Crumb Rubber Modifier in Asphalt Pavement

Appendix D

Typical Specifications

California Department of Transportation

California Special Provision -- Gap-Graded Asphalt Rubber (12-13-94)

10-1. Rubberized Asphalt Concrete (Type G - Asphalt Rubber)

Rubberized asphalt concrete (Type G-Asphalt Rubber) shall be asphalt rubber hot mix-gap graded (ARHM-GG) and shall consist of furnishing and mixing gap graded aggregate and asphalt-rubber binder and spreading and compacting the mixture. Type G rubberized asphalt concrete shall conform to the requirements specified for Type A asphalt concrete in Section 39, "Asphalt Concrete," of the Standard Specifications and these special provisions.

The last sentence of the first paragraph in Section 39-2.01, "Asphalts," of the Standard Specifications and the fifth, sixth, seventh and eighth paragraphs of Section 39-3.03, "Proportioning," of the Standard Specifications shall not apply to Type G rubberized asphalt concrete. The swell, moisture vapor susceptibility, and stabilometer value requirements in Section 39-2.02, "Aggregate," of the Standard Specifications shall not apply to Type G rubberized asphalt concrete.

The second paragraph in Section 39-3.05, "Asphalt Concrete and Asphalt Concrete Base Storage," of the Standard Specifications is amended to read:

Storage silos shall be equipped with a surge-batcher sized to hold a minimum of 4,000 pounds of material. A surge-batcher consists of equipment placed at the top of the storage silo which catches the continuous delivery of the completed mix and changes it to individual batch delivery and prevents the segregation of product ingredients as the completed mix is placed into storage. The surge-batcher shall be center loading and shall be thermally insulated or heated or thermally insulated and heated to prevent material buildup. Rotary chutes shall not be used as surge-batchers.

The surge-batcher shall be independent and distinct from conveyors or chutes used to collect or direct the completed mixture being discharged into storage silos and shall be the last device to handle the material before it enters the silo. Multiple storage silos shall be served by an individual surge-batcher for each silo. Material handling shall be free of oblique movement between the highest elevation (conveyor outfall) and subsequent placement in the silo. Discharge gates on surge-batchers shall be automatic in operation and shall discharge only after a minimum of 4,000 pounds of material has been collected and shall close before the last collected material leaves the device. Discharge gate design shall prevent the deflection of material during the opening and closing operation.

GENERAL.

Binder for Type G rubberized asphalt concrete shall be, at the Contractor's option, either Type 1 or Type 2 asphalt-rubber binder conforming to the requirements of these special provisions.

The amount of asphalt-rubber binder to be mixed with the aggregate for Type G rubberized asphalt concrete will be determined by the Engineer using the samples of aggregates furnished by the Contractor in conformance with Section 39-3.03, "Proportioning," of the Standard Specifications. The Engineer will determine the amount of asphalt-rubber binder to be mixed with the aggregate in accordance with California Test 367, except as follows:

The specific gravity used in Section B. "Voids Content of Specimen" of California Test 367 will be determined using California Test 308, Method A.

Section C. "Optimum Bitumen Content" of California Test 367 shall be as follows:

Using Figure 2, record in Step 1 of the pyramid the asphalt content of the four specimens with the maximum asphalt content used in the square farthest to the right.
Plot asphalt content versus void content for each specimen on Form TL-306 (Figure 3), and connect adjacent points with straight lines.
From Figure 3, select the theoretical asphalt content that has 3.0 percent voids. Record this amount in Step 4 of the pyramid.
Record the asphalt content in Step 4 as the Optimum Bitumen Content (OBC).
To establish a recommended range, OBC as the high value and 0.3 percent less as the low value.

The temperature of the aggregate at the time the asphalt-rubber binder is added shall be not more than 325°F.

(Editor's Note: All figures and forms referred to here can be found in California Test 367, published by the California Department of Transportation.)

ASPHALT-RUBBER BINDER

The grade of paving asphalt to be used in asphalt-rubber binder will be either grade AR-i 000, AR-2000, or AR-4000, as determined by the Engineer from recommendation by the asphalt-rubber binder supplier.

The reclaimed vulcanized rubber shall be produced primarily from the processing of automobile and truck tires. The rubber shall be produced by ambient temperature grinding processes only.

