Learnings

Outcomes

Weathering Steel for Structures
Under Feasibility Study, a concept desktop review conducted on a 132 kV chair gantry layout from the Alfreton substation which verified that a weathering steel design satisfies all structural stability criteria. The Robot Structural Analysis modelling showed that maximum serviceability limit state (SLS) deflections and member utilisations remain well within acceptable limits. The study established that weathering steel naturally forms a fine-grained protective surface oxide layer, or patina, over four to eight years under standard C2 or C3 low-to-medium corrosivity environments typical of inland UK utility sites. This self-healing patina limits long-term material thickness losses to approximately half that of uncoated non-alloyed steel, enabling a potential design life of 100-120 years that far exceeds the standard 43-year lifespan of standard 85-micron galvanised structures. By completely removing the need for maintenance painting or hot-dip galvanisation baths, the material speeds up initial construction times, eliminates microplastic shedding and volatile organic compound (VOC) hazards, and lowers long-term maintenance costs. Because standard rolled universal beam (UB) and universal column (UC) weathering sections require substantial bulk minimum orders (such as 15-50 tonnes) with no stock currently held in the UK by suppliers like British Steel, fabricating structures from readily available flat steel plates pressed into open channels or using Corten profiles from the United States of America emerged as the primary procurement methodology.

With a detailed structural analysis, detailed 3D frame checks based on full equipment parameters from the Biggleswade 132/400kV substation project, modelling a 9.9-meter-high chair gantry supporting two disconnectors, alongside a 3.115-meter post insulator support column. To comply with the UK highway structure standard CD 361 and account for potential corrosion loss over the asset's lifespan, a conservative 2 mm material thickness allowance was added to all open-section plate profiles. While this extra thickness increased the chair gantry's weight from 7,115 kg to 8,142 kg and raised initial embodied carbon calculations by 22% (up to 24,670 kg CO2), a separate study on a 2.85-meter-high Bridgewater Earth Switch hollow section structure with a 1 mm corrosion allowance required no thickness increase, achieving an 11% reduction in total embodied carbon. Over an extended 120-year operational lifecycle, weathering steel significantly reduces cumulative carbon footprint and network service disruptions by removing the need for multiple, high-impact structure replacement cycles and outage windows. To mitigate bimetallic or galvanic corrosion when connecting weathering steel to dissimilar metals or equipment interfaces, engineering connection specifications recommend utilizing insulated neoprene top-hat washers, non-metallic barriers, or dedicated ASTM F3125 Grade A325 Type 3 weathering steel bolts containing copper, chromium, and nickel alloys. Furthermore, to prevent internal moisture trapping that accelerates corrosion from the inside out, designs must incorporate internal drainage holes in hollow sections as mandated by National Grid technical specifications.

 To address bimetallic corrosion risks, connection detailing incorporates insulated interfaces such as neoprene washers, non-metallic barriers, or weathering steel-compatible fasteners (e.g. ASTM F3125 Grade A325 Type 3 bolts). Drainage provisions are also included in hollow sections to prevent internal moisture accumulation, in line with National Grid requirements.

As part of the ongoing Stage 3 trials, three weathering steel structures have been installed at the Deeside Centre for Innovation to validate real-world performance:

• A 1.6 m high single-phase CVT support structure
• A 1.6 m high single-phase surge arrester support structure
• A 2.0 m high three-phase post insulator (PI) support structure

The two single-phase structures will be installed with operational equipment, while the three-phase PI support structure has been intentionally left unequipped, fitted only with bolts and washers in accordance with detailed design drawings. This approach allows for controlled monitoring and future removal of connections to directly assess any bimetallic interaction between fixings and weathering steel surfaces.

 These trials are critical in validating both structural performance and connection durability, with findings to inform future design standards, material specifications, and long-term adoption across substation infrastructure.

Graphene Enhanced Concrete:

GEC infuses a single atomic layer of carbon atoms arranged in a hexagonal lattice directly into the concrete mix to alter the underlying cement matrix. This process accelerates the internal hydration chemical reaction, causing cement particles to form dense fibrous crystals rather than conventional powder structures. 

Under Stage 1 and Stage 2, technical evaluation and material analysis confirmed that Graphene Enhanced Concrete (GEC) is a feasible solution for substation infrastructure. By incorporating graphene into the cement matrix, the material enhances hydration, resulting in improved strength, stiffness, and durability compared to conventional concrete. Collaboration with the Graphene Engineering Innovation Centre (GEIC) from the University of Manchester, enabled the use of their graphene admixture, which allows safe and practical integration into standard batching processes. Laboratory testing from the literature review indicated improved mechanical and durability performance, supporting the case for reduced cement content while maintaining structural capacity and enhancing resistance to cracking and ingress.

