In line with the Group Sustainability goals, for the first time across our countries and European Union member countries, Limak Cement has received the ETA (European Technical Assessment) product certificate that enables coal bottom ash, a waste product of thermal plants, to be used as an additive in the cement production.
We asked Ms. Ebru Sipahioğlu, Limak Cement Group Quality Director, about R&D activities of Limak Cement, Certification Process of Coal Bottom Ash and Use and the areas of us.
Could you tell about R&D activities of Limak Cement Group?
As Limak Cement Group, we have a Cement Central Laboratory and Ready-Mix Concrete Laboratory certified with TS EN ISO / IEC 17025 Accreditation Certificate from TURKAK, independent from our plant and facility laboratories, where we carry out our R&D activities. In addition to the regular product inspections, we perform special experiments such as alternative product optimization, burnability tests, waste analyses, grinding efficiencies.
As is well known, “Sustainable Development Goals (SDG Compass)” has been published in 2015 as a common agenda for entire world under the leadership of United Nations. As an action plan for 2030, these principles address key elements necessary to achieve a certain prosperity in the economic, social and environmental areas from the zero hunger to the clean energy, from the responsible producer to the life below water. This action constitutes a crucial guidance for business world on what can be done with respect to the “Sustainable Development Goals”. According to this new approach embraced under the name of SDG Compass, 13th Item, of 17 Goals, is the Climate Action.
Being aware of the important role cement industry played in the climate change, sustainability and development goals of our group is closely aligned with climate action under the short and mediumterm goals. With respect to the management of the climate changerelated risks, it is clear and evident that we should consider the activities such as improvement of energy efficiency, minimization of greenhouse gases and other emissions, using alternative fuels and raw material, product development, participation in local and international initiatives.
In this context, our R&D activities have aimed at recovering the fly ash, coal bottom ash, and synthetic gypsum generated by the thermal plants via an effective quality and product management process to the use of cement producers and accordingly we steered our activities.
What is Coal Bottom Ash? How is it generated? Could you enlighten us?
In thermal plants, coal is first ground and then fed to the boiler, and during the combustion process in the combustor, organic components of the pulverized coal such as carbon and other combustible compounds are consumed in seconds, as a result, producing heat. Inorganic part of the coal composed of impurities such as clay, shale, quartz, feldspar remains suspended within the flue gases, transforming into ash particles in various sizes and chemical composition. A part of the suspended ash consists of relatively bigger particles. These particles fall on the bottom of boiler in the form of solid or melt depending on the type of boiler and coal. These materials accumulated on the bottom of boilers are called as “Coal Bottom Ash”. In short, coal bottom ash (BA) is a waste product generated by thermal plants.
Okay, but why Coal Bottom Ash?
Turkey has a 332 million tonnage of proven hard coal reserve and 8.3 billion tonnage of lignite reserve. In our country, coal sites are indispensable energy sources for potential thermal plants. According to the data published by TÜİK, our country’s 66 thermal plants fueled by coal, natural gas or fuel oil is generating 24.2 million tonnage of mineral waste (ash, fly ash, slag, gypsum). Although the applications in the construction industries in the World have pioneered the recovery of fly-ash, it is observed that recovery rate of fly-ash significantly varies from one country to another. Whilst the world average is at the levels of 25%, published data in our country, however limited, reports that this rate is at the lower levels.
On the other hand, while the energy and raw material consumed during the production of Portland cement increases the CO2 emissions, which is harmful for our environment, the use of environment-friendly mineral additives will certainly reduce the CO2 emissions. Therefore, in our industry recovery of Coal Bottom Ash BA) can contribute in efforts under the climate action.
What is Cement with Coal Bottom Ash? Could you tell us about it?
Using mineral admixtures, in place of clinker, in the cement production have important contribution in reduction of the energy consumption and harmful gas emissions. Natural and artificial mineral admixtures positively contribute in the strength and durability of the cement. The most common mineral admixtures are fly-ash, silica fume, blast furnace slag, coal bottom ash (BA), marble powder. Coal bottom ash is a side-product, which has chemical properties close to fly-ash depending on the combustion efficiency and process conditions of the plant (pulverized, fluidized bed) but is different in terms of physical properties. Therefore, coal bottom ash can be used as an admixture in cement due to its pozzolanic property just as in fly-ash. The grinding is the basic requirement for using coal bottom ash as a chemical admixture. Just as in other pozzolanic admixtures, as the substitution rate increases, so does the water demand. Using an optimized coal bottom ash having suitable chemical properties as a concrete admixture, it is observed that, compared to the Portland cement in the same strength grade, it has lower early-strength, higher compressive strength by 28 days and later, lower hydration heats, lower volume expansion due to slowed down hydration kinetics, longer setting times, and BAcontaining cements have easier grindability than Portland Cement.
What are the application areas of these products?
