Following topics to be discussed in this article.
1 Scope
2 References
3 General
3.1 Roadways
3.2 Subgrades and Subbases
3.3 Stage Construction
4 Materials
4.1 Asphalt Prime Coat
Table I – Asphalt Prime Coat
4.2 Sand
4.3 Asphalt Cement
4.4 Tack Coat
4.5 Aggregate
4.6 Asphalt Concrete Mixtures
Table II – Asphalt Concrete Base Course
Table III – Asphalt Concrete Surface Course
Table IV – Crushed Aggregate Base (AASHTO M 147)
Table V – Quality Control Tests
Table VI – Job-Mix Formula Tolerances per Single Test
5 Placement Requirements
5.1 Prime Coat
5.2 Asphalt Base Course
5.3 Tack Coat
5.4 Asphalt Surface Course
6 Weather and Temperature Precaution
7 Equipment
7.1 Prime Coat
7.2 Asphalt Base Course
7.3 Tack Coat
7.4 Asphalt Surface Course
8 Construction Methods – Prime Coat
8.1 General
8.2 Asphalt Prime Coat Application
8.3 Sand Cover Application
9 Construction Methods – Asphalt Base Course, Tack Coats and Asphalt Surface Course
9.1 General
9.2 Preparing the Mixture
9.3 Placing the Mix
9.4 Joints
1. Scope
This Procedure details the materials, equipment and operations required for the construction of asphalt concrete paving and roadways. Asphalt Institute MS-2 and MS-22 are part of this specification.
2. References
See Civil Engineering Works Standards and Codes .
3. Construction Of Asphalt Concrete Paving and Roadways
Areas of permanent work requiring compacted asphalt concrete paving are indicated on design drawings. The asphalt paving system shall consist of an asphalt concrete surface course over an asphalt concrete base course and prepared and compacted subgrade. The prepared and compacted subgrade shall comply with the applicable requirements of SES C02-S01 and C02-S02.
The surface of nonasphalt base courses shall be primed as specified below prior to constructing asphalt surface courses. Asphalt surface course for such areas shall consist of a mixture of coarse and fine aggregate with or without mineral filler, uniformly mixed with asphalt cement, then placed and compacted in accordance with this specification. Asphalt surface course shall be constructed in one or more layers to conform to the lines, grades, thickness, and typical cross sections shown on the design drawings.
3.1 Roadways
3.1.1 Hot-mixed, hot-laid asphaltic concrete paving shall consist of an asphalt concrete base and asphalt concrete surfacing, composed of graded aggregates uniformly coated with asphaltic cement. The materials used and densities acquired shall conform to this specification.
3.1.2 Crushed aggregate base shall be composed of well graded aggregates compacted in two equal lifts to 97 percent dry density as specified in ASTM D 1557. The California Bearing Ratio (CBR) shall be 70 percent minimum as specified in ASTM D 1883. This finished crushed aggregate base shall be spray-treated with a cut-back liquid asphalt spray of Grade MC-70 at a temperature of 40 to 80 C (100 to 180 F). The materials shall conform to this specification.
3.1.3 Primary roads, secondary roads, access ways and parking areas shall conform to 3.1.1 and 3.1.2.
3.1.4 Tertiary road pavement shall consist of crushed aggregate base as in 3.1.2.
3.1.5 The shoulders of roadways shall conform to 3.1.2.
3.2 Subgrades and Subbases
3.2.1 Roadways and shoulders shall be built on approved subgrades and subbases that meet the requirements of SES C02-S01 and C02-S02.
3.2.2 Roadway subgrades and subbases shall conform to the lines, grades and typical cross-section given on the design drawings.
3.3 Stage Construction
Stage construction may be employed by initially constructing the aggregate base course and asphalt base course to accommodate construction traffic. The asphalt surface course may then be constructed near completion of project upon re-preparation of the base and subbase and correction of deficiencies.
4. Materials
4.1 Asphalt Prime Coat
The grades, specification references, and application temperatures for the liquid asphalt primer are given in Table . The grade used shall be as dictated by local conditions and shall be approved by Company.
