Microsurfacing - VSS System
The following specification is for microsurfacing. It may be used in lieu of polymer modified slurry seal where rutting or other multi-stone resurfacing is required or where a more rapid set is required.. Uneven surfaces such as humps or ridges should be ground flat before placing microsurfacing. These areas should be designated on the plans and language should be added to the special provisions for grinding. A separate bid item should also be used for rut filling and the areas that are to be filled with microsurfacing should be designated on the plans. Both Type II and Type III aggregates are detailed therefore the user must remove whichever is not to be used. If used for airport pavements suitable variations must be made.
1.01 SCOPE
This work shall consist of mixing polymer modified asphalt emulsion, aggregate, mineral filler, set-control additives, and water and spreading the mixture on a surfacing or pavement where shown on the plans, as specified in these special provisions, and as directed by the Engineer. The mix should be capable of being spread in variably thick cross sections (wedges, wheel path depressions, scratch courses and surfaces) which, after curing and initial traffic consolidation, resists deformation throughout the entire design tolerance range of bitumen content and variable thickness to be encountered.
2.01 MATERIALS
The material for microsurfacing immediately prior to mixing shall conform to the following requirements:
2.02 (a) ASPHALT EMULSION
Asphalt emulsion shall be homogenous and shall be a polymer modified quick-setting, quick- traffic cationic asphalt emulsion conforming to the requirements of Section 94 "Asphalt Emulsions" and these Special Provisions. The polymer material shall be milled or blended into the asphalt or blended into the emulsifier solution prior to the emulsification process.
2.02 (b) WATER AND ADDITIVES
Water shall be of such quality that the asphalt will not separate from the emulsion before the microsurfacing is in place on the pavement. If necessary for workability, a set-control agent that will not adversely affect the microsurfacing, may be used.
2.02 (c) MINERAL FILLER
Mineral filler shall be any recognized brand of non-air entrained Portland cement or hydrated lime that is free of lumps. The type and amount of mineral filler needed shall be determined by the laboratory mix design and will be considered as part of the mineral gradation requirement. An increase or decrease of less than one percent may be permitted when the microsurfacing is being placed if it is found to be necessary for better consistency or set times.
2.02 (d) AGGREGATE
The mineral aggregate used shall be of the type and grade specified for the particular use of the microsurfacing. The aggregate shall be manufactured crushed stone such as granite, slag, limestone, or other high quality aggregate, or combination thereof. The material shall be free from vegetable matter and other deleterious substances. All aggregate shall be free of caked lumps and oversize particles.
The aggregate, prior to the addition of emulsion shall conform to the requirements of this section. If aggregates are blended each component aggregate shall meet the sand equivalency and abrasion resistance and shall be 100% crushed as tested in accordance with California Test 205. The definition of a crushed particle in California Test 205 Section D, is amended to read: "Any particle having 2 or more fresh mechanically fractured faces shall be considered a crushed particle."
The percentage composition by mass of the aggregate shall meet the following grading requirements when tested in conformance with California Test 202:
The Type ll aggregate shall conform to the following additional quality requirements:
* Abrasion Resistance is to be performed on the parent aggregate before crushing.
The percentage composition by mass of the aggregate shall meet the following grading requirements when tested in conformance with California Test 202:
The Type lll aggregate shall conform to the following additional quality requirements:
* Abrasion Resistance is to be performed on the parent aggregate before crushing.
2.03 MIX DESIGN
At least 7 working days before microsurfacing placement commences, the Contractor shall submit to the Engineer for approval a laboratory report of tests and a proposed mix design covering the specific materials to be used on the project.
The tests and mix design shall be performed by a laboratory capable of performing the applicable International Slurry Surfacing Association (ISSA) tests. The proposed microsurfacing mixture shall conform to the requirements specified when tested in accordance with the following tests:
* TB = Technical Bulletin
The original laboratory report shall be signed by the laboratory that performed the tests and mix design and shall show the results of the test on individual materials, comparing their values to those required by the specifications. The report shall clearly show the proportions of aggregate, filler, water (minimum and maximum), set control additive, and asphalt solids content (minimum and maximum) based on the dry mass of aggregate. The laboratory shall also report the quantitative effects of moisture content on the unit mass of the aggregate (bulking effect). Previous laboratory reports covering the same materials may be accepted provided they are made within the previous 12 months. The mix design will further show recommended changes in cement, water and additive proportions for high temperature weather conditions by reporting proportions of materials required for 60 seconds of mix time with materials heated to 38°C. This 38°C mixing report will not be required for projects requiring night time application or application in cool weather conditions.
