Displaying items by tag: Calcined Clay

Cuba: The production of ‘low-carbon’ (LC3) cement consisting of clinker, calcined clay, limestone and gypsum has begun at Marta Abreu University’s 1460t/yr pilot integrated cement plant in Las Villas. The Granma newspaper has reported that the plant is currently producing 4t/day of cement, and plans to double this to 8t/day when fully operational.

Cement and concrete products with sustainability credentials have increased in recent years as societies start to demand decarbonisation. In spite of the recent drop in the European Union (EU) Emissions Trading Scheme (ETS) price, there has been a trend in recent years in the construction industry towards offerings with better environmental credentials. Indeed, this week’s position paper from Cembureau on a carbon border mechanism concerns directly the growth of these kinds of products within Europe. Typically, the higher profile projects have been slag cement or concrete implementations such as Hanson’s use of its Regen cement substitute in a London sewer project or David Ball Group’s Cemfree concrete in a road project also in the UK. In this short review we’ll take a selective look at a few of the so-called low carbon cement and concrete products currently available.

Table 1: Some examples of methods to reduce embodied CO₂ in cement and concrete. Note - the product examples are selective. In some cases many other products are available.

Looking at cement first, the easiest way for many producers to bring a lower carbon product to market has been to promote cements made using secondary cementitious materials (SCM) such as granulated blast furnace slag or fly ash. These types of cements have a long history, typically in specialist applications and/or in relation to ease of supply. For example, cement producers in eastern India often manufacture slag cements owing to the number of local steel plants. However, cement producers have more recently started to publicise their environmental credentials as they reduce the clinker factor of the final product. Alongside this though, in Europe especially, a number of so-called low carbon cement producers have appeared on the scene such as EcoCem and Hoffman Green Technologies. These newer producers tend to offer SCM cement products or other low carbon ones built around a grinding model. It is likely that their businesses have benefitted from tightening EU environmental legislation. How far cement producers can pivot to SCM cement products is contentious given that slag and fly ash are finite byproducts of other industries that are also under pressure to decarbonise. Although it should be noted that other SCMs such as pozzolans exist.

As will be seen below a few of the methods to reduce embodied CO₂ in cement and concrete can be used in both materials. SCMs are no exception and hold a long history in concrete usage. As mentioned above David Ball Group sells Cemfree a concrete product that contains no cement. Harsco Environmental, a minerals management company, invested US$3m into Carbicrete, a technology start-up working on a cement-free concrete, in late 2019.

Limestone calcined clay cements are the next set of products that are starting to make an appearance through the work of the Swiss-government backed LC3 project, more commercial offerings like FutureCem from Cementir and H-EVA from Hoffman Green Technologies and today’s announcement about ThyssenKrupp’s plans to fit the Kribi cement plant in Cameroon with its Polysius activated clay system. They too, like SCM cements, reduce the clinker factor of the cement. The downside is that, as in the name, the clay element needs to be calcined requiring capital investment, although LC3 make a strong case in their literature about how fast these costs can be recouped in a variety of scenarios.

Calcium silicate cements offer reduced process emissions by decreasing the lime content of the clinker lowering the amount of CO₂ released and bringing down the temperature required in the kiln to make the clinker. Solidia offers its calcium silicate cement as part of a two-part system with a CO₂ cured concrete. In the US LafargeHolcim used Solidia’s product in a commercial project in mid-2019 at a New Jersey paver and block plant. Solidia’s second core technology is using CO₂ to cure concrete and reducing water usage. They are not alone here as Canada’s CarbonCure Technologies uses CO₂ in a similar way with their technology. In their case they focus more on CO₂ mineralisation. In Germany, Schwenk Zement backed the Celitement project, which developed a hydraulic calcium hydro silicate based product that does not use CO₂ curing. Celitement has since become part of Schwenk Zement.

Solidia isn’t the only company looking at two complementary technologies along the cement-concrete production chain. A number of companies are looking at recycling concrete and demolition waste. Generally this splits into coarse waste that is used as an aggregate substitute in concrete and fine waste that is used to make cement. LafargeHolcim has Evopact for the coarse waste and Susteno for the fine. HeidelbergCement has EcoCrete for the coarse and is researching the use of fines. Closing the loop for heavy building material producers definitely seems like the way to go at the moment and this view is reinforced by the involvement of the two largest multinational producers.

