Net-zero roads using basalt fiber composites.
The success of an industry-first Skanska UK and National Highways low carbon concrete trial to be extended to permanent roads.
Over the past year Skanska, a development and construction company, alongside the National Composites Centre UK, Tarmac, Basalt Technologies, and National Highways, has carried out a trial on a low-carbon reinforced concrete solution. The results show that the solution has led to a reduction of more than 50 percent in carbon. It has also proven equally as resilient when compared to conventional reinforced concrete using steel. A report with findings from the trial carried out at Skanska’s M42 junction 6 projects for National Highways, has now been published.
The trial has proved such a success that Skanska is now working collaboratively with National Highways and High Speed 2 Ltd (HS2) on the next phase. The plan is to trial the low-carbon combination on a permanent road and capture all the data and analysis for future publication. The ultimate aim is to roll out the low-carbon solution across the UK’s strategic road network.
Skanska is also working with HS2’s innovation managers to progress the learning from the trial and use the innovative combination of materials in other structurally reinforced concrete elements beyond roads.
Skanska’s Highways Director, Glennan Blackmore said: “The results of the trial are extremely encouraging. By working together, we have been able to speed up the process of testing and analyzing a new solution for de-carbonizing our road network, with the aim of getting it to market so the whole industry can benefit.
What was involved in the first trial
Tarmac provided two types of concrete for the trial: a mix comprising conventional blended cementitious material and a low-carbon alternative mix incorporating an Alkali Activated Cementitious Material (AACM) in place of the cement. This low-carbon concrete solution was mixed at a conventional concrete plant located close to the project and installed in exactly the same way as traditional materials. This new sustainable product delivers a carbon footprint up to 80 percent lower than a standard CEM I concrete.
The reinforcement steel replacement was a basalt fiber-reinforced polymer rebar. This is five times lighter and twice as strong as its steel counterpart and is naturally resistant to corrosion, alkalis, and acids. The main component of Bastech® rebar is basalt fiber which is manufactured directly from the most common rock on the earth’s surface, basalt, in a single-melt process, and comprises only a single raw material. It has on average 60 percent less CO2 emission than steel and is a cost-effective substitute.
The trial involved the construction of four concrete slabs at the M42 junction 6 highways improvement scheme. The slabs were laid in December 2021 and were made up of:
Slab A – conventional concrete + steel reinforcement
Slab B – low carbon concrete + steel reinforcement
Slab C – conventional concrete + basalt reinforcement
Slab D – low carbon concrete + basalt reinforcement The road was heavily used by construction vehicles throughout the trial period, with in-situ and laboratory tests carried out over a number of months. Full-scale specialist lab tests involved bending and shear testing of the four types of slabs.
The results have provided knowledge of the curing process, ease of construction, safety benefits, functional properties, and structural behavior of the various concrete and reinforcement combinations. This has given insight into the future use of longer-lasting materials in construction.