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B-1 A P P E N D I X B Nevada Construction Report In a collaborative effort with University of Nevada, Reno and its NCHRP 9-58 research team, the Washoe County of Northern Nevada implemented a major rehabilitation project on Matterhorn Blvd (PWP-WA-2015-179) to study the influence of rejuvenators on hot mix asphalt (HMA) with high recycled asphalt pavement (RAP) materials. The Matterhorn Blvd is a low volume road with a single lane in each direction located 17 miles north of Reno, Nevada. The existing pavement before rehabilitation had 3.5 to 5.0 inches of HMA on top of the aggregate base and it was severely damaged by thermal cracking. The old asphalt pavement layer was constructed using lightweight Allite aggregates with a water absorption of the aggregate being around 5.3%. The rehabilitation project consisted of pulverization and compaction of the existing asphalt pavement and base to the depth of 6 inches and placing a new 3 inch thick overlay on top. Five test sections were constructed in September 2015 and the description of each section is given in Table B.1. The test sections were laid out on Matterhorn Blvd as shown in Figure B.1. Each section spreads to about 24 ft wide and 2000 ft long. Table B.1: Description of Nevada test sections noitpircseDsnoitceS Section 1 (Virgin section) PG64-28NV/ No RAP / No Recycling Agent Section 2 (Control section with 0.3RBR) PG64-28NV/ 0.30 RAP Binder Ratio (RBR)/ No Recycling Agent Section 3 (T2 section) PG64-28NV/ 0.30 RBR / T2 Section 4 (A2 section) PG64-28NV/ 0.30 RBR / A2 Section 5 (Control section with 0.15RBR) PG64-28NV/ 0.15 RBR / No Recycling Agent
B-2 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios Figure B.1: Nevada test sections layout. PWP-WA-2015-179 project
Nevada Construction Report B-3 B.1. MATERIALS AND HMA PRODUCTION The aggregates and RAP materials were obtained from a pit in Lockwood and the asphalt binder was a PG64-28NV polymer-modified. The RAP material was a mixture of plant rejects and locally obtained old pavement materials processed to meet the ½â RAP specification of the Orange Book Standard Specifications for Public Work Construction (SSPWC) from Washoe County. The job mix formula (JMF) was obtained by combining five aggregate stockpiles: ¾â crushed aggregates (17%), ½â crushed aggregates (10%), 3/8â crushed aggregates (15%), #4 crusher fines (14%), and #4 Natural fines (10%); all the percentages are by total weight of mixture. The contractor conducted the Marshall Mix designs (50 blows) for Type 2 HMA mixes according to the Orange Book (SSPWC). The volumetric properties of the designed mixes are summarized in Table B.2. Figure B.2 shows the pictures of raw materials at the mixing plant. The coarse and fine aggregates were marinated with 1% hydrated lime and stored in separate stockpiles prior to mixing. The marinated aggregates were mixed with asphalt in a continuous mixing drum (Figure B.3 b) at 335°F. The recycling agents were heated at 120°F and injected to the asphalt line during mixing as recommended by the manufacturer. Mixed HMA mixtures were transferred to the silos for storage. The silo time (storage time) varied between 30 minutes and 3 hours throughout the production. The average temperature of HMA when discharged from the silo into the hauling truck was 320°F. The construction site was located at about 23 miles from the mixing plant and the average hauling time was around 30 minutes. Figure B.3 shows the pictures of the asphalt mixing plant at Lockwood. Table B.2: Summary of the Nevada Test Sections Mix Designs Section 1 Section 2 Section 3 Section 4 Section 5 RAP, % 0 33 33 33 15 RA type, % - - T2 1, 2.0% A21, 2.0% - RAP Binder Ratio (RBR) 0 0.324 0.332 0.324 0.144 Optimum total binder content, %TWM2 5.37 4.60 4.50 4.60 5.04 Virgin binder content, %TWM2 5.37 3.11 3.01 3.11 4.32 VMA, % 13.3 13.7 13.9 14.0 13.3 VFA, % 69.8 71.1 71.2 71.8 69.8 1 T2-Evoflex, A2-Reclamite 2 TWM denotes âTotal Weight of Mixâ
B-4 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios (a) (b) (c) Figure B.2: Picture of (a) Aggregate stockpiles; (b) Processed RAP stockpile; and (c) Marinated aggregate stockpile along with asphalt binder tanks at the asphalt plant.
Nevada Construction Report B-5 (a) (b) (c) Figure B.3: Picture of (a) Array of aggregate bins; (b) Continuous mixing drum; and (c) Storage silos at the asphalt plant. B.2. CONSTRUCTION The pulverization and compaction of the existing asphalt pavement and base was completed few days prior to the construction of the new asphalt pavement layer. The pulverized and compacted base layer was wetted and levelled by a motor grader before placing the HMA. The air temperature varied between 77 and 84°F and the wind speed varied between 5 and 15 mph during construction. The HMA was transported to the construction site using belly dump trucks with the capacity of 40 ton. The HMA was placed in a window on top of the compacted base.
B-6 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios Figure B.4 shows the belly dump truck and the HMA material placed in a windrow. A windrow elevator picked up the HMA and transferred it into the paver hopper. A paver (Figure B.5) laid down the HMA on top of the base. The HMA layer was placed in one lift since the target thickness of the layer was 3 inches. One lane (12 ft) was paved at a time and the other lane was kept open to the traffic. The paved HMA mixtures were compacted using three types of rollers; CAT CB64 vibratory roller, Volvo DD38 vibratory roller, and CAT CC34 pneumatic rollers. The breakdown roller (CAT CB64) did four vibratory passes and one static pass followed by two static passes by the pneumatic roller. The Volvo DD38 was used to compact the joints properly and finish the compaction with two static passes. A pass here is defined as both wheels of the compactor rolling over a specific point on the mat. Figure B.6 shows the fleet of compactors and the break down compactor behind the paver. A summary of the windrow temperature and beginning and end station marks of each test section are given in Table B.3. Physical or functional differences were not observed between mixtures with recycling agents and regular HMA mixes during the mixing and compaction process in the field. Figure B.7 shows the pictures of pavement surfaces of the test sections. The mat densities were measured after the completion of compaction using nuclear density gauges by both contractor and consultant.
Nevada Construction Report B-7 (a) (b) Figure B.4: Picture of (a) Belly dump truck; and (b) HMA placed in a windrow. Figure B.5: Picture of the windrow lifter and paver.
B-8 Evaluating the Effects of Recycling Agents on Asphalt Mixtures with High RAS and RAP Binder Ratios (a) (b) Figure B.6: Picture of (a) Fleet of compactors; and (b) Breakdown roller behind the paver. Table B.3: Summary of the windrow temperature and station locations Construction Date Section number RBR Recycling agent Lane Start station Stop station Windrow HMA Temp. (°F) 10-Sept. 2015 4 0.30 A2 SB 279 304 305 NB 279 304 290-310 1 0.00 None SB 252+70 279 295-305 NB 252+70 279 295-305 11-Sept. 2015 3 0.30 T2 SB 226 252+70 310-320 NB 232+50 252+70 302 2 0.30 None SB 198+50 226 290-305 NB 197+55 232+50 310-320 16 and 17- Sept. 2015 5 0.15 None SB 102 198+50 300-310 NB 102 197+55 300-310
Nevada Construction Report B-9 (a) (b) (c) (d) Figure B.7: Picture of compacted pavement surface of (a) Section 1-virgin; (b) Section 2- control with 0.3 RBR; (c) Section 3-0.3 RBR with T2; (d) Section 4-0.3 RBR with A2; and (e) Section 5-control with 0.15 RBR. (e)
