the direction of the Engineer. The mixing machine shall be equipped with a water pressure system and nozzle type spray bars to provide a water spray immediately ahead of the spreader box.
The mixing machine shall be equipped with an approved fines feeder that provides a uniform, positive, accurately metered, pre-determined amount of a mineral filler, if used, at the same time and location that the aggregate is fed.
The slurry mixture shall be uniformly spread by means of a controlled spreader box conforming to the following requirements:
The spreader shall be capable of spreading a traffic lane width and shall have strips of flexible rubber belting or similar material on each side of the spreader box and in contact with the pavement to prevent loss of slurry from the box. The box shall have baffles, or other suitable devices, to insure uniform application on super-elevated sections and shoulder slopes. Spreader boxes shall be maintained in such a manner as to prevent chatter(wash boarding) or other surface defects that will affect the esthetic value of the finished slurry seal mat.
The rear flexible strike-off blade shall make close contact with the pavement and shall be capable of being adjusted to the various crown shapes so as to apply a uniform slurry seal.
Slurry mixture, to be spread in areas inaccessible to the controlled spreader box, may be spread by other approved methods.
The slurry seal shall not be placed if either the pavement or the air temperature is below 55 degrees F (13C) and falling, but may be applied when both the air and pavement temperature is 45 degrees F (7C) or above and rising. The mixture shall not be applied if high relative humidity prolongs the curing beyond a reasonable time.
Before placing the slurry seal, the pavement surface shall be cleaned by sweeping, flushing or other means necessary to remove all loose particles of paving, all dirt and all other extraneous material.
48 hours prior to the slurry seal operations, the contractor shall notify all residents, businesses and agencies with an approved written notice detailing the streets and limits of work to be done along, with the hours of work. The contractor shall also post all streets with temporary "No Parking - Tow Away" signs at 75 foot staggered intervals. These signs shall also state the day of the week and hours of no parking.
Immediately before commencing the slurry seal operations, all surface metal utility covers (including survey monuments) shall be protected by thoroughly covering the surface with an appropriate adhesive and paper or plastic. No adhesive material shall be permitted to cover, seal or fill the joint between the frame and cover of the structure. Covers are to be uncovered and cleaned of slurry material by the end of the same work day.
Hand tools shall be available in order to remove spillage. Ridges or bumps in the finished surface will not be permitted. The mixture shall be uniform and homogeneous after spreading on the existing surface and shall not show separation of the emulsion and aggregate after setting.
Adequate means shall be provided to protect the slurry seal from damage from traffic until such time that the mixture has cured sufficiently so that the slurry seal will not adhere to and be picked up by the tires of the vehicles.
For the purpose of this project, the construction zone is defined to include all stockpile staging areas and travel routes to/from streets where the slurry seal is to be applied.
The Contractor shall abide, at all times, to the State of California, Department of Transportation's "Manual of Traffic Controls for Construction and Maintenance Work Zones" as applicable to this project.
Any deviations shall not be made without prior written approval from the project engineer.
Slurry seal will be measured and paid for by the square yard for the actual surface areas covered.
The contract price paid per square yard for slurry seal shall include full compensation for furnishing all labor, materials, tools, equipment and incidentals and for doing all the work involved in the furnishing and placing of the slurry seal complete in place, including cleaning the surface and protecting the slurry seal until it has set, all as shown on the plans, as specified in these specifications and as directed by the Engineer.
Last Updated (Wednesday, 09 December 2009 12:47)