Low Carbon Concrete Project

Allied Concrete is building on its reputation as the industry’s technical leader and has taken a range of initiatives to reduce its carbon footprint in its concrete products. Recently, it has introduced its “ecrete” range of low carbon concrete to the market. An award-winning product range, ecrete took home the Excellence in Concrete Innovation award at the 2023 Concrete NZ Nauhria Awards.

The ecrete range utilises supplementary cementitious material (SCM) and other concrete mix technology to achieve lower carbon outcomes for the industry through cement substitution of up to 60%. Allied Concrete’s vision in embarking on this project has been to provide the construction sector with high utility concrete options whilst meeting New Zealand’s low carbon aspirations.

For several months, Allied Concrete has undertaken extensive research into SCMs, investigating the influence of replacement materials for Portland cement in order to lower the amount of embodied carbon in concrete. Replacing a certain portion of cement is one of the most effective and tangible methods to reduce the environmental impact of concrete whilst dealing with waste products from other key heavy industries. Allied Concrete has developed its ecrete range with the use of fly ash and ground granulated blast-furnaced slag (GGBFS) – commonly known as slag – as its SCMs. Fly ash is a by-product of thermal generation. GGBFS is a by-product of steel manufacture during the production of pig iron in a blast furnace. GGBFS has only recently become available in New Zealand, with Holcim NZ commissioning a GGBFS manufacturing facility in Auckland.

Ecrete can reduce embodied carbon by up to 60%, depending on the mix. The core mixes in the range are e10, e20, e30, e40, and e60 concrete mixes. The embodied carbon content of e10 concrete mix is 10% lower than that of the Infrastructure Sustainability Council (ISC) benchmark, while the embodied carbon content of the e60 concrete mix is 60% lower than that of the ISC benchmark.

Allied Concrete’s ecrete range not only contains significantly less embodied carbon, but also exhibits reduced shrinkage, an increase in long term compressive and flexural strength, reduced peak temperature, and an increase in durability. All key concrete properties can be dialled up or down to achieve specific outcomes for the complexity of customers’ applications. Technical challenges associated with development of mixes have required an innovative, meticulous, and detailed approach with the end user in mind.