Asphalt Pavement Temperature Profile For Tropical Climate in Indonesia

Asphalt pavement temperature, its value varies is influenced by several factors such as air temperature, solar radiation, wind speed, and reflectance of the asphalt pavement surface. Variations in air temperature directly affect the asphalt pavement temperature variations and this is very important to know in connection with determining the use of asphalt performance classes and the resulting structural capacity.

Indonesia is located at a relatively small latitude (6⁰ LU - 11⁰ LS) crossed by the equator so that it has a tropical climate and receives heat from high intensity sunlight. Indonesia's territory is traversed by two monsoon wind movements (west monsoon and east monsoon) experiencing two seasons, namely the rainy season in the October-March period and the dry season of the April-September period. On the other hand, around 70% of the territory is in the form of water, so it has a sea climate with often cloudy air, high humidity and rainfall. With these climate characteristics, it is important to know the asphalt pavement temperature profile.

1.       The method of measuring temperature and humidity and asphalt pavement temperature in the field is carried out with a thermocouples equipped with a data logger. In general, the equipment can be described as follows.

2.       Sensor and signal conditioning using DS18B20 type, is a type of digital temperature sensor with a resolution of 9 to 12 Bit, ± 0.5 ⁰C. This sensor has a data communication system with a 1 wire BUS line.

3.       Signal processing, using the ATMega 8 microcontroller which functions as a signal processor, and controlling data communication between sensors with a computer.

4.       Interfacing, functions as an interface between the microcontroller and the computer, in a serial data format.

5.       Display, functions to display the measurement data. using a computer monitor, through a custom-made application program.

6.       Data recorder, functions to record measurement data. In this case it was created through an application program, which was built based on a visual basic programming language.

Observation stations are installed on 4 (four) national roads in the Province of Bali to monitor air temperatures, humidity and pavement temperatures at various depths. Monitoring is carried out in the dry season, sunny weather and in periods of maximum air temperatures. Measurements were taken every day for seven days with a recording time interval of every 30 minutes. Asphalt pavement temperature measurement position is on the surface (0 mm), a depth of 20 mm, ie in the middle of the thickness of the surface layer (asphalt concrete wearing course - AC-WC) and at a depth of 65 mm, ie in the middle of the intermediate layer (asphalt concrete binder course - AC-BC). Local air temperature is measured at an altitude of 1 to 2 meters above the asphalt pavement surface.

The air temperature starts to increase at 6:00 AM and the increase varies with a maximum value of 36.28 ⁰C at 2:00 PM, after which the pattern decreases with a minimum value of 24.92 ⁰C at 5:00 AM. In contrast to air humidity, it increased from 5:00 PM to a maximum value of 83.69% at 06:00 AM, after which the pattern of air humidity decreased to reach a minimum value of 50.31% at 2:00 PM.

For all asphalt pavement temperature values, the pattern is relatively the same. There was a process of increasing and decreasing the temperature in a relatively similar time scale. Along with the increase in air temperature an increase in asphalt pavement temperature, where the maximum temperature occurs at 2:00 PM (T. amb = 36.28 ⁰C, T. 0 mm = 45.65 ⁰C, T.20 mm = 43.59 ⁰C and T. 65 mm = 38.54 ⁰C). Looking at the data above, the thing to note is that the asphalt pavement temperature has a higher value than the air temperature. In the heating process, the surface response of asphalt pavement (00 mm) is faster than the pavement layer below so that the temperature is higher. Conversely in the process of cooling the response is also faster so that in this phase the surface temperature of the pavement (00 mm) is lower than the pavement layer below it.