ITEM 304A – SLURRY SYSTEM FOR ROAD SURFACE TREATMENT
304A.1 Description
This item shall consist of either a blend of Cold Seal Bitumen (CSB), aggregate, water and additives (Slurry Surface Treatment – SST) applied over a prime coated base, or a slurry seal or micro-surfacing on a bituminous concrete surface or on a concrete paved surface (PCCP) in accordance with the Plans and Specification.
304A.2 Material Requirements
304A.2.1 Quantities of Materials
The approximate amounts of materials per square meter and sequence of operations for Slurry Surface Treatment (SST) shall be as provided in Table 304A. 1.
The quantities given in the above-mentioned table are those of aggregates having a bulk specific gravity of 2.65 as determined by AASHTO T 84 and T 85. Proportionate correction shall be made when the aggregate furnished on the job has a bulk specific gravity above 2.75 or below 2.55. In such case, the corrected amount shall be the product c the quantity shown in the Table and the ratio of the bulk specific gravity of aggregate to 2.65.
The amounts given in the said Table are approximate and the exact amounts shall be set by the Engineer. The Engineer, as necessary to fi the conditions, may vary the total amount of bituminous material per square meter, but the total amount of aggregate per square meter, after adjusting for specific gravity, shall not be changed.
Table 304A.1 - Quantities of Materials and Sequence of Operations Using Emulsified Cold Seal Bitumen
| Aggregate Grading and Sequence of Operations | SST |
|---|---|
Priming:
Apply Cold Seal Bitumen Type 1 (CSB-1), L/m2
Chip Course:
Apply Cold Seal Bitumen Type 2 (CSB-2), L/m2
Spread Cover Coat Aggregates (Grading B),
Kg/m2
|
0.90 - 2.25
1.20 - 2.00
1 1.00 - 16.00
(+/- 10%)
|
Fog Seal:
Apply Cold Seal Bitumen Type 3 (CSB-3), L/m2
(Diluted with water at a ratio of 1:1)
|
1.00
|
Slurry Course:
Apply the mixture of Cold Seal Bitumen (CSB- 3),
aggregates, mineral filler, water and additives
|
See Note 1
|
Note 1 - Depends on the Job Mix Design created by the CSB source in accordance with the International Slurry Surfacing Association:
- Technical Bulletin 111 - Outline Guide Design Procedure for Slurry Seal
- Technical Bulletin A105 Recommended Performance Guidelines for Emulsified Asphalt Slurry Seal Surface.
- Technical Bulletin A143 Recommended Performance Guidelines for Polymer Modified Micro-surfacing
Or as approved by the Engineer.
304A.2.2 Bituminous Materials
304A.2.2.1 Emulsified Asphalt
The emulsified asphalt to be used shall conform to the requirements of Item 702, Bituminous Materials. It shall have the following additional specifications:
Table 304A.2 – Emulsified Asphalt Requirements
| Slurry Seal | Micro-surfacing | Cape Seal |
|---|---|---|
CSB-3, CSB-3Q, CSB-
3HD* |
CSB-33HD*
|
CSB 1 (priming)
CSB 2 (chip seal) CSB, CSB-3HD*, CSB-3Q (fog seal & slurry seal) |
*Additional Specifications:
- With minimum 3% polymer solids/natural cationic latex/synthetic cationic latex based on asphalt weight.
- Storage stability, 24 hrs – 1% max
- Asphalt residue from distillation – 62% min
- Softening point (asphalt residue) – 570C minP
- enetration (asphalt residue) – 40 – 90 dmm
Each load of emulsified asphalt shall be accompanied with a Certificate of Analysis/Compliance to indicate that the emulsion meets specifications.
Bituminous material, CSB-1, CBS-2, CBS-3 (or derivatives) all straight or modified Bitumen emulsions shall conform to the requirements of Items 702 and must also conform to the minimum specifications stated in Table 304A.3. Slurry Course Mix based on Note 1 shall also conform to the performance specifications set in ISSA Technical Bulletin or must meet the minimum performance properties shown on the Table 304A.7.
