602 - HOT MIX ASPHALT (HMA) CONSTRUCTION (Quality Control/Quality Assurance (QC/QA))
600-10 (2) Preparation of Mineral Aggregate. When the mineral aggregate is composed of 2 or more ingredients,
combine as shown in the approved JMF.
a.Temperature Requirements. Dry the aggregate fo r the mixture and heat to a temperature to obtain an asphalt-aggregate mixture temperature immediately after mixing within the 75 to 150 second Saybolt viscosity range of the aspha lt binder used. Obtain the temperature for this viscosity range from the MRC or the Asphalt Binder Producer. No mixing or compaction temperatures are to exceed 340ºF without approval from the Field Mate rials Engineer. The minimum temperature may be revised by the DME provided it is demonstrated that satisfactory results may be obtained at a lower temperature. In such event, deliver the HMA to the paver at a temperature sufficient to allow the material to be satisfactorily placed and comp acted to the specified density and surface tolerance requirements.
3.Preparation of HMA. Introduce asphalt binder into the prepared aggregate in the proportionate amount determined by the P br in the JMF.
a.Basis of Rejection. HMA will be rejected if th e aggregate, as it is discharged from the drum or the pugmill, contains sufficient moisture to cause foaming of the mixture, or if the temperature of the aggregate is such that the as phalt-aggregate mixture temperatur e is outside the range specified in SECTION 601 .
b.Mixing Time. Operate drum mixers at a rate to provide uniform aggregate coating in a continuous operation. For batch and continuous ty pe plants, the minimum wet mixing time is 40 seconds. In all cases, mix a sufficient time to produce a uniform mixture in which all the aggregate particles are thoroughly coated. On batch plants, begin the timing at the start of the asphalt binder introduction into the pugmill, and end upon the opening of the discharge gate. For continuous flow plants, mixing time in seconds shall equal: [pugmill dead capacity in pounds] divide d by [pugmill output in pounds per second].
c.Manufacturer’s Specifications. Operate all drying, pumping and mixing equipment within the limits specified by the manufacturer, unless it can be demonstrated to the satisfaction of the Engineer that such limits may be exceeded without detriment to the HMA. (d) Batcher Operation. Coordinate HMA batchers (Gob Hoppers) with the plant production rate at all times so the hopper is more than ¾ full before the gates open, and the gates close before material can drop through the gob hopper directly into the surge bin, weigh hopper or truck. (e) Wasted Material. Wasted mate rial is not measured for pay. If after an interruption of production, the drum-mixer contains cold, uncoated or otherwise unsuitable material, waste material through a diversion chute. In a continuous or batch plant drier, waste unsuitable material through the pugmill. At the end of a production run, waste any segregated material in the cone of the storage bin.
4.End of Day Quantities. At the end of each day of production provide the E ngineer with a document signed by the Plant Foreman or the Project Manager listing the dry weight of each aggreg ate, mineral filler, RAP, and WMA chemical or organic additive; the tons of asphalt binder, the tons of anti-strip agent used for the project during the day, and the tons of water used in the WMA foaming process. The dry weight is the tons of the material less the water content.
b.Road Surface Preparation.
1.Preparation of Earth Su bgrade. When the HMA is placed on a prepared subgrade, and unless other subgrade preparation is called for in the Co ntract Documents, perform the following: At all grade control points, such as existing pavements and bridges, excavate the subgrade according to the specified grades and lines, prior to any subgrade treatment. Prior to the delivery of materials for the base course, prepare the subgrade surface by sprinkling with water, lightly scarifying wh ere necessary, and blad ing and rolling, until the proper crown is obtained. Disturb the originally compacted crust or top portion of the subgrade as little as possible. Maintain the subgrade as pr epared until it is covered with the base course. Repair any defects which may develop, at the Contractor’s expense, to the satisfaction of the Engineer. (2) Trimming of Subgrade (Untreated, Treated or Modi fied), Aggregate Base or Granular Sub-base for HMA Pavement. Before placing the subsequent layer of the pavement structure, trim the subgrade (untreated, treated or modified), aggregate base or granular subbase. Use an auto mated, electronically controlled machine that trims with a rotary cross-shaft trimmer to establish and control the line, grade and typical cross-section as shown in the Contract Documents. The Engineer may waive the use of automatically controlled equipment on areas of narrow width or 602 - HOT MIX ASPHALT (HMA) CONSTRUCTION (Quality Control/Quality Assurance (QC/QA))
600-11 irregular dimensions. Operate all trimming equipment far enough in advance of the paving operation to allow ample
opportunity to check the grade and make any needed corrections. Prior to paving, construct ditches and drains to drain the highway effectively. Maintain the finished subgrade in a smooth and compacted condition to readily drain. Do not place pavement upon a frozen or muddy subgrade.