All the component materials used in the mix design shall be representative of the materials proposed by the contractor to be used on the project.
Once the proportions of materials to be used are approved by the Engineer, no substitution of other materials will be permitted unless the materials proposed for substitution are first tested and a laboratory report is submitted for the substituted design as specified above. Substituted materials shall not be used until the mix design for those materials is approved by the Engineer
2.04 PROPORTIONING Aggregate, mineral filler, asphalt emulsion, water, and additives, including set-control agent if used, shall be proportioned by volume utilizing the mix design approved by the Engineer. If more than one kind of aggregate is used, the correct amount of each kind of aggregate to produce the required grading shall be proportioned separately, prior to adding the other materials of the mixture, in a manner that will result in a uniform and homogeneous aggregate blend.
The percentages of each individual material required shall be shown in the laboratory report. Adjustments may be required during the construction, based on field conditions. The component materials shall be within the following limits:
The completed mixture, after addition of water and any set-control agent, shall be such that the microsurfacing mixture has proper workability and (a) will permit a traffic flow without pilot-car-assisted traffic control on the microsurfacing within one hour after placement, and (b) will prevent development of bleeding, raveling, separation or other distress within 15 days after placing the microsurfacing. However, when ambient temperatures are below 25°C traffic may not be permitted on the microsurfacing until it has sufficiently cured. The time for sufficient curing shall be mutually agreed upon between the contractor and the Engineer.
The aggregate shall be proportioned using a belt feeder operated with an adjustable cutoff gate. The height of the gate opening shall be readily determinable. The emulsion shall be proportioned by a positive displacement pump. Any variable rate emulsion pump, if used, shall be calibrated and sealed in it's calibrated condition in accordance with California Test 109 prior to usage.
Uniformity of distribution of asphalt will be determined by extraction test in accordance with California Test 310. The bitumen ratio (kg of asphalt per 100 kg of dry aggregates) shall not vary more than 0.5 percent of asphalt above or 0.5 percent of asphalt below the amount based on the dry aggregate mass approved by the Engineer.
The delivery rate of aggregate and emulsion per revolution of the aggregate feeder shall be calibrated at the appropriate gate settings for each mixer-spreader truck used on the project in accordance with California Test 109 and the requirements of these special provisions.
The aggregate belt feeder shall deliver aggregate to the pugmill with such volumetric consistency that the deviation for any individual aggregate delivery rate check-run shall not exceed 2.0 percent of the mathematical average of three runs of at least 3 tonnes in duration each. The emulsion pump shall deliver emulsion to the pugmill with such volumetric consistency that the deviation for any individual delivery rate check-run shall be within 2.0 percent of the mathematical average of three runs of at least 1135 liters each in duration. The water pump shall deliver water to the pugmill with such volumetric consistency that the deviation for any individual delivery rate check-run shall be within 2.0 percent of the mathematical average of three runs of at least 1135 liters each in duration.
The emulsion storage located immediately before the emulsion pump shall be equipped with a device which will automatically shut down the power to the emulsion pump and aggregate belt feeder when the emulsion level is lowered sufficiently to expose the pump suction line.
A temperature-indicating device shall be installed in the emulsion storage tank at the pump suction level. The device shall indicate temperature of the emulsion and shall be accurate to within 5°C.
The belt delivering the aggregate to the pugmill shall be equipped with a device to monitor the depth of aggregate being delivered to the pugmill. Said device for monitoring depth of aggregate shall automatically shut down the power to the aggregate belt feeder whenever the depth of aggregate is less than the target depth of flow. A second device shall be located where it will monitor movement of the aggregate belt by detecting revolutions of the belt feeder. The device for monitoring no flow or belt movement, as the case may be, shall automatically shut down the power to the aggregate belt when aggregate belt movement is interrupted. This second device will not be required where the aggregate delivery belt is an integral part of its drive chain. To avoid erroneous shutdown by normal fluctuation, a delay of 3 seconds between sensing and shutdown of the operation will be permitted.