The specific gravity of reclaimed vulcanized ground rubber shall be not less than 1.10 nor more than 1.20, and shall conform to the following gradation when tested in accordance with ASTM Designation C 136:

Sieve Size	Percent Passing
No. 8	100
No. 10	95-100
No. 16	40-80
No. 30	5-30
No. 50	0-15
No. 200	0-3

Rubber for use in asphalt-rubber binder shall be free of loose fabric, wire and other contaminants except that up to 4 percent (by weight of rubber) calcium carbonate or talc may be added to prevent caking or sticking of the particles together. The rubber shall be sufficiently dry so as to be free flowing and not produce foaming when blended with the hot paving asphalt.

At least two weeks before its intended use, the Contractor shall furnish samples of the asphalt-rubber binder proposed for use on the project. The samples shall consist of 4 one-quart size cans of the asphalt-rubber binder, together with the formulation and the grade of paving asphalt used.

The method and equipment for combining the rubber and paving asphalt shall be so designed and accessible that the Engineer can readily determine the percentage by weight for each material being incorporated into the mixture.

Equipment utilized in the production and proportioning of asphalt-rubber binder shall include the following:

An asphalt heating tank with hot oil heat transfer to heat the paving asphalt to the necessary temperature before blending with the granulated rubber. This unit shall be equipped with a thermostatic heat control device.

A mechanical blender for proper proportioning and thorough mixing of the paving asphalt and rubber. This unit shall have both an asphalt totalizing meter (gallons or liters) and a flow rate meter (gallons per minute or liters per minute).

An asphalt-rubber binder storage tank equipped with a heating system to maintain the proper temperature of the binder and an internal mixing unit capable of maintaining a homogeneous mixture of asphalt and rubber.

The asphalt-rubber mixture shall not be used as a binder after it has been retained for more than 48 hours.

TYPE 1 BINDER.

Type 1 asphalt-rubber binder shall be a uniform and reacted mixture of compatible paving grade asphalt and reclaimed vulcanized rubber. The length of the individual rubber particles shall not exceed 3/16 inch.

Type 1 asphalt-rubber binder shall contain not less than 14 percent nor more than 20 percent rubber, by weight, of the total asphalt-rubber binder.

The temperature of the paving asphalt shall be between 350°F and 425°F at the time the rubber is blended with the paving asphalt. The paving asphalt and rubber shall be combined and mixed together in a blender unit, pumped into the agitated storage tank, and then reacted for a minimum of 45 minutes from the time the rubber is added to the paving asphalt. The asphalt-rubber binder shall be maintained at a temperature of not less than 325°F nor more than 375°F during the reaction period.

The viscosity of the asphalt-rubber binder after the reaction period, when tested in accordance with ASTM Designation D 2196, shall be not less than 1,500 centipoise nor more than 3,000 centipoise at 350°F (Brookfield).

The asphalt-rubber binder, after reaching the desired consistency, shall not be held at temperatures over 325°F for more than 4 hours.

TYPE 2 BINDER.

Type 2 asphalt-rubber binder shall be a uniform and reacted mixture of compatible paving grade asphalt, extender oil, natural rubber and reclaimed vulcanized rubber.

Extender oil shall be a resinous, high flash point, aromatic hydrocarbon conforming to the following:

Test	ASTM Designation	Requirement
Viscosity, SSU, at 100°F	D 88	2,500 Min.
Flash Point, COC, °F	D 92	390 min.
Molecular Analysis: Asphaltenes, percent by weight	D 2007	0.1 max
Aromatics, percent by weight	D 2007	55 min.

The paving asphalt and extender oil, when combined, shall form a material that is chemically compatible with the rubber.

The extender oil shall be added to the paving asphalt at a rate of not less than 2 percent nor more than 6 percent by weight of the paving asphalt, the exact amount to be as determined by the Engineer from recommendation by the asphalt-rubber binder supplier. The asphalt shall be at a temperature of not less than 350°F nor more than 425°F when the extender oil is added.

Rubber for use in Type 2 asphalt-rubber binder shall consist of reclaimed vulcanized rubber and shall contain not less than 20 percent nor more than 30 percent, by weight, natural rubber, when tested in accordance with ASTM Designation D 297: The rubber shall contain no particles longer than 1/4 inch in length.

The paving asphalt-extender oil blend and rubber shall be combined and mixed together in the blender unit to produce a homogeneous mixture.