Table I – Asphalt Prime Coat
4.2 Sand
Sand cover shall be clean, granular, mineral material meeting the following grading requirements. When tested with laboratory sieves, 100 percent shall pass the 4.75 mm (No. 4) sieve and from zero to 2 percent shall pass the 75 micron (No. 200) sieve.
4.3 Asphalt Cement
Asphaltic cement shall be prepared from petroleum. It shall be uniform in character, free from water and shall not foam when heated to 175 C (350 F). It shall meet Grade 60-70 in conformance with ASTM D 946 or SASO 915.
4.4 Tack Coat
4.4.1 The tack coat shall be applied between the asphalt base course and the surface course using liquid asphalt Grade RC-70 (cut-back) meeting the requirement of AASHTO M 81.
4.4.2 Oiling of crushed aggregate bases shall be applied directly to the approved compacted base using liquid asphalt Grade MC-70 (cut-back) meeting the requirement of AASHTO M 82.
4.5 Aggregate
4.5.1 The mineral aggregate for the surface course mixture shall be crushed stone, crushed gravel, crushed slag, sharp-edge natural sand, mineral filler, or a combination of two or more of these materials. Fifty percent by weight of the combined coarse aggregate, other than naturally occurring rough-textured aggregate, shall consist of crushed pieces having one or more faces produced by fracture.
4.5.2 Crushed, coarse aggregate is defined for the purpose of this specification as material passing a 50 mm sieve and retained on a 2 mm (No. 10) sieve.
4.5.3 Fine aggregate is defined as material passing the 2 mm (No. 10) sieve and retained on the 75 micron (No. 200) sieve.
4.5.4 Filler is defined as material passing the 75 micron (No. 200) sieve. If filler in addition to that naturally present in the aggregate is necessary, it shall consist of thoroughly dry stone dust, volcanic ash or Portland cement. As delivered to the mixer, it shall be free from lumps of loosely bonded aggregations. The use of up to one (1) percent of hydrated lime may be used in the mix, particularly with aggregates that are subject to stripping. Fly ash shall not be used as filler. Mineral filler shall meet the requirements of ASTM D 242.
4.5.5 If steel slag aggregates are used to make asphalt concrete, no aggregates greater than 4.75 mm (No. 4 sieve) shall be used in the mixture. Up to 50 percent of the material passing the 4.75 mm (No. 4) sieve may consist of iron blast furnace slag aggregates or natural aggregates or a combination thereof. The rate of feed of each type of aggregate shall be maintained within 20 percent of the amount set. Adequate means shall be provided for controlling and checking the accuracy of the feeder.
4.6 Asphalt Concrete Mixtures
4.6.1 Dense Asphalt Concrete Base and Surfacing
4.6.1.1 The asphalt concrete mixtures shall consist of a uniform mixture of coarse crushed aggregate, fine aggregate, mineral filler and asphalt materials. The combined aggregates, including filler, shall meet the requirements of the following gradation using methods detailed in ASTM C 117 and C 136. AASHTO T 11 and T 27 specifications are also acceptable.
4.6.1.2 Asphalt Concrete Base Course. The job-mix formula for the asphalt concrete base course mixture shall be within the limits of Table II. Asphalt content shall be between 4.0 and 6.0 percent by weight of total mix and the grade shall be as specified in 4.3.
Table II – Asphalt Concrete Base Course
4.6.1.3 Asphalt Concrete Surface Course. The job-mix formula for the asphalt concrete surface course mixture shall be within the limits of Table III. Asphalt content shall be between 4.5 and 6.0 percent by weight of total mix and the grade shall be as specified in 4.3.
Table III – Asphalt Concrete Surface Course
4.6.2 Crushed Aggregate Base. The crushed aggregate base material shall consist of a uniform mixture of crushed coarse aggregate, fine aggregate and filler. The combined aggregates including the filler shall meet the requirements of the gradation in Table IV using methods described in ASTM C 117 and C 136.
