Erwin Kohler

Active Crack Control for Continuously Reinforced Concrete Pavements

Continuously reinforced concrete pavements (CRCP) traditionally have been allowed to crack naturally. This type of passive crack control has resulted in nonuniform crack spacing, which has led to premature distress development. Although the accuracy of the mean crack spacing prediction has greatly improved, punchout and spalling distresses on CRCP have been found to occur primarily at locations of small crack spacing, divided cracks, cluster cracks, and Y-cracks. The findings of previous research results on active crack control for CRCP in Texas are presented, along with the results from recent full-scale test sections constructed at the University of Illinois. The active crack control process used two systems: automated tape insertion and early entry saw cut. Active crack control was found to eliminate crack meandering, Y-cracks, divided cracks, and cluster cracking. The active crack control sections also propagated 90% of the cracks in the first month after construction, whereas the passive crack sections took 18 months to reach a similar number of cracks. Both active and passive cracks propagated only in the winter months. Crack opening measurements showed that active crack control resulted in slightly smaller movements relative to the natural crack sections. By using active crack control on CRCP, more uniform, straighter, and early-age transverse cracks result, which will increase the expected service life of CRCP.

Crack spacing and crack width investigation from experimental CRCP sections

Crack width (CW) and crack spacing (CS) data from full-scale continuously reinforced concrete pavement (CRCP) test sections were collected and analyzed for this study. In order to compare CWs obtained under different temperature conditions, the CRCP CW model presented in the new mechanistic–empirical pavement design guide (MEPDG) was utilized to standardize the measurements. The MEPDG CS model was compared first to the measured data due to its direct link to CW prediction. Based on the measured material properties, pavement geometry, and climatic conditions, the predicted CS and the CS distribution matched the observations on the three main CRCP sections. Using the same inputs provided in the CS prediction, the CW model in the MEPDG significantly over predicted the measured CW. The CW model was calibrated with the measured data in order to compare CWs between sections acquired at various temperature conditions. At the standard temperature condition, the measured CW varied from 0.031 to 0.116 mm and was smaller for higher reinforcement ratios. The CW formula was modified to allow computation of CW at any slab depth. A study of CW variability in one test section showed a skewed distribution with a right tail.

Comparison of Surface Characteristics and Pavement/Tire Noise of Various Thin Asphalt Overlays

ABSTRACT Traffic noise has become a major concern in the last decade and many countries have been looking for solutions to reduce noise levels. The California Department of Transportation (Caltrans) has been using different open graded mixes to reduce highway noise levels and improve wet weather driving conditions. There is a need to identify their noise reduction properties, durability, and safety, and to compare these with other asphaltic mixes. Caltrans initiated a long-term program to investigate and monitor field performance of different open graded mixes and other commonly used asphalt surface mixes. This paper summarizes part of the first-year measurements of relevant parameters from asphalt pavements with different surface mixes. It was confirmed that open graded mixes generally reduce the tire/pavement noise level, and the amount of reduction is correlated with air-void content and surface texture.

Acoustical Absorption of Porous Pavement

Acoustical absorption coefficients of more than 140 pavement cores were obtained by the impedance tube method with two microphones and cross-spectral analyses. The effectiveness of the impedance tube in predicting noise reduction for different mixes was evaluated by comparing the correlations between onboard sound intensity levels and absorption. Theoretical predictions of acoustical absorption due to friction between air and porous matrix and thermal relaxation were compared with measured results for an idealized porous structure. The model was used to infer porosity, tortuosity, and pore size from measured acoustical absorption spectra for manufactured porous asphalt and extrapolate test results to nonnormal angles of incidence, assuming isotropy of the porous structure. This model will help improve mix designs to increase the absorption of pavement surfaces and can be used to estimate porous pavement properties.

Field Investigation of Acoustic Performance of Various Asphalt Surface Mixes

This study investigates the level and trend of tire/pavement noise on pavements with various asphalt surface mixes, and the effect of mix design factors on tire/pavement noise. Noise data were collected on the California highway network, using a newly-developed on-board sound intensity (OBSI) method, in three consecutive years from various asphalt pavements. Results show that tire/pavement noise generally increases with pavement age. Compared to conventional dense-graded mixes, open-graded mixes and rubberized gap-graded mixes can reduce noise, but with different noise reduction life spans. Open-graded mixes can retain noise reduction benefits for about five to seven years, while gap-graded mixes can only retain the benefit for a short period. The noise reduction benefit mainly comes from higher air-void contents in the open- or gap-graded mixes, while the rougher surfaces of open- or gap-graded mixes contribute to the increase of noise at low frequency levels.

