
In March 2023 Metrail Construction completed a trial to stabilise a heavily trafficked section of asphalt pavement carriageway on the A1014 in Thurrock in East London.
The challenge
The substrata on this particular section had become defective due to water ingress washing out the Type 1 base material under the tarmac, causing deflection and reducing the strength of the road. Attempts by the local authority to solve the problem by simply resurfacing the road did not provide a lasting solution to the problem.
Excess water causes the subsoil to lose load bearing capacity resulting in significant deformation of the pavement. The winter cycle of freeze and thaw conditions also creates pot holes. A permanent solution can only be achieved if the substrata is stabilised.

Facts & Figures
When?
March 2023
Where?
400m section on the A1014 in Thurrock in East London
How?
Injecting a silica based resin
Technology
A two-component silicate resin, which cures to 90% full strength within 15 minutes. Full compressive strength of c.50n/mm2 is achieved
within the hour.
Result
Deflectometer testing confirmed the pavement to be fully stabilised with any excess water driven out
Solution approach
As a solution to the problem Metrail Construction proposed to use its innovative slab stabilisation process which is based on injecting a silica based resin into the sub-base to drive out water and fill any voids. The resin permeates the sub-base and cures to a strength of 50 newtons/mm2 in 15 minutes.
The two-component silicate resin, which is mixed on site, is a cost-efficient solution for the repair and maintenance of damaged pavement compared to the alternative of completely relaying the road.
A key characteristic of the silica material, which is non–permeable and semi flexible, is that it has a density of 1.4 times that of water which means it displaces water and fills any voids under the pavement.
The silica resin allows for dynamic loads from traffic above without cracking, which often occurs with traditional methods of repairs.


Execution
The work was carried out over five nightshifts. The high traffic volumes meant that the carriageway could not be closed during the day and night working could only be carried out in one lane with other carriageway remaining open to traffic.
The 400m section to be stabilised was marked out to ensure accurate drill spacing for the resin injection.
The two component resin is mixed on site from a purpose built vehicle in a one to one ratio and pumped through the packers inserted in the hole to drive out the water and fill any voids.
During each shift, the full cycle of drilling and resin injection was completed and the road surface cleaned so that the carriageway could be opened to traffic as soon as the work was completed.
The Outcome
“Before and after” deflectometer testing has confirmed the trial was a complete success with any excess water driven out, voids filled and the pavement fully stabilised to allow resurfacing with the elimination of deflection and potholes.