Table IV – Crushed Aggregate Base (AASHTO M 147)
4.6.3 Quality Control of Materials. Quality control of the materials in various uses shall meet the limits of Table V.
Table V – Quality Control Tests
Table VI – Job-Mix Formula Tolerances per Single Test
5. Placement Requirements
5.1 Prime Coat
Prime coat shall be applied when the air temperature is above 10C (50 F) and rising, the air temperature being taken in the shade and away from artificial heat. Primer shall not be placed when general weather conditions are not suitable. Prime coat application temperature should be maintained as close to 70 C as practical.
5.2 Asphalt Base Course
The base course shall be laid as detailed in 5.4.
5.3 Tack Coat
Temperature of application of RC-70 tack coat shall be 49to 88 C (120 to 190 F). A temperature-volume correction shall be applied.
5.4 Asphalt Surface Course
Asphalt surface course mixture shall be placed only when the specified density can be obtained. Precautions shall be taken to compact the mixture before it cools too much, to obtain the required density. The mixture shall not be placed on wet surfaces or when weather conditions will otherwise prevent its proper handling or finishing. Asphalt surface course mixture shall be placed when the base course surface is dry and its surface temperature is at least 10 C. The temperature of asphalt mixture at the time of placing shall be between 110 C and 150 C.
6. Weather and Temperature Precaution
The minimum air temperature, in the shade, at which asphaltic concrete may be laid shall be 5 C if rising or 10 C, if falling. At the time of laying the asphalt concrete, the air temperature shall not be greater than 40 C. No construction shall be permitted during sand storms. When the weather condition may prevent proper leveling and thorough consolidation, the contractor shall stop the laying of the asphalt concrete. The restart of work shall be after SABIC approval.
7. Equipment
The mixing plant shall have a capacity sufficient to produce the asphalt mixture at the rate required for the satisfactory execution of the job and within the specified time. Equipment shall be approved by SABIC.
7.1 Prime Coat
Equipment used shall include a power broom, a power blower, or both; mechanical or selfpropelled aggregate spreading equipment that can be adjusted to uniformly spread the sand cover; a pressure distributor; and equipment for heating the asphaltic material. The distributor shall be equipped with devices and charts to provide for accurate and rapid determination and control of the amount of bituminous materials being applied per square meter of surface under the operation conditions, and shall have a tachometer, reading speeds in meters per minute.
7.2 Asphalt Base Course
Equipment for construction of the asphalt base course shall include: asphalt mixing plant; selfpowered pavers; smooth metal-bedded haul trucks with covers when required; asphalt pressure distributor; steel-wheeled, pneumatic-tired, or vibrating rollers capable of attaining the required density and smoothness; power broom or power blower.
7.3 Tack Coat
Equipment used shall include a power broom, a power blower, or both; mechanical or selfpropelled aggregate spreading equipment that can be adjusted to uniformly spread the sand cover; a pressure distributor; and equipment for heating the asphaltic material. The distributor shall be equipped with devices and charts to provide for accurate and rapid determination and control of the amount of bituminous materials being applied per square meter of surface under the operation conditions, and shall have a tachometer, reading speeds in meters per minute.
7.4 Asphalt Surface Course
Equipment for construction of the asphalt surface course shall include: asphalt mixing plant; self-powered pavers; smooth metal-bedded haul trucks with covers when required; pressure distributor; flat rollers capable of attaining the required density and smoothness; power broom or power blower.
8. Construction Methods – Prime Coat
8.1 General
The area to receive asphalt primer shall be substantially true to line and grade. It shall have a dry or slightly damp, firm, and properly prepared surface before priming operations begin. Loose and foreign material shall be removed.
8.2 Asphalt Prime Coat Application
8.2.1 The approximate application rate of asphalt primer shall be 1.0 to 2.0 L/m, and shall be such that the amount applied will be completely absorbed by the surface being treated in a period of 24 hours. The appropriate application rate shall be determined in accordance with ASTM D2995.
8.2.2 Application of asphalt primer shall be made uniformly with a pressure distributor, and within the temperature ranges specified in Table I. When heating is required, precautions shall be taken to avoid fire hazard.
