The £1.5bn A14 Cambridge to Huntingdon scheme is Highways England’s biggest single project in construction. Over a 30-month period, using local primary and secondary aggregate supply sources, around 800,000 tonnes of asphalt and 500,000 tonnes of Cement Bound Granular Material (CBGM) will be installed. Dominic Browne finds out more
Known locally as one of hell’s highways, the A14 can often either be a congested slog or a nerve-wracking ride as freight lorries rumble past from Felixstowe heading on to the Midlands’ so-called ‘Golden Triangle’ of logistics.
It has been the subject of long-standing and numerous calls for safety works and capacity increases and the current massive upgrade is perhaps the standout project to be delivered within the first Road Investment Strategy.
Scheduled to open for traffic in December 2020 – although some finishing work, such as the removal of the A14 viaduct in Huntingdon will continue beyond that – the scheme will upgrade the 21-mile stretch of dual carriageway between Cambridge and Huntingdon to three lanes in each direction and includes a new 17-mile bypass south of Huntingdon, 34 new bridges and structures, and a 750-metre viaduct crossing of the River Great Ouse.
Aggregate Industries was selected by IDT to exclusively deliver surfacing works. It won the £70m contract after a 12-month process of early contractor involvement and then had the happy headache of having to actually live up to expectations on this flagship project. Its low noise asphalt known as SuperThin will be used on the project. This is a HAPAS-approved thin surface course polymer modified bitumen, designed to meet the scheme specification of a low noise surface course material that is also durable and rut and spray resistant and offers high performance characteristics for high speed road network.
Aggregate Industries will also lay down a concrete foundation, as well as a base and binder surface course. Paddy Murphy, director of contracting at Aggregate Industries, tells Transport Network: ‘The road will use a flexible composite – a concrete foundation overlaid with flexible asphalt.
‘As we are laying the concrete road we induce cracks into the concrete while it is still wet. It makes a checkerboard of smaller slabs. A rigid concrete road will crack when you drive over it. Our flexible concrete acts like a raft so it is able to move ever so slightly and gently adjust to different stresses. These roads are very robust and really well-engineered. We are seeing more composite roads on motorway schemes, particularly new build.’
Aggregate Industries plans to utilise existing aggregates on-site to supplement the hard stone coming in from its quarry in Leicestershire, Barton Hill. The quarry material is coming by rail for efficiency and to minimise the impact on the local road network.
Once off the rail network, the deliveries are taken to the site in HGVs, which itself presents a huge challenge. There are around 100,000 vehicle movements over a 20-month period for this project.
The site is divided into sections. Vehicle movements are controlled between one section and another. Marshalls are used on site to monitor the vehicles through the different zones and special safety helmets with earphones and microphones are used to help communication.
While there are regular rail deliveries, the scheme also keeps a stockpile of two or three days of materials on-site. Some of the asphalt materials will be covered, Mr Murphy says, and some of the concrete materials will just be in a dampened down pile.
Aggregate Industries also has an aspiration to use recycled asphalt pavement (RAP) as much as possible.
‘The RAP would go into asphalt typically at around 15%. We will try and get approval to increase that where possible. In the concrete works we are using native sand and gravels that are present on site. We would screen it and use it in the concrete cement bound material (CBM). We would probably look to use 70% on-site materials for that.’
The scheme is demanding, with high output and high productivity. As part of its investment for the project and in order to deliver an efficient solution, Aggregate Industries invested in a new £3.5m mobile asphalt plant capable of producing 240 tonnes per hour. It will also be erecting two further mobile cementitious continuous mixing plants within the site compounds.
‘We would expect to lay 2,000 to 3,000 tonnes every day in a 24-hour day,’ Mr Murphy says.
As part of gearing up for this level of production, Aggregate Industries is heavily investing in plant and staff.
Mr Murphy says: ‘We envisage that we are going to have increase our staffing, probably next year, to bring in 25 or 26 new staff. We have bought 20 new asphalt pavers and are currently in the process of replacing pretty much our entire roller fleet. That is more than 50 rollers throughout the year. Manufacturers will only supply a certain number per month. There is a high demand for equipment.’
As well as reducing potential downtime, modern new machines can boost productivity by being able to self-adjust. This means, along with other recent schemes, the A14 project will be ‘pinless’, Mr Murphy explains. ‘This means the technology can achieve the surface elevation without an engineer out there banging pegs into the ground. It is done by GPS. The machine knows where it is on the road and how many metres above sea level it is, so it can lay the road to the exact tolerance level. You don’t have to spend too much time adjusting and setting them up.’
Highways magazine has previously reported on the innovations Aggregate Industries has made in creating digital road readings – creating a digital recording of the exact nature of the road from quarry to transport to laying. This is being taken a step further on the A14 scheme.
‘Now we have what we call AIT, which is Automatic Inspection and Testing. We trialled this in 2017 on the M1. We have an approval to use that. So it basically gives you a digital ‘as built’ on the works, so an asset owner can take ownership at the end of the contract of exactly how the road was built.’ This includes data on weather conditions, road texture, the number of passes from the rollers and where the material is from, and is described as ‘a fingerprint of that road – a marrying of Building Information Modelling and reality all at once’.
The A14 project has the potential to provide new best practice for the industry and set higher standards both in terms of delivering a major project and in terms of recording and benchmarking its achievements. This is certainly one area that Aggregate Industries has worked on since working with Highways England.
‘We have started to produce short interval control (SIC) sheets. We have introduced this to our asphalt and concrete plant and are currently installing it on our asphalt pavers. The principle is you look at your process in a similar way to a conveyor belt.
‘With SIC sheets, every time a key component stops you have to come up with a reason. Over a period of time, you build up a picture of why you stopped producing material and then you go and tackle those problems. Every day you measure yourself against best demonstrated practice (BDP) – the average of the best three days of production you had in an entire year. If the A14 used to be known as a road to hell, its users should know when it comes to improving it, there are certainly no idle hands.
