Development of Microstrip Antenna Sensor for Concrete
The microwave reflection type sensor using microstrip disk antenna is developed. The purpose of developing the sensor is to monitor the fresh concrete hardening and to determine concrete curing point. The structure of microstrip disk antenna is divided into three parts i.e. radiation surface, su...
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| Main Author: | |
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| Format: | Thesis |
| Language: | English English |
| Published: |
2001
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| Subjects: | |
| Online Access: | http://psasir.upm.edu.my/id/eprint/9313/1/FSAS_2001_46.pdf |
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| Summary: | The microwave reflection type sensor using microstrip disk antenna is developed. The
purpose of developing the sensor is to monitor the fresh concrete hardening and to
determine concrete curing point.
The structure of microstrip disk antenna is divided into three parts i.e. radiation
surface, substrate and ground plane. This antenna is developed from polytetra
fluoroethlene (PTFE) or random micro fibre glass substrate (RTD 5880) with dielectric
constant &r = 2.2. The RTD 5880 substrate is selected based on its suitability to operate
at the resonant frequency of 10.7 GHz.
In developing the microstrip antenna, parameters such as radius of disk, resonant
frequency, resistance at resonance, total quality factor, efficiency and bandwidth has to
be taken into consideration. The difference between calculation and experimental
results of the resonant frequency and resistance at resonance is about 5%.
The measurements on fresh concrete and concrete curmg are done in via two
techniques namely contact and non-contact. The samples were prepared based on water to cement ratio 0.5, 0.55 and 0.6. These samples are left to dry in natural condition and
at room temperature for 1, 3, 7, 14 and 28 days.
The results of both techniques showed that reflection from non-contact technique have
readings higher than 100 mW and was more stable compared to contact technique. The
non-touching technique was also easy to manage when applied to fresh concrete
compared to the touching technique.
Studies had shown that the power reflection is inversely proportional with concrete
curing time. Significant power reflection reduction had occurred during the first three
days of curing process. This phenomena was due to accelerated hydration process that
happening inside the concrete during that period. As the curing process resumed,
hydration process slowed down then reaching approximately a constant rate. It is
during this period that the concrete had hardened and gained its strength.
Realising the relationship between microwave, moisture content inside the concrete and
concrete strength, the microwave moisture sensor is developed to measure the water or
moisture content. This approach can be utilized as a technique in non-destructive
testing for concrete to monitor concrete hardening process and predict the anticipated
concrete strength in order to fulfill design requirements |
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