8.2.3 Application shall be made only when the surface is dry or slightly damp.
8.2.4 Before beginning application, building paper shall be spread over the surface from the joint and back for a sufficient distance for the spray bar to begin spraying and be operating at full force when the surface to be treated is reached. After the asphalt is applied, the building paper shall be removed and destroyed.
8.2.5 The spray bar shall be shut off instantaneously at each construction joint to assure a straight line and the full application of asphalt prime up to the joint. If necessary to prevent dripping, a drip pan shall be inserted under the nozzle when the application is stopped.
8.2.6 A hand spray shall be used to apply primer material necessary to touch up spots unavoidably missed by the distributor.
8.2.7 After application of the asphalt primer at least 24 hours shall elapse before applying the sand cover if required.
8.3 Sand Cover Application
8.3.1 If the asphalt primer has not been completely absorbed by the treated surface 24 hours after application, sufficient sand shall be spread over the surface with a mechanical spreader to blot up the excess asphalt.
8.3.2 Before placing an asphalt surface course or surface treatment, loose sand shall be swept from the primed surface.
9 Construction Methods – Asphalt Base Course, Tack Coats and Asphalt Surface Course
9.1 General
9.1.1 The area to be paved shall be substantially true to line and grade. It shall have a dry, firm, and properly prepared surface before paving operations begin. Loose and foreign material shall be removed.
9.1.2 When the compacted base on which the asphalt surface is to be placed is a nonasphalt base, it shall be primed in accordance with section 8.
9.1.3 When the asphalt surface course is to be placed on compacted asphalt base, the base surface shall receive a tack coat of 0.1 to 0.3 L/m2 of surface. The tack coat shall be allowed to cure before placing the asphalt surface course.
9.1.4 The tack coat shall be applied on only as much base as can be covered with asphalt surface mixture in the same day.
9.1.5 When the asphalt surface course is constructed in layers, a tack coat shall be applied as specified in 9.1.3 and 9.1.4, prior to placement of each layer of the surface course.
9.2 Preparing the Mixture
9.2.1 Coarse and fine aggregates shall be stored separately at the paving plant in a manner that will prevent intermingling. Stockpiles shall be built in a manner that will
prevent segregation of aggregate sizes. If the aggregate tends to segregate during handling it shall be supplied and stockpiled in two or more sizes.
9.2.2 When necessary to blend aggregates from one or more sources to produce the combined gradation, each source or size of aggregate shall be stockpiled individually. Aggregate from the individual stockpiles shall be fed through separate bins to the cold elevator feeders and shall not be blended in the stockpile.
9.2.3 Cold aggregates shall be fed carefully to the plant so that surpluses and shortages will not occur, thus causing breaks and disrupting the continuous operation.
9.2.4 The aggregate shall be dried and heated to provide a paving mixture temperature immediately after mixing within the range of 130to 177 C.
9.2.5 Heated and dried aggregates shall be screened and stored in sizes that may easily be recombined into a gradation meeting the requirements of the job-mix formula.
9.2.6 The heated and dried aggregates shall not contain so much moisture as to cause the mixture to slump, the asphalt to foam, or the aggregate to segregate during hauling and placing.
9.2.7 The asphalt shall be heated at the paving plant to a temperature prescribed in 4.3, so that it can be uniformly applied to the aggregate.
9.2.8 Mixing time shall be the shortest time that will produce a satisfactory mixture. It shall be established by the testing laboratory based on the procedure for determining the percentage of coated particles described in AASHTO T 195 (ASTM D 2489).
9.2.9 The mixing times for surface course mixtures shall be set to achieve 95 percent of coated particles for dense aggregate and 90 percent of coated particles for
honeycombed aggregate.
9.2.10 For batch plants, dry mixing time shall not exceed 50 seconds.
9.2.11 For continuous mix plants, the mixing time shall be computed from the following formula:
Mixing time, seconds = Pugmill dead capacity, liters/ Pugmil output, liters/second
9.3 Placing the Mix
The base and surface course mixture shall be placed with an asphalt paver to provide the thickness specified on the design drawings. The minimum lift thickness shall be at least double the maximum particle size or 50 mm, whichever is more. The maximum lift thickness shall be that which can be laid in a single lift and compacted to the required uniform density and smoothness. Placing the mixture shall be a continuous operation. Irregularities shall be corrected before final compaction of the mixture. The mixture placing temperature range shall be from 110to 150 C.
