Sustainable precast concrete is no longer a niche specification, it is what large infrastructure clients now expect as standard. At Shay Murtagh, four decades of manufacturing precast concrete rests on a straightforward principle: carbon reduction and structural performance are not a trade-off, provided the mix design and testing regime are right.
The company now uses ground granulated blast-furnace slag (GGBS) at 40% across its applications, built on CEM III/A cement blends containing at least 36% GGBS. As Director Gillian Murtagh puts it, “GGBS has become a pillar of what we’re doing.” GGBS is a recycled by-product of iron production, and replacing a portion of Portland cement with it cuts the embodied carbon of every unit produced without altering the finished product’s function.
The main technical hurdle with high-GGBS mixes is early strength gain, since slag cures more slowly than standard cement in the first days after casting. Shay Murtagh’s quality testing programme addressed this directly, refining mix designs so that required concrete grades are reliably achieved within three days, keeping production schedules intact.
The approach has been proven on demanding projects, including HS2’s Solihull interchange station, where Shay Murtagh supplied 15 precast concrete bridge beams, each 46 metres long and weighing up to 565 tonnes. Alongside the lower-carbon mix, value engineering on the beam design reduced material volume while maintaining structural integrity, cutting both cost and embodied carbon on the scheme.
GGBS also improves long-term durability, offering greater resistance to sulfate and chloride attack and extending a structure’s design life, a factor that matters as much to asset owners as the initial carbon figure. This combination of lower carbon, proven strength and durability sits behind Shay Murtagh’s environmental commitments and its wider sustainability strategy, and continues to shape how the business specifies concrete for infrastructure clients across Ireland and the UK.
