Pavement Preservation Journal - Spring 2015 - (Page 35)

Thin Overlays Can Preserve Pavements as Well as Reduce Surface Noise T hin overlays are non-structural preventive maintenance HMA mixes used for the routine maintenance and rehabilitation of existing pavements. These overlays are commonly placed in thin lifts of about 1 in. thick, and are mainly used to preserve pavements exhibiting surface distresses such as raveling, aging, bleeding, minor cracking, minor disintegration, texture loss, and skid resistance loss. Thin HMA overlays enhance pavement performance and extend pavement service life, including functional characteristics such as improved user serviceability (i.e., smoothness, comfort, and quiet ride), skid resistance, splash and spray reduction, and noise reduction. IMAGE CREDIT: TREVINO, UTA STUDYING NOISE MITIGATION The noise mitigating properties of some of these mixes have been studied in the field in Austin, Tex., by The University of Texas Center Detail of thin overlay mix on I-35, north of Austin; measured sound on a par with, or better than, conventional porous friction courses for Transportation Research, and the results show that these surfaces are even quieter than some permeable [or open-graded] friction courses, which are commonly regarded as the quietest asphalt mixes. Research has shown some of the advantages of using thin lift asphalt mixtures include: * Improved ride quality * Reduced noise levels * Reduced life cycle costs * No loose stones, and * No curing time required. Most asphalt maintenance is needed to address functional issues, and not structural issues. Therefore, increasing the thickness of the pavement is not always necessary, and thin overlays are often sufficient to improve the surface smoothness and quality. If placed and compacted properly, good performance should be obtained. The application of thin overlays is not always viable, but may be appropriate for rehabilitating low-volume roads and for pavement preservation of all asphalt roads. For pavement preservation, thin overlays are capable of providing long-lasting surfaces that are also economical and provide good performance; for the case of interest of this article, these surfaces also provide the important benefit of reducing tire/ pavement noise. FIELD MEASUREMENTS For the case of the overlays studied in Austin, some thin overlay mixes recently have recently been tested for noise, on both high- and low-volume roads. The On-Board Sound Intensity IMAGE CREDIT: TREVINO, UTA By Manuel Trevino, Ph.D. On-Board Sound Intensity (OBSI) equipment and vehicle (OBSI) method for close-proximity tire/pavement noise measurement [AASHTO] was utilized. Some examples of these surfaces that have been studied are: * I-35 main lanes, from the Bell/ Williamson county line to Lakeway Drive * RM 12, one mile south of U.S. 290 to Wimberley city limits, and * RM 3238, just north of U.S. 290, between Bee Cave and Dripping Springs. These three thin overlay mixes have proved to be very quiet in recent tests. The preliminary noise test results from these surfaces are very promising. For the I-35 pavement the average noise level was 97.5 dBA, for RM 12 it was also 97.5 dBA, and for RM 3238, it was 99.8 dBA, all of which can be considered very quiet, quieter than many other porous friction courses. Further testing will be done to follow the sections' performance over time.  Dr. Trevino is affiliated with the Center for Transportation Research, University of Texas at Austin Spring 2015 pavement preservation journal 35

Table of Contents for the Digital Edition of Pavement Preservation Journal - Spring 2015

President’s Message
Hot, Cold In-Place Recycling Gets Boost at Western States Conference
Fort Collins HIR Project Provides Delegates with Up-Close Look
NCAT Reports 2012 Cycle Results, 2015 Preservation Activities
New Congress Means New Push Toward Reauthorization
FP² at TRB
Pavement Preservation in Spotlight at World of Asphalt 2015 in March
Control Potholes by Sealing Cracks, Joints in Advance
‘Thinlay’ Asphalt Overlays Next Word in Pavement Preservation
Texas Considers Ultra-Thin HMA Alternatives to Seal Coats
Thin Overlays Can Preserve Pavements as Well as Reduce Surface Noise
In California, Scrub Seals Gain Favor for Cost, Crack Sealing
IGGA Recognizes Leaders in Grooving, Grinding
Index of Advertisers

Pavement Preservation Journal - Spring 2015