Displaying items by tag: Slag cement

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.

Russia: Sibirsky Cement Holding (Sibtsem) subsidiary Topkinsky Cement has announced that it has entered commercial production of a new Mita slag Portland cement with granulated blast furnace slag (GBFS) at its 2.7Mt/yr integrated plant in Topki, for which it received a certification of conformity with ‘cement for general construction’ standards on 16 January 2020. Nina Poputnikova, Topkinsky Cement laboratory and quality department head, said that it is producing the cement in response to ‘construction companies’ increased interest in cement for use in reinforced, precast concrete in monolithic structures such as buried and hydraulic structures.’

“In the near future we plan to certify two new cements,” said Topkinsky Cement managing director Alexey Ospelnikov. One will be a low-heat general-purpose cement for large-sized concrete structures and the other a sulphate-resistant Portland cement. “Expanding the assortment will help strengthen the company’s position in the Russian cement market.”

India: JSW Cement has launched its ‘Comp Cem’ product in Goa. It is a blend of clinker, ground granulated blast furnace slag and fly ash, according to the United News Of India. The new product is intended to help the cement producer expand its distribution network in the southern and western parts of the country.

India: JSW Cement plans to increase the production capacity to 3.6Mt/yr at its Salboni grinding plant in West Bengal. The unit has a capacity of 2.4Mt/yr at present, according to the Economic Times newspaper. The cement producer plans to strengthen its presence in eastern India starting with West Bengal, Bihar, Odisha and Jharkhand. The plant manufactures Portland Slag Cement and it hopes to tap into local demand for this product with the upgrade.

Sri Lanka: Insee Cement is the first cement company to use the newly diversified Hambantota International Port. Bulk carrier Ithaca Patience docked at Hambantota to discharge 27,150t of slag, according to the EconomyNext. Thusith Gunawarnasuriya, Director of Procurement and Logistics, Insee Cement, the consignee of the slag cargo, said that the company is considering monthly or bi-monthly shipments via Hambantota. Insee Cement has previously used ports at Colombo, Trincomalee and Galle.

India: A report by the Cement Sustainability Initiative (CSI) shows that the local cement sector is on track to meet its 2030 targets from the low carbon technology roadmap (LCTR). Direct CO₂ emission intensity fell by 5% in 2017 in the Indian cement sector compared to the 2010 baseline. CO₂ emission intensity, including onsite or captive power plant (CPP) power generation, was reduced by 6.8% compared to the 2010 baseline. The alternative fuels thermal substitution rate (TSR) increased by 5 times from 2010 to 2017. The sector consumed more than 1.2Mt of alternative fuels in 2017.

“Sustainability is a journey, not a destination. In our globalised and interconnected world, no one can solve alone the challenges ahead of us and the only opportunity to succeed is through collaborative partnerships, where the common interests of all are considered as more important than the sum of individual interests. This is exactly the spirit that has animated the CSI’s low carbon journey since 1999. This flagship project - with its members - has developed, implemented and shared collective solutions for measuring, reporting and improving its greenhouse gas reduction performance, year after year,” said Philippe Fonta, managing director CSI.

The CSI and the International Energy Agency (IEA) worked with nine local CSI member companies - ACC, Ambuja Cements, CRH, Dalmia Cement (Bharat), HeidelbergCement, Orient Cement, Shree Cement, UltraTech and Votorantim Cimentos - to carry out the status review on the sector’s performance trends, continuous implementation measures and notable achievements based on the milestones set in the 2013 LCTR. The Status Review Report was developed in consultation with Confederation of Indian Industry (CII), with support from International Finance Corporation (IFC) and the Cement Manufacturers Association (CMA).

The findings of the report show that the direct CO₂ emission intensity was reduced by 32kgCO₂/t cement to 588kgCO₂/t cement in 2017 mainly due to an increased use of alternative fuel and blended cement production, coupled with a reduction in clinker replacement factor. However, the study also shows that significant efforts will be needed to meet the 2050 objectives of 40% reduction. The CO₂ emission intensity (including onsite or CPP power generation) has reduced by 49kgCO₂/t cement to 670kgCO₂/t cement in 2017 compared to the baseline year. The report has highlighted the adoption of waste heat recovery (WHR) systems by local cement plants.

