Key Turkish chemicals producer Akkim Kimya has undertaken laboratory- and industrialscale trials for a large domestic cement producer using its Akkim low-carbon cement additive. Aimed at being a strength enhancer, the new grinding aid has also proven to improve other process parameters.
by Dr. Uğur Erşen Şenbil & Furkan Karatay, Korhan Dönmez, Erdi Türkeri, Akkim Kimya, Construction Chemicals R&D and Sales Team
The article with the title “Adding to the Low-Carbon Transition” of Akkim Construction Solutions Team, which compiles the laboratory and industrial trials results of our new AKGRİN LC Series, that enables the production of low carbon cement, is in the June issue of the prestigious sectoral publication ICR (International Cement Review)
One of the strategies to mitigate the negative environmental impact of cement production is the utilisation of supplementary cementitious materials (SCMs) in the manufacture of cement.1 The most commonly-used SCMs are limestone, fly ash, silica fume, granulated blastfurnace slag, natural pozzolana and metakaolin.2 The goal of the research project by Turkish chemicals producer Akkim Kimya was to reduce the clinker content of cement with a limestone substitute in the presence of Akkim’s low-carbon cement additive as a compressive strength enhancer, and avoid strength loss due to the reduced clinker content in the cement’s composition.
Materials and methodology
The trials were carried out in Akkim’s R&D centre for one of the largest Turkish cement producers. During the trials, two types of cement were evaluated, both of which the raw materials were supplied by the cement plant:
• C-1 – the current cement composition at the Turkish cement factory
• C-2 – cement with a 3kg/t clinker reduction in its composition.
The cement works produces 0.7Mta of C-1. Therefore, if the clinker content is reduced by 3kg/t, a total of 2100tpa of clinker can be saved. As CO2 emissions are approximately 849-868kg/t,3 when 2100tpa of clinker is taken into account, an average of 1.8Mt of CO2 emissions can be avoided by using the low-carbon cement additive series.
Akkim Kimya’s low-carbon cement additive has undergone laboratory and industrial-scale trials with promising results
A laboratory ball mill was used to grind both cement types for a duration of 60min each (see Table 2). The cement plant currently uses the AKGRİN 456 grinding aid as a compressive strength enhancer. AKGRİN LC 1048 is the low-carbon additive series designed especially for this factory.
To determine the physical and mechanical properties of the cements, tests on the specific surface area (SSA) according to Blaine, air jet sieving, packset index, particle size distribution (PSD) and two-, seven- and 28-day compressive strength were carried out (see Figures 1-5).
Results
The laboratory trials showed that the new AKGRİN LC 1048 additive has a better grinding performance compared to the AKGRİN 456 additive and also has better compressive strength values compared to the current composition, even with the clinker content reduced and the limestone content increased.
Based on these results it became evident that the clinker/limestone substitution in the presence of the new low-carbon additive could be used at an industrial level.
Industrial-scale trials
The next step was to test the new additive at the cement plant under real industrial conditions to find out whether the results would be in parallel with the laboratory findings. As the mills are in continued operation and sensitive to untried changes, the plant decided to first try the new low-carbon additive with the existing composition and compare the results with the laboratory trials.
Process parameters
During the industrial-scale trials, production of cement with the current composition was observed for 6h in the presence of the current additive. After that, the new low-carbon additive was introduced and observed for 8h. Trials were carried out, aimed at a residue of 4.0- 4.5 per cent on a 45μm sieve. During the industrial process, mill output, separator cycle and energy consumption were recorded. These results are presented in Table 3 with average values of the 6h and 8h trial times.
The new low-carbon additive showed better performance than the existing additive in terms of mill output, separator cycle and energy consumption. The AKGRİN LC 1048 reduced energy consumption by 3.3 per cent and the separator cycle by one per cent, while mill output increased by 1.8 per cent. Although the main aim was to increase compressive strength, it was encouraging to note that the other process parameters were not negatively affected but in fact improved.
Fineness, compressive strength and concrete performance
The two industrial cement samples were then taken to Akkim’s R&D centre to carry out tests based on fineness, compressive strength and concrete performance.
When the fineness and compressive strength results were evaluated, the industrial trial cements showed results that were in line with the laboratory trials. In particular, the compressive strength results were very promising as the final compressive strength of the AKGRIN LC 1048 at 28-days is 5.2MPa higher than the current additive (see Table 4). This result encourages the substitution of clinker with limestone to reduce CO2 emissions.
Concrete performance using these two samples was also measured. A concrete admixture was not used so that the pure effects of the cements could be seen. The concrete performance results using these two cements are presented in Table 5.
The two cements showed similar fresh concrete properties and the AKGRIN LC 1048
additive gave higher compressive strength values at all ages. The result shows that the low-carbon cement additive not only gives a higher performance in cement, but also in concrete.
Conclusions
Overall, the results from this research project revealed the following:
• Laboratory trials showed that the performance of the low-carbon additive is satisfactory when substituting clinker with limestone.
• This additive also showed better performance across various process parameters, including mill output, separator cycle and energy consumption.
• The industrial trial results were in parallel with the laboratory test results.
• The concrete performance of the low-carbon additive is better than the current additive used at the cement plant, especially in terms of compressive strength.
All these results showed that clinker substitution with limestone is possible with AKGRİN LC 1048 to reduce CO2 emissions without compromising technical performance.
REFERENCES
1 PACEWSKA, B, WILIŃSKA, I (2020) ‘Usage of supplementary cementitious materials: advantages and limitations’ in: Journal of Thermal Analysis and Calorimetry, 142 (1), p371–393 (2020).
2 SCRIVENER KL, JOHN, VM, GARTNER, EM (2018) ‘Eco-efficient cements: potential economically viable solutions for a low-CO2 cement-based materials industry’ in: Cement and Concrete Research, 114 (5), p2-26
3 PRAKASAN, S, PALANIAPPAN, S AND GETTU, R (2020) ‘Study of Energy Use and CO2 Emissions in the Manufacturing of Clinker and Cement’ in: Journal of Institute of Engineering, Series A, 101, p221-232.
Acknowledgement
The authors wish to express their deepest thanks to Akkim Kimya for its valuable support during this scientific study.
