Accelerating ultra low-carbon reinforced concrete in railway construction

Low carbon alkali activated cementitious materials (AACMs) have the potential to significantly reduce the environmental impact of concrete (upto **80% reduction in embodied carbon**). However, their uptake has been slow due to the limited evidence base for their performance in use, with suppliers consequently unwilling to invest to increase manufacturing capacity.

One of the main issues is the level of protection afforded to steel reinforcement with long-term durability data needed for reinforced concretes, especially in aggressive environments. The use of non-corroding basalt fibre reinforcement (BFR) eliminates this risk.

**Demonstration and performance monitoring** of BF-reinforced AACM concrete in field trials at GCRE will provide **evidence of** **fitness-for-purpose**, addressing user/specifier concerns, providing data to support standards development and encouraging the supply chain to invest in capacity.

The project will deliver a feasibility study to **align recent innovations in AACM/BFR concrete with applications for concrete structures at the GCRE**. The objective will be to carry out a Phase 2 project to manufacture and 'install' concrete components made using AACMs and BFR at priority applications at GCRE, supported by a targeted testing programme to better characterise and address technical barriers to use at scale. We will build upon the knowledge from our recent National Highways M42 haul Road project to utilise a combination of AACM Geopolymer concrete and Basalt fibre rebar to offer a minimal feasible embodied carbon solution whilst attaining long-term durability through removal of the corrosion risk associated with steel rebar. Linear and/or discrete ground-retaining structures would present a strong option although other applications will also be considered. The structure/s will incorporate sensing technologies to enable us to verify stress vs applied load and the design prediction and to enable long term performance monitoring exposed to real world weathering and fatigue and ultimately performance validation of these new material systems.

**The learning generated will provide confidence** to users and support the development of standards. It will also enable challenges associated with the manufacture of larger scale manufacturing to be understood and supply chains to be reengineered to facilitate wider uptake.

The feasibility study will be led by Bastech Ltd (basalt fibre reinforcement), with Tarmac (manufacture of concrete made using AACM), Skanska (rail sector-focused construction contractor), the Building Research Establishment (durability and performance of cementitious materials including AACMs) and the National Composited Centre (structural performance monitoring, composite rebar design support and sustainability).