The alternative fuels TSR increased to 3% in 2017 from 0.6% in 2010. More than 60 cement plants in India have reported continual usage of alternative fuels, with 24% of the total alternative fuels consumed as biomass. The share of blended cements used in the total quantity of cement manufactured increased to 73% in 2017 from 68% in 2010, largely due to the market’s growing acceptance of blended cement, emerging awareness of sustainability concepts, the availability of fly ash from thermal power plants and the use of advanced technology. The production of Pozzolana Portland Cement grew to 65% in 2017 from 61% in 2010. The share of Portland Slag Cement in cement production remained flat, at less than 10%, over the same period. The clinker factor reduced to 0.71 in 2017 from 0.74 in 2010.

In August 2018 the Global Cement and Concrete Association (GCCA) said it was taking over the work previously done by the CSI from 1 January 2019.

India: Jindal Steel & Power (JSP) plans to build a 2Mt/yr slag cement plant at Angul in Odisha. The US$68m unit will use ground granulated blast furnace slag sourced from a nearby steel plant operated by JSP, according to the Business Standard newspaper. A recent expansion at the steel plant to 6Mt/yr has allowed it to support a cement plant of this size. Land for the project has been acquired and the company hopes to obtain it from the state government by early 2019.

India: Dalmia Bharat has launched a fine blend composite cement product called Dalmia FBC. The product is a mix of slag and silica and it is intended to combine the properties of Portland Slag Cement and Portland Pozzolona Cement. The new brand was launched by BK Singh, Senior Executive Director, Group Marketing and Communications, Dalmia Bharat Group and Indrajit Chatterji, Executive Director Sales and Marketing (East) Dalmia Bharat Cement.

There is lots to mull over for the cement industry from last week’s Global Slag Conference that took place in Prague.

One striking map from Michael Connolly, TMS International, showed the status of slag and steel products in the US. It was a multi-coloured patchwork of different regulatory statuses from approval to be used as a product to regulatory exclusion. This won’t come as a surprise to many readers but even within one country the way slag can be used legally varies.

As this column reported last year after the Euroslag Conference, the European Union can be presented in a similar way. The irony here is that increased use of slag and other secondary cementitious materials (SCM) is exactly the kind of change the cement and concrete industries need to make to decrease their carbon emissions. Constant quibbles over whether slag is a product or a waste undermine this. Happily then that Connolly was able to report progress in the US as lobbying by industry and the US National Slag Association have led to more states legally accepting slag as a product.

However, cement producers have other concerns in addition to environmental ones when it comes to slag usage as Doug Haynes from Smithers Apex explained. Haynes, a former UK steel industry worker turned consultant, spoke around a market report on the future of ferrous slag. His take on Basic Oxygen Furnace (BOF) slag was that despite fuel savings, decreased CO₂ emissions and the benefits of embodied iron when it is used as a raw material for clinker production, it is in the interests of cement producers for slag to be a waste because they then get it for free or at a reduced rate. It’s a similar story to the use of waste-derived fuels powering cement plant kilns where producers want lower fuel costs but waste collectors want value for their product. Unsurprisingly, Haynes wanted cement producers to accept the value embodied in BOF slag.

Charles Zeynel of ZAG International, an SCM trader, then laid out the situation where global SCM supplies are remaining static but cement demand is growing. Coal-fired power station closures are reducing supplies of fly ash, another SCM, placing pressure on existing granulated blast furnace slag (GBS) slag supplies. The message was very much in a slag trader’s favour but instructive nethertheless. If slag is in demand then the price will rise. Anecdotally, the increased number of cement producers at the conference seemed to indicate increased interest of the cement industry in the product.

Lots more speakers followed on topics such as slag beneficiation, grinding advances and new innovations. On grinding, one surprise that popped up was that Spain’s Cemengal has sold a Plug & Grind Vertical mill to CRH Tarmac’s cement plant at Dunbar in Scotland. It is the first such sale of this product in Europe. The last speaker, Jürgen Haunstetter of the German Aerospace Centre, stuck out particularly with his presentation on using slag as a thermal energy storage medium in a concentrated solar power (CSP) plant. This may not seem connected to the cement industry but it is along similar lines to Italcementi’s project at the Aït Baha cement plant in Morocco, which uses a CSP process that can be used with the plant’s waste heat recovery unit.

The Global Slag Conference will return in April 2019 in Aachen, Germany.

Read the full review of the 13th Global Slag Conference 2018