Smart Solution

by Tony Roe, on July 23, 2020

A Stress Absorbing Membrane Interlayer delivered stronger, safer and more reliable running lanes for the M3 smart motorway project in Surrey.

As discussed in last week’s blog, asphalt reinforcement systems interact with the bitumen bound layer of pavements to add tensile stiffness, limiting strain and reducing reflective crack development in the pavement surface.

These composite systems comprise a geogrid bonded to a fabric that act together to form a Stress Absorbing Membrane Interlayer (SAMI) and a moisture barrier. They can reduce construction costs and extend service life, and also minimise maintenance and future disruption.

M3 Smart Motorway project

One scheme to benefit from a SAMI solution was Highways England’s M3 Smart Motorway project. This saw the capacity of this congested three lane section increased, with hard shoulders converted to an additional running lane, to relieve congestion, smooth traffic flow and to improve journey reliability.

The road was in poor condition, with reflective cracking of the asphalt due to movement of the underlying layers of both lean mix concrete and bituminous road base. Repairs were needed to strengthen the road and to prevent further cracking, which could have led to water ingress and further deterioration of the concrete.

Consultant Aecom had specified asphalt reinforcement in the pavement design and asphalt surfacing contractor Tarmac, subcontractor Foster Contracting and Tensar International proposed Tensar’s SAMI Glasstex solution.

A Glasstex SAMI reduced construction costs and extended service life, as well as minimising maintenance on the M3 Smart Motorways project.

A total of 300,000m2 of Tensar’s Glasstex P100 composite was laid by Foster Contracting, on both the northbound and southbound carriageways, along the 26km stretch of road (ie a total of 52km). A straight run bitumen 160/220 bond coat was used to adhere the Glasstex to the underlying pavement structure, which, as discussed in last week’s blog, is the optimum spray rate to maximise performance.

An added benefit of installing a SAMI Glasstex solution on motorway projects is speed. Work typically has to be carried out at night, which obviously limits the amount of time available. Using Glasstex means the reconstruction depth is far shallower: on the M3 it was just 120mm to 150mm, rather than a minimum 360mm with a standard approach, which obviously saved time and, as a result, construction costs.

Tensar asphalt reinforcement products

Our asphalt composite products interact with the bitumen bound layer to add tensile stiffness, limiting strain and reducing crack development. Our systems have been subject to extensive independent research and testing at many leading international institutions, including the UK’s University of Nottingham, with performance experience gained from several monitored installations in many countries.

To find out more, visit the Asphalt Reinforcement pages of our website.

Also, to catch up with all the news on our highways solutions and projects, download the latest issue of our Tensar Road Technology magazine.