Concrete is the world’s most frequently used construction material and demand for it will only increase over the coming years. Given this reality, new ideas are needed for the construction industry to meet its net zero targets. With its cement additives and concrete admixtures, Sika already makes a key contribution to CO2 reduction and is carrying out in-depth research into new solutions. In this interview, Evelyne Prat, Core Technology Head Cementitious Technology, explains how the company is driving innovation.

Evelyne Prat, Core Technology Head Cementitious Technology
Image: Evelyne Prat, Core Technology Head Cementitious Technology

In November 2022, the world population passed the eight-billion mark. According to UN forecasts, the number of people on the planet will peak in the 2080’s at around 10.4 billion. As humanity faces this future, it will be a particular challenge for the construction industry to achieve net zero targets. Concrete contains about 80% aggregates and water and around 15% cement. A few decades ago, clinker accounted for 95% of cement. However, thanks to concrete admixtures and additives, the clinker content has been continuously reduced through the introduction of alternative binders. Nevertheless, the production of clinker is still responsible for up to 8% of all global carbon dioxide emissions.

Enabling Clinker Reduction

Cement substitutes that reduce the proportion of clinker make a significant contribution to the reduction of CO2 emissions. The demand for these materials is considerable, as the construction industry aspires to – and must – reduce its CO2 footprint. Sika is therefore anticipating that the market volume supplementary cementitious materials – or SCMs for short – will roughly double to around CHF 37 billion between 2022 and 2030. Yet there is a major challenge to be overcome because the quantity of available SCMs is currently limited. That’s why Sika is working intensively on new additives and concrete admixtures to enable the use of a variety of SCMs so that the clinker content in cement can be reduced. “As market leader, we have a responsibility to drive solutions to reduce the amount of clinker in cements and increase the use of substitutes,” emphasizes Evelyne Prat, Core Technology Head Cementitious Technology at Sika. 

Evelyne, how did you get into this business? What’s your background?

I come from cosmetics. You have no idea how close they are, cosmetics and mortars. It’s all about texture and the holistic experience of the applicator.

Why are cement-free/low-clinker construction products so important? Please explain the environmental benefits. Are there more benefits other than environmental? 

It’s because clinker, the main component of cement, is the biggest contributor to CO2 emissions along with steel. Clinker is responsible for 2.1 metric gigatons of carbon dioxide emissions per year globally. At Sika, we need to replace and reduce the amount of cement in the mortars we manufacture. 

With our formulation expertise, we can replace clinker with so-called supplementary cementitious materials (SCMs) in our mortars and grouts. At the same time, we enable much better performance. 

Can you illustrate the benefits using the example of specific Sika products – maybe a product you are personally excited about?

Over the last 3 or 4 years, we’ve designed a whole range of high-end repair products, structural repair products, grouts, and waterproofing membranes where SCMs have replaced between 25% and 40% of the cement content. The products launched recently include high-end repair mortars such as SikaGrout®-800 and -3320. These products are better in terms of both sustainability and performance. They’re also better for the applicator, with more comfort, safety, and esthetics. This brings me back to cosmetics: the person who uses the products feels the difference. 

Do cement-free/low-cement products have limitations in terms of their efficacy, what materials and substrates they can be used with, what climates, what building environments, and so on? Conversely, are there ways in which they’re superior to conventional products or suitable for new or extended applications?

There is no limitation on the substrate. Our mission is to make sure applicators can use the new product in any familiar technical application without any difference and with better performance. 

While there are no technical limitations, it’s harder to formulate these new products because their behavior in the fresh state differs widely from one mortar to another. But that’s Sika’s problem, not the customer’s. We’re cooks whose job is to put the right “salt and pepper” in the formula to get the desired results. 

It’s easier to cook with cement than with SCMs, but if you’re a good cook you can meet the most demanding expectations. When you look at a bag of mortar, you have no idea how much engineering went into it. 

Is this even more of a challenge because there are now more and more variations of SCMs in varying qualities?

Exactly. It’s not one size fits all. You must change the recipe because you never get the same SCM. It’s local.

Cashew fruit hanging on tree
Image: In Ivory Coast, Sika uses cashew shell ash (pictured: cashew tree with its fruits) as a substitute for cement. The shell ash replaces part of the cement in the tile adhesive SikaCeram®-80 CI.
How do you substitute for cement? What role do Sika’s additives and know-how play?

Mortar contains mineral particles and organics which interact with each other. When you change from Portland cement to an SCM, you change the interaction totally. You must re-adapt the “salt and pepper” because the interaction with the binder is different. It takes a lot of time to fix the behavior in the fresh state of the paste, as well as the early strength development and the final performance. We have to change everything so that nothing changes! 

At Sika, we have long-established expertise in the design and formulation of a very broad variety of chemistries, which enables us to adapt all these interactions.

Is that the main reason you’re able to successfully develop mortars with lower or zero Portland cement content?

It helps a lot, because we have people with the organic and mineral know-how to understand the interaction between the components and how it will change the behavior in the fresh state. As well as exchanging a lot within the Sika R&D community, we also work with universities to help us understand the hydration mechanism of these new SCM binders with the organic molecules.

How do you consider customers’ needs and preferences when you develop new products?

We have different customers with different needs. Contractors need products that meet the standards and will ask for a sustainability certification. They want performance plus rapid return to service, so we must have products that deliver fast. Applicators need products that are easy to use and safe that allow them to go home quickly and be less tired after finishing the job. The end customers – you and me – want to live in safe environments, which means that Sika products have to meet the most stringent requirements related to things like health, air, and water. 

Cashew shell ash as a cement substitute
How do you interact with your customers to find out what they want?

There’s close networking between R&D, marketing, and procurement to discuss customer requirements, visit job sites to understand what end-users want, and conduct trials with selected customers relatively early in the innovation process. 

Mortars are normally quite a “local” product, with local production and local suppliers. Some types of SCMs are available in all regions, some more on a local level. How do you approach this situation in R&D? How do you coordinate the R&D activities on the global, regional, and local levels? 

Alongside our global technology centers, we liaise very closely with the people in the hundred-plus countries of Sika to evaluate the “golden nuggets” they’ve discovered locally. If their discovery makes sense, we try to understand what they’re doing, then implement and replicate it in other countries as well. It’s a very practical approach. It’s about networking and collaborating with the other functions, like marketing and procurement, to ensure that the prototype fits the local needs of the market.

How has Sika’s business with cement-free/reduced-clinker products developed in recent years? How do you see this business evolving in the years to come?

Today, we substitute around 14% of the cement content of our mortars across all categories, and in some countries we’re already up to 33%.

With a new generation, we’re confident that we will reach our target of 50% cement replacement over the next few years.

Can you quantify how much greenhouse gas emissions can be reduced with this?

So far, we have been able to save around 210 kilotons annually. We reckon that by 2025, a reduction of 480 kilotons will be feasible globally. 

What would you say to a customer considering moving over to a cement-free or low-cement alternative?

To customers who care about CO2 but are afraid they might lose performance with cement reduction, I’d say, “Go for it. There’s no detrimental effect. On the contrary. You’ll get better workability and durability.”