2.05 EQUIPMENT
The self-propelled mixing machine shall be 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 material retention time in the pug mill shall be less than three seconds. No retention of mixed material 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. All indicators required in the section entitled "Proportioning" shall be in working order prior to commencing mixing and spreading operations.
Mixer-spreader trucks shall be equipped to proportion emulsion, water, aggregate, and set-control additives by volume. All rotating and reciprocating equipment on mixer-spreader trucks shall be covered with metal guards.
The mixer-spreader truck shall not be operated unless all low-flow and no-flow devices and revolution counters are in good working condition and functioning and all metal guards are in place. All indicators required by these special provisions shall be visible while walking alongside the mixer-spreader truck.
Aggregate feeders shall be connected directly to the drive on the emulsion pump. The drive shaft of the aggregate feeder shall be equipped with a revolution counter reading to the nearest one-tenth of a revolution.
In addition to the requirements of the fourth paragraph of Section 5-1.10, "Equipment and Plants," of the Standard Specifications, the identifying number of mixer-spreader trucks shall be at least 2 inches in height, located on the front and rear of the vehicle.
The microsurfacing mixture shall be spread by means of a spreader box conforming to the following requirements:
2.06 SPREADER BOX
The spreader box 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 positively prevent loss of microsurfacing from the ends of the box. All spreader boxes over 2.38 meters in application width shall have baffles, reversible motor driven augers, or other suitable means, to insure uniform application on superelevated sections and shoulder slopes. Spreader box skids shall be maintained in such manner as to prevent chatter (wash boarding) in the finished mat.
The spreader box shall have a double strike-off blade design at the rear of the box. The first strike-off blade shall be made of steel or stiff rubber and the second strike-off blade (attached to the first blade) shall be made of a flexible material. Rear flexible strike-off blades 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 microsurfacing coat. A secondary strike-off blade attached to the rear of the spreader box (located behind the double strike-off blades at the rear of the spreader box) shall be provided and shall be adjustable. It shall be designed and operated such that a uniform texture is achieved in the finished surface of the microsurfacing.
Flexible fabric drags attached to the rear of the spreader box shall not be allowed. Strike-off blades (rubber) shall be cleaned or changed daily if problems with cleanliness and longitudinal scouring occur.
2.07 WHEEL PATH DEPRESSION (RUT) BOX
The wheel path depression box shall be designed as a double chambered box with adjustable screens to regulate depth and shall have a width of between 1.52 meters and 1.81 meters. Hydraulic augers set at an angle shall move the mixed material from the rear to the front of the filling chamber. The augers shall push the larger aggregate into the center, deeper section of the wheel path depression and send the fine material toward the edges of the pass to act as a mastic and for feathering down the longitudinal joint along the wheel path.
The microsurfacing spreader box in use shall be clean and free of microsurfacing and emulsion, at the start of each work shift.
Microsurfacing mixture, to be spread in areas inaccessible to the controlled spreader box, may be spread by other methods approved by the Engineer.
2.08 PLACING
The microsurfacing mixture shall be uniformly spread on the existing surfacing within the rate specified.
Microsurfacing shall only be placed when the ambient and pavement surface temperature is 10°C minimum and rising. Microsurfacing shall not be placed if rain is falling or is imminent or if there is the possibility that the finished product will freeze within 24 hours.
Before placing the microsurfacing, 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.
When wheel path depressions have a cross section that is deformed 12.5 mm or more the individual wheel paths must first be filled utilizing a wheel path depression box meeting the requirements of these special provisions. Filling of wheel path depressions shall be accomplished using Type lll aggregate. Wheel path depression spread rates will vary with depression depth. Maximum single application for wheel path depressions shall be 37.5 mm. Greater depths may require multiple applications in each depression.
Wheel path depression repair shall be constructed with a slight crown to permit initial traffic compaction of the microsurfacing.
At least 12 hours of traffic compaction shall be allowed on freshly filled wheel path depressions before additional lifts are applied as surface courses. This may be replaced by rolling with an unballasted pneumatic tyred roller at the discretion of the contractor supervisor.