3.Preparation of an Existing Asphalt Pavement. Clean the surface to remove all foreign material and broom to remove dust. Excavate areas shown in the Contract Documents to be patched to a depth directed by the Engineer. Fill with HMA and compact.
4.Preparation of an Existing Concrete or Brick Pavement. Clean all foreign material and broom to remove dust. Clean and fill cracks and joints, and construct surface leveling as shown in the Contract Documents.
5.Tack Coat. Prior to placing the HMA, apply a tack coat to the existing surface, as shown in the Contract Documents. When warranted by weather conditions, the Engin eer may authorize a change in the asphalt for tack coat. When such changes are made, the price per ton of material being used will be the unit price bid for the material designated in the contract plus or minus the difference in th e invoice price per ton of the 2 materials at the refinery as determined at the time of application.
c.Weighing Operations. See SECTION 109 for details regarding weighing operations.
d.Hauling Operations . Schedule operations to minimize hauling over a surface course. Deliver HMA to the paver at a temper ature sufficient to allow the material to be placed and compacted to the specified density and surface tolerance.
e.Paving Operations. Except when placing SM-4.75A, SM-9.5A or SR-9.5A asphalt mixtures, remix the material transferred from the hauling unit, prior to placement. Use equipment such as a mobile conveyor, material transfer device, shuttle buggy material transfer vehicle, material transfer paver or paver with remixer conveyor system. After starting the project with the equipment listed above, and after producing HMA pavement density within the limits specified in TABLE 602-7 , the Engineer will consider other types of equipment or modifications to pavers that will produce less segregation. The use of equipment as noted above shall not relieve the Contractor of the responsibility to comply with TABLE 602-7 . The Engineer will check the pavement for longitudinal streaks and other irregularities. Make every effort to prevent or correct any irregularities in the pavement, such as changing pavers or using different and additional equipment. Do not raise (dump) the wings of the paver receiving hopper at any time during the paving operation. The Engineer may waive this requirement if it is determined that raising (dumping) the wings will not produce detrimental segregation. If segregation or irregularities in the pavement surface or de nsity are noted, review the plant, hauling and paving operations and take correct ive action. The recommendations made in KDOT’s "Segregation Check Points" sh ould reduce the segregation and irregular ities to an acceptable level. Copies of KDOT’s "Segregation Check Points" may be obtained from the KDOT District Of fice or Field Engineer. Spread the HMA and finish to the specified crown and grade using an automatically controlled HMA paver. Operate the paver at a speed to provide a uniform rate of placement without undue interruption. At all times, keep the paver hopper sufficiently full to prevent non-uniform flow of the HMA to the augers and screed. If the automatic grade control devices break down, the E ngineer may allow the paver to operate to the close of the working day, provided the surface is satisfactory. Do not operate the paver without working automatic control devices upon another lift that was laid without automatic controls.
