SECTION 406 – HIGH PERFORMANCE THIN OVERLAY
406.01 Description
This Section describes the requirements for constructing high performance thin overlay (HPTO).
406.02 Materials
406.02.01 Materials
Provide materials as specified: Tack Coat Polymer Modified Emulsified Asphalt, Grade CRS-1P................................ ................................ ............ 902.01.03 HPTO ................................ ................................ ................................ ................................ .......................... 902.08
406.02.02 Equipment
Provide equipment as specified: Materials Transfer Vehicle (MTV) ................................ ................................ ................................ .............. 1003.01 HMA Paver................................ ................................ ................................ ................................ ................. 1003.03 Spray Paver................................ ................................ ................................ ................................ ................. 1003.04 HMA Compactor ................................ ................................ ................................ ................................ ........ 1003.05 HMA Plant ................................ ................................ ................................ ................................ ................. 1009.01 HMA Trucks ................................ ................................ ................................ ................................ ............... 1009.02 Provide a thin-lift nuclear density gauge according to ASTM D 2950.
406.03 Construction
406.03.01 High Performance Thin Overlay
A.Paving Plan. At least 20 days before the start of placing the HPTO, submit a detaile d plan of operation to the RE for approval as specified in 401.03.07.A.
B.Weather Limitations. If within the 3 hours before paving th e National Weather Service locally forecasts a 50 percent chance or greater of precipitation during the scheduled placement, postpone the placement of HPTO. Do not place HPTO if it is precipitating and do not allow trucks to leave the plant when precipitation is imminent. The Contractor may resume paving operations when the chance of precipitation is less than 50 percent and the surface is dry. Do not pave if the surface temperature of the underlying pavement is below 50 °F.
C.Test Strip. At least 14 days prior to production of the HPTO, construct a test strip as specified in 401.03.07.C except for the allowance to continue paving. Submit test strip results to the RE. The RE will analyze the test strip results in conjunction with the ME’s results from the HMA plant to approve the test strip. Do not proceed with production paving until receiving written permission from the RE.
D.Transportation and Delivery of HMA. Transport and deliver HMA as specified in 401.03.07.D.
E.Spreading and Grading. Use of a MTV is required for the construction of HPTO. If HPTO is only for bridge deck paving, the use of a MTV is optional. Ensure that the surface where the HPTO is placed is clean of foreign and loose material. Clean the surface of existing pavement using a self -propelled power broom equipped with a vacuum collection system before placement. Ensure that the surface is dry before paving begins. Do not start paving of the HPTO until the RE has approved the underlying surface. In areas where the existing pavement is not being milled, remove traffic stripes and traffic markings as specified in 610.03.08. Apply tack coat as specified in 401.03.05. Place HPTO at the laydown temperature recommended by the supplier of the asphalt binder or the supplier of the asphalt modifier without exceeding 330 ºF maximum discharge temperature. Spread and grade HPTO as specifie d in
401.03.07 E.
F.Compacting. Compact as specified in 401.03.07.F. If vibratory compaction causes aggregate breakdown, or forces liquid asphalt to the surface , or both, operate rollers in static mode only. If compacting HPTO on a bridge deck, operate rollers in static mode only.
G.Opening to Traffic. Remove loose material from the traveled way before opening to traffic. Do not allow construction equipment or traffic on the HPTO until the mat cools to a temperature of less than 140 °F.
H.Air Void Requirements on Roadway. Drill cores as specified in 401.03.08. Mainline lots are defined as the area covered by a day’s paving production of the same job mix formula for the traveled way and auxiliary lanes. The RE may combine daily production areas less than 500 tons with previous or subsequent production areas. If a day’s production is greater than 2,000 tons, the RE may divide the area of HMA placed into 2 lots with approximately equal areas. Ramp pavement lots are defined as approximately 10,000 square yards of pavement in ramps. The RE may combine ramps with less than the minimum area into a single lot. If 2 or more ramps are included in a single lot, the RE will require additional cores to ensure that at least 1 core is taken from each ramp. Other pavement lots are defined as approximately 10,000 square yards of pavement in shoulders and other undefined areas. The ME will calculate the percent defective (PD) as the percentage of the lot outside the acceptable range of 1 percent air voids to 7 percent air voids. The acceptable quality limit is 10 percent defective. For lots in which PD < 10, the Department will award a positive pay adjustment. For lots in which PD > 10, the Department will assess a negative pay adjustment. The ME will determine air voids from 5 cores taken from each lot in random locations. The ME will determine air voids of cores from the values for the maximum specific gravity of the mix and the bulk specific gravity of the core. The ME will determine the maximum specific gravity of the mix according to NJDOT B-3 and AASHTO T 209, except that minimum sample size may be waived in order to use a 6 inch diameter core sample. The ME will determine the bulk specific gravity of the compacted mixture by testing each core according to AASHTO T 166. The ME will calculate pay adjustments based on the following:
1.Sample Mean (X̅ ) and Standard Deviation (S) of the N Test Results (X 1, X2,…, XN). Calculate using the formula as specified in 401.03.07.H.1.
2.Quality Index (Q). Calculate using the formula as specified in 404.03.01.H.2.
3.Percent Defective (PD). Using NJDOT ST for the appropriate sample size, the Department will determine PDL and PDU associated with QL and QU, respectively. PD = PDL + PDU
5.Outlier Detection. If PD < 10, the ME will not screen for outliers. If PD ≥ 10, the ME will screen all acceptance cores for outliers using a statistically valid procedure. The following procedure applies only for a sample size of 5 or 10.
1.The ME will arrange the core results in ascending order, in which X1 represents the smallest value and XN represents the largest value.
2.If XN is suspected of being an outlier, the ME will calculate: R = XN − X(N−1) XN − X1
3.If X1 is suspected of being an outlier, the ME will calculate: R = X2 − X1 XN − X1
4.For N = 5 if R > 0.642, the value is judged to be statistically significant and the core is excluded. For N = 10 if R > 0.412, the value is judged to be statistically significant and the core is excluded. If an outlier is detected for N = 5 and no retest is warranted, the Contractor may replace that core by taking an additional core at the same offset and within 5 feet of the original station. If an outlier is detected and a retest is justified, take a replacement core for the outlier at the same time as the 5 additional retest cores are taken. If the outlier replacement core is not taken within 15 days, the ME will use the initial core results to determi ne PPA. If an outlier is detected for N = 10, the Contractor may replace that core by taking an additional core at the same offset and within 5 feet of the original station. If the outlier replacement core is not taken within 15 days, the ME will use the initial core results to determine PPA.
6.Retest. If the initial series of 5 cores produces a percent defective value of PD 30 for mainline or ramp lots, or PD 50 for other pavement lots, the Contractor may elect to take an additional set of 5 cores a t random locations chosen by the ME. Notify the RE within 15 days of receipt of the initial core results to take the additional cores. If the RE is not notified within the 15 days, the ME will use the initial core results to determine
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Source: Standard Specifications for Road and Bridge Construction, 2019 (rev. 2022-12-21) Edition. Pages 215–217 of 651. View official source ↗