A22 Vibration Control and reduction
Working for East Sussex Highways, Geobear was contacted to address slab movement on a section of the A22. The joints between the concrete road slabs on part of the road in Lower Dicker were experiencing failure due to voiding under the joints (Figure 1).
The voiding led to rocking of the slabs under axle load which was leading to accelerated degradation of the bays. To remedy this the voids needed filling and the sub-base compacting, the outcome would be the stabilisation of the slabs thus extending their life.
A secondary issue was the level of vibration caused by the rocking slabs. This is a consequence of the continued slab movement resonating through the ground to the nearby residential houses.
Using a Geobear geopolymer to stabilise the slabs would reduce the vibration impact felt by nearby properties. This project presented the opportunity to collect data to measure the additional vibration reduction properties using a geopolymer resin.
The affected area comprised two 3m x 15m concrete bays. The Geobear-designed solution used a specific geopolymer resin injected directly beneath the slab through drilled holes. The geopolymer is injected as a liquid and a reaction occurs resulting in an expansive resin filling voids and compacting the base. Each slab would require injections of a predetermined quantity of geopolymer at 20 specific points (Figure 2).
Prior to the injection work, Geobear installed 8 accelerometer sensors at four locations (Figure 3). The sensors were buried 100mm below ground level and 200mm away from the kerb edge. Each sensor recorded the vibration levels at the site pre-treatment and post-treatment which accumulated 16gb of data.
To ensure consistency in data interpretation, the analysis focused on the data collected on the Tuesday prior to the works and the Tuesday post works between the hours of 4:00 pm and 12:00am (Figure 4).
- RED = Pre-treatment measurement on 22nd of September
- BLUE = Post-treatment measurement on 28th of September
By comparing peaks on the vibration records graphs a reduction of up to 83% was recorded (Figure 5); specifically:
- Reduction of 83% in the number of times the vibrations exceeded 0.25m/s2 post-treatment.
- Reduction of 72% in the number of times the vibrations exceeded 0.5m/s2 post-treatment.
Based on the findings the use of a geopolymer resin used as compaction and void-filling material beneath concrete slabs not only stabilises, but also acts to dampen the vibration potential of the asset.
The added value of the use of a geopolymer resin to stabilise rocking slabs provides:
- Fast implementation of solution, bays completed within one shift
- No road closure requirements
- No excavation
- 75% less carbon emissions (based on report by Carbon Footprint)
- 83% reduction in vibration exceeding 0.25m/s2