Of the rest of the other low carbon cement methods detailed in table 1 these cover other non-Ordinary Portland Cement (OPC) such as geopolymer and calcium sulphoaluminate cements. The former are a type of alkali activated binder and generally lack common standards. The latter are similar to slag cements in that they are established specialist products with lower CO₂ emissions than OPC.

With concrete when trying to make a low carbon product the first choice is whether to choose a low-carbon cement as the binder or even not to use cement at all in the case of Regen or Cemfree. From here the next step is to simply use less cement in a concrete mixture. There are a number of ways to do this from optimising aggregate gradation, following performance specifications more closely, using strength tests like maturity methods and generally adhering to quality control protocols better to deliver more consistency. Read the Mineral Production Association (MPA) publication Specifying Sustainable Concrete for more detail on this. Using concrete admixtures can also help make concrete more sustainable by improving quality and performance at construction sites through the use of plasticisers and accelerators, by decreasing embodied carbon through the use of water reducers and by improving the whole life performance of concretes. The use of locally-sourced aggregates is also worth noting here since it can reduce associated transport CO₂ emissions.

More novel methods of reducing embodied CO₂ emissions in concrete include the use of geopolymer concrete in the case of Zeobond Group’s E-Crete or adding graphene as Concrene does. Like geopolymer cements, geopolymer concretes are relatively new and lack common standards. Products like Concrene, meanwhile, remain currently at the startup level. Finally, if all else fails, offsetting the CO₂ released by a cement or concrete product is always an option. This is what Cemex has done with its Vertua Ultra Zero product. The first 70% reduction in embodied CO₂ is gained through the use of geopolymer cement. Then the remaining 30% reduction is achieved through a carbon offsetting scheme via a carbon neutral certification verified by the Carbon Trust.

As can be seen, a variety of methods exist for cement and concrete producers to reduce the embodied CO₂ of their products and call them ‘low-carbon.’ For the moment most remain in the ‘novelty section’ but as legislators promote and specifiers look for sustainable construction they continue to become more mainstream. What has been interesting to note from this short study is that some companies are looking at multiple solutions along the production and supply chain whilst others are concentrating on single ones. The companies looking at multiple methods range from the biggest building material producers like LafargeHolcim and HeidelbergCement to smaller newer ones like Solidia and Hoffman Green Technologies. Also of note is that many of these products have existed already in various forms for a long time like SCM cements and concretes or the many ways concretes can be made more sustainable through much simpler ways such as changing aggregate sourcing or working more efficiently. In many cases once markets receive sufficient stimulus it seems likely that low carbon cement and concrete products will proliferate.

Global Cement is researching a market report on low carbon cement and concrete. If readers have any comments to make please contact us at This email address is being protected from spambots. You need JavaScript enabled to view it.

Cameroon: Germany-based Thyssenkrupp Industrial Solutions has won an engineering, procurement, construction and commissioning (EPCC) contract with Netherlands-based Cimpor Global Holdings for the installation of a clay calcination plant at its new integrated Kribi cement plant in the Port of Kribi in South Cameroon. The system calcines clay at just 800°C, which can then replace clinker at a ratio of one to two, lowering the finished cement’s clinker factor by up to 33%.

ThyssenKrupp says that use of the system, the first of its kind in Cameroon and second at a Cimpor Global Holdings cement plant, will help cut CO₂ emissions by 120,000t/yr, corresponding to a reduction of 40%.

There was fantastic news for fans of novel cements this week, when Cementos Argos announced the completion of work on a new 0.45Mt/yr calcined clay production line at its Rio Claro plant in Colombia. This artificial pozzolanic material, developed and promoted by the Swiss-led LC3 consortium in recent years, can dramatically lower cement CO₂ emissions by replacing slag and/or fly ash in cement mixes. The Rio Claro plant is the first major cement plant to install such a line following smaller trials in Switzerland, India and Cuba.