Table 304A.3 – Properties of Cold Seal Bitumen
| Properties | Test Method | CSB-1 | CSB-2 | CSB-3 |
|---|---|---|---|---|
Viscosity, Saybolt Furol @ 250C,
seconds Storage Stability, Settlement (24hrs), % mass Cement Mixing Test, Percentage of Break, % mass Sieve Test, Sample Retained, % mass Particle Charge Test Residue by Evaporation, % mass Examination of Residue Obtained by Evaporation: -Penetration Number @ 250C, dmm -Ductility @ 250C, Cm -Solubility in Trichloroethylene, % mass |
ASTM D 244
ASTM D 244 ASTM D 244 ASTM D 244 ASTM D 244 ASTM D 6 ASTM D 1113 ASTM D 2042 |
15 – 50
1.0 max 2.0 max 0.10 max Negative 60 min 40 – 90 40 min 97.5 min |
100 – 200
1.0 max - 0.10 max Positive 65 min 100-250 40 min 97.5 min |
15 – 50
1-0 max - 0.10 max Positive 60 min 40 – 90 40 min 97.5 min |
- CSB-3 may be set to achieve specific conditions such as quick set, quick traffic, latex modified or polymer modified emulsions as approved by the Engineer.
304A.2.3 Aggregates
304A.2.3.1 Gradation
The aggregates shall be cleaned, crushed stone, crushed slag, or crushed gravel. Only one type of aggregate shall be used in a project unless alternative types are approved. The gradation for the Cover Coat Aggregates shall conform to Table 304.3 (Grading A or B). The gradation for the aggregates to be used in the slurry course shall conform to table 304A.4 and shall be chosen based on the type of application or as approved by the Engineer (or as indicated in Note 1).
Table304A.4 - Slurry System Aggregate Requirements
| Sieve Designation | Mass percent Passing | Stockpile Tolerance from the Mix Design Gradation |
|||
|---|---|---|---|---|---|
| Standard, mm | Alternate US Standard |
Type I | Type II | Type III | |
| 9.5 4.75 2.36 1.18 0.60 0.33 0.15 .075 |
3/8" No. 4 No. 8 No. 16 No. 30 No. 50 No. 100 No. 200 |
100 100 90 - 100 65 - 90 40 – 65 25 – 42 15 – 30 10 - 20 |
100 90 – 100 65 – 90 45 – 70 30 - 50 18 – 30 10 – 21 5 - 15 |
100 70 – 90 45 – 70 28 – 50 19 – 34 12 – 25 7 – 18 5 - 15 |
±5% ±5% ±5% ±5% ±4% ±3% ±2% |
| Mix Type | Gradation | ||||
| Slurry Seal Micro-Surfacing |
Type I, Type II, Type III, Type II or Type III |
||||
The aggregate shall have a mass percent of wear not exceeding 40 when tested by AASHTO T 96. When crushed gravel is used, not less than 50 mass percent of the particles retained on the 4. 75 mm (No. 4) sieve shall have at least one fractured face. When crushed slag is used, it must be of uniform density and quality and shall have a density not less 960 kg/m3 as determined by AASHTO T 19.
304A. 2.3.2 Quality Tests
The aggregate shall meet the minimum requirements of Table 304A.5 for slurry sealing and micro-surfacing.
Table 304A.5 -Aggregate Quality Requirements
| Test Method | Specification | |||
|---|---|---|---|---|
| Test | AASHTO | ASTM | Slurry Seal | Micro-surfacing |
Sand Equivalent Value
of Soils &
Fine Aggregate
|
T 176 | D 2419 | 45 min | 65 min |
Soundness of
Aggregate by Use of
Sodium Sulfate or
Magnesium Sulfate
|
T 104 | C 88 | 15% max w/ Na2SO425% max w/ MgSO4 |
Na2SO4 25% max w/ MgSO4 |
Resistance to
Degradation of
Small-size Coarse
Aggregate by
Abrasion and Impact
in the Los Angeles
Machine
|
T 96 | C 131 | 35% max | 30% max |
304A.2.4 Mineral Filler
Mineral filler shall be used if required by the mix design for slurry sealing and micro-surfacing. It can be Portland Cement, hydrated lime, limestone dust, fly ash or other approved filler meeting requirements ASTM D 242. Typical use levels are normally 0.0 - 3.0% and may be considered part of the aggregate gradation. Mineral filler may be used improve mixture consistency and to adjust mixture breaking and curing properties.
304A.2.5 Water
The water shall be free of harmful salts and contaminants. If the quality of the water is in question, it should be submitted to the laboratory with the other raw materials for the mix design.
304A.2.6 Additives
Additives may be used to accelerate or retard the break/set of the slurry seal and micro-surfacing. Appropriate additives and their applicable use range should be approved by the laboratory as part of mix design.
