Zero cement structural concrete offers opportunity not threat

The global construction market is expected to grow by over 70% by 2025 (Global Construction 2025, 2013) and so it is unlikely that demand for concrete, the most used construction material on the planet, is likely to decrease. However, Ordinary Portland Cement (OPC), a major component of concrete, is also the third highest manmade producer of CO₂ and this has put considerable pressure on the industry to decrease its carbon emissions whilst meeting the ever-increasing demand for cement.

GGBS

There have been many attempts to reduce the carbon legacy of OPC through the substitution of other materials such as silica fume, pulverised fuel ash, and most commonly ground granulated blastfurnace slag (GGBS).

GGBS is a byproduct of the blastfurnaces manufacturing iron for steel making. This is a process that has been used all over the world since the mid-1800s. GGBS-concrete blends have a proven track record in increasing the durability of concrete and can be used as a replacement for OPC by as much as 95%. GGBS has long been considered the key to reductions in the cement industry’s carbon legacy.

However, these mixes still require an alkali, usually OPC, to activate the GGBS within the blend, seriously undermining the green credentials of these alternatives. If an alkali is not used, the GGBS will not activate, compromising the compressive strength of the material to below 30 Mpa. This means it cannot be used as a structural concrete and limits the use of the material to less strength-dependent applications, such as freestanding retaining walls, light-duty house floors and driveways.

Zero cement structural concrete

After many years of research and development, David Ball Group PLC recently launched the world’s first truly sustainable, zero cement structural concrete, Cemfree.

As with its blended counterparts, Cemfree is more durable than OPC. The patented activator is able to hydraulically activate GGBS at 95% concentration, providing an ultra-low carbon alternative to concrete mix designs that traditionally use OPC, and crucially, is also strong enough to be used in structural applications.

Cemfree consists of a major component that has latent hydraulic capability and a minor, but important, component known as the ‘activator’. Microstructural analysis has revealed that the activator releases the encapsulated hydraulic components and optimises the resulting solidifying mass in a manner not dissimilar to the hydration of OPC.

Cemfree offers up to a 95% reduction in CO₂ emissions compared with OPC. This presents the construction industry with the opportunity to reduce the CO₂ legacy of concrete by 25% globally, based upon the current availability of raw materials.

In addition, there are multiple characteristics of Cemfree that show the material to outperform its OPC and blended mix counterparts. For example, whilst the typical compressive strength of OPC is 44 Mpa after 90 days, Cemfree has a compressive strength of 60 Mpa over the same time period. The flexural strength of OPC is also improved upon in Cemfree, from 4 Mpa to 4.5 Mpa, respectively.

Importantly for areas where water is limited, Cemfree also requires less of it, making it of considerable interest to countries such as Kuwait, Qatar and the United Arab Emirates. Incidentally, these countries are also experiencing considerable industrial growth, requiring a substantial increase in construction and development of infrastructure.

Cemfree has a lower thermal crack control steel reinforcement requirement than conventional OPC-based mix designs, typically realising a 15% decrease in steel reinforcement, with a greater thermal mass compared to traditional concrete, lending itself to additional applications traditional concrete would not be able to fulfill.

In comparison with OPC, the durability of Cemfree for both acid, chloride and sulfate resistance is also significantly greater.

The material uses existing infrastructure and practices, design and installation principles, ensuring it can be widely adopted throughout the industry without change to established procedures or the acquisition of new equipment.

What does Cemfree mean for the cement industry?

The launch of Cemfree is a good news story for the cement industry.

Cemfree cannot fully replace Portland cement as there are not enough raw materials to do so. However, by adopting Cemfree and using it to replace some of the global cement output, the industry has a real opportunity to improve its green credentials and reduce its CO₂ emissions by as much as 25%.

This new innovation is another example of the cement industry using leading innovations to bolster its green credentials. David Ball Group is keen to work with the cement industry and sees Cemfree being one of a number of green options the industry can use to not only improve its own emissions targets but also help reduce emissions on an international scale.

The company has ambitious plans for Cemfree, which has already received industry awards including the coveted Skanska award in Supply Chain Green Solutions and the prestigious CONSTRUCT award for materials and product innovation.

Green and sustainable building construction is predicted to grow on average 22.8% per year between 2012 and 2017, creating a clear opportunity for the cement industry, but only if green solutions are adopted and the issue is tackled before it is simply too late. David Ball Group hopes that the introduction of Cemfree to the market will stimulate the development of further green solutions for the industry in the future.

Bibliography

• Ecobuild 2014, The Future of the Built Environment (October 2014).
• Global Construction Perspectives and Oxford Economics, Global Construction 2025 (July 2013).

Written by David Ball, David Ball Group Plc. This is an abridged article from World Cement's February 2015 issue. Subscribers can read the full issue by signing in, and can also catch up on-the-go via our new app for Apple and Android. Non-subscribers can access a preview of the February 2015 issue here.

Read the article online at: https://www.worldcement.com/europe-cis/30012015/zero-cement-structural-concrete-article/