THE BRIEF

A full scale demonstration site was set up between junction 28 and 30 of the M5 motorway to showcase a new standard adopted by National Highways.

The new E/21 Stone Mastic Asphalt (SMA) specification is a next generation, low carbon road surfacing standard which aims to tackle premature surface deterioration, inconsistent ride quality and the elevated carbon impact associated with frequent resurfacing cycles.

The project, part of the Low Carbon Innovation Fund, sought to validate the real-world performance of next-generation materials and to produce robust technical and performance data that will help inform the wider rollout of E/21 SMA across the Strategic Road Network.

Holcim UK was commissioned to provide the solution working closely with National Highways and Shell Bitumen.

Holcim UK provided its Prolay Ultra system for use in the project.

Designed with a carefully balanced aggregate matrix, increased bitumen content, and Polymer Modified Bitumen (PMB), ProLay Ultra achieves a low in-situ void content for enhanced resilience and long-term performance.

Due to Holcim’s forward-thinking approach to product development, ProLay Ultra already meets National Highways E21 SMA specification which is another reason it was commissioned.

The project delivery was supported by Smoothride digital paving control technology, integrating LiDAR scanning, 3D modelling undertaken by Driven International and MK Surveys and precision milling using Topcon and Wirtgen systems operated by Tripod Crest. Topcon’s SmoothRide technology delivers a fully digital and highly accurate approach to road resurfacing, utilising race track technology into the design of the road.

Using vehicle-mounted 3D scanners, the system captures precise surface data without the need for manual surveying. This information is converted into a detailed digital design, which guides milling machines and pavers to automatically adjust depth and alignment in real time.

By optimising every stage of the process, SmoothRide produces exceptionally smooth and consistent pavement surfaces, reduces material waste, increases efficiency and significantly shortens programme durations. The result is a faster, more accurate and sustainable method of delivering high-quality resurfacing across complex highway environments.

This meticulous process, coupled with echelon paving, eliminates weak joints and ensures a consistently smooth and durable surface.

All surfacing operations, including full pavement construction, were delivered by Holcim crews with 20,000 tonnes of materials being supplied directly from Holcim’s plants at Westleigh in Somerset and Moorcroft in Plymouth.

Throughout the scheme, Holcim’s Quantity Surveying team maintained clear and consistent communication with all stakeholders. Daily diary and resource sheets provided transparency on labour, plant and material usage, while weekly progress meetings with the broader value chain ensured alignment on programme performance, risks, weather impacts and commercial controls. This structured approach ensured the project remained on schedule and within budget.

The new E/21 specification is designed to extend pavement life from 15 to 20 years through the use of high-grade Polymer Modified Bitumen (PMB) and a low-void structure, enabling improved durability, fewer maintenance interventions and reduced whole-life carbon.

Holcim’s AIT system was employed across the scheme, which delivers the latest digital quality control processes throughout the project. This included material mapping from plant to site, temperature monitoring across all stages of manufacture and installation, digital footprint of each load laid on site, and compaction mapping of rollers. The latest laser scanning was employed by TRL, which showed full compliance with the new CC202 standards.

Early monitoring of the scheme has shown strong and consistent performance, with results meeting and exceeding the expectations set by the E/21 specification. Laboratory testing has confirmed that ProLay Ultra satisfies all durability, rutting and ageing requirements, validating its suitability as a long-life, high-performance surface course. Ongoing assessment will continue to track long-term behaviour and whole-life carbon benefits.