Better Roads

September 2013

Better Roads Digital Magazine

Issue link:

Contents of this Issue


Page 8 of 82

TRANSGUARD® 4000 Re US Ab le CONCRETE CURING COVERS Sy eA Thermal segregation in a mat may be detected with a hand-held infrared thermometer or an infrared camera, which will document cooled spots (see illustration, page 5). These spots indicate where low temperatures will cause increases in air void content, decreasing the strength of the pavement. Essential to the good rolling pattern are foremen and operators who pay attention and know what it takes to produce a quality mat. Consistency can be expected if the crew is knowledgeable. Density measurements are important for QC and acceptance for agencies and contractors because correct in-place densities are correlated with improved long-term performance of asphalt pavements. These are obtained in the field during construction via nuclear or the new non-nuclear density gauges and by cores of as-built pavements. iNS Conventional compaction procedures have some limitations. They provide little or no feedback on the fly. Corings for density measurement are not analyzed until after compaction and may not be representative of the entire section. Overcompaction can occur, resulting in shattered aggregate and streaks on the mat. Intelligent compaction (IC) of base materials and bituminous pavements is the newest, most promising means of executing quality control/quality assurance in the field. Reduced compaction and labor costs, optimized construction schedules and performance outcomes and detailed computerized construction records are among the benefits. IC will become an important part of QC/QA in the years to come. "Intelligent compaction is an equipment-based technology for better quality control that results in longer pavement lives," according to the FHWA. "IC machines are vibratory rollers with accelerometers mounted on the axle of the front drums, global positioning system, infrared temperature sensors (for asphalt) and on-board computers that can display color-coded maps in real-time to track roller passes, asphalt surface temperatures and stiffness of compacted materials." While intelligent compaction technology is applicable to soil compaction as well as asphalt, in 2013, the FHWA has been ramping up its field studies of intelligent compaction for asphalt pavements. IC devices offer a number of advantages for highway projects, according to the FHWA, including: • Optimized labor deployment and construction time. Contractors can roll the right amount of material with the right amount of compactive effort (via cumulative stiffness readings) on each pass to ensure long-term performance, enhancing onsite quality control. • Reduced compaction costs and maintenance requirements. The flexibility to make fewer passes to achieve the correct compaction level – today, measured from detected stiffness – will minimize fuel use and equipment wear and tear, saving time and money. • Ability to make midcourse corrections. Adjustment during compaction of one layer before additional layers are placed ensures subsurface problems don't affect the entire road surface. Again, a quality-control issue. • Ability to maintain construction records. Data from the IC, along with global positioning system (GPS) coordinates of compaction activity, can be downloaded into construction quality databases and stored for future reference. It's here that IC becomes an integral part of QA, as models of what was compacted, where and when – and at what temperature, in some iterations – can be constructed from the raw data. "Some IC-equipped rollers use GPS technology to continuously calculate and record the position of the roller, while a measurement system on the roller is N Tio llA TA Intelligent Compaction coNcReTe SlAbS bRiDGeS & RoADS flexible liGhTweiGhT NATURAl coloReD polypRopyleNe ReDUceS cRAckiNG foR fielD AND pRecAST ApplicATioNS Complies with AASHTO specification M-1 and ASTM C-1 for reflection 71 71 and moisture retention. tollfree 1.800.231.6074 9209 Almeda Genoa Rd. • Houston, Texas 77075 P: 713.507.4251 • F: 713.507.4295 Email: • Text INFO to 205-289-3789 or visit Reef_BR0113pg33.indd 1 RoadScience_BR0913.indd 7 Better Roads September 2013 7 12/26/12 1:33 PM 8/30/13 8:20 AM

Articles in this issue

Links on this page

Archives of this issue

view archives of Better Roads - September 2013