| dc.description.abstract | Asphalt concrete (AC) is a sensitive material with temperature, its stiffness is greatly influenced by ambient temperature. As the temperature of the asphalt concrete increases, its stiffness decreases that may lead to rut occurring on the asphalt pavement from wheel loads. A decrease in asphalt concrete stiffness results in lower structural capacity to support vehicle loads. Therefore, the mechanical property of flexible pavement is affected by temperature deeply.
In this study, based on field temperature measurements obtained from a test site simulating actual pavement structures of freeways, the pavement temperature distribution in Taiwan’s freeway were discussed in details. The results indicated the temperature of pavement changes with the climate within a year. Since the thickness of freeway pavements in Taiwan is relatively thick, the temperature distribution of the AC and bituminous treated base (BTB) layers was found to be different. Thus, separate temperature prediction model was established according the characteristic of each asphalt layer.
Based on the test results, the effective temperature depth of pavement was affected by the temperature distribution of AC and BTB. Through the analysis on pavement structural responses, it is indicated that the 1/2 depth of AC layer and the 2 cm under the top of BTB layer are considered appropriate depth as effective temperature for strautural analysis of pavements. Also, separate temperature prediction model were established for AC and BTB layers, respectively.
Besides, considering the pavement temperature variation within 24 hours and traffic loads applied on freeway pavement, the damage per pass of each load axle was calculated for different times in a day. It was found that the damage increases as pavement temperature increases in the daytime and reduces as the temperature decreases in nighttime. In other words, the temperature cycle within a day has a great effect on the damage level caused by traffic loads in flexible pavement. Moreover, with the thick pavement structure used by Taiwan’s freeway, it was found that the fatigue damage will occur earlier than permanent deformation.
Various time-durations, ranging from 1-hour to 1-year, for average temperature input to predict pavement service life and/or design ESAL were evaluated carefully. The effects of pavement average temperature of various time periods and traffic loads on pavement damage ratio and service life were determined. It was found that the 1-hr time period with average pavement temperature could simulate the actual response of freeway pavement under the pavement temperature cycle and traffic loadings. Segmentation of the pavement temperature and traffic loading into 1-hr period will produce a pavement damage ratio greater than that into 1-yr period. This indicates that the actual damage of freeway pavement is more severe than that expected by considering the yearly average temperature only. The adjustment coefficient of pavement service life established the relationship for the apparent difference between the yearly based average temperature and the real situation of in-situ pavement temperature. Using the pavement service life calculated using 1 hr period as the basis, a correlation is established for different time periods for average temperature. It provides an exact relationship obtained from the average temperature of 1 hr period and a yearly period for pavement structure design and the estimation of remaining pavement service life.
| en_US |