The amount of rubber to be added to the paving asphalt-extender oil blend shall be not less than 17 percent nor more than 23 percent by weight of the combined mixture of paving asphalt, extender oil, and rubber. The exact amount will be as determined by the Engineer from recommendation by the asphalt-rubber binder supplier. The paving asphalt-extender oil blend shall be at a temperature of not less than 350°F nor more than 425°F when the rubber is added.

The asphalt-rubber binder shall be reacted for a minimum of 45 minutes from the time the rubber is added to the paving asphalt-extender oil blend. The asphalt-rubber binder shall be maintained at a temperature between 375°F and 425°F during the reaction period.

The viscosity of the asphalt-rubber binder after the maximum reaction period, when tested in accordance with ASTM Designation D 2196, shall be not less than 1,500 centipoise nor more than 3,000 centipoise at 375°F (Brookfield).

The asphalt-rubber binder, after reaching the desired consistency, shall not be held at temperatures over 375°F for more than 4 hours.

AGGREGATE.

The aggregate for Type G rubberized asphalt concrete shall conform to the following grading and shall meet the quality requirements specified for Type A asphalt concrete in Section 39-2.02, "Aggregate," of the Standard Specifications, except the loss at 500 revolutions from the Los Angeles Rattler test shall be 40 percent maximum.

The symbol "X" in the following table is the gradation which the Contractor proposes to furnish for the specific sieve.

Aggregate Grading Requirements
Percentage Passing
½" maximum

Sieve Size	Limits of Proposed Gradation	Operating Range	Contract Compliance
3/4"	&nbsp	100	100
1/2"		90-100	90-100
3/8"	79-87	X ± 5	X ± 7
No. 4	32-40	X ± 5	X ± 7
No. 8	18-24	X ± 4	X ± 5
No. 30	9-12	X ± 4	X ± 5
No. 200		2-7	0-8

The symbol "X" in the following table is the gradation which the Contractor proposes to furnish for the specific sieve.

Aggregate Grading Requirements
Percentage Passing
¾" maximum

Sieve Size	Limits of Proposed Gradation	Operating Range	Contract Compliance
1/2"		90-100	90-100
3/8"	0-68	X ± 5	X ± 7
No. 4	32-40	X ± 5	X ± 7
No. 8	18-24	X ± 4	X ± 5
No. 30	9-12	X ± 4	X ± 5
No. 200		2-7	0-8

CONSTRUCTION.

After the material has reacted for at least 45 minutes, the asphalt-rubber binder shall be metered into the mixing chamber of the asphalt concrete production plant at the percentage determined by the Engineer.

When batch type asphalt concrete plants are used to produce Type G rubberized asphalt concrete, the asphalt-rubber binder and mineral aggregate shall be proportioned by weight.

When continuous mixing type asphalt concrete plants are used to produce Type G rubberized asphalt concrete, the asphalt-rubber binder shall be proportioned by an asphalt meter of the mass flow, coriolis effect type. The meter shall be calibrated in accordance with California Test 109.

Type G rubberized asphalt concrete shall be spread at a temperature of not less than 275°F nor more than 325°F, measured in the hopper of the paving machine.

Pneumatic tired rollers shall not be used to compact Type G rubberized asphalt concrete. Alternative compacting equipment as specified in Section 39-6.03, "Compacting," of the Standard Specifications shall be used to compact the Type G rubberized asphalt concrete.

Traffic shall not be allowed on the Type G rubberized asphalt concrete for at least one hour after final rolling operations have been completed.

When ordered by the Engineer to prevent tracking by public traffic from the surface of Type G rubberized asphalt concrete, prior to opening a traffic lane, sand shall be spread on the surface at the approximate rate of from one to two pounds per square yard. Sand shall be free from clay or organic material and shall be of such gradation that at least 90 percent will pass the No.4 sieve and not more than 5 percent will pass a No.200 sieve. When ordered by the Engineer, excess sand shall be removed from the pavement surface by sweeping.

MEASUREMENT AND PAYMENT.

Rubberized asphalt concrete (Type G-asphalt rubber) will be measured and paid for by the ton in the same manner specified for asphalt concrete in Section 39-8, "Measurement and Payment," of the Standard Specifications.

Full compensation for furnishing, spreading, and sweeping sand cover shall be considered as included in the contract price paid per ton for rubberized asphalt concrete (Type G-asphalt rubber), and no separate payment will be made therefor.

