Antigo Breakers Ltd

The future of Runway Rehabilitation

With the arrival of bigger, heavier aircraft, such as the super jumbo Airbus A380, many existing international airport pavements will be tested to the limits. This, with the growing demand for air travel and the subsequent increase in airport capacity together with the rapidly ageing pavements at some of the world’s international airport, will require new innovative methods of reconstruction if the industry is to meet this commercial challenge. Traditional methods of replacing concrete pavements [URC] are costly and time consuming. To minimise cost, disruption and to meet environmental considerations, alternative methods of rehabilitation must be found and utilised.

The challenge for rehabilitation teams is that airfield pavements are often significantly thicker than highways, and have to accommodate very heavy aircraft loadings travelling at low speeds and at relatively lower frequencies than highway pavements are subjected to.

Antigo have accepted this challenge and developed two in-situ methods of recycling concrete pavements to meet the varying levels of deterioration found on existing airfields. The cracking and seating process, initially developed for highway pavements, is the first consideration for in-situ recycling of airfield pavements. Rubblization of existing pavements has been developed for those pavements that show signs of destabilisation beyond that considered suitable for cracking & seating.

These processes are anticipated to grow on both civilian and military airfields due to their unique advantages and have been utilised as far a field as Afghanistan and China.

What is Cracking & Seating?

Cracking & seating involves fracturing the existing pavement into consistent sections, and then rolling or ‘seating’ the processed slab with a heavy pneumatic tyre roller.
The fractures are induced with the use of a Guillotine type breaker purposely designed to produce vertical hairline cracks into the existing concrete pavement to form small “platelets”. The introduction of these platelets changes the way the pavement behaves when contracting and expanding due to temperature fluctuations.
After cracking the pavement still retains structurally sound characteristics due to the interlocking of the aggregate across the fine vertical cracks. This allows the asphalt overlay to be applied significantly less for the same design life, than specified for a conventional flexible construction. Cracking & seating reduces the risk of reflective cracking together with all the other advantages of recycling.
Cracking & Seating process has been adopted by the BAA pavement and infrastructure team for the reconstruction of the Southern Taxiways at Heathrow Airport. This project involves processing the existing concrete pavements that are up to 500mm thick and applying a 150mm of asphalt overlay.

Antigo Breakers Ltd are the most experienced specialist contractor in the field of ridge pavement maintenance, Antigo’s world wide expertise extends from cracking & seating to the innovative rubberising technique for pavements which, without this unique process, would need to be demolished and removed.

What is Rubblization?

Rubblization is a process that is more aggressive than cracking & seating, and therefore can be applied to pavements that have deteriorated beyond a state that in the past would be removed.
Rubberising eliminates reflective cracking. After rubberising the pavement, as with the cracking & seating process, it still retains some of its structural stiffness so that the asphalt overlay can be kept to the most economical thickness. However, unlike cracking & seating, the existing pavement is broken through the 45 degree shear planes creating smaller sizing of the concrete on the surface and increasing the particle sizing throughout the thickness. Consequently, the maximum bearing capacity with the interface of the underlying sub grade is retained.
The interlocking product produced by rubberising enables the processed pavement to retain stiffness, and is considered a structural layer within the new re-constructed composite pavement.
The advantages of rubberising are that this process is the only effective alternative to removal, and minimises the subsequent costs, risks and disruption involved with full depth re-construction methods.

The first Rubberised Runway Reconstruction: Selfridge Air National Guard Base, Michigan USA.

In 2002, this project was the first runway of substantial thickness, [530mm] to be rubberised The successful implementation of this process, by Antigo Construction Inc., confirmed the fact that rubblization of airfield pavements is an effective means of maximising the structural integrity of existing concrete pavements.

Up to the end of 2004, Antigo have processed some 12 million square metres of airport pavements and a grand total of 126 million square metres of pavements in general.

Since Antigo introduced their new concepts in pavement maintenance the global tendency is towards in-situ recycling in preference to the removal methods of total reconstruction.

Antigo breaks technological barriers at Heathrow Airport

The arrival of the Airbus A380 at Heathrow Airport, and impending taxiway reconstruction prompted the BAA team to look beyond traditional runway rehabilitation techniques to achieve cost savings, minimise disruption, and save time.

A worldwide study of airfield taxiways revealed that the crack and seat technique had been used on several civil and military airfields, but none carried traffic of the weight and frequency that Heathrow’s new taxiways would experience. Full-scale trials established that a crack and seat solution was suitable for heavyweight aircraft travelling at relatively low frequency on concrete pavements. Monitoring of actual deflections on Heathrow’s taxiways verified its suitability, and in May 2004 work commenced on the first crack & seat pavement at Heathrow.

Antigo Breakers utilised the latest technologically developed guillotine breaker to cope with the 420mm depth of 30-year-old concrete on the taxiways. This breaker has solid tyres fitted to the rear axle, a variable drop height, and improved hydraulic technology for the drop cycle, all vital factors in minimising the risk of ‘over cracking’. The interlocking friction on the cracked faces is paramount in the transfer of loadings between the ‘platelets’.

Another technical challenge for the pavement team was to find a reliable and cost effective means of getting power to the Aircraft Guidance Lighting (AGL). The solution was to lay the electrical supply cabling for the AGL into chases in the lower layer of stone mastic asphalt (SMA), and cover it in the final pass.

The benefits of utilising cracking & seating at Heathrow included:

1. A 90% reduction in construction traffic compared to conventional rehabilitation, helped by using up to 10% asphalt planings in the resurfacing.



2. Time on site cut by more than 15%.



3. In terms of cost per square metre crack and seat, with 150mm of SMA, is 25% cheaper than a PQ pavement. And overall it saves at least 10% on the project costs.



4. Reducing vehicle movements helped to reduce disruption to the local community on local airport roads, and also minimised the logistical difficulties of crossing live runways.

The conclusive success of utilising this method at Heathrow, demonstrated smarter investment in airfield infrastructure.

On airfields and highways, Antigo’s unique processes of cracking & seating and rubberising have shown cost savings of up to 40% when compared with traditional methods of pavement refurbishment.

Contact Details
	T: + 44 (0) 1235 869 021
	F: + 44 (0) 1235 869 022
	E: mailbox@antigobreakers.co.uk
	W: www.antigobreakers.co.uk