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A-1 A P P E N D I X A Texas Construction Report The Texas Department of Transportation (TxDOT) executed the Texas State Highway 31 (SH 31) reconstruction project (Project ID CSJ 064-01-068) in the summer of 2014. This reconstruction project, located in northeast Texas, included an approximately 1.4-mi-long asphalt overlay placement. This project used five test sections to study and evaluate the effects of different rejuvenators on the performance of asphalt mixtures with high RAP and RAS content. Originally, this project was initiated under a research study sponsored by TxDOT. The overlay was constructed in the first week of June 2014. The general contractor provided the materials and paved the overlay. SH 31, at this project site, is a divided rural highway with two lanes in each direction. Typical roadbed width, in each direction, was 30 ft including two 12-ft travel lanes and a 3-ft shoulder on each side. The contractor placed five test sections on the eastbound outside travel lane and right shoulder. These test sections were located between the east side of the city of Murchison and the west side of the city of Brownsboro, Texas (Figure A.1). The new construction of these test sections included 1-inch crack attenuating mix (CAM) followed by one layer of hot rubber seal coat and 2-inch dense-grade Type C mix as a surface course. The inner part of the existing pavement structure before this reconstruction included a 4-inch HMA layer and 6-inch cement concrete layer. The outside (6 ft) of the existing pavement structure included a 4-inch HMA layer, then another 6-inch HMA layer, and 4 inches of iron core base at the bottom. Figure A.2 shows the typical existing pavement structure. Pavement widening at some point in the past attributed to this unusual pavement structure. Annual average daily traffic in each direction measured in 2013 was approximately 5000 with 18 percent truck traffic. Each of the five test sections had a different surface mix design for the Type C mixture, as shown in Table A.1.
A-2 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS And RAP Binder Ratios Section 5 Section 4 Section 2 Section Section 1 Figure A.1: Layout of Five Test Sections on SH 31. Figure A.2: Typical Existing Section. Table A.1: Test Sections with Five Different Mixtures. Section Section Description Additive/Rejuvenator Dosage No. Name 1 Virgin Mix Only virgin aggregate with N/A PG 70-22 binder 2 Control Mix 10% RAP and 5% MWAS with WMA additive: 0.5% of total AC by PG 64-22 + WMA additive weight 3 T1 10% RAP and 5% MWAS with T1: 0.2% of total mix by PG 64-22 + T1 weight (0.75% weight of RAP + )SAR fo thgiew %0.1 4 T2 10% RAP and 5% MWAS with T2: 3.7% of total AC by PG 64-22 + T2 + weight WMA additive WMA additive: 0.3% of total AC by thgiew 5 E1 10% RAP and 5% MWAS with E1: 1.3% of total AC by weight PG 64-22 + E1
Texas Construction Report A-3 right next to the Section 3. Besides the test sections, other areas of the roadbed were paved with the control mix. Production began with the mixture used in Section 1 (virgin aggregate with PG 70-22 binder) at 7:15 a.m. on June 03, 2014, at a rate of 200 tons/hr. Table A.2 presents the mixture production schedule with temperature. Table A.2: Production, Paving, and Ambient Temperatures Section Mixture Date of Plant Mix Paving Ambient Production Temp, Â°F Temp, Â°F Temp, Â°F 1 Virgin Mix 06/03/2014 325â327 285â290 75â80 2 Control Mix 06/03/2014 275â280 255â260 80â84 3 T1 06/03/2014 280â290 265â270 86â88 4 T2 06/04/2014 275â285 240â250 74â78 5 E1 06/04/2014 280â287 260â265 81â84 A.2.1. Section 1: Virgin Mix Section 1 was paved on the morning of June 3, 2014. It started at Station 472+37 and ended at Station 490+00 (global positioning system [GPS] coordinate N 32.28094/W 095.73956 to N 32.28194/W 095.73400). The ambient temperature was 75Â°F during the paving of this section. The virgin mix was produced at around 310Â°F and then hauled to the paving side in 30 min. The hauling truck (a âflow boyâ) directly dumped the mix into the shuttle buggy (material transfer device), and then the mix was transferred to the paver (Figure A.5). The temperature behind the paver was around 290ÂºF, measured using infrared temperature gun. In addition, an infrared Pave-IR bar was used to measure the asphalt mat temperature behind the paver. A steel-wheel vibratory (breakdown) roller closely followed the paver. The compaction was achieved by two passes at vibrating mode and two passes at static mode (Figure A.5 a), followed by four passes of a pneumatic roller (Figure A.6 b) and then two passes of a static steel finish roller (Figure A.6 c). Figure A.7 shows the compacted mat. A.1. MATERIALS AND MIXTURES Figure A.3 and A.4 present the mixture designs used for this construction project. Two types of binders were used: an unmodified PG 64-22 and an SBS modified PG 70-22. The specific source of the RAP is unknown, since it came from several highway sections. RAS was produced by shredding and grinding manufacturer waste shingles. The TxDOT Class A (granite) aggregate came from a quarry in Oklahoma, while the TxDOT Class B (limestone) aggregate came from a quarry located in Bridgeport, Texas. All mixtures for this project were produced at the contractor's hot-mix plant located just west of Tyler, Texas. Table A.2 summarizes the production, placement, and ambient temperatures during laydown for different mixes. A.2. PRODUCTION OF MIX AND PAVING For each test section, 350 tons of mix was produced and placed. Sections 1, 2, and 3 were constructed on June 3, 2014. All the area was paved with the control mix except sections 1, 3, 4, and 5; each section was approximately was 1800 ft long. Note that Section 2 was established between Sections 1 and 3. Sections 4 and 5 were paved on June 4, 2014. Section 4 mix was placed
Figure A.3: Mixture Design of Virgin Mix Placed on Section 1 (Virgin Mix).
