Displaying items by tag: Calcium silicate cement

One unusual thing about coverage of cement in the media is the way that discussions often centre precisely on its absence – that is, on alternatives to cement. These alternatives boast unique chemistries and performance characteristics, but are all produced without Portland cement clinker. They are generally called ‘alternative cements,’ perhaps because ‘cement-free cement’ does not have such a commercially viable ring to it. This contradictory tendency reached a new high in the past week, with developments in alternative cement across Asia, Europe, the Middle East and North America. Together, they hint at a more diverse future for the ‘cement’ industry than the one we know today.

Asia

In Indonesia, Suvo Strategic Minerals has concluded tests with Makassar State University of a novel nickel-slag-based cement. Huadi Nickel-Alloy Indonesia supplied raw materials, and tests showed a seven-day compressive strength of 37.5MPa. Suvo Strategic Minerals says that a partnership with Huadi Nickel-Alloy Indonesia for commercial production is a likely next step.

Europe

Cement producer Mannok and minerals company Boliden partnered with the South Eastern Applied Materials (SEAM) research centre in Ireland to launch a project to develop supplementary cementitious materials (SCMs) from shale on 7 October 2024. The project will additionally investigate CO₂-curing of cement paste backfill for use in mines. Irish state-owned global commerce agency Enterprise Ireland has contributed €700,000 in funding.

UK-based SCM developer Karbonite expects to launch trial production of its olivine-based SCM with a concrete company in 2025. The start-up launched Karbonite Group Holding BV, with offices in the Netherlands, to facilitate this new phase. Karbonite’s SCM is activated at 750 – 850°C and sequesters CO₂ in the activation process, resulting in over 56% lower CO₂ emissions than ordinary Portland cement (OPC). Managing director Rajeev Sood told Global Cement that talks are already underway for subsequent expansions into the UAE and India.

Back in the UK, contractor John Sisk & Son has received €597,000 from national innovation agency Innovate UK. John Sisk & Son is testing fellow Ireland-based company Ecocem’s <25% clinker cement technology in concrete for use in its on-going construction of the Wembley Park mixed development in London.

At the same time, Innovate UK granted a further €3.23m to other companies for concrete decarbonisation. Recipients included a calcined clay being developed by Cemcor, an SCM being developed from electric arc furnace byproducts by Cocoon, a geopolymer cement technology being developed by EFC Green Concrete Technology UK and an initiative to develop alternative cement from recycled concrete fines at the Materials Processing Institute in Middlesbrough. Also included was the Skanska Costain Strabag joint venture, which is working on the London stretch of the upcoming HS2 railway. The joint venture, along with partners including cement producer Tarmac and construction chemicals company Sika UK, will test low-kaolinite London clay as a raw material with which to produce calcined clay as a cement substitute in concrete structures in HS2’s rail tunnels.

Middle East

Talks are underway between UK-based calcined clay producer Next Generation SCM and City Cement subsidiary Nizak Mining Company over the possible launch of a joint venture in Riyadh, Saudi Arabia. The joint venture would build a 350,000t/yr reduced-CO₂ concrete plant, which would use alternative cement based on Next Generation SCM’s calcined clay.

North America

Texas-based SCM developer Solidia Technologies recently patented its carbonatable calcium silicate-based alternative cement, which sequesters CO₂ as it cures.

Meanwhile, C-Crete Technologies made its first commercial pour of its granite-based cement-free concrete in New York, US. C-Crete Technologies says that the product offers cost and performance parity with conventional cement, with net zero CO₂ emissions. Its raw material is globally more abundant than the limestone used as a raw material for clinker. Other abundantly available feedstocks successfully deployed within C-Crete Technologies’ repertoire include basalt and zeolite.

Across New York State, in Binghamton, KLAW Industries has succeeded in replacing 20% of concrete’s cement content with its powdered glass-based SCM, Pantheon. KLAW Industries has delivered samples to local municipalities and the New York State Department of Transportation. Its success expands the discussion of possible circular cement ingredients from the industrial sphere into post-consumer resources.

In Calgary, Canada, a novel SCM has drawn attention from one of the major cement incumbents: Germany-based Heidelberg Materials. It invested in local construction and demolition materials (CDM)-based SCM developer EnviCore on 9 October 2024. The companies plan to build a pilot plant at an existing Heidelberg Materials CDM recycling centre.

Conclusion

Alternative cement developers are still finding the words to talk about their products. They may be more than ‘supplementary’ up to the point of entirely supplanting 100% of clinker. Product webpages offer ‘hydraulic binder,’ ‘pozzolan’ and even ‘cement.’ As alternative ‘cements’ are developed, they build on the work of pioneers like Joseph Aspdin and Louis Vicat. Start-ups and their backers are now reaching commercial offerings, on a similar-but-different footing to cement itself. None of these novel materials positions itself as the sole, last-minute ‘super sub’ in the construction sector’s confrontation with climate change. Rather, they are a package of solutions which can combine into a net zero-emissions heavy building materials offering, hopefully before 2050.

Related to this is the need for ‘technology neutral’ standards, as championed this week by the Alliance for Low-Carbon Cement and Concrete (ALCCC), along with 23 other European industry associations, civil society organisations and think tanks. The term may sound new, but the concept is critical to the eventual uptake of alternative cements: standards, the ALCCC says, should be purely performance-based. They ought not attempt to define what technology, for example cement clinker, makes a suitable building material. According to the ALCCC, Europe’s building materials standards are not technology neutral, but instead ‘gatekeep’ market access, to the benefit of conventional cement and the exclusion of ‘proven and scalable low-carbon products.’