When there is a contract item of asphalt emulsion to be used for paint binder, the pavement surface shall be coated with an SS,CSS or CQS (-1 or -1h) grade asphalt emulsion meeting the requirements of Section 94, "Asphalt Emulsions" of the Standard Specifications. The asphalt emulsion shall be mixed in the proportion of one part of emulsion to three parts water. The mixture shall be applied at the approximate rate of 0.16 to 0.32 liters per square meter. The paint binder shall be allowed to cure before application of microsurfacing.
When used for full lane width passes microsurfacing mixture shall be spread at a rate within 7.0 to 10.0 kg of dry aggregate per square meter.( type II) The exact rate will be determined by the Engineer after taking into account the surface demand of the pavement, the size of the largest particles of aggregate and using the specific mass of the aggregate determined in the mix design. The completed spread will be within 10 percent of the rate determined by the mix design.
When used for full lane width passes microsurfacing mixture shall be spread at a rate within 13.0 to 17.0 kg (type III) of dry aggregate per square meter. The exact rate will be determined by the Engineer after taking into account the surface demand of the pavement, the size of the largest particles of aggregate and using the specific mass of the aggregate determined in the mix design. The completed spread will be within 10 percent of the rate determined by the mix design.
On concrete pavements (bridge decks and roadways) the microsurfacing mixture shall be spread at a minimum rate of 16.0 kg of dry aggregate per square meter. A paint binder shall be placed on new concrete surfaces, highly polished concrete surfaces or when designated by the Engineer.
Longitudinal joints shall correspond with the edges of traffic lanes. The Engineer may permit other patterns of longitudinal joints, if such patterns will not adversely affect the quality of the finished product, as determined by the Engineer.
Longitudinal joints common to two driving lanes, shall be butt joints with overlaps not to exceed 76.2 mm. Building paper shall be placed at transverse joints, over previously placed microsurfacing, or other suitable methods, approved by the Engineer, used to avoid double placement of microsurfacing. Hand tools shall be available in order to remove spillage. Ridges or bumps in the finished surface shall not be permitted.
The mixture shall be uniform and homogeneous after spreading on the surfacing and shall not show separation of the emulsion and aggregate after setting.
Adequate means shall be provided to protect the microsurfacing from damage by traffic until such time that the mixture has cured sufficiently so that the microsurfacing will not adhere to and be picked up by the tires of vehicles.
2.09 MEASUREMENT
Microsurfacing will be measured by the tonne. The quantity of microsurfacing to be paid for will be the combined mass of the aggregate and asphalt emulsion used in the microsurfacing mixture. The mass of added water and set-control additives used in the microsurfacing mixture will not be included in the mass of the microsurfacing to be paid for. The mass of aggregate and asphalt emulsion will be determined as provided in Section 9-1.01, "Measurement of Quantities." except that no deduction will be made for water in the aggregate and asphalt emulsion.
2.10 PAYMENT
The contract price paid per tonne for microsurfacing shall include full compensation for furnishing all labor, materials, tools, equipment, and incidentals, and for doing all the work involved in constructing the microsurfacing, complete in place, including testing for and furnish mix design, cleaning the surface, furnishing added water and set-control additives, mixing water with asphalt emulsion for coating the pavement and protecting the microsurfacing until it has set, all as shown on the plans, and as specified in these special provisions, and as directed by the Engineer.
1.01 SCOPE
This work shall consist of mixing polymer modified asphalt emulsion, aggregate, mineral filler, set-control additives, and water and spreading the mixture on a surfacing or pavement where shown on the plans, as specified in these special provisions, and as directed by the Engineer. The mix should be capable of being spread in variably thick cross sections (wedges, wheel path depressions, scratch courses and surfaces) which, after curing and initial traffic consolidation, resists deformation throughout the entire design tolerance range of bitumen content and variable thickness to be encountered.
2.01 MATERIALS
The material for microsurfacing immediately prior to mixing shall conform to the following requirements:
2.02 (a) ASPHALT EMULSION
Asphalt emulsion shall be homogenous and shall be a polymer modified quick-setting, quick- traffic cationic asphalt emulsion conforming to the requirements of Section 94 "Asphalt Emulsions" and these Special Provisions. The polymer material shall be milled or blended into the asphalt or blended into the emulsifier solution prior to the emulsification process.