California Special Provision -- Dense-Graded Asphalt Rubber (12-13-94)

10-1. Rubberized Asphalt Concrete (Type D - Asphalt Rubber)

Rubberized asphalt concrete (Type D-Asphalt Rubber) shall be asphalt rubber hot mix-dense graded (ARHM-DG) and shall consist of furnishing and mixing dense graded aggregate and asphalt-rubber binder and spreading and compacting the mixture. Type D rubberized asphalt concrete shall conform to the requirements specified for Type A asphalt concrete in Section 39, "Asphalt Concrete," of the Standard Specifications and these special provisions.

The last sentence of the first paragraph in Section 39-2.01, "Asphalts," of the Standard Specifications and the fifth, sixth, seventh and eighth paragraphs of Section 39-3.03, "Proportioning," of the Standard Specifications shall not apply to Type D rubberized asphalt concrete. The swell, moisture vapor susceptibility, and stabilometer value requirements in Section 39-2.02, "Aggregate," of the Standard Specifications shall not apply to Type D rubberized asphalt concrete.

The second paragraph in Section 39-3.05, "Asphalt Concrete and Asphalt Concrete Base Storage," of the Standard Specifications is amended to read:

Storage silos shall be equipped with a surgebatcher sized to hold a minimum of 4,000 pounds of material. A surge-batcher consists of equipment placed at the top of the storage silo which catches the continuous delivery of the completed mix and changes it to individual batch delivery and prevents the segregation of product ingredients as the completed mix is placed into storage. The surge-batcher shall be center loading and shall be thermally insulated or heated or thermally insulated and heated to prevent material buildup. Rotary chutes shall not be used as surge-batchers.

The surge-batcher shall be independent and distinct from conveyors or chutes used to collect or direct the completed mixture being discharged into storage silos and shall be the last device to handle the material before it enters the silo. Multiple storage silos shall be served by an individual surge-batcher for each silo. Material handling shall be free of oblique movement between the highest elevation (conveyor outfall) and subsequent placement in the silo. Discharge gates on surge-batchers shall be automatic in operation and shall discharge only after a minimum of 4,000 pounds of material has been collected and shall close before the last collected material leaves the device. Discharge gate design shall prevent the deflection of material during the opening and closing operation.

GENERAL.

Binder for Type D rubberized asphalt concrete shall be, at the Contractor's option, either Type 1 or Type 2 asphalt-rubber binder conforming to the requirements of these special provisions.

The amount of asphalt-rubber binder to be mixed with the aggregate for Type D rubberized asphalt concrete will be determined by the Engineer using the samples of aggregates furnished by the Contractor in conformance with Section 39-3.03, "Proportioning," of the Standard Specifications. The Engineer will determine the amount of asphalt-rubber binder to be mixed with the aggregate in accordance with California Test 367, except as follows:

The specific gravity used in Section B, "Voids Content of Specimen" of California Test 367 will be determined using California Test 308, Method A.

Section C, "Optimum Bitumen Content" of California Test 367 shall be as follows:

Using Figure 2, record in Step 1 of the pyramid the asphalt content of the four specimens with the maximum asphalt content used in the square farthest to the right.
Plot asphalt content versus void content for each specimen on Form TL-306 (Figure 3), and connect adjacent points with straight lines.
From Step 1 of the pyramid, select the three highest asphalt contents that do not exhibit moderate or heavy surface flushing, and record these asphalt contents in Step 2. See Note 1.
From Figure 2, select the theoretical asphalt content that has 3.0 percent or more voids and is within the asphalt range listed in Step 2 of the pyramid. Always stay as close to 3.0 percent voids as possible. Record this amount in Step 4 of the pyramid.
Record the asphalt content in Step 4 as the Optimum Bitumen Content (OBC).
To establish a recommended range, use the Optimum Bitumen Content (OBC) as the high value and 0.3 percent less as the low value.

The temperature of the aggregate at the time the asphalt-rubber binder is added shall be not more than 325°F.

ASPHALT-RUBBER BINDER.

The grade of paving asphalt to be used in asphalt-rubber binder will be either grade AR-1 000, AR-2000, or AR4000, as determined by the Engineer from recommendation by the asphalt-rubber binder supplier.

The reclaimed vulcanized rubber shall be produced primarily from the processing of automobile and truck tires. The rubber shall be produced by ambient-temperature grinding processes only.