Figure A.4: Mixture Design of Control Mix Placed on Section 2 (Control Mix).
A-6 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS And RAP Binder Ratios Figure A.5: Shuttle Buggy and Paver. (a) Vibratory Roller (b) Pneumatic Roller (c) Steel Finish Roller Figure A.6: Rollers Used for Compaction. Figure A.7: Finished Test Section 1: Virgin Mix.
Texas Construction Report A-7 A.2.2. Section 2: Control Mix Section 2 was the control mix section with 10 percent RAP and 5 percent RAS. This section was a warm-mix asphalt section. It started at Station 501+50 and ended at Station 520+00 (GPS coordinate N 32.28265/W 095.73025 to N 32.28371/W 095.72421). The mix temperature measured at the dump truck at the project site was around 275â280Â°F, and the mat surface temperature behind the paver was around 260Â°F. The rolling pattern was similar to that of Section 1 except that the breakdown roller had three passes in vibratory mode and one pass in static mode followed by four passes with the pneumatic roller and then two passes with the static steel finish roller. Some minor segregation was observed after the laydown at the center of the mat (Figure A.8 a), but they were not noticeable on the compacted mat (Figure A.8 b). (a) (b) Figure A.8: Section 2; (a) Observed Segregation on Loose Mat, and (b) Finished Surface. A.2.3 Section 3: Control Mix with Rejuvenator T1 Section 3 started at Station 536+00 and ended at Station 557+00 (GPS coordinate N 32.28460/W 095.71922 to N 32.28585/W 095.72226). The mix temperature measured at the dumping truck was around 290Â°F, although it was supposed to be a warm-mix temperature of 275Â°F or below according to the experimental design. The mat temperature behind the paver was around 270Â°F. Section 3 employed the same rolling pattern as Section 2. Again, some segregation was observed on the loose mat (Figure A.9 a), but the finished surface did not show any sign of segregation (Figure A.9 b).
A-8 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS And RAP Binder Ratios (a) (b) Figure A.9: Section 3; (a) Observed Segregation on Loose Mat of Section 3, and (b) Finished Surface. A.2.4. Section 4: Control Mix with Rejuvenator T2 Section 4 started at Station 557+00 and ended at Station 580+00, (GPS coordinate N 32.28585/W 095.72226 to N 32.287081/W 095.70523). Note that the end of Section 3 was the beginning of Section 4. Section 4 and Section 2 had the same rolling pattern. Section 4 was paved in the early morning at around 8:30 a.m. In the beginning, the mix temperature measured at the dumping truck was around 270Â°F. The mat temperature behind the paver was around 230â240Â°F. However, obvious segregation was observed on the loose mat (Figure A.10). The paving crew asked to increase the production temperature. After the speed limit sign (Figure A.11), the mix dumping temperature measured from the truck was 285Â°F. However, segregation issue was not resolved (Figure A.12). Figure A.10: Segregation behind the PaverâSection 4.
Texas Construction Report A-9 Figure A.11: Mix with Higher Production Temperature Placed beyond Speed Limit Sign. Figure A.12: Observed Segregation Even after Increasing the Production Temperature. A.2.5. Section 5: Control Mix with Rejuvenator-ERA-1 Section 5 started at Station 607+00 and ended at Station 527+00, (GPS N 32.28858/W 095.69669 to N 32.28970/W 095.69034). Section 5 was paved on the afternoon of June 4 starting at around 1:00 p.m. The mix temperature measured at the dumping truck was around 287Â°F, although it was supposed to be a WMA temperature of 275 F or below. The mat temperature behind the paver was around 265ÂºF. A rolling pattern similar to Section 2 was used to compact the mat. No obvious segregation (Figure A.13) was observed in Section 5.