Suitable clays are more widely available than slag and fly ash, alleviating some of the difficulty and cost of obtaining supplementary cementitious materials. They also need to be calcined at just 800°C, offering massive savings in terms of fuel costs, CO₂ emissions and embodied energy compared to Ordinary Portland Cement (OPC) production. Karen Scrivener from the École Polytechnique Fédérale de Lausanne (EPFL), the leading academic party in the LC3 consortium, explained that calcined clays are at their best when in ternary (three-way) blends alongside clinker and limestone in the September 2019 issue of Global Cement Magazine. “It has long been known that calcined clays can be pozzolanic,” she explained. “When used alone, the maximum substitution level is around 30%, which gives a moderate saving in CO₂ emissions. However, if we substitute a further 15% of the clinker with limestone, we get a significant reduction in CO₂ emissions, with a product that has almost identical properties to the blend that contains just the calcined clay.”

While the exact composition of Rio Claro’s new products is unclear, it will enable Cementos Argos to produce ternary cement blends with CO₂ emissions 38% lower than OPC. Energy consumption is also cut by 30%, which provides secondary benefits in terms of reduced off-site CO₂ emissions. At the plant’s launch, Cementos Argos’ President Juan Esteban Calle clearly stated that calcined clays were the way forward, announcing, “With this project we are sowing the seeds of the Argos of the future. It starts today with a new production line at Rio Claro. In our commitment to climate change, this project makes us very proud.”

The response from Argos’ consumers will be keenly watched, especially in Europe. Just this week LafargeHolcim and Vicat, along with France’s Technical Association of the Hydraulic Binders Industry (ATILH), called on the European Commission and European Committee for Standardisation to hurry up and publish ternary cement standards across the European Union (EU). At the moment these producers are primarily concerned with CEMII / C-M and CEM VI cements. These classes of cement comprise a range of ternary blends that contain clinker and limestone, plus a third component, be it slag, fly ash, natural pozzolans or calcined clay. They claim that placing low-clinker cements on the market could reduce the amount of CO₂ emitted by 127kg/t, around 20% of the 656kg/t average in Europe at present.

Frustrated with the delays at Commission level, cement producers have now taken things into their own hands. The plan is to establish the same standard within each EU Member State at the national level, rather than waiting in vain for standards from ‘on high.’ One pressing driver for this behaviour is the rapid approach of the Phase 4 of the EU Emissions Trading Scheme (ETS) in January 2021. In Phase 4 it is likely that EU cement producers will be allocated only 80% of the free allowances they have become accustomed to. They will have to buy the remainder at market prices, currently Euro25.1/t of CO₂ (17 February 2020). This will represent a massive new expense for some producers. The opportunity to sell cement that emits only 58% of the CO₂ of OPC is clearly exceedingly attractive as a way to reduce outgoings. CO₂ emissions will be reduced, of course but, as usual, the way to make companies do things is to hit them in the wallet.

Indeed, on this point, Vicat seemed to almost goad or ‘troll’ its competitors in Europe this week by announcing that it has never sold any EU ETS allowances and is sitting atop a 5Mt CO₂ reserve worth Euro120m. This is sufficient to last it until 2030 at current prices. The key part of that last sentence is ‘current prices,’ which are subject to change. In its press release, Vicat was keen to point out that it is not resting on its laurels, highlighted by its advocacy for ternary blends and continued development of alternative fuels. This may be wise, considering that EU ETS allowances will likely cost more once Phase 4 kicks in.

With clinker factors of just 50 - 65% for CEMII / C-M, and 35 - 50% for CEM VI, Edelio Bermejo, director of research and development (R&D) at LafargeHolcim insists, "These cements are no longer at the research and development stage. They have been widely validated and we are ready to produce them, especially as their manufacture does not require modification of our facilities." The establishment of Cementos Argos’ Rio Claro calcined clay plant proves his point. We can expect to hear a lot more about these blends in the coming months. In the words of Bermejo, “The future is here!”

Colombia: Cementos Argos’ Rio Claro cement plant has completed construction of a new 0.45Mt/yr production line for calcined clays, an artificial pozzolan. This innovation makes the cement less environmentally damaging, as the production process’ CO2 emissions are 38% lower, with energy consumption 30% lower than ordinary Portland cement.

“With this project we are leading the industry and sowing the seeds of the Argos of the future, which today starts a new production line at Rio Claro,” said Juan Esteban Calle, President of Cementos Argos. “It has gigantic growth potential in all geographies, not only from the point of view of the product, but because it is a concrete action for the sustainability of our industry. In our commitment to climate change, this project clearly makes us very proud.”