9.4 Joints
Well-boned and sealed joints are required. Joins between successive days’ work shall be made in a way that ensures a through and continuous bond between the surfaces. The edge of the previously laid course shall be cut back to its full depth to expose a fresh surface, after which the hot mixture shall be placed in contact with it and raked to a proper depth and grade.
Hot smoothers or tampers shall be used to heat up the pavement sufficiently to ensure a proper bond. Before placing mixture against them, the contact surfaces of, for example cold longitudinal joints, curbs, gutters, headers and manholes shall be cleaned and painted with a thin uniform tack coat of the type specified herein. In making the joint along any adjoining edge placed by the finishing machine, just enough hot material shall be carried back to fill any space left open. This joint shall be properly arranged with the back of a rake at the proper height and bevel to receive the maximum compression under rolling. Edges on new paving shall not be feathered. Transverse or longitudinal joints accumulating mud, dust or other foreign materials shall be trimmed back so that a proper bond of asphalt concrete will be obtained at all joints.
9.5 Compacting the Mixture
The mix shall be compacted immediately after placing. Initial rolling with a steel-wheel tandem roller, steel three-wheeled roller, vibratory roller, or a pneumatic-tired roller shall follow the paver as closely as possible. If needed, intermediate rolling with a pneumatic-tired roller shall be done immediately behind the initial rolling. Final rolling shall eliminate marks from previous rolling. No kerosene, naphtha, oils or similar products shall be used to clean the roller wheels while the roller is on the mixture. In areas too small for the roller, a vibrating plate compactor or a hand tamper weighing not less than 12 kilograms and having a bearing area not exceeding
300 cm2 shall be used to achieve thorough compaction.
9.6 Acceptance Requirements
9.6.1 Density
9.6.1.1 Target density shall be determined by taking, for each lot, the average density of six laboratory-prepared specimens representing two samples (approximately 9 to 12 kg each) chosen on a random basis, taken from trucks delivering mixture to the jobsite. By quartering, each subsample shall be reduced to obtain three sample units, each of sufficient weight (approximately 1 to 1.5 kg) to prepare a specimen approximately 50 mm (2 in) in height. The specimens shall be compacted in accordance with ASTM D 1559, except that the temperature of the mixture immediately before compaction of the specimens shall be within the range specified in 9.2.4. The sample of mixture can be placed in an oven for not more than 30 minutes to maintain the temperature, but shall not be reheated if it cools before use. The compacting apparatus shall be in accordance with ASTM D 1559.
9.6.1.2 Acceptance of the compacted pavement density shall be based on the average of five density determinations for each lot of asphalt mixture placed. Cores drilled from the surface course shall be used to test the density of the pavement by either ASTM D 1188 or D 2726, whichever is applicable. Each lot of the compacted surface will be accepted when the average of the five density determinations is equal to or greater than 97 percent of the average density of the six laboratory prepared specimens, and when no individual determination is lower than 95 percent.
9.6.1.3 A lot will be equal to one day’s production. Less than a half-day’s production will not be considered a lot, but will be added to the lot immediately preceding. The location of sampling sites within a lot’s placement area will be chosen on a random basis through the use of an appropriate random numbers table.
10 Sampling and Testing
10.1 Sampling
10.1.1 Asphalt. Sampling of asphalt materials shall be in accordance with AASHTO T 40 (ASTM D 140) and SASO 916.
10.1.2 Mineral Aggregate. Sampling of sand cover and mineral aggregate shall be in accordance with AASHTO T 2 (ASTM D 75).
10.1.3 Asphalt Mixture. Sampling of the asphalt mixture shall be in accordance with AASHTO T 168 (ASTM D 979).
10.2 Testing Methods
10.2.1 General. Material samples shall be tested for the requirements of section 4 by the applicable methods specified below.
