Both the materials and the source of the supply must be approved by the Engineer or the designated representative of the Engineer prior to the delivery of any materials.
(Ordinance 2007-106, App. B, adopted 3/20/07)
A.
Aggregate.
Composition of the mineral aggregate shall be of both a course aggregate and a fine aggregate and may include a mineral filler.
1.
Coarse Aggregate.
The coarse aggregate shall consist of that part of the aggregate retained on a No. 10 sieve. The coarse aggregate shall consist of clean, tough, durable fragments of stone, crushed gravel, or a combination of both, as specified herein, and shall be of a uniform quality throughout free from dirt, organic or other injurious matter occurring either freely in the material or as a coating of the aggregate. The coarse aggregate shall have a maximum percent abrasion of 40 when subjected to the Los Angeles Abrasion Test (Tex-410-A) and a maximum percent loss of 30 when subjected to the 5 cycle Magnesium Sulfate Soundness Test (Tex-411-A).
2.
Fine Aggregate.
The fine aggregate shall be that part of the aggregate passing the No. 10 sieve and consist of sand and fine aggregate particles from the coarse aggregates’ material sources or a combination thereof. The sand shall be composed of durable particles free from injurious foreign matter and shall be limited to 15% of the total fine aggregate. Screenings shall be of the same or similar materials as specified for coarse aggregates. The plasticity index of that passing the No. 40 sieve shall be a maximum six (6) when tested by AASHTO T-89 and T-90. Unless otherwise shown on the plans, stone screenings are required and shall be the result of a rock crushing operation and meet the following gradation requirements, when tested in accordance with Test Method Tex-200-F, Part I.
Percent by Weight |
Passing the 3/8" sieve..... 100 |
Passing the No. 10 sieve..... 70-100 |
Passing the No. 200 sieve..... 0-15 |
3.
Mineral Filler.
The mineral filler shall consist of thoroughly dry stone dust, Portland cement, fly ash or other mineral dust approved by the Engineer or the designated representative of the Engineer. The mineral filler shall be free from foreign and other injurious matter. The mineral filler shall meet the following grading requirements when testing in accordance with Tex-200-F, unless the plans show otherwise:
Percent by Weight |
Passing a No. 30 sieve..... 95 to 100 |
Passing a No. 80 sieve, not less than..... 75 |
Passing a No. 200 sieve, not less than..... 55 |
B.
Asphalt.
The grade of the asphalt shall be AC-20. If more than one (1) type of asphaltic concrete mixture is specified for the project, only one (1) grade of asphalt will be required for all types of mixtures. The asphaltic materials shall be homogeneous, free from water, and shall not foam when heated to 350°F. The material shall meet the following requirements:
ASPHALT CEMENT | ||
|---|---|---|
Viscosity Grade | AC-20 | |
Property | Min. | Max. |
Viscosity, | ||
140° F, poises | 1600 | 2400 |
275° F, poises | 2.5 | – |
Penetration,77°F | ||
100g, 5 sec | 55 | – |
Flash Point, C.O.C., F | 450 | – |
Solubility in Trichloroethylene, % | 99.0 | – |
Spot Test | Negative | |
Tests on Residue from Thin Film Oven Test: | ||
Viscosity, 140°F, poises | – | 6000 |
Ductility, 77°F,5 cm per min., cm | 70 | –- |
All asphalt shall be obtained from TxDOT pretested stock.
Asphalt material for the prime coat shall be MC-30 and asphalt material for the tack coat shall be RC-250 or SS-1 and must meet the following requirements:
CUTBACK ASPHALT | ||||
|---|---|---|---|---|
Type-Grade | MC-30 | RC-250 | ||
Property | Min. | Max. | Min. | Max. |
Kinematic Viscosity @ 140° F, cst | 30 | 60 | 250 | 400 |
Water, percent | – | 0.2 | – | 0.2 |
Flash Point, T.O.C., F | 100 | – | 80 | – |
Distillation Test: Distillate, percentage by volume of total distillate to 680° F | ||||
to 437°F | – | 25 | 40 | 75 |
to 500°F | 40 | 70 | 65 | 90 |
to 600°F | 75 | 93 | 85 | – |
Residue from distillation, volume % | 50 | – | 70 | – |
Tests on Distillation Residue: | ||||
Penetration, 100 g, 5 sec., 77°F | 120 | 250 | 80 | 120 |
Ductility, 5 cm/min, 77°F, cm | 100* | – | 100 | – |
Solubility in Trichloroethylene, % | 99.0 | – | 99.0 | – |
Spot Test | Negative | Negative | ||
*If the penetration is more than 200 and the ductility at 77° F is less than 100 cm, the material will be acceptable if its ductility at 60° F is more than 100. |
ANIONIC EMULSIONS | ||
|---|---|---|
Type-Grade | SS-1 | |
Property | Min | Max |
Viscosity, Saybolt Furol at 77° F, sec | 20 | 100 |
Sieve Test, % | - | 0.10 |
Miscibilty (Standard Test) | Passing | |
Cement Mixing, % | - | 2.0 |
Storage Stability, 1 day, % | - | 1 |
Freezing Test, 3 cycles* | Passing | |
Distillation Test: | ||
Residue by Distillation, % by weight | 60 | - |
Oil Distillate, % by volume of emulsion | - | 1/2 |
Tests on Residue from Distillation: | ||
Penetration at 77°F, 100g, 5 sec | 120 | 160 |
Solubility in Trichlorethylene, % | 97.5 | - |
Ductility at 77° F, 5 cm/min, cm | 100 | - |
*Applies only when the material is designated for winter use. |
All prime coat or tack coat materials shall be obtained from TxDOT pretested stock.
