Rare 10-year study shows benefits of apshalt reinforcement

10/11/2020
Richard Carr

Richard Carr of ABG - a leader in high performance geosynthetic systems -  discusses a 10-year trial showing geosynthetic asphalt reinforcement can save on maintenance costs.

More than just a bump in the road

Increasing traffic volumes, heavier loadings and the frequency of flooding events all place an excessive strain on the UK’s road infrastructure, resulting in defects from reflective cracking and potholes.

Asphalt Industry Alliance (AIA) put an astronomical price tag of almost £11bn to repair every pothole in England and Wales.

Highway repairs in England cost anywhere between £6,500 to £120,000 per mile depending on the extent of the damage, making more cost-effective, long-term fixes to road renovations paramount.

Why reinforce asphalt?

In civil engineering, the principle of adding a tensile element into a weaker material to make it stronger is well established, with the most obvious example being steel reinforced concrete.

Asphalt reinforcement utilises the same principle, low strain elements absorbing load pressures, reducing movement and preventing the development of cracks.

Many laboratory tests and anecdotal evidence show reinforced pavements last significantly longer, or can be constructed at a reduced thickness to achieve the same design life. However, it has always been very hard to prove on an actual heavily trafficked road due to accessibility issues and the difficulty of monitoring, plus the ad hoc maintenance by utility companies obscuring results, especially over a long period such as 10 years.

Normally councils do not have the resources or budget to continually monitor a road over that time period.

Meltham Mills road trial of long-term reinforcement

An ideal opportunity arose in 2009 when Meltham Mills Road, which acts as a bypass to the town of Meltham in West Yorkshire, needed to be fully resurfaced.

A machine installing the geosynthetic system

The road happens to run alongside an estate of industrial units serving a number of factories including ABG Geosynthetics Ltd.

ABG approached Kirklees Council with a proposed trial of their asphalt reinforcement material placed along a proportion of the road, including across the entrance to their factory where the heaviest traffic occurred.

The whole of Meltham Mills Road was planed 100mm and the trial area of geosynthetic installed and overlain with a binder and surface course.

Typical asphalt reinforcement installation build up

Monitoring of the site was easy since the firm’s engineers walk along the road each workday to access the site entrance and could note any changes in condition over the whole 10-year period.

A time lapse camera was fixed to the wall of the entrance to the ABG factory to record vehicle movements throughout the day and night to give a record of the type and frequency of traffic along Meltham Mills Road.

This gave the opportunity to record a vehicle movement count and intensity, with peak flows reaching eight vehicle movements per minute. In addition to the car and van movements, there were 189 HGV vehicle movements per day. This is three times the average traffic for a minor urban road in the Yorkshire region. The entrance to ABG factory saw vehicles turning and manoeuvring, placing high stress on this area.

SCANNER Survey

After 10 years of heavy trafficking the surface showed distinct signs of distress in the non-reinforced areas. SCANNER (Surface Condition Assessment of the National Network of Roads) results from Kirklees Council provided a dataset of road surface cracking for the longitudinal profile of the road for each lane.

The reinforcement installation area (blue) and highly trafficked area (pink) show a correlation with SCANNER results. There are obvious deformations in the unreinforced and heavily trafficked zone (pink) but no notable defects in the heavily trafficked reinforced zone (blue/pink stripes). See figure 1 below.

Figure 1 – SCANNER crack survey mapped to geosynthetic installation. The heavily trafficked/ reinforced sections (blue and pink stripes) show no sign of cracking, whereas adjacent to this heavy cracking occurs.

The benefit of geosynthetic asphalt reinforcement

After the 10 year period Kirklees agreed that the trial had been a success, providing the much needed evidence that asphalt reinforcement extends the life of a road. Kirklees had used similar treatments on other roads in the borough, which, while not monitored as closely, showed the same increase in performance.

Graham Mallory, who was the group engineer, highways and operations at Kirklees Council at the time of the trial, said: 'The trial enabled evidence and comparison of road surface performance at a single site with and without the use of the reinforcement layer.

'As a consequence of using the reinforcement layer we can clearly see the effectiveness in reducing reflective cracking, a longer service life, reduced reactive maintenance works, financial savings over time, and reduced disruption to businesses and the travelling public.'

Based on this long term study it is clear that asphalt reinforcement can provide a significant cost benefit. The initial £5 per m2 cost to install the geosynthetic is recouped by year six owing to the reduction in maintenance required. Comparing a 22-year lifecycle for an unreinforced maintained road with a 26-year lifecycle, the reinforced road saves 21% in maintenance costs alone and it is estimated the overall cost savings will be over 50%.