1.Surface Quality. Spread the HM A without tearing the surface. Strike a finish that is smooth, free of segregation, true to cross section, uniform in density and texture and free from surface irregularities. If the pavement does not comply with all of these requirements, plant production and paving will be suspended until the deficiency is corrected. The Engineer will check segregation and uniformity of density using methods outlined in Section 5.8.3 - Segregation Check Using the Nuclear Density Gauge, Part V. Fo r shoulders with a plan width of less than or equal to 3 feet, and placed at the same time as the traveled way, do not take nuclear density readings on the shoulder nor within 1 foot of the shoulder unless the paveme nt section is uniform across the entire roadway. The acceptable criteria for density uniformity are in TABLE 602-7 . 602 - HOT MIX ASPHALT (HMA) CONSTRUCTION (Quality Control/Quality Assurance (QC/QA))
600-12 Table 602-7: Segregation and Uniformity of Density Check
Mix Designation Maximum Density Range (highest minus lowest) Maximum Density Drop (average minus lowest) All 4.4 lbs./cu. ft. 2.2 lbs./cu. ft. Whenever the results from 2 consecutive density profiles fail to comply with both of the requirements listed in TABLE 602-7 , plant production and paving will be suspended. Fo llow the procedures listed in the Profile Evaluation Subsection of Section 5.8.3-Segregation Check Using the Nuclear Density Gauge, Part V until production may be resumed. Joint density testing and the associated requirements listed below do not apply for HMA lift thicknesses less than or equal to 1 inch. Evaluate the longitudinal joint density using methods outlined in Section 5.8. 4-Joint Density Evaluation Using the Nuclear Density Gauge, Part V. Although it is the Contractor’s responsibility to perform the joint density evaluation, the Engineer may make as many independent joint density verifications as deemed necessary at the random sample locations. The Engineer’s results will be used for acceptance for joint density, whenever available. The acceptable criteria for joint density are in TABLE 602-8 . TABLE 602-8: JOINT DENSITY REQUIREMENTS Nuclear Gauge Readings Requirement Interior Density minus Joint Density ≤ 3.0 lbs./cu. ft. OR Joint Density ≥ 90.00% of G mm If the results of 2 consecutive density profiles fail to comply with TABLE 602-8 , the plant production and paving operations will be suspended. Follow the procedures listed in the Joint Evaluation Subsection of Section 5.8.4-Joint Density Evaluation Using the Nuclear Density Gauge, Part V, until production may be resumed.
2.Leveling Courses. In general, sp read leveling course mixtures by the method to produce the best results under prevailing conditions to secure a smooth base of unifo rm grade and cross section. The leveling course may be spread with a properly equipped paver or motor grader.
3.Lift Thickness. Except for leveling courses or when shown otherwise in the Contract Documents, TABLE 602-9 applies. The Engineer may adjust lift thickness to utilize the most efficient method of acquiring specified density and surface quality. The minimum lift thickness for any HMA mixture is 3 times the nominal maximum aggregate size, unless otherwise designated in th e Contract Documents or a pproved by the Engineer. TABLE 602-9: NOMINAL COMPACTED THICKNESS Lift Maximum Nominal Compacted Thickness Surface 2 inches Base 4 inches
4.Grade Control. Achieve grade control by use of 1 or more of the following grade reference devices. Approval of any of these devices will be based upon satisfactory performance.
a.Traveling Stringline. Attach a traveling stringline or ski type attachment, a minimum length of 30 feet, to the paver and operate parallel with its line of travel.
b.Reference Shoe. Attach a short reference shoe or joint matching de vice to the paver for control in matching surface grades along longitudinal joints.
c.Erect Stringline. Use an erected stringline cons isting of a tightly stretched wire or string offset from and parallel to the pavement edge on 1 or both sides. Erect the stringline parallel to the established pavement surface grade and support at in tervals as necessary to maintain the established grade and alignment.
d.Stringless Paving. Control line, grade and pavement cross-section as shown in the Contract Documents. Use electronic guidance systems that meet the requirements and tolerances listed in SECTION 802 . Horizontal control is guided by GPS. Vertical control is guided by Total Stations. GPS will not be allowed for Vertical control. 602 - HOT MIX ASPHALT (HMA) CONSTRUCTION (Quality Control/Quality Assurance (QC/QA))
600-13 When paving on a fresh subgrade that has not been trimmed by an automatically controlled
machine, use an erected stringline or stringless paving to establish grade. Use either of these options on the first or second lift. When directed by the Engineer, use an erected stringline or stringless paving to match grade control points such as bridges.
