FOSAAERODROME

The Journal of the Friends of Sywell Aerodrome

No. 17 Summer 2010

The story of how we built the first concrete runway for 50 years

The approval for the All-Weather runway from the Secretaries of State was received in November 2007 which was followed by a three month period when a legal challenge could have been mounted if those that oppose us, including the Council, had found grounds. However, a challenge was not forthcoming.

In the meantime Ben Verrall of Jacobs Gibb was working hard on producing construction drawings and specifications. Ben has been with this project since 1998 and he played a major role in the Public Inquiry. In the lead up to the construction work commencing and even after it had begun I was having sleepless nights over the construction programme. We had received quotations for the design and build of the runway from two major contractors but the prices were far more than we had expected and out of reach for our business model.

Therefore the decision was taken by the Board of Directors to undertake the construction ourselves using specialist contractors where necessary. This meant that Sywell Aerodrome took on all the risk and the management of the construction work in exchange for substantial savings in cost. This obviously placed a great deal of responsibility on my shoulders.

I needed a Team and some specialist Plant to build this runway, Porky and I could not do it on our own. On my search I came across a chap called John Moore who led me to Colin Jailler of Castellan who was to be instrumental in giving me the confidence that we could do it ourselves. He also provided the contacts of those who had the plant we needed. Then I needed some people. I first contacted Richard Payne to enquire whether he would be interested in taking on the challenge of being Project Manager and thankfully he agreed.

The final hurdle before work could commence was to discharge the drainage condition. Having received approval from the Environment Agency, it was not until the 19th June that the Council confirmed the condition was discharged. We started stripping top soil on 24th June.

Stripping off top soil.
Stripping off top soil.

Cut and fill subsoil.
Cut and fill subsoil.

Wirtgen stabilising machine.
Wirtgen stabilising machine.

Caterpillar grader.
Caterpillar grader.

But there were still gaps in the construction plan which continued giving me sleepless nights until all the pieces fell into place. It was early August when we held "The Grey Head Team" meeting of all the party principals involved. My basic idea was that the experience of "The Grey Heads" would outweigh theory and b.s. We talked through the project and the commitment required if we were to be successful. I sensed a real passion amongst "The Grey Head Team" to deliver the first concrete runway for over 50 years. I could now sleep easier.

Stripping the top soil was carried out in glorious sunshine that was to stay with us until that was finished along with the subsoil cut and fill. While doing this we decided to alter the runway profile to a straight gradient from one end to the other and get rid of the large dip in the middle of the land contour. This entailed lifting the centre of the runway by approx. a metre which required a huge amount of clay subsoil fill, care of Doug at Storefield, to make up the large area to be lifted. As the subsoil was layered it was stabilised with cement and lime and consolidated to ensure there would be no future movement. Once the cut and fill was complete and graded to within +25-30mm, it was ready to hand over to Des Ferguson of Powerbetter, the stabilising gang with their huge Wirtgen machine which literally eats up the ground, mixes it with cement, lime and water and spits it out to be consolidated by a vibrating roller to a density of 95%. Once set the stabilised subsoil achieved a CBR of 30, strong enough thankfully for a heavy HGV to drive on it by accident without even marking the surface. Quite incredible.

Powerbetter then handed us back the 300mm stabilised subsoil layer trimmed to +0/-50mm by the grader - an ex-MOD Caterpillar Grader that had been beautifully restored driven by an old paddy puffing away on a roll up permanently perched on his lip.

Stabilising concrete compound.
Stabilising concrete compound.

Stabilising subsoil on runway.
Stabilising subsoil on runway.

Building up subsoil.
Building up subsoil.

Pushing type 1 up runway.
Pushing type 1 up runway.

Each phase of the process was surveyed and checked by our engineer, Jimmy and his small team from Samsett. Having set out the levels of each phase of work, they would go back and survey the finished surface to ensure they were within tolerance. Jimmy looks like an old hippy and is quite a character but has an incredible ability for mental maths. Richard Anstee and his small team from Soil Mechanics were also testing and checking the construction strengths. Both teams would stay with the project to the end of concreting providing me with the results of their surveys and testing to ensure all phases of the construction were up to specification. Richard, a Welshman, had a huge voice. He and his laughter could be heard all through the Hotel in the evenings increasing in volume in accordance with the volume of beer consumed!

Tippers delivering type 1.
Tippers delivering type 1.

Stabilising the type 1.
Stabilising the type 1.