Comparison of tire-pavement noise characteristics of rubberized and conventional asphalt concrete mixes

This study compares tire/pavement noise characteristics of flexible pavement sections in California using the On-Board Sound Intensity (OBSI) method. Two experiments are presented in this work. The first one compares noise properties of pavement sections of different ages constructed with open-graded rubberized asphalt concrete (RAC-O) and gap-graded rubberized asphalt concrete (RAC-G) versus sections with conventional open-graded asphalt concrete (OGAC) and dense-graded asphalt concrete (DGAC). The second experiment compares the performance of trial sections that used different modified rubberized asphalt mixes as surface course. The results show that, compared with conventional asphalt concrete surface course of the same age, rubberized asphalt concrete surface courses have lower tire-pavement noise levels. The reduction comes mainly from better durability of rubberized asphalt concrete mixes. Additional information analyzed in this quieter pavement research study includes the effect of mix design variables and pavement surface distresses on tire-pavement noise characteristics of rubberized and conventional asphalt concrete mixes.

California-Denmark Study on Acoustic Aging of Road Pavements

Knowledge of acoustic aging of road pavements is needed by road administrators when developing policies and strategies for noise abatement. It is important to know how noise-reducing pavements, as well as pavements without such acoustic properties, perform over time. Methods such as the American traffic noise model method or the Nordic NORD2000 method use acoustic aging for accuracy in predicting noise. Noise performance models for road pavements are necessary if noise is to be integrated as an active parameter in pavement management systems. This paper contributes to ongoing international development in the field of acoustic aging by performing a comprehensive analysis of results from four Californian and Danish long-time noise measurement studies on asphalt pavements. There is not much information on which changes in the surface structure cause an increase in noise in the period between when the bitumen film is worn off and when the pavement begins to deteriorate with distresses such as raveling, cracking, and so forth. This study analyzes and compares trends in the development of noise over time. The development of the noise spectra is also analyzed. The increase of noise has normally been analyzed in relation to the age of pavements. The traffic load and an artificial indicator, defined as the change of noise predicted as a combination of actual physical age and traffic load, are investigated.

Nondestructive Testing for Crack Width and Variability on Continuously Reinforced Concrete Pavements

Previous research has shown that the main failure mode in continuously reinforced concrete pavements (CRCP) is the punchout, a distress associated with the loss of load transfer capacity across transverse cracks. Despite the fact that crack width is widely recognized as one of the most important factors in CRCP punchout development, little research has been focused on effectively quantifying this variable. This paper presents results of crack width determined by measuring the crack closing movement under the action of vertical loads. The CRCP crack width data were acquired by using a rolling wheel load and a falling weight deflectometer (FWD) measuring technique. Crack width was successfully determined with an FWD, which enables future use of this device and technique to determine field CRCP crack widths. Crack width distribution is difficult to assess initially on CRCP test sections because the zero-crack width temperature needs to be known and the average pavement temperature must be less than this valu...

Assessment of Tire Noise on Concrete Pavement in California Highways

A 2-year initial study, recently completed in California, measured and compared tire–pavement noise levels with the onboard sound intensity method on existing concrete pavements. The study included 120 pavement subsections at 47 sites; most sections were measured twice in the 2 years. The surfaces encountered were classified into five texture categories: burlap drag, diamond ground, diamond grooved, longitudinally broomed, and longitudinally tined. The experiment was not balanced for age, traffic level, or climate region. The surfaces were further categorized as having new, aged, or worn-out texture. The differences within and between surface types were assessed for spectral content and overall sound intensity. The results revealed a large overlap in the onboard sound intensity levels between texture types. The quietest sections overall were measured on diamond ground surfaces. However, on the basis of the average noise level of the evaluated sections of each texture type, the longitudinally broomed surfaces as a group were the quietest, although they were represented by a small sample in the experiment. The study indicated that the sound intensity of concrete pavements in California ranged from about 99 to about 107 dB(A). The measured onboard sound intensity levels included the effects of joint slap, faulting, and sealant, if present, in addition to the texture.

Evaluation of effects of pavement characteristics on the OBSI levels using Principal Components Regression

Tire/pavement noise is a major contributor to traffic noise at highway speeds. Tire/pavement noise is affected by different pavement properties. A study conducted in California measured the noise levels of different mix types and the mix characteristics affecting noise levels. In this study, tire/pavement noise was measured using the on‐board sound intensity (OBSI) method. Data was collected on four different types of pavement mixes: conventional open graded asphalt concrete (OGAC), rubberized asphalt concrete that are open graded (RAC‐O), rubberized asphalt concrete that are gap graded (RAC‐G), and dense graded asphalt concrete mixes (DGAC). A total of 72 field pavement sections were included in the study, all of which were less than 8 years old at the time of the measurements. This paper evaluates the pavement characteristics affecting noise levels using principal components regression. This technique was used due to the multicollinearity found among the variables. Two principal components were extracte...