304A.2.7 Proportioning of Mixture for Slurry Seal and Micro-surfacing
The proportion of bituminous material components and other components on the basis of total dry aggregate, shall be in accordance to Table 304A.6. The exact percentage to be used shall be fixed by the Engineer in accordance with the job-mix formula and the other quality control requirements.
Table 304A.6 -Job Mix Design for Slurry Seal and Micro-surfacing
| Properties | Test Method | Specification | |
|---|---|---|---|
| Slurry Seal | Micro-surfacing | ||
Mix time @ 250C
|
ISSA TB 113 | Controllable to 180 sec min |
Controllable to 120 sec min |
Slurry Seal
Consistency |
ISSA TB 109 |
2.0 - 3.0 cm |
- |
Wet Cohesion
@ 30 minutes min (Set) @ 60 minutes min (traffic) |
ISSA TB 139 (For quick-traffic systems) |
12 kg-cm min 20 kg-cm or Near Spin min |
12 kg-cm min 20 kg-cm or Near Spin min |
Wet Stripping
|
ISSA TB 114 | Pass (90% min) | Pass (90% min) |
Wet-Track Abrasion
Loss One-hour Soak Six-day Soak |
ISSA TB 100 |
807g/m2 max |
538 g/m2 max 807g/m2 max |
Excess Asphalt by
Loaded Wheel Tester (LWT) Sand Adhesion |
ISSA TB 109 (Critical in heavy traffic areas |
538 g/m2 max |
538 g/m2 max |
Lateral Displacement
Specific Gravity after 1000 cycles of 56.71 kg |
ISSA TB 147 |
- |
5% max 2.10 max |
Classification
Compatibility |
ISSA TB 144 |
- |
II Grade Points min (AAA, BAA) |
304A.3 Construction Requirements
304A.3.1 Rates of Application/Spreading of Asphalt and Aggregates
The rates of application/spreading of asphalt and aggregate for the slurry surface treatment (sst) shall be within the range given in Table 304A.1. These quantities are given as guide only and will vary considerably according to the type and condition of the surface, the grading, type, shape and absorbency of the aggregate, the weather condition and the traffic. The actual quantities to be used for surface treatment shall be determined by the Contractor in accordance with the design methods for one-size aggregate given in the Asphalt Institute Manual (MS-13), Asphalt Surface Treatment. The proposed design shall be subject to the approval of the Engineer.
The slurry seal or micro-surfacing mixture shall be of the proper consistency at all times so as to provide application rate required by the surface condition. The application rate shall be in accordance to Table 304A.8
Table 304A.8 - Application Rates for Slurry Seal/Micro-surfacing
| Aggregate Type | Location | Application Rate | |
|---|---|---|---|
| Slurry Seal | Micro-surfacing | ||
| Parking Areas Urban & Residential Streets Airport Runways | 4.3 - 6.5 kg/m2 | - | |
Type II
| Urban & Residential Streets Airport Runways | 5.4 - 9.8 kg/m2 | 5.4 - 9.8 kg/m2 |
Type III
| Primary & Interstate Routes | 8.1 - 12.0 kg/m2 | 8.1 - 12.0 kg/m2 |
Suggested application rates are based on dry weight of aggregate in the mixture.
The Contractor shall furnish the Engineer a certified vendor's certificate in duplicate immediately upon delivery of asphaltic material to the site.
The Contractor shall provide weighing equipment on the site to control the application of aggregates. The weighing equipment shall have an approved multiple beam type scale with indicator and other necessary dials for accurately weighing the aggregate. The scale shall be protected by a weatherproof house with a floor area not less than 10 m2. The Contractor shall, at his own expense, have the scale tested and approved by the Department of Public Works and Highways.
304A.3.2 Equipment
The equipment for Priming, Chip Course and Fog Sealing must conform to Subsection 304.3.2, Equipment.
The machine slurry sealing and micro-surfacing shall be specifically designed and manufactured to apply slurry seal or micro-surfacing. The material shall be mixed by an automatic-sequenced, self-propelled, mixing machine of either truck-mounted or continuous-run design. Either type shall be able to accurately deliver and proportion the mix components through a mixer and to discharge the mixed product on a continuous-flow basis. If continuous-run equipment is used, the machine shall provide the operator with the full control of the forward and reverse speeds during the application. It shall be equipped with opposite-side driver stations to assist in alignment. Sufficient storage capacity for all mix components is required to maintain an adequate supply to the proportioning controls.