As part of the Stage 3 trial phase, a GEC foundation measuring 10 m × 1 m × 0.55 m was successfully poured at the Deeside Centre for Innovation. During this trial, the cement content was reduced by 10%, contributing to embodied carbon savings. Initial laboratory cube results indicate early-age strength gain, with further monitoring required to validate long-term performance. Overall, GEC has demonstrated strong potential; however, final validation remains subject to ongoing trial outcomes and in-situ performance data.

Light Weight Foam Foundations:

Under Stage 1 of this research, a comprehensive technical evaluation and feasibility study determined that the use of lightweight foam foundations is Not Feasible for substation infrastructure applications. The proposal sought to investigate expanding polyurethane foam as a lightweight, fast-setting alternative to traditional carbon-intensive mass concrete foundations for minor civil assets. The engineering process uses a two-part polymer mix that expands using heat, pressure, and blowing agents to generate a robust cellular foam structure to fill the void around deep-set poles. The investigation confirmed several notable material advantages, including an ultra-fast setting time where structures hold steady in 3 to 5 minutes and achieve an 80% structural cure within 60 minutes, removing the need for conventional water mixtures or on-site tamping machinery. Additionally, cured polyurethane foam is inherently hydrophobic, exhibiting a negligible water absorption rate of just 0.02% while providing excellent internal electrical resistance, high carbonation immunity, and strong chemical resistance to saltwater, sulfuric acid, gasoline, and diesel fuels. Destructive load testing and structural calculations proved that the lateral earth pressure on a standard 550mm x 550mm x 1400mm deep fence post hole provides sufficient overturning moment resistance to satisfy utility safety standards. 

However, the proposal concluded that lightweight foam is entirely unfeasible for business-as-usual substation use due to critical engineering and commercial barriers. Polyurethane foam exhibits a low flexural strength compared to concrete and cannot support any bolted connections, making the removal, adjustment, or reinstallation of substation equipment impossible. Most critically, market research highlighted that all expanding foam products currently available on the UK market are certified exclusively for domestic use. Industrial-grade alternatives capable of structurally supporting utility configurations are manufactured solely in the USA. Importing these materials would drive up procurement costs by 25% to 300% over concrete, while creating massive shipping emissions that contradict net-zero carbon goals. Furthermore, none of the current market options hold a British Board of Agrément (BBA) utility certification, and the material is entirely non-recyclable at the end of its lifecycle, requiring specialized high-temperature incineration for safe site disposal. Consequently, foam foundations are rejected for critical assets and remain restricted to temporary, non-critical ancillary items like road signs, pedestrian segregation barriers, and light internal security fencing.

Ashcrete and Ferrock Foundations:

Under Stage 1 and Stage 2 of this research, a comprehensive technical evaluation and detailed life-cycle analysis determined that while both materials show great promise, Ferrock is Not Feasible for substation deployment, whereas Ashcrete is Feasible strictly as a temporary, short-term intermediary concrete solution. The project investigated these alternative binder technologies to replace carbon-intensive Portland cement, which traditional clinker production makes responsible for high global emissions. Ashcrete utilizes high volumes of fly ash, an industrial waste product from coal combustion in energy generation. Ferrock blends recycled waste iron dust from the steel industry with silica from ground glass, reacting with carbon dioxide during a unique carbonation curing process to form a high-strength iron carbonate matrix that traps up to 50 kg of CO2 per equivalent unit. 

Structurally, both options achieved satisfactory engineering marks. Ashcrete demonstrates reduced water demand, improved workability, minimized thermal shrinkage cracks, enhanced sulfate resistance, and high long-term strength development. Historical case studies prove high-volume fly ash mixes can deliver a successful service life. Furthermore, detailed carbon calculations for a sample two-pad foundation design cut total embodied emissions by 21.8% for standard blends and up to 36.2% for high-volume mixes. Despite these major structural and environmental scoring points, severe long-term commercial hurdles were identified. Ferrock is completely unavailable in the commercial market, with its single patent held by a foreign start-up company. It also requires a complex carbon dioxide gas injection environment during curing, adding immense handling difficulty on active construction sites. Conversely, fly ash is a heavily constrained material due to the worldwide shift toward energy decarbonization. The planned closure of domestic coal-fired power plants means fresh fly ash production is ceasing entirely. While there are large, stockpiled reserves estimated at 100 million tonnes, added processing barriers, agglomeration risks, and a low five-year depletion window mean the industry will soon depend entirely on expensive overseas imports. 

Therefore, while Ferrock is rejected, Ashcrete is feasible only as a temporary transition solution to maximize existing stockpiles before supply constraints emerge.

