1 00:00:00,159 --> 00:00:05,159 (gentle music) (air whooshes) 2 00:00:07,169 --> 00:00:09,270 (vehicles whooshing) (horn blaring) 3 00:00:09,270 --> 00:00:11,520 - [Narrator] High quality surfaces are paramount 4 00:00:11,520 --> 00:00:15,840 on roadways being built and resurfaced across Texas. 5 00:00:15,840 --> 00:00:18,810 A well compacted and smooth asphalt pavement 6 00:00:18,810 --> 00:00:21,870 is often achieved by paving in multiple layers 7 00:00:21,870 --> 00:00:25,290 or lifts using an asphalt paving machine. 8 00:00:25,290 --> 00:00:28,980 Researchers at the Texas A&M Transportation Institute 9 00:00:28,980 --> 00:00:32,130 are working with the Texas Department of Transportation 10 00:00:32,130 --> 00:00:34,860 to evaluate a specialized paving machine 11 00:00:34,860 --> 00:00:36,720 called a tamper bar paver 12 00:00:36,720 --> 00:00:38,220 that may be able to lay 13 00:00:38,220 --> 00:00:41,400 thick lifts of asphalt more efficiently. 14 00:00:41,400 --> 00:00:44,430 - Thick lift paving is when you place asphalt concrete 15 00:00:44,430 --> 00:00:46,770 in lifts that are greater than what's allowed 16 00:00:46,770 --> 00:00:48,570 by the TxDOT specifications. 17 00:00:48,570 --> 00:00:49,860 So this lets you put down, 18 00:00:49,860 --> 00:00:53,310 let's say, four or six inches of asphalt at one time 19 00:00:53,310 --> 00:00:56,100 instead of breaking it up into two or three different lifts. 20 00:00:56,100 --> 00:00:57,570 - Can we be more efficient? 21 00:00:57,570 --> 00:01:00,090 Can we place this all in the six-inch lift 22 00:01:00,090 --> 00:01:02,430 or can we be even more extreme and place this in, 23 00:01:02,430 --> 00:01:03,930 say, an eight-inch lift 24 00:01:03,930 --> 00:01:05,700 and still get the same performance 25 00:01:05,700 --> 00:01:08,070 and the same density and the same quality? 26 00:01:08,070 --> 00:01:10,860 - The problem is that thick lift paving has its own hurdles. 27 00:01:10,860 --> 00:01:11,850 One, there's concerns 28 00:01:11,850 --> 00:01:14,220 that you're not gonna get uniform compaction 29 00:01:14,220 --> 00:01:15,513 or uniform density. 30 00:01:16,380 --> 00:01:18,390 There's concerns that it's gonna take a long time 31 00:01:18,390 --> 00:01:19,680 to cool down, 32 00:01:19,680 --> 00:01:23,340 and it's more difficult to get a good ride quality. 33 00:01:23,340 --> 00:01:26,760 So a tamper bar paver is a special piece of equipment 34 00:01:26,760 --> 00:01:29,130 that puts down more compaction right behind the screed. 35 00:01:29,130 --> 00:01:31,350 So the objective of the research was to see 36 00:01:31,350 --> 00:01:33,390 if a tamper bar paver could effectively place 37 00:01:33,390 --> 00:01:34,530 thick lift asphalt, 38 00:01:34,530 --> 00:01:36,990 and what are the best practices to do that? 39 00:01:36,990 --> 00:01:41,160 We got tamper bar pavers onto some thick paving projects, 40 00:01:41,160 --> 00:01:46,160 and we placed those layers somewhere 6, 8, 10-inches thick. 41 00:01:46,230 --> 00:01:48,360 And we placed them with a single lift 42 00:01:48,360 --> 00:01:49,320 and with two lifts. 43 00:01:49,320 --> 00:01:51,870 We modified the compaction settings, 44 00:01:51,870 --> 00:01:53,520 changed the rolling patterns, 45 00:01:53,520 --> 00:01:54,810 and we evaluated, 46 00:01:54,810 --> 00:01:57,750 you know, how long did it take to cool down? 47 00:01:57,750 --> 00:01:59,790 How good was the compaction quality? 48 00:01:59,790 --> 00:02:01,920 And what was the final ride quality? 49 00:02:01,920 --> 00:02:04,740 So we've found that using thick lift paving, 50 00:02:04,740 --> 00:02:07,053 you can actually get better compaction, 51 00:02:07,053 --> 00:02:08,670 more uniform compaction, 52 00:02:08,670 --> 00:02:10,830 than if you did it in separate lifts 53 00:02:10,830 --> 00:02:13,200 'cause you're eliminating that interface 54 00:02:13,200 --> 00:02:16,230 that has poor compaction quality. 55 00:02:16,230 --> 00:02:17,910 So using a thick lift, 56 00:02:17,910 --> 00:02:20,580 you actually get a higher quality, 57 00:02:20,580 --> 00:02:23,070 possibly a better, longer lasting pavement. 58 00:02:23,070 --> 00:02:25,890 - The tamper bar paver did give more uniform 59 00:02:25,890 --> 00:02:28,770 air-void distribution throughout the depth. 60 00:02:28,770 --> 00:02:31,170 However, when they placed these eight 61 00:02:31,170 --> 00:02:33,090 or maybe even 10-inch lifts, 62 00:02:33,090 --> 00:02:36,000 what they found is the top tended to cool off 63 00:02:36,000 --> 00:02:39,270 but the inside stayed warm for a very, very long time. 64 00:02:39,270 --> 00:02:41,040 So we still had to keep it closed to traffic 65 00:02:41,040 --> 00:02:43,410 for eight to 10 hours until it cooled off. 66 00:02:43,410 --> 00:02:45,680 - Given the very limited use of tamper bar pavers 67 00:02:45,680 --> 00:02:46,920 in the United States 68 00:02:46,920 --> 00:02:50,040 and the challenges with temperature and ride quality, 69 00:02:50,040 --> 00:02:51,540 TxDOT decided against modifying 70 00:02:51,540 --> 00:02:53,190 their lift thickness requirements. 71 00:02:53,190 --> 00:02:55,260 - Had this panned out completely, 72 00:02:55,260 --> 00:02:59,370 I think it would have been a really good option 73 00:02:59,370 --> 00:03:02,820 to placing a larger base material 74 00:03:02,820 --> 00:03:04,620 prior to putting surface mix. 75 00:03:04,620 --> 00:03:07,200 I do still think that there's a potential for that, 76 00:03:07,200 --> 00:03:10,020 but it also kind of gave us an idea of, 77 00:03:10,020 --> 00:03:12,390 you know, can we do this with traditional pavers 78 00:03:12,390 --> 00:03:13,890 and just put an extra roller? 79 00:03:13,890 --> 00:03:16,620 So I do think there's still room to expand 80 00:03:16,620 --> 00:03:17,790 from that perspective. 81 00:03:17,790 --> 00:03:18,990 - [Announcer] For more information 82 00:03:18,990 --> 00:03:21,930 and to find the publications for this project, 83 00:03:21,930 --> 00:03:24,510 please visit the TxDOT Research Library 84 00:03:24,510 --> 00:03:26,223 at the link shown below.