The mixture shall be spread uniformly by means of a conventional surfacing spreader box attached to the mixer and equipped to agitate and spread the material evenly throughout the box. The machine must be able to lay based on the specifications stated in Design Mix and approved by the Engineer.
304A.3.3 Weather Limitations
Slurry seal, micro-surfacing or slurry surface treatment (sst) shall not be applied if either the pavement or air temperature is below 100C and falling. The mixture shall not be applied when weather conditions prolong opening to traffic beyond a reasonable time.
304A.3.4 Application of Bituminous Mixture
304A.3.4.1 Bituminous Material for Slurry Surface Treatment (SST)
It shall conform to Subsection 304.3.3, Application of Bituminous Material.
304A.3.4.2 Slurry Seal and Micro-surfacing
If required, it is recommended that a test strip be placed in conditions similar to those expected to be encountered in the project.
When local conditions warrant, the surface shall be fogged with water ahead of the spreader box. The rate of application of the fog spray may be adjusted as the temperature, surface, texture, humidity and dryness of the pavement change.
The slurry seal/micro-surfacing shall be of the appropriate consistency upon leaving the mixer. A sufficient amount of material shall be carried in all parts of the spreader at all times so that complete coverage is obtained.
304A.3.5 Surface Preparation
Prior to applying the slurry seal or micro-surfacing, loose material, oil spots, vegetation and other objectionable material shall be removed. If water is used, cracks shall be allowed to dry thoroughly before application.
Normally tack coat is not required unless the surface to be covered is extremely dry and raveled or is concrete or brick. If required, tack coat shall be applied in accordance to Item 302 - Bituminous Tack Coat. The tack coat shall be allowed to cure sufficiently before the application of slurry seal or micro-surfacing.
It is recommended to treat cracks wider than 0.64 cm in the pavement surface with an approved crack sealer prior to application of slurry seal or micro-surfacing.
304A.3.6 Spreading of Aggregate
It shall conform to Subsection 304.3.4, Spreading of Aggregates.
304A.3.6.1 Mixture
The mixture shall possess sufficient stability so that premature breaking of the material in the spreader box does not occur. The mixture shall be homogeneous during and following mixing and spreading. It shall be free of excess liquids which create segregation of the aggregate.
304A.3.6.2 Handwork
Areas which cannot be accessed by the mixing machine shall be surfaced using hand -squeegees to provide complete and uniform coverage. As much as possible, handwork shall exhibit the same finish as that applied by the spreader box.
304A.3.6.3 Rolling
Rolling shall be by a self-propelled, 10-tonne (max) pneumatic tire roller equipped with a water spray system. All tires shall be inflated per manufacturer's specifications. Rolling shall not start until the slurry seal/micro-surfacing has cured sufficiently to avoid damage by the roller. Areas which require rolling shall receive a minimum of two (2) full coverage passes.
304A.3. 7 Quality Control
If required, representative samples of the slurry seal or microsurfacing may be taken directly from the machine. Residual asphalt content (ASTM D 2172 Standard Test Method for Quantitative Extraction of Bitumen from Bituminous Paving Mixtures or ASTM D 6307 Standard Test Method for Asphalt Content of Hot-Mix Asphalt by Ignition Method) tests may be• run in the samples. If ASTM D 6307 is used, further analysis can be done on the recovered aggregate to verify the aggregate gradation used.
Data obtained from the proportioning devices on the slurry seal or micro-surfacing machine may be used to determine individual material quantities and application rate.
304A.3.8 Control of Traffic
It shall conform to Subsection 304.3.5, Control of Traffic.
304A.4 Method of Measurement
The surface treatment shall be measured by the square meters (m2). The quantity to be paid for shall be the number of square meters of the treatment placed in the accepted base or pavement.
304A.5 Basis of Payment
The accepted quantities, measured as prescribed in Section 304A.4, shall be paid for at the contract unit price for Slurry Surface Treatment (SST), Slurry. Seal or Micro-surfacing which price and payment shall be full compensation for furnishing and placing all materials and for all labor, equipment, tools and incidentals necessary to complete this Item.
Payment will be made under:
Pay Item Number
|
Description
|
Unit of Measurement
|
|---|---|---|
| 304A (1) 304A (2) 304A (3) |
Slurry Surface Treatment (SST)
Slurry Seal
Micro-surfacing
|
Square Meter Square Meter Square Meter |
Post a Comment