Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/86539
RoadScience by Tom Kuennen, Contributing Editor SPECIAL SERIES A nating corporate forensic pavement knowledge will help assure exceptional performance in this area in the future." Acknowledging that staff turnover and retirements were depleting the acquired engineering expertise of Texas DOT, the writers in 2005 outlined creation of a knowl- edge database of rigid (portland cement concrete), and later, in 2007, fl exible (bituminous concrete) pavements, all accessible to Texas DOT employees via the Texas i-Way learning content management system. The Chemistry of Road Building Materials What Went Wrong, and Why Forensic Studies Give Clues to Pavement Failure W hether the pavement is black or white, fl ex- ible or rigid, asphalt or concrete, pavement forensic testing is the key to preventing future pavement failures in either paving medium. In the lab or in the fi eld, engineers examine pavement condition, cores or entire cut-out sections to ascertain what went wrong, and why. "Forensic pavement analysis is a core function of every department of transportation," say Paul E. Krugler, Carlos M. Chang-Albitres and Robert L. Robideau, Texas Transpor- tation Institute, in their paper Development of a Rigid Pavement Forensics Knowledge Management System to Retain TxDOT Corporate Knowledge. "Excellence in this technical area allows selection of proper and most cost-effective rehabilitation options, with potential monetary benefi ts to the department of millions of dollars annually," they write. "Capturing and dissemi- 18 October 2012 Better Roads Tools for Detective Work Poor quality construction can occur due to a number of complex and sometimes competing variables, reports the Texas DOT, including reduced inspection staffi ng, employ- ee turnover, variability of inspectors' and project manag- ers' experience levels, incompatibilities between new admixtures and construction materials, implementation of new technologies and construction methods, environ- mental constraints, recycled materials and other issues unforeseen during design and construction phases. "To prevent, and to reduce the probability of premature pavement failures and poor long-term pavement per- formance, the root causes of these problems have to be identifi ed," Texas DOT says in its Pavement Design Guide. "In conducting forensic studies, a thorough review and analy- sis of existing quality construction records and tests, non- destructive testing like ground penetrating radar (GPR) and the falling weight defl ectometer (FWD) are essential to identify problematic areas and probable causes." "When a pavement fails earlier than expected – with early cracking or rutting – we conduct forensic investi- gations to determine why that happened so soon," says Timothy R. Clyne, P.E., MnROAD forensic engineer for Minnesota DOT's MnROAD pavement test facility. MnROAD – a full-scale accelerated pavement test facility – tests pavement materials, structural designs and con- struction techniques. It's unique in that in addition to a low-volume roadway test track that simulates conditions on rural roads, it includes an actual test section of I-94 that carries live Interstate traffi c. "We will do a forensic investigation on good roads to fi nd out what we did right, or what were the conditions that made things go so well with that section," Clyne says. "But most of the time our forensic investigations are on early failures." MnROAD also will conduct forensic inves- tigations for pavements throughout the state, either for Minnesota DOT or local agencies.