IN Brief:
- CemBlend and Hepworth Clay have established a partnership to distribute UK-manufactured HepCem to cement and concrete producers.
- HepCem is certified to BS 8615-1:2019+A1:2026 and typically substitutes for 20–35% of Portland cement in suitable formulations.
- The supplier's embodied carbon estimate remains preliminary; mix-level performance checks and a verified product EPD are still required for project claims.
CemBlend and Hepworth Clay are bringing HepCem, a UK-manufactured calcined clay addition, to the cement and concrete market through a new supply partnership. Hepworth’s product has independent conformity certification under BS 8615-1:2019+A1:2026, while the commercial arrangement is intended to extend its availability to producers. The companies describe typical substitution of 20–35% of Portland cement in suitable formulations; the proportion remains subject to the specified concrete performance and binder combination.
The partnership combines CemBlend’s blending and distribution capability with material manufactured by Hepworth at Crow Edge, near Sheffield. Hepworth selects and prepares clay minerals before controlled calcination and fine grinding, producing a purpose-made reactive powder rather than simply crushing discarded ceramics. Its existing expertise comes from clay processing for vitrified drainage products, but supplying a material for concrete binders also requires repeatable mineral and physical characteristics from one batch to the next.
Calcination changes suitable clay minerals into aluminosilicate phases that can react with calcium hydroxide released during Portland cement hydration. The resulting pozzolanic reaction forms additional cementitious hydrates that contribute to the concrete matrix, while allowing a proportion of the clinker-based binder to be displaced. Reactivity is affected by the composition and fineness of the powder and by how the concrete is batched and cured. It cannot be inferred from a replacement percentage alone that a finished mix will reach the same early strength or durability as its reference formulation.
Construction Products Certification (CPC) has certified conformity with BS 8615-1:2019+A1:2026, supported by factory production control surveillance and product testing. The certification, documented before the October CemBlend partnership announcement, covers the Crow Edge product for use as a pozzolanic constituent with Portland cement. Ceramics UK’s account identifies certificate CP 00281, authorised on 24 August 2026. Independent control of factory processes and sampling helps establish consistency; it does not replace concrete producers’ responsibility to demonstrate compliance in each intended application.
A claimed substitution range of 20–35% is a useful starting point for mix development, but it is not a fixed specification for every concrete grade. Producers still have to establish strength, setting and curing performance for the cement combination selected under BS 8500 and the exposure class required by the project. The water and admixture demand of a mix can also change when fine powders are introduced. Such trials matter particularly where reliable formwork stripping times, pumping behaviour or strength at early ages is a condition of construction delivery.
Hepworth’s product information acknowledges that higher replacement levels can delay early strength development in some formulations. That can affect precast works, where demoulding rates determine throughput, differently from mass concrete pours, where heat evolution and the risk of thermal cracking may carry greater weight. The company describes the material as suitable for combinations with limestone or other supplementary cementitious materials, including slag or fly ash, provided the complete binder system is tested for its intended use.
The material can be used with other supplementary components, including limestone, ground granulated blast furnace slag and pulverised fuel ash, to create blended binder systems. The correct combination is dependent on material availability, compatibility, strength development and the required durability performance. CemBlend says its operation supplies and combines cementitious powders to customer specifications, allowing manufacturers to consider the new clay within established batching and supply arrangements rather than necessarily adopt an entirely new production method.
Lowering the proportion of Portland clinker can reduce the embodied carbon associated with cement because clinker manufacture consumes fuel and releases carbon dioxide when limestone is calcined. The substitution product nevertheless carries its own emissions from quarrying, thermal processing, grinding and transport. An appropriate project comparison must consider the mass of all binder ingredients needed to achieve the specified concrete performance, rather than equate a 20–35% cement substitution directly with a 20–35% reduction in the whole concrete mix’s carbon footprint.
Hepworth reports preliminary modelling of about 200kg CO₂ equivalent per tonne for A1–A3 product stages under trial production conditions. It says processing parameters and electricity allocation are being refined, with a formal lifecycle assessment and independently verified environmental product declaration planned after steady-state production has been established. Those provisional figures should therefore not be presented as a verified product EPD or as a guaranteed carbon value for concrete supplied to a construction project.
The new market development is the CemBlend supply partnership, not the invention or first certification of calcined clay as an addition to concrete. Hepworth’s existing certification and technical testing provide evidence for producers evaluating HepCem, while the reported launch at the Precast and Masonry Expo on 22 October provides the immediate commercial context. Uptake will depend on repeatable supply and acceptance in project specifications, with practical mix trials determining how far clinker content can be reduced without compromising required construction performance.