| Tests on Emulsion | ||
| Test | Test Method | Requirement |
| Viscosity SSF @ 25° C | AASHTO T 59 | 15 - 90 sec |
| Sieve | AASHTO T 59 | 0.30 % max |
| Settlement , 5 days | ASTM D244 | 5 % max |
| Storage Stability, 1 day | AASHTO T 59 | 1 % max |
| Residue by distillation | California Test 331 | 62 % min |
| Tests on Residue | ||
| Test | Test Method | Requirement |
| Penetration @ 25°C 100 gm, 5 sec. |
AASHTO T 51 | 40-90 mm |
| Softening Point | AASHTO T 53 | 57°C min |
2.02 (b) WATER AND ADDITIVES
Water shall be of such quality that the asphalt will not separate from the emulsion before the microsurfacing is in place on the pavement. If necessary for workability, a set-control agent that will not adversely affect the microsurfacing, may be used.
2.02 (c) MINERAL FILLER
Mineral filler shall be any recognized brand of non-air entrained Portland cement or hydrated lime that is free of lumps. The type and amount of mineral filler needed shall be determined by the laboratory mix design and will be considered as part of the mineral gradation requirement. An increase or decrease of less than one percent may be permitted when the microsurfacing is being placed if it is found to be necessary for better consistency or set times.
2.02 (d) AGGREGATE
The mineral aggregate used shall be of the type and grade specified for the particular use of the microsurfacing. The aggregate shall be manufactured crushed stone such as granite, slag, limestone, or other high quality aggregate, or combination thereof. The material shall be free from vegetable matter and other deleterious substances. All aggregate shall be free of caked lumps and oversize particles.
The aggregate, prior to the addition of emulsion shall conform to the requirements of this section. If aggregates are blended each component aggregate shall meet the sand equivalency and abrasion resistance and shall be 100% crushed as tested in accordance with California Test 205. The definition of a crushed particle in California Test 205 Section D, is amended to read: "Any particle having 2 or more fresh mechanically fractured faces shall be considered a crushed particle."
The percentage composition by mass of the aggregate shall meet the following grading requirements when tested in conformance with California Test 202:
| Type ll | |
| Sieve Size | Percentage Passing |
| 9.5-mm | 100 |
| 4.75-mm | 94 - 100 |
| 2.36-mm | 65 - 90 |
| 1.18-mm | 40 - 70 |
| 600-um | 25 - 50 |
| 75-um | 5 - 13 |
The Type ll aggregate shall conform to the following additional quality requirements:
| Test | Method | Requirement |
| Sand Equivalent | ASTM D2419 | 65 minimum |
| Durability Index | California Test 229 | 55 minimum |
| Abrasion Resistance* | ASTM C131 | 30% maximum after 500 revolutions |
* Abrasion Resistance is to be performed on the parent aggregate before crushing.
The percentage composition by mass of the aggregate shall meet the following grading requirements when tested in conformance with California Test 202:
| Type lll | ||
| Sieve Size | Percentage Passing | |
| 9.5-mm | 100 | |
| 4.75-mm | 70 - 90 | |
| 2.36-mm | 45 - 70 | |
| 1.18-mm | 28 - 50 | |
| 600-um | 19 - 34 | |
| 75-um | 5 - 13 | |
The Type lll aggregate shall conform to the following additional quality requirements:
| Test | Method | Requirement |
| Sand Equivalent | ASTM D2419 | 65 minimum |
| Durability Index | California Test 229 | 55 minimum |
| Abrasion Resistance* | ASTM C131 | 30% maximum after 500 revolutions |
* Abrasion Resistance is to be performed on the parent aggregate before crushing.
2.03 MIX DESIGN
At least 7 working days before microsurfacing placement commences, the Contractor shall submit to the Engineer for approval a laboratory report of tests and a proposed mix design covering the specific materials to be used on the project.