Just as the stabilising of the subsoil was nearing the end it started to rain and did it rain. The original plan was to lay a 150mm sub-base layer consisting of a mixture of crushed concrete, road planings and lime stone. All these materials were readily available locally at a good price. However, I was concerned about the rain knowing how crushed concrete can go to mush when wet and how on earth we were going to place this layer without making a mess and damaging the foundation layer.

Cubes for testing type 1.
Cubes for testing type 1.

Installing ducts for lights.
Installing ducts for lights.

So I decided to switch to type 1 granite from Croft Quarry in Leicestershire, albeit at extra cost. Granite does not absorb water so it remains stable when wet. So we reversed the tippers along the service track at the middle of the runway, tipped them up on the edge and the CAT pushed the granite out, first at a depth of 300mm. We kept tipping and pushing until we had pushed the granite out over the stablised subsoil to the top of the runway creating a wide roadway. We then pushed the granite back down the runway pushing it out to depth of 160mm leaving the grader and old paddy to finish off at 155mm depth trimmed to a tolerance of +0/- 35mm. This worked well we were able to work all through that long period of rain without damaging the stabilised layer beneath.

Stoning apron base.
Stoning apron base.

Concreting apron.
Concreting apron.

Pushing out subsoil.
Pushing out subsoil.

First 80 metre trial slab.
First 80 metre trial slab.

While this was going on we were still sourcing aggregates for the concrete mix. We were very fortunate to have had the help of a very capable "Concrete Doctor", namely Peter Able of Laing O'Rourke along with his assistant Bill Halley. We scoured the Country for aggregates with samples arriving daily at Hall Farm for trial. Finally a mix was agreed. The carboniferous limestone came from Cloud Hill in Derbyshire, the sand from Needingworth in Cambridgeshire, the PFA & cement from Yorkshire and the additives from BASF.

While all this was going on Powerbetter's Wirtgen was stabilising the 150mm type 1 granite layer and the grader trimming it to a tolerance of +0/-25mm. The stabilised type 1 granite performed very well achieving a strength of around 11n/mm2.

Bill Hailey and Peter Able.
Bill Hailey and Peter Able.

Tippers loading concrete.
Tippers loading concrete.

Harry the Batcher.
Harry the Batcher.

First runway slab.
First runway slab.

Following up behind Powerbetter, Andy and his team from AC Construction laid the lighting ducts and Porky and his gang put in the large drainage pipes under the runway formation. Jon Gammons and his men were concreting the apron and the taxiway on the base prepared by Porky and his gang.

Drilling type 1 to fix pins.
Drilling type 1 to fix pins.

Setting the string levels.
Setting the string levels.

The "Main Circus" arrived in August. The Concrete plant supplied by Richard of Stelex Ltd arrived in mid August to be built up on the foundations that Andy of AC Construction had already built along with aggregate bays and a large yard area. The concrete plant was up and running ready for trials when technical problems hit the controls. Trials had to be delayed waiting for spares to be flown in from Germany. Paul Baird and his men from Select Plant Ltd then delivered the huge slip form paver along with the texture machine and a whole load of ancillary plant. It took them a good week to assemble both machines ready for tests and trials.

Spraying type 1 with bitumen seal.
Spraying type 1 with bitumen seal.

The plan was to start laying concrete on 1st September, but the weather was terrible, just as well as the trials could not be done due to niggling problems. Anyway we finally laid our first 80 metre trial length of concrete on 4th September in the rain.

Concrete samples for testing.
Concrete samples for testing.

Aubrey and his concrete.
Aubrey and his concrete.

Ben abd Brian inspect cores.
Ben abd Brian inspect cores.

Checking surface tolerance.
Checking surface tolerance.

There were problems with the concrete and the finish. But both Peter Able and Bill Halley were on hand to help. Peter very politely asked Harry, the Batcher, if he could play with his computer controlling the concrete plant. Bill was on the paver. They both had two way radios. I watched as Peter, the Maestro, played the keyboard of the computer like a piano making slight changes to each load of concrete sent to the paver, then asking Bill on the radio what difference there had been. Finally after a couple of hours Peter said "That's it, Harry" and locked the formula into the computer's memory "You can crack on making concrete".

Paver being fed concrete by 360.
Paver being fed concrete by 360.

Peter then told me how lucky we were to have the mix work "straight out of the box" as he said "It can take days". I thought about what he had said and then it dawned on me. Peter had the choice of all the ingredients available, free of any financial constraint to compromise his mix. That is why I think it worked "straight out of the box" as he said.

