Evaluation of Grind and Groove (Next Generation Concrete Surface) Pilot Projects in California
This research report presents the results of tire/pavement noise, friction, drainability, and profile measurements performed on conventional diamond grind (CDG) and grind and groove (GnG) concrete pavement surface textures as a part of the California Department of Transportation (Caltrans) Quieter Pavement Research (QPR) study to investigate tire/pavement noise on concrete pavements. The On-board Sound Intensity (OBSI) method (AASHTO TP 76) was used to measure tire/pavement noise. Longitudinal profile data were collected at the same time as the OBSI data using an inertial profiler (ASTM E950) and were used to calculate the International Roughness Index (IRI). Friction was measured using the Towed Skid Trailer (ASTM E274) and the California Portable Skid Tester (CT 342), and estimated using the Circular Track Meter (ASTM E2157) and Dynamic Friction Tester (ASTM E1911). Drainability was measured using the Outflow Meter (ASTM E2380). Seven pilot projects scheduled for CDG were selected for this research study. They include one each in San Diego, San Joaquin, and Yolo counties, and four in Sacramento County. At these seven sites, measurements were made before and after construction, and in between construction phases when possible. The GnG surface texture was found to be quieter than the CDG, with lane average OBSI values on the GnG texture ranging from 99.5 dBA to 101.7 dBA, with an average of 100.8 dBA, compared with a range of 100.6 dBA to 104.7 dBA, and an average of 102.8 dBA measured on the CDG surface texture. The average OBSI level for all GnG sections was 100.8 dBA compared with an average of 102.8 for all CDG sections. OBSI values on the CDG texture on the San Diego 5 project decreased by 0.5 dBA over 1.3 years where OBSI was measured several times after initial construction. This reduction was attributed to flattening of the “fins” produced by CDG during construction. The average OBSI for all sections prior to treatment was 104.4 dBA, although not all sections had measurements of both CDG and GnG. The IRI measurements showed that both CDG and GnG texturing treatments improved smoothness substantially compared with the pretreatment values. The average IRI was reduced from 142 in./mi for the preconstruction surface textures to 64 in./mi on average after the CDG treatment and to 49 in./mi on average after the GnG texture treatment. Both the OBSI and IRI are improved by CDG and even more so by the GnG texturing. Both CDG and GnG remove sealant overbanding and reduce or eliminate faulting at joints and cracks. Both processes also remove imperfections in the slabs caused by curling, warping, and most of whatever roughness was introduced during initial construction. All of these changes that result from CDG and GnG are likely to contribute to reductions in both noise and roughness. In this study, however, the individual contributions of removal of faulting and overbanding to noise and roughness reductions were not measured. The few friction measurements on the GnG texture using CT 342 were not sufficient to draw conclusions, indicating that further attention should be given to use of this test on this texture if Caltrans continues to use the test. The skid tests using ASTM E 274 indicated that both the CDG and GnG textures passed specifications used by most state highway departments.