Better Roads Digital Magazine
Issue link: https://read.dmtmag.com/i/348335
Better Roads July 2014 5 with other pavement preservation techniques, reports IGGA. It involves the removal of a thin layer of the cured con- crete surface using a dedicated, self-propelled machine with closely-spaced diamond-coated circular saw blades. Diamond grinding restores rideability by removing surface irregulari- ties. The immediate effect of diamond grinding is a significant improvement in the smoothness of a pavement, and a substan- tial increase in surface macrotexture with improvement in skid resistance, noise reduction and safety. Grooving and grinding – and associated concrete pavement restoration techniques – are elements of the pavement pres- ervation "tool box" used by government agencies to prolong pavement life. For example, pavement preservation has been a part of the Minnesota Road Research Project (MnROAD) test facility north of Minneapolis since it first opened in 1994, and grooving and grinding have been part of it. The two MnROAD road segments are a 3.5-mile, two-lane interstate mainline carrying live I-94 traffic, averaging 26,500 vehicles per day with 13 percent trucks for the westbound lanes; and a 2-1/2-mile, two-lane closed loop low volume road. Traffic on the low-volume, closed loop is restricted to a MnROAD 18-wheel, five-axle, tractor/trailer which aver- ages 70 laps a day. (For "Minnesota's New Solutions for Aging Pavement," go to betterroads.com/minnesotas-new-solutions-for-aging- pavement.) Materials tested include asphalt and concrete; regarding the latter, MnROAD has completed tests involving bonded and unbonded concrete overlays, concrete partial depth repairs, full-depth joint repairs, and PCC diamond grinding. Recent innovations in diamond grinding techniques are a result of tests at the MnROAD facility. Working through a pooled fund study, several diamond grinding configurations first developed at Purdue University were field-tested on the low-volume road in 2007. MnROAD staff since has been monitoring them to determine their long term performance with regards to noise, texture and friction. The successful per- formance of these textures at MnROAD has led to their imple- mentation in several projects in Minnesota and other states. Preserving Nashville's I-440 Grooving and grinding helped preserve I-440 from I-40 East to I-40 West in Nashville. The heavily used, existing pavement had experienced faulting, spalled joints, some random crack- ing and there was a need to address skid resistance. After having first considered 4-inch asphalt concrete resurfac- ing and shot blasting as options to renew the texture, Tennessee DOT decided to use concrete pavement preservation, including full-depth slab replacement, as its rehabilitation method. The project included 10,000 square yards of pavement re- placement, 2,000 square yards of spall repair, 350,000 square yards of diamond grinding and grooving, and 450,000 linear feet of joint cleaning and resealing. Working around the multitude of sporting events in the area, the state incorporated full weekend closures to accelerate the construction progress. As the highway is so heavily traveled, work was performed at night to avoid the congestion problems caused by the high-traffic volumes during the day. Further, the team performed longitudinal grooving to enhance safety. "This project grew in scope after traffic was diverted and we had the opportunity to perform a closer inspection of pave- ment," said Doug Hagar, project engineer for the Tennessee DOT. "But by completing all the necessary repairs while the contractor was on site, Tennessee road users can expect many years of smooth, uninterrupted service." With a project value of $4.3 million, the final cost of the treatments – including dowel bar retrofit, diamond grinding and full-depth slab replacement – was about $400,000 per mile. Further, this preservation project resulted in a smoother riding surface and improved skid resistance, which not only increased the aesthetic appeal but made the roadway safer for travelers. "We now have a smoother, safer roadway for travelers," said Jay Norris, special projects engineer for the Tennessee DOT. Team members included Tennessee DOT, LoJac Inc. (prime contractor), Penhall Company (grinding), and Truline Coring & Cutting (sawing). Diamond grind smoother than SMA? Diamond-ground portland cement concrete can be smoother than stone matrix asphalt (SMA), as was demonstrated by high- speed profile testing of adjacent sections on I-290, the Eisen- hower Expressway (a.k.a. the "Ike"), on Chicago's West Side. Recently, Ames Engineering of Ames, Iowa, conducted pro- file testing of three lanes in both directions of I-290 between Austin Avenue and Sacramento Boulevard. The profile testing was conducted to compare the SMA ride qualities with those of the conventional diamond-ground pavement. That's because a year earlier, on this section of roadway, both a stone matrix asphalt overlay and a conventional diamond- ground surface were constructed. The project, which extended