5.Compaction of Mixtures. Uniformly compact th e HMA as soon after spreading and strike-off as possible without shoving or tearing. Use self-propelled rollers operated at speeds slow enough to avoid displacement of the HMA. Equipment and rolling procedures whic h result in excessive crushing of the aggregate are prohibited. Use a sufficient number and weight of rollers to compact the HMA to the required density, using a minimum of 2 rollers. See subsections 602.4e.(6) for exceptions to the minimum number of rollers. Perform final rolling with a steel roller unless otherwise specified. On th e final pass, operate finishing, vibratory rollers in the static mode. Coordinate the frequency, amplitude and forward speed of the vibratory roller to achieve satisfactory compaction without objectionable undulations. For HMA lifts wi th a compacted thickness less than 1¼ inch, operate vibratory rollers in the static mode. Keep rollers in operation as necessary so all parts of the pavement receive substantially equal compaction at the proper time. The Engineer will suspend HMA delivery to the project at any time proper compaction is not being performed. Remove, replace with suitable material and finish acco rding to these specifications any mixture that becomes loose, broken, mixed with foreign material or which does not comply in all respects with the specifications.
6.Density Requirements.
a.For mixes with a specified thickness greater than or equal to 1 ½ inches: For lots 1 and 2, control density as shown in subsection 602.4e.(6)(b) . Before beginning production, the Contractor has th e option to accept the pay adjustme nt for density on both Lots 1 and 2, or only Lot 2. If the Contractor choose s to accept the pay adjustments for density on both Lots 1 and 2, or only Lot 2, control the density as shown in subsections 602.4e.(6)(a)(i-ii) . If the Contractor chooses to accept pay adjustment for density on Lot 1, the pay adjustment can not be rejected on Lot 2. (i) HMA Overlay. For lots 3 and greater, the lot density requirements and appropriate density pay adjustment factors are shown in subsection 602.9b. as the percent of the G mm value based on the average of the density tests. The standard lot size is 10 density tests. Smaller lot sizes may result as outlined in TABLE 602-10 . Normally, the G mm value used to calculate the density percentage is the average value of all G mm tests conducted the same day the lot was placed and compacted. If less than 3 G mm values were obtained that day, use the mo ving average value (last 4 tests prior to the end of the day). When starting a mix and less than 4 G mm values have been determined, use the average value of those ava ilable at the end of each day. (ii) HMA Surface, HMA Base and HMA Pavement. For lots 3 and greater, the lower specification limit (LSL) value for density is given in subsection 602.9c. along with the appropriate density pay adjustment factor equations. The LSL value is given as a percentage of G mm. Lot density is determined using the measured density values for all sublots in a lot. The standard lot size is 10 density tests. Smaller lot sizes may result as outlined in TABLE 602-10 . Normally, the G mm value used to calculate the density percentage is the average value of all G mm tests conducted the same day the lot was placed and compacted. If less than 3 G mm values were obtained that day, use the moving average value (last 4 tests prior to th e end of the day). When starting a mix and less than 4 G mm values have been determined, use the aver age value of those available at the end of each day.