The specific gravity of reclaimed vulcanized ground rubber shall be not less than 1.10 nor more than 1.20, and shall conform to the following gradation when tested in accordance with ASTM Designation C 136:

Sieve Size	Percent Passing
No. 8	100
No. 10	95-100
No. 16	40-80
No. 30	5-30
No. 50	0-15
No. 200	0-3

Rubber for use in asphalt-rubber binder shall be free of loose fabric, wire, and other contaminants except that up to 4 percent (by weight of rubber) calcium carbonate or talc may be added to prevent caking or sticking of the particles together. The rubber shall be sufficiently dry so as to be free flowing and not produce foaming when blended with the hot paving asphalt.

At least two weeks before its intended use, the Contractor shall furnish samples of the asphalt-rubber binder proposed for use on the project. The samples shall consist of 4 one-quart size cans of the asphalt rubber binder, together with the formulation and the grade of paving asphalt being used.

The method and equipment for combining the rubber and paving asphalt shall be so designed and accessible that the Engineer can readily determine the percentage by weight for each material being incorporated into the mixture.

Equipment utilized in the production and proportioning of asphalt-rubber binder shall include the following:

An asphalt heating tank with hot oil heat transfer to heat the paving asphalt to the necessary temperature before blending with the granulated rubber. This unit shall be equipped with a thermostatic heat control device.

A mechanical blender for proper proportioning and thorough mixing of the paving asphalt and rubber. This unit shall have both an asphalt totalizing meter (gallons or liters) and a flow rate meter (gallons per minute or liters per minute).

An asphalt-rubber binder storage tank equipped with a heating system to maintain the proper temperature of the binder and an internal mixing unit capable of maintaining a homogeneous mixture of asphalt and rubber.

The asphalt-rubber mixture shall not be used as a binder after it has been retained for more than 48 hours.

TYPE 1 BINDER.

Type 1 asphalt-rubber binder shall be a uniform and reacted mixture of compatible paving grade asphalt and reclaimed vulcanized rubber. The length of the individual rubber particles shall not exceed 3/16 inch.

Type 1 asphalt-rubber binder shall contain not less than 14 percent nor more than 20 percent rubber, by weight, of the total asphalt-rubber binder.

The temperature of the paving asphalt shall be between 350°F and 425°F at the time the rubber is blended with the paving asphalt. The paving asphalt and rubber shall be combined and mixed together in a blender unit, pumped into the agitated storage tank, and then reacted for a minimum of 45 minutes from the time the rubber is added to the paving asphalt. The asphalt-rubber binder shall be maintained at a temperature of not less than 325°F nor more than 375°F during the reaction period.

The viscosity of the asphalt-rubber binder after the reaction period, when tested in accordance with ASTM Designation D 2196, shall be not less than 1,500 centipoise at 350°F (Brookfield).

The asphalt-rubber binder, after reaching the desired consistency, shall not be held at temperatures over 325°F for more than 4 hours.

TYPE 2 BINDER.

Test	ASTM Designation	Requirement
Viscosity, SSU, at 100°F	D 88	2,500 Min.
Flash Point, COC, °F	D 92	390 min.
Molecular Analysis: Asphaltenes, percent by weight	D 2007	0.1 max
Aromatics, percent by weight	D 2007	55 min.

The paving asphalt and extender oil, when combined, shall form a material that is chemically compatible with the rubber.

The extender oil shall be added to the paving asphalt at a rate of not less than 2 percent nor more than 6 percent by weight of the paving asphalt, the exact amount to be as determined by the Engineer from recommendation by the asphalt-rubber binder supplier. The asphalt shall be at a temperature of not less than 350°F nor more than 425°F when the extender oil is added.

Rubber for use in Type 2 asphalt-rubber binder shall consist of reclaimed vulcanized rubber and shall contain not less than 20 percent nor more than 30 percent, by weight, natural rubber, when tested in accordance with ASTM Designation D 297. The rubber shall contain no particles longer than 1/4 inch in length.

The paving asphalt-extender oil blend and rubber shall be combined and mixed together in the blender unit to produce a homogeneous mixture.

The amount of rubber to be added to the paving asphalt-extender oil blend shall be not less than 17 percent nor more than 23 percent by weight of the combined mixture of paving asphalt, extender oil, and rubber. The exact amount will be as determined by the Engineer from recommendation by the asphalt-rubber binder supplier. The paving asphalt-extender oil blend shall be at a temperature of not less than 350°F nor more than 425°F when the rubber is added.

