Background
The concrete slabs that for the taxiway at Luton Airport have been in place for 12 years. Whilst the vast proportion of slabs themselves are operationally sound, in some areas there is rocking occurring as a consequence of the fines beneath the slab being gradually washed out over time.
The client required an urgent repair to an area that was being maintained on a daily basis by Ryebridge Civils using temporary repair measures. A daily cost was incurred for the maintenance and with a busy christmas schedule ahead the client was looking for a more cost effective, immediate alternative.
Geobear Solution
Following a private message sent to Geobear’s Head of Infrastructure, we consulted our design teams and returned a proposal within 24hrs. On acceptance of the proposal we mobilised our units and were on site just 24 hrs later.
The area of treatment was four slabs off Charlie taxiway. All of the slabs were rocking due to voiding beneath and seriously compromising the ability of air traffic to use the area. There was also a serious health and safety implication for the continued use of the slabs using the temporary repair, which could ultimately cause a major break up of the already cracked slabs.
Our solution was designed to provide a permanent stabilised foundation for the affected slabs. The treatment sees us drill small 14mm holes at 1.5m centres across the slabs and inject one of our geopolymer materials suited to the site conditions. Our geopolymer material is injected as a two component liquid beneath the slab, as the components mix before release into the affected area, a reaction starts which results in the fast expansion of geopolymer. This polymerisation fills the voids beneath the slab and forces out residual water in the area.
Whilst the material is injected beneath the slab, we monitor any movement with lasers which indicate just 0.25mm of movement, we can either purely stabilise the slab in its existing position or lift back to the required levels.
Within 15 minutes of injection, that area of slab becomes fully stabilised and is operational. Our solution for this project was delivered over one night enabling the client to re-open this area of taxiway without the need for any further daily repairs.
Alternative solution
The only options available to the client was the continued, costly daily repairs to the site or a complete breakout of the slab with a new foundation and slab introduced. It would have taken almost a week of full night closures with a daytime closure of the taxi way to achieve this.
Why Geobear
Geobear was chosen to deliver the geopolymer solutions because the speed of the work meant only one night would be required to fix the foundations and stabilise the slabs. The client was also accustomed to our customer first ethos, whereby our design team and operations teams were able to accomodate this urgent work.
The overall pace at which we could mobilise is a further reason Geobear is chosen ahead of alternative solutions. To have first contact with the client and be on-site delivering works within 72 hrs is a feat we are proud of in itself.
Summary
Rocking slab
Describe solution (area, length, depth):
4Nr 4m x5m slabs
History/ cause of problem:
Damaged through time / constant use
Client requirements:
4 slabs need stabilisation.