A-10 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS And RAP Binder Ratios Figure A.13: No Obvious Segregation in Section 5. A.3. DESCRIPTION OF ASPHALT MIX PLANT All the mixtures were produced at an asphalt mix plant located on the west side of Tyler, Texas. The average distance between the plant and the test sections was about 20 mi, or a 25-min drive. This plant was unique in the sense that it had two drums: one for drying the aggregates and the other for mixing. Figure A.14 shows the overview of this hot-mix plant. RAP and RAS were added with hot aggregate just outside the drying drum before they entered into the mixing drum. The binder was directly injected into the mixing drum. The admixtures and rejuvenators were injected into the AC line. This plant, manufactured in 1997, has a capacity of 400 tons of mixture per hour. The parallel mixing drum has a dimension of 18 ft long by 6 ft diameter with a 15-ft-long mixing zone. The counterflow drying drum has a dimension of 38 ft long by 9 ft diameter. This natural-gas-fueled plant has a conventional baghouse emission system where part of the fines is returned to the drum. The plant has six bins for virgin aggregates and three bins for RAP and RAS. There are also three insulated silos with a storage capacity of 200 tons of mix each. The plant has three horizontal binder storage tanks. The plant produced typically 200 tons per hour of mix during the construction of the test sections. The storage temperatures at the tanks were 304Â°F and 294Â°F for the PG 70-22 and PG 64-22 binders, respectively. The additives and recycling agents were kept at an ambient temperature.
Texas Construction Report A-11 Figure A.14: Overview of the Asphalt Mix Plant. A.4. SAMPLE COLLECTION Plant mix was collected from the trucks at the plant by climbing on scaffolding. Figure A.15 shows the sample collection at the plant. Due to the demand from multiple research projects and universities involved, a large amount of plant mix was collected in 5-gal buckets from multiple trucks. Small amounts of the plant mix were brought back to the onsite laboratory for immediate compaction. The plant mix samples were collected usually after 200 tons of production for any given section. The material sampling scheme is presented in Table A.3. With the help of the contractor, the research team also collected forty 6-inch-diameter cores from the test sections. These cores were obtained from the outside shoulder. The team also collected quality-control cores at random locations. Table A.3: Material Sampling Scheme. Sample Type Material Point of Sampling Lab Mixed, Lab Compacted Fine Aggregate Stockpile Coarse Aggregate Stockpile elipkcotSPAR elipkcotSSAR Admixture/Rejuvenators Storage Tank (plastic tote in tnalPta)egaclatem PG 64-22 Asphalt Terminal PG 76 -22 Asphalt Terminal Plant Mixed, Lab Compacted Loose Mix Truck at Plant Plant Mixed, Field Compacted edluohSseroC r
A-12 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS And RAP Binder Ratios Figure A.15: Collection of Loose Mix from Truck at Asphalt Mix Plant. A.5. ONSITE SPECIMEN COMPACTION Twenty specimens 6.0 inches diameter by 2.4 inches height were compacted onsite at the laboratory located within the plant premises. Loose plant mix collected from the trucks was quickly brought to the laboratory and placed in the oven between 1 to 2 hr to achieve its compaction temperature. The researchers compacted these specimens using a Superpave gyratory compactor to 7 Â± 1 percent air voids. Specimens were compacted at 270Â°F and 250Â°F for mixtures with PG 70-22 (Section 1) and PG 64-22 binders, respectively. A.6 STOCKPILES AND PLANT DETAILS Figure A.16 shows the separate conveyor belts carrying virgin aggregates and RAP/RAS to the different parts of the asphalt plant. Figure A.17 depicts the entry point of admixture/rejuvenator into the AC line. Figure A.18 through A.20 depict RAS, RAP, and aggregate stockpiles. None of the stockpiles was covered. Moisture content of RAP, RAS, screenings, and sand was 5.5 percent, 6.4 percent, 5.4 percent, and 8.1 percent, respectively. Average moisture content of 5.0 percent was input during the production. The RAP was screened over a 2-inch sieve before mixing with the aggregate. RAS was produced by shredding the manufactured waste shingles using a shredder located on site.
Texas Construction Report A-13 Figure A.16: Aggregate and RAP/RAS on Separate Conveyor Belts. Figure A.17: Admixture/Rejuvenator Injected Directly into the AC Line.
A-14 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS And RAP Binder Ratios Figure A.18: RAS Stockpile. Figure A.19: RAP Stockpile.
Texas Construction Report A-15 Figure A.20: Aggregate (One of Several) Stockpile