The asphalt-rubber binder shall be reacted for a minimum of 45 minutes from the time the rubber is added to the paving asphalt-extender oil blend. The asphalt-rubber binder shall be maintained at a temperature between 375°F and 425°F during the reaction period.

The viscosity of the asphalt-rubber binder after the reaction period, when tested in accordance with ASTM Designation D 2196, shall be not less than 1,500 centipoise nor more than 3,000 centipoise at 375°F (Brookfield).

The asphalt-rubber binder, after reaching the desired consistency, shall not be held at temperatures over 375°F for more than 4 hours.

AGGREGATE.

The aggregate for Type D rubberized asphalt concrete shall conform to the 3/4" maximum, medium grading and shall meet the quality requirements specified for Type A asphalt concrete in Section 39-2.02, 'Aggregate," of the Standard Specifications, except the loss at 500 revolutions from the Los Angeles Rattler test shall be 40 percent maximum.

CONSTRUCTION.

After the material has reacted for at least 45 minutes, the asphalt-rubber binder shall be metered into the mixing chamber of the asphalt concrete production plant at the percentage determined by the Engineer.

When batch type asphalt concrete plants are used to produce Type D rubberized asphalt concrete, the asphalt-rubber binder and mineral aggregate shall be proportioned by weight.

When continuous mixing type asphalt concrete plants are used to produce Type D rubberized asphalt concrete, the asphalt-rubber binder shall be proportioned by an asphalt meter of the mass flow, coriolis effect type. The meter shall be calibrated in accordance with California Test 109.

Type D rubberized asphalt concrete shall be spread at a temperature of not less than 275°F nor more than 325°F, measured in the hopper of the paving machine.

Pneumatic tired rollers shall not be used to compact Type D rubberized asphalt concrete. Alternative compacting equipment as specified in Section 39-6.03, "Compacting," of the Standard Specifications shall be used to compact the Type D rubberized asphalt concrete.

Traffic shall not be allowed on the Type D rubberized asphalt concrete for at least one hour after final rolling operations have been completed.

When ordered by the Engineer to prevent tracking by public traffic from the surface of Type D rubberized asphalt concrete, prior to opening a traffic lane, sand shall be spread on the surface at the approximate rate of from one to two pounds per square yard. Sand shall be free from clay or organic material and shall be of such gradation that at least 90 percent will pass the No.4 sieve and not more than 5 percent will pass a No.200 sieve. When ordered by the Engineer, excess sand shall be removed from the pavement surface by sweeping.

MEASUREMENT AND PAYMENT.

Rubberized asphalt concrete (Type D-asphalt rubber) will be measured and paid for by the ton in the same manner specified for asphalt concrete in Section 39-8, "Measurement and Payment," of the Standard Specifications.

Full compensation for furnishing, spreading, and sweeping sand cover shall be considered as included in the contract price paid per ton for rubberized asphalt concrete (Type D-asphalt rubber), and no separate payment will be made therefor.

California Special Provision -- Open-Graded Asphalt Rubber (12-13-94)

10-1. Rubberized Asphalt Concrete (Type O - Asphalt Rubber)

Rubberized asphalt concrete (Type 0-Asphalt Rubber) shall be asphalt rubber hot mix-open graded (ARHM-OG) and shall consist of furnishing and mixing open graded aggregate and asphalt-rubber binder and spreading and compacting the mixture. Type 0 rubberized asphalt concrete shall conform to the requirements specified for open graded asphalt concrete in Section 39, "Asphalt Concrete," of the Standard Specifications and these special provisions.

The last sentence of the first paragraph in Section 39-2.01, "Asphalts," of the Standard Specifications and the fifth, sixth, seventh, and eighth paragraphs of Section 39-3.03, "Proportioning," of the Standard Specifications shall not apply to Type 0 rubberized asphalt concrete.

The second paragraph in Section 39-3.05, "Asphalt Concrete and Asphalt Concrete Base Storage," of the Standard Specifications is amended to read:

Storage silos shall be equipped with a surge-batcher sized to hold a minimum of 4,000 pounds of material. A surge-batcher consists of equipment placed at the top of the storage silo which catches the continuous delivery of the completed mix and changes it to individual batch delivery and prevents the segregation of product ingredients as the completed mix is placed into storage. The surge-batcher shall be center loading and shall be thermally insulated or heated or thermally insulated and heated to prevent material buildup. Rotary chutes shall not be used as surgebatchers.