b.For mixes with a specified thickness less than 1½ inches: These mixes will not have a density pay adjustment. Control density using an approved rolling procedure with random nuclear gauge de nsity determinations. Include a method for controlling density in the QCP. Designate a "Compaction Foreman". This person shall control compaction procedures, review nuclear gauge results as they are obtain ed, adjust compaction procedures as needed to optimize compaction and report any changes in the compaction process and results of nuclear gauge testing to the Engineer. The compaction foreman may also be the nuclear gauge operator. The nuclear gauge operator shall continuously monitor compaction procedures. As a minimum, take 10 random nuclear gauge density determinations per day and report results to the Engineer. Throughout the day, nuclear gauge results shall be available for review by the Engineer. The 602 - HOT MIX ASPHALT (HMA) CONSTRUCTION (Quality Control/Quality Assurance (QC/QA))
600-14 compaction foreman shall document at a minimum of once every 2 hours th at the approved rolling
sequence is being followed. Documentation incl udes roller passes, the mat temperature at each pass, amplitude setting of rollers and roller speed. Provide the documentation to the Engineer. Determine and periodically update an approved rolling procedure and pe riodically, as outlined in this section. As a minimum, evaluate the initial rolling procedure using 3 rollers. If the hot mix plant is operating at over 275 tons per hour, use a minimum of 4 rollers in the initial evaluation. Operate vibratory rollers according to SECTION 151 . Evaluate HMA paver screed operation with the nuclear gauge at various vibration settings. For screed evaluation, take the nuclear gauge readings directly behind the screed and before rolling. The Compaction Foreman and Engineer will evaluate the densities obtained with the various roller combinations and screed settings to determine the initial approved rolling procedure. Together, the Compaction Foreman and Engineer will determine when new rolling procedures are required. HMA production may be stopped by the Compaction Foreman or Engineer whenever rolling is not being performed according to the approved rolling procedure.
c.For all lots, achieve the maximum density before the temperature of the HMA falls below 175 F. When using WMA, achieve the maximum density before the temperature of the WMA falls below oF. Do not crush the aggregate. Wh en the mat temperature falls below 175 F or 165F for WMA, roller marks may be removed from the mat with a self-propelled static steel roller. TABLE 602-10: DAILY PRODUCTION VS NUMBER OF SUBLOTS AND TEST REQUIREMENTS Daily Production (tons) Number of Sublots No. of Cores or Nuclear Density Tests** No. of Verification Cores or Nuclear Density Tests** 0-599 3* 6* 3* 600-999 4* 8* 4* 1000 or more 5 10 5 *Minimum number for mixes with a specified thickness of 1½ inches or greater: The Contractor may choose to obtain the number required for 1000 or more tons. If the Contractor choose s to test 5 sublots (10 tests) , KDOT will obtain 5 verification tests. **For mixes with a specified thickness less than 1½ inch: Verification testing may be perfo rmed, but is not required. Additional testing may be performed by the Cont ractor. A minimum of 10 tests are required.
7.Contact Surfaces. Coat contact su rfaces of curbing, gutters, manholes a nd similar structures with a thin uniform coating of asphalt material. Pl ace the HMA uniformly high n ear the contact surfaces so that after compaction it shall be approximately ¼ inch above the edge of such structures.
8.Adjustment of Manholes (Set Price). When required, this work will be performed and paid for under SECTION 816 .
9.Construction Joints.
a.Transverse Construction Joints. Use a met hod of making transverse construction joints to provide a thorough and c ontinuous bond, provide an acceptable surface texture and meet density requirements. Do not vary the surface elevation more than 3/16 inch in 10 feet, when tested longitudinally across the joint. When required, repair the joints or paving operations will be suspended.
b.Longitudinal Joints. Construct well bonded a nd sealed longitudinal joints to obtain maximum compaction at the joint. If deemed necessary by the Engineer to properly seal the joint, apply a light coat of asphalt emulsion or asphalt binder to the exposed edge before the joint is made. Before placing the fresh HMA against a cut joint or against old pavement, spray or paint the contact surface with a thin uniform coat of asphalt emulsion or asphalt binder. Where a finishing machine is used, make the longitudinal joint by depositing a sufficient amount of HMA to form a smooth and tight joint. Offset the longitudinal joint in successive courses by 6 to 12 inches. Comply with traffic lane edges for the width of the surf ace of top course placement.
10.Shoulder Surfacing and Widening. When the placement width of shoulders or uniform width widenings is less than can be accomplished with a regular paver, spread each course with a me chanical spreading device.
11.Rumble Strips. When designated, construct rumble strips according to the Contract Documents.
f.Maintenance of Traffic . Maintain traffic according to DIVISION 800 and the following:
Source: Kansas Standard Specifications for State Road and Bridge Construction, 2015 Edition. Pages 247–251 of 978.