Ground Granulated Blast Furnace Slag (GGBS)

Ground Granulated Blast Furnace Slag (GGBS) is a finely milled hydraulic binder produced by grinding dried GBS to a controlled fineness, typically 350 to 500 m²/kg as measured by the Blaine method. The grinding process activates the latent hydraulic properties of the glassy slag, enabling it to react with calcium hydroxide released during Portland cement hydration to form calcium silicate hydrate gel, the primary strength-giving compound in hardened concrete.

GGBS is classified as a supplementary cementitious material and is governed in European markets by EN 15167-1, which sets minimum requirements for chemical composition, fineness, glass content, and strength activity index. Compliance with this standard is a prerequisite for structural concrete across most European specifications and is increasingly required in Middle Eastern and North African construction markets.

GGBS offers well-documented technical advantages in concrete performance. Its slower rate of hydration compared with Portland cement reduces peak heat of hydration, which is particularly valuable in mass concrete pours where thermal cracking is a design risk. The denser microstructure produced by GGBS hydration reduces concrete permeability, improving resistance to chloride ingress, sulphate attack, and alkali-silica reaction. This makes it the preferred binder for marine structures, tunnels, and chemically aggressive environments.

ROCC Global supplies GGBS in bulk tanker, big bag, and 25 kg bag formats, sourced from certified producers operating to EN 15167 and equivalent international standards.

GGBS is widely specified as a partial replacement for Portland cement in ready-mix concrete, precast products, and site-batched structural concrete. At replacement levels of 30 to 50%, it delivers improved workability, reduced heat of hydration, and enhanced long-term compressive strength compared with equivalent Portland cement mixes. At 50 to 70% replacement, it is the preferred binder where elevated sulphate resistance and reduced chloride permeability are required, including marine foundations, harbour structures, tunnels, and below-ground infrastructure in aggressive ground conditions. Its low heat of hydration makes it well-suited to mass concrete elements such as raft foundations and retaining walls, where thermal gradient control is critical to preventing early-age cracking. GGBS is also specified in high-performance precast cladding, architectural concrete, and self-compacting mixes where surface finish and colour consistency matter.