The surge-batcher shall be independent and distinct from conveyors or chutes used to collect or direct the completed mixture being discharged into storage silos and shall be the last device to handle the material before it enters the silo. Multiple storage silos shall be served by an individual surge-batcher for each silo. Material handling shall be free of oblique movement between the highest elevation (conveyor outfall) and subsequent placement in the silo. Discharge gates on surge-batchers shall be automatic in operation and shall discharge only after a minimum of 4,000 pounds of material has been collected and shall close before the last collected material leaves the device. Discharge gate design shall prevent the deflection of material during the opening and closing operation.

GENERAL.

Binder for Type 0 rubberized asphalt concrete shall be, at the Contractor's option, either Type 1 or Type 2 asphalt-rubber binder conforming to the requirements of these special provisions.

The amount of asphalt-rubber binder to be mixed with the aggregate for Type 0 rubberized asphalt concrete will be determined by the Engineer using the samples of aggregates furnished by the Contractor in conformance with Section 39-3.03, "Proportioning," of the Standard Specifications. The Engineer will determine the amount of asphalt-rubber binder to be mixed with the aggregate in accordance with California Test 368, except the test temperature in Section D, "Test Procedure," shall be 325°F.

The temperature of the aggregate at the time the asphalt-rubber binder is added shall be not more than 325°F.

ASPHALT-RUBBER BINDER.

Sieve Size	Percent Passing
No. 8	100
No. 10	95-100
No. 16	40-80
No. 30	5-30
No. 50	0-15
No. 200	0-3

Rubber for use in asphalt-rubber binder shall be free of loose fabric, wire, and other contaminants except that up to 4 percent (by weight of rubber) calcium carbonate or talc may be added to prevent caking or sticking of the particles together. The rubber shall be sufficiently dry so as to be free flowing and not produce foaming when blended with the hot paving asphalt.

At least two weeks before its intended use, the Contractor shall furnish samples of the asphalt-rubber binder proposed for use on the project. The samples shall consist of 4 one-quart size cans of the asphalt-rubber binder, together with the formulation and the grade of paving asphalt used.

The method and equipment for combining the rubber and paving asphalt shall be so designed and accessible that the Engineer can readily determine the percentage by weight for each material being incorporated into the mixture.

Equipment utilized in the production and proportioning of asphalt-rubber binder shall include the following:

An asphalt heating tank with hot oil heat transfer to heat the paving asphalt to the necessary temperature before blending with the granulated rubber. This unit shall be equipped with a thermostatic heat control device.

A mechanical blender for proper proportioning and thorough mixing of the paving asphalt and rubber. This unit shall have both an asphalt totalizing meter (gallons or liters) and a flow rate meter (gallons per minute or liters per minute).

An asphalt-rubber binder storage tank equipped with a heating system to maintain the proper temperature of the binder and an internal mixing unit capable of maintaining a homogeneous mixture of asphalt and rubber.

The asphalt-rubber mixture shall not be used as a binder after it has been retained for more than 48 hours.

TYPE 1 BINDER.

TYPE 2 BINDER.

Type 2 asphalt-rubber binder shall be a uniform and reacted mixture of compatible paving grade asphalt, extender oil, natural rubber, and reclaimed vulcanized rubber.

Extender oil shall be a resinous, high flash point, aromatic hydrocarbon conforming to the following:

Test	ASTM Designation	Requirement
Viscosity, SSU, at 100°F	D 88	2,500 Min.
Flash Point, COC, °F	D 92	390 min.
Molecular Analysis: Asphaltenes, percent by weight	D 2007	0.1 max
Aromatics, percent by weight	D 2007	55 min.

The paving asphalt and extender oil, when combined, shall form a material that is chemically compatible with the rubber.

The extender oil shall be added to the paving asphalt at a rate of not less than 2 percent nor more than 6 percent by weight of the paving asphalt, the exact amount to be as determined by the Engineer from recommendation by the asphalt-rubber binder supplier. The asphalt shall be at a temperature of not less than 350°F nor more than 425°F when the extender oil is added.

Rubber for use in Type 2 asphalt-rubber binder shall consist of reclaimed vulcanized rubber and shall contain not less than 20 percent nor more than 30 percent, by weight, natural rubber, when tested in accordance with ASTM Designation D 297. The rubber shall contain no particles longer than 1/4 inch in length.

The paving asphalt-extender oil blend and rubber shall be combined and mixed together in the blender unit to produce a homogeneous mixture.