The tests and mix design shall be performed by a laboratory capable of performing the applicable International Slurry Surfacing Association (ISSA) tests. The proposed microsurfacing mixture shall conform to the requirements specified when tested in accordance with the following tests:
| Test | ISSA Test | Requirement |
| Wet Cohesion | TB* 139 @ 30 min. (set) |
12 kg-cm minimum |
| @ 60 min. (traffic) |
20 kg-cm minimum (or near spin) |
|
| Excess Asphalt | TB 109 | 540 g/m2 maximum |
| Wet Stripping | TB 114 | Pass (90% minimum) |
| Wet Track Abrasion | TB 100 Six day soak loss |
810 g/m2 maximum |
| Displacement | TB 147A Lateral |
report |
| Specific Gravity after 1000 cycles of 56.8 kg |
report | |
| Classification Compatibility |
TB 144** | (AAA,BAA) 11 grade points minimum |
| Mix Time @ 25°C | TB 113 | Controllable to 120 seconds minimum |
* TB = Technical Bulletin
The original laboratory report shall be signed by the laboratory that performed the tests and mix design and shall show the results of the test on individual materials, comparing their values to those required by the specifications. The report shall clearly show the proportions of aggregate, filler, water (minimum and maximum), set control additive, and asphalt solids content (minimum and maximum) based on the dry mass of aggregate. The laboratory shall also report the quantitative effects of moisture content on the unit mass of the aggregate (bulking effect). Previous laboratory reports covering the same materials may be accepted provided they are made within the previous 12 months. The mix design will further show recommended changes in cement, water and additive proportions for high temperature weather conditions by reporting proportions of materials required for 60 seconds of mix time with materials heated to 38°C. This 38°C mixing report will not be required for projects requiring night time application or application in cool weather conditions.
All the component materials used in the mix design shall be representative of the materials proposed by the contractor to be used on the project.
Once the proportions of materials to be used are approved by the Engineer, no substitution of other materials will be permitted unless the materials proposed for substitution are first tested and a laboratory report is submitted for the substituted design as specified above. Substituted materials shall not be used until the mix design for those materials is approved by the Engineer
2.04 PROPORTIONING Aggregate, mineral filler, asphalt emulsion, water, and additives, including set-control agent if used, shall be proportioned by volume utilizing the mix design approved by the Engineer. If more than one kind of aggregate is used, the correct amount of each kind of aggregate to produce the required grading shall be proportioned separately, prior to adding the other materials of the mixture, in a manner that will result in a uniform and homogeneous aggregate blend.
The percentages of each individual material required shall be shown in the laboratory report. Adjustments may be required during the construction, based on field conditions. The component materials shall be within the following limits:
| Residual Asphalt | 5.5% to 9.5% by dry mass of aggregate |
| Mineral Filler | 0% to 3% by dry mass of aggregate |
| Additive | As needed |
| Water | As required to produce proper mix consistency |
The completed mixture, after addition of water and any set-control agent, shall be such that the microsurfacing mixture has proper workability and (a) will permit a traffic flow without pilot-car-assisted traffic control on the microsurfacing within one hour after placement, and (b) will prevent development of bleeding, raveling, separation or other distress within 15 days after placing the microsurfacing. However, when ambient temperatures are below 25°C traffic may not be permitted on the microsurfacing until it has sufficiently cured. The time for sufficient curing shall be mutually agreed upon between the contractor and the Engineer.
The aggregate shall be proportioned using a belt feeder operated with an adjustable cutoff gate. The height of the gate opening shall be readily determinable. The emulsion shall be proportioned by a positive displacement pump. Any variable rate emulsion pump, if used, shall be calibrated and sealed in it's calibrated condition in accordance with California Test 109 prior to usage.
Uniformity of distribution of asphalt will be determined by extraction test in accordance with California Test 310. The bitumen ratio (kg of asphalt per 100 kg of dry aggregates) shall not vary more than 0.5 percent of asphalt above or 0.5 percent of asphalt below the amount based on the dry aggregate mass approved by the Engineer.
The delivery rate of aggregate and emulsion per revolution of the aggregate feeder shall be calibrated at the appropriate gate settings for each mixer-spreader truck used on the project in accordance with California Test 109 and the requirements of these special provisions.
The aggregate belt feeder shall deliver aggregate to the pugmill with such volumetric consistency that the deviation for any individual aggregate delivery rate check-run shall not exceed 2.0 percent of the mathematical average of three runs of at least 3 tonnes in duration each. The emulsion pump shall deliver emulsion to the pugmill with such volumetric consistency that the deviation for any individual delivery rate check-run shall be within 2.0 percent of the mathematical average of three runs of at least 1135 liters each in duration. The water pump shall deliver water to the pugmill with such volumetric consistency that the deviation for any individual delivery rate check-run shall be within 2.0 percent of the mathematical average of three runs of at least 1135 liters each in duration.