A BA-containing product which optimization and control is ensured has equivalent properties with all kinds of cement-added product having a pozzolanic property. They can be used in every areas where pozzolanic cements can be used.
How was the process of “National Technical Approval (NTA)” for this product? What processes did you undergo in Turkey?
To use a product as a cement additive, it must be defined in the “Standard TS EN 197-1: General Cements-Composition, Specifications and Conformity Criteria”. Although coal bottom ash has the mineral additive properties, it is not defined in the Standard TS EN 197-1.
The Regulation on the Criteria Requirements of Construction Materials published on 8/29/2014 stipulates that the products not covered by harmonized standard (TS EN 197-1) can be issued with Marking G by the producer of the side products such as coal bottom ash under the National Standards. So, Marking G allows said side products to be introduced to the market, while National Technical Approval Certificate (NTA) legally permits them to be used as an alternative cement admixture. As Limak Cement Group, we apply to CPC Belgelendirme Muayene ve Deney Hizmetleri Ltd. Şti. firmasına (CPC), the body authorized by R. of T. Ministry of Environment and Urbanization for using the coal bottom ash, and then the Guidance Document prepared by CPC carefully and fully is submitted to R. of T. Ministry of Environment and Urbanization (The document constitutes the framework of a technical specifications having a binding nature across all national technical approval activities to be carried out later with respect to said product or product group). On 2/28/2017, “Cement With Coal Bottom Ash Guidance Document” is approved by R. of T. Ministry of Environment and Urbanization, initiating the regular product certification process. Monthly periodic sampling is performed in the plant, followed by the analyses to carry out the conformity assessments, and finally the National Technical Approvals No CPC-UTO-17/155 and CPC-UTO-17/156 are issued on 4/11/2017. Finally, product becomes marketable with Marking G in the domestic market.
Is construction and cement industry in Turkey aware of such applications?
I think that in our country cement producers approach NTA applications with a caution. Therefore, I would like to give details of NTA applications.
Our country has thermal plants and therefore fly-ash and coal bottom ash resources. However, the criteria for using fly-ash in cement and ready-mix concrete are not described in Standards TS EN 197-1 and TS EN 450-1. These standards require complete satisfaction of all specified criteria. Even if only one criterion is not met, then product is deemed non-standard, and therefore cannot be used. From the perspective of these requirements, it is possible that fly-ash generated in existing plants can be non-conforming, as well as coal bottom ashes can be useable. Since ready-mix concrete is directly used, it is not even mentioned in NTA applications. However, they can be included in NTA applications with optimizations such as cement-side grinding, gypsum use etc. The crucial points in NTA applications with respect to cement production is to ensure keeping a constant track of the quality parameters of both input and product and to optimize the product by keeping a track of the performance of cement and particularly ready-mix concrete. If these actions will be performed, then product should be marketed with NTA application.
Could you tell us about ETA and EOTA application processes for Cement with Coal Bottom-Ash? How did you involve in this process?
As I said above, I have the opinion that NTA application is not well-known in our industry. When we look at European Countries, the products are assessed on the criteria such as support provided to mineral additive use, and environmentfriendly product requirements, then we applied to EOTA, the European address of NTA application in our country.
EOTA is European Organisation For Technical Assessment. Looking at the practice, the applications to EOTA cannot be made directly by a firm, but through the member bodies. In our country, CPC Belgelendirme Muayene ve Deney Hizmetleri Ltd. Şti. firm is a member of EOTA, and we made our application to CPC in June, 2018. The first draft study was conducted on 10/22/2018 for LİMAK ÇİMENTO SAN. Ve TIC. A.Ş. as a preparation for the “EAD 150043-00-0301 / Cement With Coal Bottom Ash” Numbered EAD (European Assessment Document) studies which were concluded by CPC Firm in coordination with EOTA (European Organization for Technical Assessment). This EAD is the first European Assessment Document issued for free circulation, sales and use of “Cement with Coal Bottom Ash” across the European Union Member Countries. The application to said EAD is made by Limak Balıkesir Plant, and two products as CCBA 42,5 R and CCBA 32,5 N are certified with Number ETA (European Technical Assessment) -19/0620, on 10/31/2019, for the first time in our country and European Union Member Countries. These efforts have opened a new horizon before cement industry, demonstrating that materials not defined in the TS EN 197- 1 Standard can be put into use with the ETA process.
Do you have anything to add for this effort of yours?
The investments made in order to meet the increasing cement demand in the world and our country has also significant implications in terms of preservation of the natural resources. While Cement Groups can ensure high quality products, they also carry out efficient use of the resources through environment-friendly technologies. In line with the “Responsible Producer and Consumer” goal among these principles, alternative raw materials must be predominantly used in order to decrease the CO2 emissions, energy costs and consumption of natural raw material resources and these efforts must be supported with NTA and ETA processes, where high quality and control can be sustained with respect to the product.