The amount of rubber to be added to the paving asphalt-extender oil blend shall be not less than 17 percent nor more than 23 percent by weight of the combined mixture of paving asphalt, extender oil, and rubber. The exact amount will be as determined by the Engineer from recommendation by the asphalt-rubber binder supplier. The paving asphalt-extender oil blend shall be at a temperature of not less than 350°F nor more than 425°F when the rubber is added.

The asphalt-rubber binder shall be reacted for a minimum of 45 minutes from the time the rubber is added to the paving asphalt-extender oil blend. The asphalt-rubber binder shall be maintained at a temperature between 375°F and 425°F during the reaction period.

The viscosity of the asphalt-rubber binder after the reaction period, when tested in accordance with ASTM Designation D 2196, shall be not less than 1,500 centipoise nor more than 3,000 centipoise at 375°F (Brookfield).

The asphalt-rubber binder, after reaching the desired consistency, shall not be held at temperatures over 375°F for more than 4 hours.

AGGREGATE.

The aggregate for Type 0 rubberized asphalt concrete shall conform to 1/2 inch maximum open graded asphalt concrete aggregate specified in Section 39-2.02, "Aggregate," of the Standard Specifications.

CONSTRUCTION.

After the material has reacted for at least 45 minutes, the asphalt-rubber binder shall be metered into the mixing chamber of the asphalt concrete production plant at the percentage determined by the Engineer.

If the Contractor selects the batch mixing method, asphalt concrete shall be produced by the automatic batch mixing method as provided in Section 39-3.03A(1 b), "Automatic Proportioning," of the Standard Specifications.

When batch type asphalt concrete plants are used to produce Type 0 rubberized asphalt concrete, the asphalt-rubber binder and mineral aggregate shall be proportioned by weight.

When continuous mixing type asphalt concrete plants are used to produce Type 0 rubberized asphalt concrete, the asphalt-rubber binder shall be proportioned by an asphalt meter of the mass flow, coriolis effect type. The meter shall be calibrated in accordance with California Test 109.

Type 0 rubberized asphalt concrete shall be spread at a temperature of not less than 275°F nor more than 325°F, measured in the hopper of the paving machine. Type 0 rubberized asphalt concrete shall be placed only when the atmospheric temperature is above 45°F.

The area to which paint binder has been applied shall be closed to public traffic. Care shall be taken to avoid tracking binder material onto existing pavement surfaces beyond the limits of construction.

In addition to the requirements in Section 39-5.01, "Spreading Equipment," of the Standard Specifications, asphalt paving equipment shall be equipped with automatic screed controls and a sensing device or devices.

When paving contiguously with previously placed mats, the end of the screed adjacent to the previously placed mat shall be controlled by a sensor that responds to the grade of the previously placed mat and will reproduce the grade in the new mat within a 0.01-foot tolerance.

Should the methods and equipment furnished by the Contractor fail to produce a layer of asphalt concrete conforming to the requirements, including straightedge tolerance, of Section 39-6.03, "Compacting," of the Standard Specifications, the paving operations shall be discontinued and the Contractor shall modify his equipment or furnish substitute equipment.

Should the automatic screed controls fail to operate properly during any day's work, the Contractor may use manual control of the spreading equipment for the remainder of that day; however, the equipment shall be corrected or replaced with alternative automatically controlled equipment conforming to the requirements in this section before starting another day's work.

Traffic shall not be allowed on the Type 0 rubberized asphalt concrete for at least one hour after final rolling operations have been completed.

When ordered by the Engineer to prevent tracking by public traffic from the surface of Type 0 rubberized asphalt concrete, prior to opening a traffic lane, sand shall be spread on the surface at the approximate rate of from one to two pounds per square yard. Sand shall be free from clay or organic material and shall be of such gradation that at least 90 percent will pass the No.4 sieve and not more than 5 percent will pass a No.200 sieve. When ordered by the Engineer, excess sand shall be removed from the pavement surface by sweeping.

MEASUREMENT AND PAYMENT.

Rubberized asphalt concrete (Type 0-asphalt rubber) will be measured and paid for by the ton in the same manner specified for asphalt concrete in Section 39-8, "Measurement and Payment," of the Standard Specifications.

Full compensation for furnishing, spreading, and sweeping sand cover shall be considered as included in the contract price paid per ton for rubberized asphalt concrete (Type 0-asphalt rubber), and no separate payment will be made therefor.