The emulsion storage located immediately before the emulsion pump shall be equipped with a device which will automatically shut down the power to the emulsion pump and aggregate belt feeder when the emulsion level is lowered sufficiently to expose the pump suction line.
A temperature-indicating device shall be installed in the emulsion storage tank at the pump suction level. The device shall indicate temperature of the emulsion and shall be accurate to within 5°C.
The belt delivering the aggregate to the pugmill shall be equipped with a device to monitor the depth of aggregate being delivered to the pugmill. Said device for monitoring depth of aggregate shall automatically shut down the power to the aggregate belt feeder whenever the depth of aggregate is less than the target depth of flow. A second device shall be located where it will monitor movement of the aggregate belt by detecting revolutions of the belt feeder. The device for monitoring no flow or belt movement, as the case may be, shall automatically shut down the power to the aggregate belt when aggregate belt movement is interrupted. This second device will not be required where the aggregate delivery belt is an integral part of its drive chain. To avoid erroneous shutdown by normal fluctuation, a delay of 3 seconds between sensing and shutdown of the operation will be permitted.
2.05 EQUIPMENT
The self-propelled mixing machine shall be 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 material retention time in the pug mill shall be less than three seconds. No retention of mixed material 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. All indicators required in the section entitled "Proportioning" shall be in working order prior to commencing mixing and spreading operations.
Mixer-spreader trucks shall be equipped to proportion emulsion, water, aggregate, and set-control additives by volume. All rotating and reciprocating equipment on mixer-spreader trucks shall be covered with metal guards.
The mixer-spreader truck shall not be operated unless all low-flow and no-flow devices and revolution counters are in good working condition and functioning and all metal guards are in place. All indicators required by these special provisions shall be visible while walking alongside the mixer-spreader truck.
Aggregate feeders shall be connected directly to the drive on the emulsion pump. The drive shaft of the aggregate feeder shall be equipped with a revolution counter reading to the nearest one-tenth of a revolution.
In addition to the requirements of the fourth paragraph of Section 5-1.10, "Equipment and Plants," of the Standard Specifications, the identifying number of mixer-spreader trucks shall be at least 2 inches in height, located on the front and rear of the vehicle.
The microsurfacing mixture shall be spread by means of a spreader box conforming to the following requirements:
2.06 SPREADER BOX
The spreader box 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 positively prevent loss of microsurfacing from the ends of the box. All spreader boxes over 2.38 meters in application width shall have baffles, reversible motor driven augers, or other suitable means, to insure uniform application on superelevated sections and shoulder slopes. Spreader box skids shall be maintained in such manner as to prevent chatter (wash boarding) in the finished mat.
The spreader box shall have a double strike-off blade design at the rear of the box. The first strike-off blade shall be made of steel or stiff rubber and the second strike-off blade (attached to the first blade) shall be made of a flexible material. Rear flexible strike-off blades 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 microsurfacing coat. A secondary strike-off blade attached to the rear of the spreader box (located behind the double strike-off blades at the rear of the spreader box) shall be provided and shall be adjustable. It shall be designed and operated such that a uniform texture is achieved in the finished surface of the microsurfacing.
Flexible fabric drags attached to the rear of the spreader box shall not be allowed. Strike-off blades (rubber) shall be cleaned or changed daily if problems with cleanliness and longitudinal scouring occur.
2.07 WHEEL PATH DEPRESSION (RUT) BOX
The wheel path depression box shall be designed as a double chambered box with adjustable screens to regulate depth and shall have a width of between 1.52 meters and 1.81 meters. Hydraulic augers set at an angle shall move the mixed material from the rear to the front of the filling chamber. The augers shall push the larger aggregate into the center, deeper section of the wheel path depression and send the fine material toward the edges of the pass to act as a mastic and for feathering down the longitudinal joint along the wheel path.
The microsurfacing spreader box in use shall be clean and free of microsurfacing and emulsion, at the start of each work shift.
Microsurfacing mixture, to be spread in areas inaccessible to the controlled spreader box, may be spread by other methods approved by the Engineer.
2.08 PLACING
The microsurfacing mixture shall be uniformly spread on the existing surfacing within the rate specified.
Microsurfacing shall only be placed when the ambient and pavement surface temperature is 10°C minimum and rising. Microsurfacing shall not be placed if rain is falling or is imminent or if there is the possibility that the finished product will freeze within 24 hours.