C.
Hot-Mix Asphalt Concrete.
Design Mixes. After being tested in accordance with these specifications and current Texas Department of Transportation methods, the design mixes and materials are subject to approval of the Engineer or the designated representative of the Engineer. Design mixes and density and stability tests are the Contractor’s responsibility and made at his expense. All certified test results, stating compliance with the specified requirements, for both the asphaltic materials and aggregates shall be furnished to the City of Magnolia, Engineer or the designated representative of the Engineer.
Density and Stability Requirements. Laboratory density and stability of the mixture shall be designed and tested in accordance with the methods outlined in the Texas Department of Transportation C-14 and meet the following:
Density % | Stability % | ||
|---|---|---|---|
Min. | Max. | Optimum | Not Less Than |
95 | 99 | 96 | 35 |
The compacted thickness of the mixture(s) used shall be as specified on the plans.
1.
Hot-Mix Asphaltic Concrete Base Course - Type “B”.
Master Grading Requirements for the Aggregates | |
|---|---|
Sieve Sizes | Total Percent Passing, by Weight |
1-1/2 inch | – |
1-1/4 inch | – |
1-inch | 100% |
7/8 -inch | 95 - 100% |
5/8 -inch | 75 - 95% |
1/2-inch | – |
3/8 -inch | 60 - 80% |
1/4-inch | – |
No. 4 | 40 - 60% |
No. 10 | 27 - 40% |
No. 40 | 10 - 25% |
No. 80 | 3 - 13% |
No. 200 | 1 - 6%* |
VMA % Minimum | 12 |
*2 - 8 when Test Method Tex-200-F, Part II (Washed Sieve Analysis) is used. |
The asphaltic material shall form three percent (3%) to eight percent (8%) of the mixture by weight.
2.
Hot-Mix Asphaltic Concrete Surface Course - Type “D”.
Master Grading Requirements for the Aggregates. | |
|---|---|
Sieve Sizes | Total Percent Passing, by Weight |
1-1/2 - inch | – |
1-1/4 - inch | – |
1 - inch | –- |
7/8 - inch | –- |
5/8 - inch | –- |
1/2 - inch | 100% |
3/8 - inch | 85 - 100% |
1/4 - inch | –- |
No. 4 | 50 - 70% |
No. 10 | 32 - 42% |
No. 40 | 11 - 26% |
No. 8 | 04 - 14% |
No. 200 | 1 - 6%* |
VMA % Minimum | 14 |
*2–8 when Test Method Tex-200-F, Part II (Washed Sieve Analysis) is used. |
The asphaltic material shall form four percent (4%) to eight percent (8%) of the mixture by weight.
D.
Type of Plant.
Mixing plants must be approved by the Engineer or the designated representative of the Engineer and have the capacity for producing mixtures that meet the specifications. Continuous mixing type and weight batching-type are both acceptable. The plant must have acceptable conveyors, power units, aggregate handling equipment, hot aggregate screens and bins, and dust collectors. The plant must provide equipment to adequately supply materials in accordance with the plant’s rated capacity and produce finished material within the specified tolerances. Essential equipment includes cold aggregate bins and proportioning device, dryer, screens, aggregate weight box and batching scales, mixer, asphalt storage and heating devices, and asphalt measuring devices.
(Ordinance 2007-106, App. B, adopted 3/20/07)
A.
Screening and Proportioning.
Screening capacity and bin sizes shall be adequate to screen and store the amount of aggregate required to properly operate and keep the plant in continuous operation at full capacity.
B.
Drying.