10.2.2 Asphalt. Asphalt materials shall be tested by the test methods of AASHTO designated in the applicable asphalt specification. If an AASHTO method of test procedure is not available, the equivalent ASTM method shall be used.
10.2.3 Sand. Sieve analysis of sand cover material shall be in accordance with AASHTO T 27 (ASTM C 136) and SASO 249.
10.2.4 Mineral Aggregates. Mineral aggregates shall be tested by the test methods from Table VII. Also it shall be tested with SASO 279.
Table VII – Mineral Aggregates Test Methods
10.2.5 Asphalt-Aggregate Mixture
10.2.5.1 The asphalt-aggregate mixture shall be tested for asphalt content by AAHSTO T 164 (ASTM D 2172). The mixture shall be tested for compliance with aggregate grading requirements by AASHTO T 30.
10.2.5.2 If the mixture is produced in a mixing plant having automatic controls and a printout system and the controls are in proper calibration, asphalt content compliance shall be determined from recorded data. Hot-bin analysis together with batch-weight readout data shall be used to determine composition compliance.
11 Accepting and Correcting Asphalt Surfaces
Any depressions that may develop on the finished asphalt concrete surface after the first rolling shall be remedied by loosening the surface depressions and bringing to a true surface. Any depressions shall not be noticeable until the final compaction has been made. The surface course shall be removed and sufficient new material laid to form a true even surface. The finished pavement surface shall show no deviation from the general surface and shall be within the tolerance specified in 12.2. Any portions of the completed pavement that are defective in finish, density, or composition, or that do not comply in all respects with the requirements of the specifications, shall be taken up, removed and replaced with suitable material, properly laid in accordance with this specification.
12 Quality Assurance
12.1 Submittals
12.1.1 Asphaltic Materials. A list of asphaltic materials to be used in the project shall be submitted to SABIC for approval prior to testing.
12.1.2 Test Reports. Certified test results for approved materials shall be submitted for SABIC approval at least one month prior to use on the project.
12.1.3 Job-Mix Formula. A formula of the exact percentages of aggregates and asphalt proposed for use on the project shall be submitted for SABIC approval prior to the
start of asphalt operations. The formula shall be determined by actual trial mixes or previous experience with the same materials. Changes may be directed by SABIC when deemed necessary.
12.1.4 Equipment List. Equipment list including spreading, rolling and spraying equipment shall be submitted for SABIC approval prior to the beginning of any asphalt operation.
12.2 Tolerances in Thickness and Surface
12.2.1 Thickness. The asphalt concrete surface shall be placed to the thickness shown on the project drawings. The thickness of asphalt concrete shall be measured by means of core sample extracted from the compacted base courses and surface courses. The thickness of any core sample shall be within the limits shown in Table VIII.
Table VIII – Asphalt Concrete Thickness Tolerances
12.2.2 Surface. The finished pavement surface shall show no deviation from the general surface in excess of 3 mm/m or a maximum of 5 mm when measured in the following manner. A three-meter straight edge shall be placed parallel to the centerline of the roadway so as to bridge any depression. Ordinates measured from the face of the straight edge to the surface of the pavement shall not exceed 3 mm for each meter in distance from the nearest point of contact, or a maximum of 5 mm.
12.3 Performance Requirement of Asphalt Concrete
13 Safety
Any depressions, unevenness, irregular spots or other failures occurring within 12 months after acceptance, shall be repaired by the Contractor at his own expense. Applicable requirements of HCIS SSD-29, OSHA 29CFR 1910, and contract documents shall be complied with during construction. Work permits shall be obtained from respective authorities, as required.
14 Roadway Signs
14.1 Roadway signs as detailed in design drawings shall be furnished and installed.
14.2 Royal Commission Section 02891 shall be used as a guide for detailing and erecting.
15 Pavement Marking
15.1 Pavement and roadway markings as detailed in design drawings shall be provided.
15.2 Royal Commission Section 02760 shall be used as a guide for detailing and marking.