16/06/2025
Tony Smith of Sika discusses lowering the CO₂ footprint of concrete for a project without impacting performance, through the specification of innovative products.
Across any project, it’s becoming more common for businesses to seek solutions which are both highly efficient and a more sustainable choice. Concrete is the second most consumed material on the planet after water. Its significant carbon footprint is associated with cement production which is responsible for around 7% of CO₂ emissions globally.
Sika is therefore constantly identifying solutions that can cut carbon but not performance, to enable more sustainable construction.
A product portfolio with purpose
The key to more sustainable concrete is reducing the use of CEM I, the primary source of emissions in conventional mixes. By leveraging advanced low-carbon admixtures, CEM I can be replaced with high levels of Supplementary Cementitious Materials (SCMs) such as GGBS or PFA—while maintaining strength, durability, and workability.
Sika has developed a product portfolio made up of admixtures and fibre technologies which enable high CEM I replacement, low overall binder content, enhanced durability, and a lower carbon footprint.
This Includes:
- SikaRapid®-950 - Low CEM I activator, enabling up to 95% replacement
- SikaRapid®-800 ECO - Low CEM I activator, enabling up to 80% replacement
- SikaRapid®-4 UK - Low CEM I accelerator, high early strength with up to 80% replacement
- SikaFiber®-200 - Sustainable, bio-based fibre solution
- SikaFiber® Force-50 - Polypropylene macro fibres, replacing traditional steel reinforcement for reduced CO2 emissions
These products offer several key benefits, including significantly lower CO₂ emissions, a reduction in CEM I content by up to 95%, and faster project turnaround times allowing formwork to be stripped within 24 hours, even with high levels of SCMs. Additionally, no extra binder is required, promoting greater sustainability without the need for additional materials. This results in substantial CO₂ savings, with up to an 81% reduction in binder-related emissions when using high levels of GGBS replacement. These products also deliver reliable performance, meeting 28-day strength requirements while maintaining or even enhancing long-term strength.
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A game-changer: Sustainability without sacrifice
Focussing specifically on SikaRapid®-800 ECO and SikaRapid®-950, there are clear benefits for specifiers.
SikaRapid®-800 ECO, a liquid hardening activator for concrete, mortar and grout, and SikaRapid®-950, the next generation powdered admixture, are designed specifically for enhancing the performance of concrete with high levels of supplementary cementitious material (SCM), such as GGBS and PFA, without increasing powder content or compromising on performance.
Suitable for ready-mixed concrete, precast concrete or power floated concrete, SikaRapid®-800 ECO and SikaRapid®-950 have the ability to increase the amount of lower carbon binder without reducing the strength performance of the mix — it is possible to exceed the strength performance of 50% GGBS with up to 80% and 95% respectively by incorporating these new admixtures.
Transitioning from a mix with 50% GGBS to one with 95% GGBS using SikaRapid®-950 can achieve in excess of 80% reduction in CO₂ emissions associated with the binder.
As illustrated in the graph below.
As specifiers know well, increased sustainability normally implies a performance penalty, however these SikaRapid® products allow professionals to lower their CO₂ footprint in an innovative way. Sika’s advanced admixtures activate and accelerate the hydration of supplementary cementitious materials like GGBS and PFA to maintain performance.
It’s truly a game-changer for the industry and something Sika is extremely proud of.
Faster turnaround
Both SikaRapid®-800 ECO and SikaRapid®-950 promote early and late age strength development without negatively influencing final strengths. The products facilitate the long-term acceleration and activation of the concrete binder which means a faster turnaround of formwork and moulds.
This is advantageous to both the contractor, who can return to work quicker, minimising any delays on a project, and the specifier, who no longer needs to specify 56-day strength compliance. Furthermore, the SikaRapid® products require no specialist equipment or management during application by concrete producers.
We have also deployed SikaRapid®-800 ECO on power-floated factory floors where set time can be accelerated, allowing a replacement of a significant proportion of the CEM I even in winter, without delays to the finishing process.
Maximising what can be done
The Sika portfolio of products is maximising what can be done within the current British standards, and the ability to achieve low carbon concrete within the existing framework mean they’re easier to specify.
Forward-thinking admixtures empower the construction industry to meet ambitious sustainability targets without compromising on performance or compliance. Specifiers and producers can confidently call upon admixtures which use significantly higher levels of cement replacement at the same or lower total binder content and expect a practical, usable concrete on site.
As the industry evolves, the use of such products supports the wider adoption of environmentally responsible practices across projects of all scales.