The mineral aggregate drying shall be done in a manner such that fine particles will not be lost with the furnace gases. A dust collector system will be required if forced draft is used. The Engineer or the designated representative of the Engineer may require that a dust collector system be used during forced draft if a substantial amount of the finer particles are escaping. The aggregate shall be continuously agitated during heating in a suitable apparatus in which the temperature can be efficiently controlled so that the aggregate will not be damaged and the finished mixture will have a temperature of between 250 degrees and 375 degrees Fahrenheit.
A recording thermometer shall be used to record the temperature of the aggregate as it leaves the dryer. The temperature record shall be a 24-hour chart, and may be equipped to record both the temperature of the rock and the temperature of the aggregate incorporated into the batch. The dryer(s) shall be of adequate size to heat and dry the required amount of aggregate to keep the plant in continuous operation.
C.
Weigh Box.
Tight cut-off gates shall be provided on the storage bins so that mineral aggregates will not leak into the weigh box. The weigh box shall be of a sufficient capacity to hold a complete batch of aggregate without wasting or leveling by hand. The weigh box shall be designed so that the entire batch will quickly discharge into the mixer. The weigh box shall have an open top so that any excess of one (1) size of mineral aggregate may be removed by the operator, during charging. The weigh box shall have a close fitting and quick operating cut-off gate so that no mineral aggregate will leak into the mixer.
D.
Scales.
Either the springless dial type or the multibeam-type scales may be used for weighing the different grades of mineral aggregate. If using a springless dial type, an adjustable indicating pointer shall be required for each grade of the mineral aggregate allowing for an accurate setting of the weight. If using a multibeam-type, there shall be sufficient weighing beams to weigh each grade of aggregate separately. All scales shall have a tare beam for balancing. The beam scale is also required to be equipped with a tell-tale dial indicator of the springless dial type indicating over and under load of at least 50 pounds. Scales that are not accurate within four (4) pounds per 1,000 pounds net load will not be considered adequate. The scales shall be insulated against shock or vibration so that neither case shall interfere with accurate weighing.
E.
Mixing.
1.
The mixer shall be the twin-pug-mill type and shall have a capacity of not less than 2,000 pounds in a single batch. The positioning and number of blades shall be sufficient to give a uniform and complete circulation of the batch in the mixer from the center to the four (4) ends of the mixer arms and then back to the center. A mixer will be considered inadequate if it fails to perform a uniform and thorough mixing with the asphalt cement and the aggregate, or it has a tendency to segregate mineral aggregate. Mixer determination will be made by mixing a standard batch for the required time, and then dumping out the batch in order to take samples from different parts of the batch for testing.
2.
All mixers shall be provided with automatic time locks on the discharge gates and weigh box and will be locked for a period of 45 seconds after all of the mineral aggregate have been introduced into the mixer. The mixture shall have a temperature of 300 degrees to 375 degrees when discharged. The mixer dump door shall be tight to the dry mineral aggregate or dust so that there will be no spilling from the pug mill. All mineral aggregate shall be thoroughly mixed for a period of five (5) to ten (10) seconds before the asphalt cement is added. Mixing will then continue for the required time, or longer if necessary to produce a mixture with uniform consistency.
F.
Heating and Weighing Asphalt.
1.
Storage for the asphalt cement shall be adequate to meet the requirements of the plans. Asphalt cement in storage shall be heated by steam coils, tight enough to prevent moisture from leaking into the asphalt. Steam for heating shall not be at a temperature in excess of 400 degrees Fahrenheit. Direct fire heating of asphalt shall not be permitted.
2.
The steam heating system shall insure that uniform draw-off heat of the asphalt cement is maintained between 250 degrees and 350 degrees Fahrenheit at the asphalt cement bucket. The temperature shall be maintained with an efficient and positive control of the heat beyond 250 degrees Fahrenheit, either before or during mixing with the mineral aggregate.
3.
The asphalt cement draw-off valve shall be of a quick cutoff type that will not leak any asphalt into the bucket after the required weight of the asphalt cement has been drawn. The asphalt supply line must be of a circulating type, and must be equipped with a recording thermometer indicating the temperature of the asphalt at the draw-off valve. The recording thermometer may be a combination thermometer used for recording the temperature of the aggregate.
4.
The asphalt cement shall flow from the asphalt cement weigh bucket into the mixer for approximately the full width of the mixer so as not to deposit the asphalt cement in the mixer in one (1) place. Scales used for weighing the asphaltic cement shall be of springless dial type arranged for quick adjustment at zero to provide for the change in tare. A pointer will indicate the weight of the asphaltic cement required in one (1) batch.
(Ordinance 2007-106, App. B, adopted 3/20/07)