Long-term asphalt reinforcement trial key findings

  • Unique 10 year repair monitoring period
  • Busy road with high HGV loadings servicing local industrial estate. Three times the average traffic volume for a minor road in West Yorkshire
  • SCANNER results show crack formation correlation between reinforced and unreinforced sections
  • Maintenance saving of 21% and total cost saving of 50% extrapolated over 26-year road life
  • Proven by SCANNER graph, no cracks within geosynthetic reinforced area
  • Reduction in CO2 emissions owing to extended maintenance and resurfacing cycles

You can find out more about asphalt reinforcement geosynthetics at an upcoming seminar from LCRIG

Latest Issue

latest magazine issue

Inside

  • Smart motorways' BCR problem
  • New lighting decision support tool

 

 

View the latest issue


Highways jobs

Highway Engineer - Reactive Maintenance

£35,354 - £40,506 incl. LWA, plus £963 car allowance
We make a difference to the environment we live in. Come and help us manage our highway infrastructure. Bracknell, Berkshire
Recruiter: Bracknell Forest Borough Council

Maintenance Manager

£43,857 to £47,782
We are currently looking for a strong candidate to take up the role of Maintenance Manager at Area 6 Boroughbridge. Boroughbridge, York
Recruiter: North Yorkshire County Council

Engineer Sustainable Development

£32,234 - £36,922 per annum
To help support this key area of work, we are looking for an enthusiastic, experienced and forward thinking Engineer to... Stafford, Staffordshire
Recruiter: Staffordshire County Council

Senior Engineer (Streetscene)

£40,632 - £45,594
We are looking for 2 Senior Engineers to join our team to help deliver effective Capital and Revenue investments programmes to... Hackney, London (Greater)
Recruiter: Hackney London Borough Council

Neighbourhood Highway Officers - West and North

£28,672 per annum
We are seeking a recruit two Neighbourhood Highway Officers (NHO), to be based in Okehampton and Tiverton, Devon. Devon
Recruiter: Devon County Council

Warehouse Assistant/Driver

£20,903 - £24,491 per annum
The successful applicants will work as part of a team in a busy work environment to carry out warehouse and... Sandwell, West Midlands
Recruiter: Sandwell Metropolitan Borough Council

Planning Policy Manager

£61.470 - £64.704
Be part of Greenwich's vision to successfully accommodate a high level of sustainable growth, which... Greenwich, London (Greater)
Recruiter: Royal Borough of Greenwich

Refuse Driver (Rolling Advert - applications checked weekly)

£30.032 - £31.610
It is an exciting time in Street Services at the Royal Borough of Greenwich. Be part of a team who are... Greenwich, London (Greater)
Recruiter: Royal Borough of Greenwich

Traffic Engineer

£32,301 - £37,491
We are currently looking for an experienced Traffic Engineer to join our Design & Engineering team.  London (Greater)
Recruiter: Hackney London Borough Council

Apprentice Civil Engineering Technician

£12,656.10
This opportunity is primarily based out of our West Offices in the heart of York. York, North Yorkshire
Recruiter: City of York Council

Traffic Enforcement Manager

£40,869 - £43,860
As part of a major service transformation, Haringey is seeking to recruit to a new number of new positions. Haringey, London (Greater)
Recruiter: Haringey London Borough Council

Refuse Driver

£30032 - £31610 per annum + (amount shown is salary plus allowances)
Refuse Driver (LGV Chargehand Driver)(starting total pay of £30,032 - this is made up of the base grade salary plus contractual overtime and allowance England, London, Woolwich
Recruiter: Royal Borough of Greenwich

Corporate Director (Environment, Communities & Leisure)

Up to £83,424 (pay award pending)
As one of our two Corporate Directors reporting to the Chief Executive to form our Senior Leadership Team your... Gedling, Nottingham
Recruiter: Gedling Borough Council

Senior Infrastructure Engineer

£45.834 - £56.141
This is a great role in a vibrant and growing team; we’re looking for people with significant experience in... Greenwich, London (Greater)
Recruiter: Royal Borough of Greenwich

Parking Service Business Manager

£43,860 - £46,839
As part of a major service transformation, Haringey is seeking to recruit to a new number of new positions. Haringey, London (Greater)
Recruiter: Haringey London Borough Council

Roads Technician

£18,812 - £23,791
This is a great opportunity for you to join Lincolnshire County Council's Technical Services Partnership as... Lincolnshire
Recruiter: Lincolnshire County Council

Roads Engineer

£25,991 - £35,745
We are looking for people to join one of our three Roads teams, made up of around 30 friendly and enthusiastic professionals. Lincolnshire
Recruiter: Lincolnshire County Council

Senior Project Manager

Up to £50,823 per annum
The role of this post is to oversee the project management, development and implementation of the County Council’s Major Transport Projects.. Leicestershire
Recruiter: Leicestershire County Council

Programme and Change Delivery Manager (Spatial Planning and Urban Design)

£43,833 - £53,115 Depending on skills and experience
Are you a change delivery manager with expertise in England’s local government spatial planning and urban design sector? Wandsworth, London (Greater)
Recruiter: London Borough of Richmond upon Thames and London Borough of Wandsworth

Bridges Manager – Highways and Transportation

£49,320 to £57,376
You will be responsible for... Northallerton, North Yorkshire
Recruiter: North Yorkshire County Council

Highways Presents

Highways on Fridays

Register now!

Latest Video