Before placing the microsurfacing, 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.
When wheel path depressions have a cross section that is deformed 12.5 mm or more the individual wheel paths must first be filled utilizing a wheel path depression box meeting the requirements of these special provisions. Filling of wheel path depressions shall be accomplished using Type lll aggregate. Wheel path depression spread rates will vary with depression depth. Maximum single application for wheel path depressions shall be 37.5 mm. Greater depths may require multiple applications in each depression.
Wheel path depression repair shall be constructed with a slight crown to permit initial traffic compaction of the microsurfacing.
At least 12 hours of traffic compaction shall be allowed on freshly filled wheel path depressions before additional lifts are applied as surface courses. This may be replaced by rolling with an unballasted pneumatic tyred roller at the discretion of the contractor supervisor.
When there is a contract item of asphalt emulsion to be used for paint binder, the pavement surface shall be coated with an SS,CSS or CQS (-1 or -1h) grade asphalt emulsion meeting the requirements of Section 94, "Asphalt Emulsions" of the Standard Specifications. The asphalt emulsion shall be mixed in the proportion of one part of emulsion to three parts water. The mixture shall be applied at the approximate rate of 0.16 to 0.32 liters per square meter. The paint binder shall be allowed to cure before application of microsurfacing.
When used for full lane width passes microsurfacing mixture shall be spread at a rate within 7.0 to 10.0 kg of dry aggregate per square meter.( type II) The exact rate will be determined by the Engineer after taking into account the surface demand of the pavement, the size of the largest particles of aggregate and using the specific mass of the aggregate determined in the mix design. The completed spread will be within 10 percent of the rate determined by the mix design.
When used for full lane width passes microsurfacing mixture shall be spread at a rate within 13.0 to 17.0 kg (type III) of dry aggregate per square meter. The exact rate will be determined by the Engineer after taking into account the surface demand of the pavement, the size of the largest particles of aggregate and using the specific mass of the aggregate determined in the mix design. The completed spread will be within 10 percent of the rate determined by the mix design.
On concrete pavements (bridge decks and roadways) the microsurfacing mixture shall be spread at a minimum rate of 16.0 kg of dry aggregate per square meter. A paint binder shall be placed on new concrete surfaces, highly polished concrete surfaces or when designated by the Engineer.
Longitudinal joints shall correspond with the edges of traffic lanes. The Engineer may permit other patterns of longitudinal joints, if such patterns will not adversely affect the quality of the finished product, as determined by the Engineer.
Longitudinal joints common to two driving lanes, shall be butt joints with overlaps not to exceed 76.2 mm. Building paper shall be placed at transverse joints, over previously placed microsurfacing, or other suitable methods, approved by the Engineer, used to avoid double placement of microsurfacing. Hand tools shall be available in order to remove spillage. Ridges or bumps in the finished surface shall not be permitted.
The mixture shall be uniform and homogeneous after spreading on the surfacing and shall not show separation of the emulsion and aggregate after setting.
Adequate means shall be provided to protect the microsurfacing from damage by traffic until such time that the mixture has cured sufficiently so that the microsurfacing will not adhere to and be picked up by the tires of vehicles.
2.09 MEASUREMENT
Microsurfacing will be measured by the tonne. The quantity of microsurfacing to be paid for will be the combined mass of the aggregate and asphalt emulsion used in the microsurfacing mixture. The mass of added water and set-control additives used in the microsurfacing mixture will not be included in the mass of the microsurfacing to be paid for. The mass of aggregate and asphalt emulsion will be determined as provided in Section 9-1.01, "Measurement of Quantities." except that no deduction will be made for water in the aggregate and asphalt emulsion.
2.10 PAYMENT
The contract price paid per tonne for microsurfacing shall include full compensation for furnishing all labor, materials, tools, equipment, and incidentals, and for doing all the work involved in constructing the microsurfacing, complete in place, including testing for and furnish mix design, cleaning the surface, furnishing added water and set-control additives, mixing water with asphalt emulsion for coating the pavement and protecting the microsurfacing until it has set, all as shown on the plans, and as specified in these special provisions, and as directed by the Engineer.
Last Updated (Thursday, 10 December 2009 17:19)