At the same time, cement itself is changing. Market research from USD Analytics showed an anticipated 5% composite annual growth rate in blended cement sales between 2024 and 2032, more than doubling throughout the period from US$253bn to US$369bn. If you can’t beat it, blend with it!

For a further discussion of alternative cement and binders in Europe, see Global Cement’s interview with ALCCC co-ordinator Joren Verschaeve in the forthcoming November issue of Global Cement Magazine on 17 October 2024.

South Korea: A recent study from Daejeon explored the potential of low-lime calcium silicate cement as a low CO₂ emission alternative to Ordinary Portland Cement. Researchers from the Korea Institute of Geoscience and Mineral Resources examined the setting and flow characteristics of a mixture of Ordinary Portland Cement and low-lime calcium silicate cement under carbonation curing conditions. The study was financially supported by the Ministry of Trade, Industry & Energy's industrial strategic technology development programme.

The study aimed to explore the reaction and microstructural characteristics of these cement pastes. The low-lime calcium silicate cement was synthesised using limestone and silica fume, with varying proportions added to the Portland cement pastes. The research findings suggest improvements in compressive strength with the inclusion of 30% or more low-lime calcium silicate cement, highlighting its ability to enhance the durability and sustainability of construction materials.

The US Department of Energy (DOE) announced a US$1.6bn investment in the cement sector this week. The funding was part of a total of US$6bn for 33 projects in over 20 states to decarbonise energy-intensive industries also including chemicals and refining, iron and steel, aluminium and metals, food and beverages, glass, process heat applications and pulp and paper. The DOE was keen to link the money to “the President’s Bipartisan Infrastructure Law and Inflation Reduction Act.” Politics is never far away it seems! The projects are part of the Industrial Demonstrations Program, managed by DOE’s Office of Clean Energy Demonstrations (OCED).

Table 1: Summary of US Department of Energy funding announced on March 2024 to decarbonise cement and concrete production

Table 1 above shows the main approaches each of the projects aim to use. The two most expensive ones involve carbon capture and sequestration (CCS) at Heidelberg Materials US’ Mitchell cement plant in Indiana and National Cement’s Lebec plant in California respectively. In a complimentary press release Chris Ward, the CEO of Heidelberg Materials North America, said “This substantial federal funding investment will help create the first full-scale deployment of carbon capture and storage on a cement plant in the US.” The proposed CCS unit at the plant will capture around 2Mt/yr of CO₂ from 2030. If Ward’s forecast is accurate (and no one beats them to it), then Heidelberg Materials will likely have set up the first full-scale CCS units at cement plants in both North America and Europe. This will be a significant achievement. The National Cement project, by contrast, is a mixed bag of approaches to decarbonising cement production that follows the multi-lever approach advocated for in many of the industry net-zero roadmaps. It intends to use agricultural by-products such as pistachio shells, as alternatives fuels to lower the fuel-based emissions, calcined clay to lower the clinker factor and CCS to capture the remaining 950,000t/yr of CO₂ emissions.

The other projects either involve using calcined clay or substituting limestone with calcium silicate. The Summit Materials proposal is noteworthy because it aims to build four clay calcination units in locations in Maryland, Georgia and Texas. None of these appear to be near Summit’s (or Cementos Argos’) cement plants. This suggests that the company may be intending to use calcined clay in ready-mixed concrete production. The Roanoke Cement Company calcined clay project will be baseEuropead at its cement plant in Troutville, Virginia.

The remaining two grant recipients, Brimstone and Sublime Systems, will both test the companies’ different methods of manufacturing cement by using calcium silicate instead of limestone. Brimstone’s method produces ordinary Portland cement (OPC) and supplementary cementitious materials (SCM). The company said in July 2023 that its OPC met the ASTM C150 standards. However, the company has released less information about its actual process. Sublime Systems’ uses an electrolysis approach to create its ASTM C1157-compliant cement. It calls this ‘ambient temperature electrochemical calcination.’

Investment on the same scale of the DOE has also been happening in Europe. In July 2023, for example, the European Commission announced an investment of Euro3.6bn in clean tech projects to be funded from the proceeds of the European Union emissions trading scheme (ETS). This was the third call for large-scale projects following previous announcements of recipients in 2021 and 2022. Euro1.6bn of the third call funding went towards cement and refining projects including five cement and lime projects in Belgium, Croatia, Germany and Greece. The money granted for each of these schemes was in the region of Euro115 - 235m.

Both the US and Europe are throwing serious finance at the cement industry to try and kickstart the various pathways towards net zero. They are also doing it in different ways, with the US aiming to boost its economy by onshoring sustainable industry, and Europe hoping to fund its approach via carbon taxation. Government-driven decarbonisation investment for cement in other large countries and regions around the world appears to be lagging behind the US and Europe but these may spring up as net zero targets are set, roadmaps drawn up and government policy formulated. These places could also benefit from watching what works and does not work elsewhere first. Back in the US and Europe the next tricky part of this process will be bridging the gap between government subsidy and commercial viability.

US: Brimstone has announced a new method of ordinary Portland cement (OPC) with a negative carbon footprint. Brimstone's method uses carbon-free calcium silicate in the place of limestone. Its calcination also produces magnesium compounds, which naturally sequester further CO₂ from the atmosphere. The technology will now proceed to the testing phase at an upcoming pilot plant in Reno, Nevada, before proceeding to commercial-scale production. Brimstone will then begin to market its OPC, along with supplementary cementitious materials produced by its process.

Brimstone's chief technology officer Hugo Leandri said “By delivering the exact same cement, we clear away the main obstacles to adoption, offering an opportunity to dramatically speed up the path to net-zero construction. The same buildings, bridges and roads being built today can be built tomorrow, without carbon."

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.