Quantifying Slab Movements in Concrete Pavements Through Magnetic Induction Sensors

Quantifying the movements of concrete slabs plays a crucial role in understanding the effects that lead to pavement distresses and failures over time. Measuring slab movements has previously been a difficult task as it requires the successful implementation of sensors embedded within the concrete pavements. Minnesota Department of Transportation pavement researchers adapted a recently developed method which utilizes magnetic induction (MI) sensors to detect subtle movements in pavement slabs with a high degree of accuracy. In 2022, 17 newly paved concrete test cells at the MnROAD facility were instrumented with two MI sensors. One sensor was to measure movement due to traffic loading and the other sensor was to measure movement due to environment factors. They are paired with an advanced data acquisition system. By strategically installing these sensors in the pavement, researchers were able to monitor movements between the slab and the underlying base layer. This paper provides an in-depth analysis on the results provided by these sensors. Despite only a few sensors successfully collecting data, some key findings were identified. Those include: Daily range of fluctuations in measured vertical displacement was approximately 0.5-1.0 mm. Larger seasonal changes in displacement were observed during times when bottom of slab temperatures indicated freeze/thaw occurrence. The average total range of displacement measured in all three cells was 4.94 mm. The largest measured displacement from the original position occurred during the coldest time periods.