 Waffle Slab Foundations:

Under Stage 1 of this research, a comprehensive technical evaluation and feasibility study determined that the use of waffle slabs is not feasible for outdoor substation equipment foundations, transformer bunds, or heavy tower bases. The proposal investigated implementing a two-way reinforced concrete rib system to replace traditional, carbon-intensive solid concrete foundations. By utilising special plastic or cardboard panels known as pods or domes, concrete is poured only in the intersecting joist gaps to leave square or triangular voids underneath. This layout reduces raw concrete volume and decreases dead weight to allow for longer structural floor spans. Laboratory tests on intermediate grid spacings verified that waffle slabs provide excellent load-bearing capacity, higher structural stiffness, lower creep, and superior vibration control under crowd movements compared to standard monolithic slabs. Additionally, an ETABS parametric analysis and plate theory calculations showed that an optimal layout of 9m x 12m with a 250 mm depth and 1500 mm rib spacing provides the most economical framework. ETABS (Extended Three-Dimensional Analysis of Building Systems) is a specialized structural engineering software primarily used by civil and structural engineers to model, analyze, and design multi-story buildings. Global case studies, including the Royal National Theatre in London, the Washington Metro system, and Chhatrapati Shivaji International Airport in Mumbai, confirm its structural effectiveness for large-scale engineering applications. However, the proposal achieved a low score of 3 out of 7 on the assessment matrix due to critical operational flaws. Waffle slabs are sensitive to fire because their thin cross-sectional profiles reduce the overall thermal insulation protecting the internal reinforcing bars. Structurally, the system is strictly limited to residential or light industrial specifications, capping maximum loading capacities at 1.2 tonnes per square metre over a 3.6-metre column span. This capacity falls short of supporting heavy outdoor substation machinery and transformer loads. Furthermore, the foundation layout fails on soft ground conditions, sloping topography, and high-wind environments, and it requires specialized site drainage setups to prevent water from pooling under the pods. Market research also identified that there are very limited suppliers in the UK, which drives up initial formwork material costs and affects project lead times due to a lack of commercial competition. While turned down for critical equipment foundations, waffle slabs remain a viable option for indoor substation spaces like control buildings or converter stations.

The other three techniques explored are briefly mentioned in the supporting attachement due to constraints on wording limit here.    

Lessons Learnt

Weathering Steel for Structures:

In terms of considerations for future projects there were two main learning points. Procuring standard rolled structural profiles in weathering steel was not straightforward and the development of alternative fabrication approaches, potentially via pressing flat steel plates into open sections, proved necessary due to strict minimum order thresholds and zero UK commercial stock. Understanding the bimetallic interaction risks and the associated complexities of the galvanic risk analysis was a significant part of the project and proved to be more complex and time consuming than originally envisaged, requiring the use of non-metallic insulation barriers or specialized alloyed fasteners to ensure connection durability. 
Also, as weathering steel has not previously been used within substation environments, earthing considerations presented a new design challenge. The formation of the protective oxide layer, which gives weathering steel its corrosion resistance, introduces uncertainty regarding electrical continuity across structural elements. As a result, bespoke earthing details have been developed specifically for these structures to ensure effective grounding and compliance with substation safety requirements. These designs will require further validation and assessment through the ongoing trial, particularly to confirm long-term performance and suitability for wider future application.

Graphene-Enhanced Concrete:

Managing project cost balancing was not straightforward and the development of alternative bulk purchasing frameworks proved necessary, as premium graphene admixtures initially drive material costs up to roughly twice the price of standard concrete, though commercial validation shows these expenses are offset over the asset lifecycle by a 10% to 20% reduction in total concrete volume, lower structural thickness requirements, and decreased field maintenance needs. Understanding the long-term lifecycle performance of novel nanoengineered mixtures and the associated complexities of the design standards analysis was a significant part of the project and proved to be more complex and time consuming than originally envisaged, requiring design teams to adopt a highly conservative approach with elevated safety factors because the technology lacks decades of empirical field benchmarks to formally verify standard 50-year utility service lifespans. 

In addition, the graphene concrete pour at Deeside required careful coordination of mixing and handling from the batching plant, and placement to ensure consistent dispersion of the admixture. This highlighted the importance of strict quality control, accurate batching, and contractor familiarity with modified concrete mixes. During the trial phase, site-specific challenges provided important practical insights. For example, foundation depth had to be revised due to the discovery of asbestos on site, requiring changes to the original design and demonstrating the need for flexibility between design assumptions and on-site constraints.

Dissemination 

An online webinar was arranged for policy and design assurance engineers.
The outputs of this project have been included in the innovation annual summary 2024 and 2026.