Displaying items by tag: Slag

Japan: Taiheiyo Cement has partnered with JFE Steel and the Global Institute for Environmental Technology to develop a carbon capture and storage system. The system will use wet alkaline earth metals extracted from steel slag to produce carbonates from exhaust gases at cement and steel plants. The partners are investigating the possibility of using these carbonates, specifically calcium carbonate and magnesium carbonate, as additives in cement production at Taiheiyo Cement’s plants. Taiheiyo Cement president Masafumi Shigehara said, “With the effects of climate change becoming apparent both in Japan and overseas, the importance of global warming counter-measures is increasing.”

Australia: A paper published in the journal Resources, Conservation and Recycling has reported that concrete made with treated slag is 8% stronger than standard slag concrete and 17% stronger than concrete made with conventional aggregates. A Royal Melbourne Institute of Technology (RMIT) team produced treated slag concrete using slag that had absorbed phosphate, magnesium, iron, calcium, silica and aluminium during use in wastewater treatment. Researcher Biplob Pramanik said, “The things that we want to remove from water are actually beneficial to concrete.” Pramanik said that the findings have promising implications for the water and concrete sectors within the circular economy.

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.

Brazil: Itaci Cement has purchased 100 hectares of land in Tabuleiro do Norte in the north-eastern Brazilian state of Ceará. Diario do Nordeste has reported that the company has invested US$66m in a development, though whether this will take the form of a clinker grinding or integrated cement plant has not been disclosed. Companhia Siderúrgica do Pecém (CSP) will reportedly supply granulated blast furnace slag to the facility when operational for use as a feedstock.

Sweden: Construction and engineering conglomerate Peab’s subsidiary Swecem has engaged German-based Gebr. Pfeiffer for the supply of one MVR 2500 C-4 grinding mill at its granulated blast furnace slag (GBFS) grinding plant in Oxelösund in Södermanland. The mill has four grinding rollers and a table diameter of 2.5m, giving it a 25t/hr slag grinding capacity.

Swecem operates a concrete plant in Kungsängen. It currently uses ground granulated blast furnace slag (GGBFS) supplied by Irish-based Ecocem’s 0.7Mt/yr Dunkirk grinding plant in France.

India: Dalmia Bharat has blamed the general election for its slow cement sales volumes growth in its first quarter. Its sales volumes of cement increased slightly to 4.55Mt. Its revenue grew by 7% year-on-year to US$365m in the first fiscal quarter to 30 June 2019 from US$340m in the same period in 2018. Its earnings before interest, taxation, deprecation and amortisation (EBITDA) rose by 27% to US$95.7m from US$75.2m.

The cement producer also said that its power and fuel costs per tonne had been negatively affected by its Kalyanpur plant operating at low capacity utilisation levels, partly due to a lack of coal. However, it noted that its raw material costs had been ‘moderated’ due to falling slag prices.

France: Hoffmann Green Cement Technologies and Bouygues Construction have signed a 30-month initial technical and commercial collaboration agreement to develop and test concrete formulations using new cement made from Hoffmann’s H-EVA technology. Hoffmann Green Cement inaugurated its pilot plant at Bournezeau, Vendée in late 2018. The unit will manufacture cement products using flash-calcined metakaolin and blast-furnace slag. Bouygues Construction is a global construction company with a presence in over 60 countries.

Charah Solutions has been steadily building up its fly ash distribution business in recent years with an eye on the supplementary cementitious materials (SCM) market. This week it opened the third of its new series of SCM grinding plants, at Oxnard in California, US. The unit sticks out because it is focusing on grinding natural pozzolans. The plant will receive natural pozzolan by truck and rail and then use Charah’s patented grinding technology to produce pozzolan marketed under its MultiPozz brand. The previous plants in this series mentioned natural pozzolans but this is the first to promote it explicitly.

The change is potentially telling because global demand for granulated blast furnace slag (GBFS) outstrips supply. Both performance benefits and environmental regulations are pushing this. It’s a similar situation for fly ash, also driven by trends to close coal-fired power stations in some countries. As Charles Zeynel of SCM trading firm ZAG International explained in the March 2019 issue of Global Cement Magazine, “...volcanic pozzolans are a potential SCM of the future. This is gaining traction, but it’s slow progress at the moment. This will be the answer for some users in some locations.”

The problem though is that natural pozzolans are down the list of preferred SCMs for their chemical properties after silica fume, GBFS and fly ash. The first is expensive but the latter two were traditionally cheap and easy to obtain if a cement or concrete producer had access to a source or a distribution network. Natural pozzolans are very much subject to variations in availability.

It’s no surprise then that Charah is promoting natural pozzolans in a Californian plant given that state’s environmental stance. It’s unclear where Charah is sourcing their pozzolan from but they are not the only company thinking about this in the US. Sunrise Resources, for example, is working on the environmental permits for a natural pozzolan mine near Tonopah in Nevada. As it described in its company presentation, California and Nevada are the most affected states in the fly ash supply crisis because they are, “...at the end of the line when it comes to rail deliveries from power stations in central and eastern USA.” It also estimated that California used 0.9Mt of pozzolan in its cement production of which about 90% is fly ash. The state produced 9.6Mt in 2015. Other companies are also mining and distributing natural pozzolans in the US as the website for the National Pozzolan Association (NPA) lists. Although, if this line-up is comprehensive, then the field is still fairly select. Most of these companies are based in the west of the country.

One last thing to consider is that various groups are tackling a potential future lack of SCMs for the cement industry by making their own pozzolanic materials through the use of calcined clay. These groups include the Swiss-government backed LC3 project and Cementir’s Futurecem products. Using clay should bypass the supply issues with natural pozzolans but the cost of calcining it requires at the very least an investment to get started.

As concrete enthusiasts often point out, a variant of pozzolanic concrete was used by the Romans to build many of their iconic structures, some of which survive to the present day. To give the last word to the NPA, “What is old is new again: natural pozzolan is back!” If environmental trends continue and steel and coal plants continue to be shut then it might just be right.

Spain: Endesa sold 0.3Mt of fly-ash from its Carboneras power plant in Almeria to cement companies in the UK and North America in 2018. The energy company also sold fly-ash to the nearby LafargeHolcim Carboneras cement plant, according to La Voz de Almería newspaper. The company has also sold 30,00t of slag and 60,000t of gypsum from its limestone plant.

Ukraine: Germany’s HeidelbergCement is selling its assets according to sources quoted by Interfax-Ukraine. It is reportedly selling to local investment group Concorde Capital and the deal will be completed during March and April 2019. The building materials local subsidiary, HeidelbergCement Ukraine, has not commented on story. The company operates integrated plants at Kryvyi Rih and Amvrosiyivka and a slag grinding plant at Kamyanske. Its loss rose by 14.4% year-on-year to around Euro14m in 2017.