Slab out of rear of paver.
Slab out of rear of paver.

We started the runway for real on 10th September and Harry, the Batcher, went on to produce 11,000 cubic meters of superbly consistent concrete. Consistency is the name of the game for the slip form paver we were using. If the consistency changes the concrete either falls over after being laid as there are no forms and shutters or the 44 ton paver cannot lay it as it is too stiff and it's a very fine line between the two. During the whole pour we did not have to breakout a single bay, which was quite incredible.

Marking the slab for cutting.
Marking the slab for cutting.

The concrete tents.
The concrete tents.

After each day's concreting the slab required sawing at 5metre intervals to induce cracks as the concrete cooled and contracted. The two cutters would come in over night to cut the slab when the concrete was ready, sometimes after midnight under floodlights.

Each day we wasted the last 8 cubic metres of concrete because that was the amount left in the paver which cannot be laid. The waste would be cut off and loaded into a tipper and dumped on our concrete heap for crushing. Well Richard's brother, Aubrey, my brother-inlaw, was building at home. He asked if I could do him a favour and let him have some of the concrete left at the end of the day. I told him he could have it with pleasure but I warned him I was doing him no favour as he was to find out. Aubrey turned up with his David Brown tractor and trailer we loaded a couple of bucket loads on to his trailer and off he went looking very pleased, the tractor bellowing out black smoke under the load. A short while later Richard received a call "help, help, it's going off" Aubrey had just discovered it was not the concrete he was used to. Its so stiff and dry it is difficult to do anything with, let alone shovel and level it. Well I think after most of the family had turned out to help, the concrete got laid. Needless to say, Aubrey didn't come back for anymore!

Progress at the start was slow. We now had about 15 Polish and Lithuanian labourers helping us but we were still very short of the daily output required to finish by the third week in October. I was pushing hard as I kept telling everyone "It's going to start raining the last week in October" and how do I know that? because it always does. We were only laying 100metres length instead of the average required of 315metres and I was worried we would have to abandon the job until after winter if we did not finish by then.

Washing down.
Washing down.

On the last slab.
On the last slab.

The weather was also hampering progress. So I purchased enough concrete tents to cover 100 metres length of concrete, which is the amount we could lay in a 2 hour period, the time required for the concrete to go off sufficiently to accept rain with no damage. But they proved a real pain to handle, like huge wings ready to take-off at anytime if you faced them the wrong way. But they did the job and meant we could make the decision to lay when the forecast suggested we shouldn't. This undoubtedly saved many days of concreting when we would have otherwise stood down.

Anyway after a few nights in the bar and a few beers later we soon started to work as a team and didn't that team just tick - like a clock all the way to the end, pushing out 450metres length or 500metres cube on good days, finishing a superb job on schedule on 22nd October!

The one tolerance I was particularly concerned about was the surface tolerance that had to be within 3mm over a 3metre length. That's very tight. We achieved between 1 to 2mm over 3 metres.

MHBB tipping the last load.
MHBB tipping the last load.

Texture machine applying friction surface.
Texture machine applying friction surface.

After laying the last piece of concrete I remember someone asking how I felt. I replied "I feel both very happy and relieved we produced such a good job, but, very sad to have to break up such a great Team". There were a few beers drunk that night and a few tears as well I can tell you. On the last day after clearing up we took all those left on site flying to show them what they had built. I saw it for the first time too. We were all blown away by the experience. It started raining the following week! I know now why this is the first concrete runway since 1957 - because it is so damn difficult in concrete. With concrete you only get one shot at it and it is either right or wrong, mistakes in tarmac are very much easier to correct. As one person said to me "What you are trying to do is precision engineering in concrete and the two don't go together".

The End.
The End.

Richard Payne and Paul Baird go flying.
Richard Payne and Paul Baird go flying.

I would like to personally thank everyone involved in making this project possible and everyone involved in the construction for their support and commitment. There is no doubt that everyone that has been involved in this project has had a passion which has resulted in going above and beyond the call of duty when the going has been tough. To think we built the runway in just 17 weeks and 3 days is just incredible and I am sure we will all have our own amusing memoirs of how we did it. Thank you all for building a great runway that should last for at least 50 years or even longer. The All-Weather runway will give Sywell a real future and give the County a facility, which can only assist in improving job prospects and improving the economic success of business in Northamptonshire.

Toast to the runway.
Toast to the runway.

M.H. Bletsoe-Brown

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