TX_1~ABS:AT/ADD:TX_2~ABS:AT 26 http://journals.cihanuniversity.edu.iq/index.php/cuesj CUESJ 2023, 7 (2): 26-30 ReseaRch aRticle Physical and Mechanical Properties of an Artificial Aggregate Made up of Ground Granulated Blast-Furnace Slag Mais A. Ibrahim1, Nihat Atmaca2, Adem Atmaca3 1Department of Civil Engineering, Cihan University-Erbil, Kurdistan Region, Erbil, 44001, Iraq, 2Department of Civil Engineering, Engineering Faculty, Gaziantep University, Gaziantep, 27310, Turkey, 3Department of Mechanical Engineering, Engineering Faculty, Gaziantep University, Gaziantep, 27310, Turkey ABSTRACT Manufacturing artificial aggregate by utilizing waste materials has gained great importance as the aggregate occupies a high volume in concrete (60–70%). In this paper, ground-granulated blast-furnace slag (GGBFS) is utilized in aggregate manufacturing. Cold bonding and sintering methods were used as production processes. The pellets were put through a series of tests such as dry density, specific gravity, water absorption, and crushing strength. The results indicated that the density of pellets increased by increasing the GGBFS dosage while the water absorption capacity was reduced. Furthermore, the highest crushed strength was recorded at 50% addition of GGBFS. Keywords: Artificial aggregate, cold bonded, ground-granulated blast-furnace slag, pelletization, waste materials INTRODUCTION The enormous expansion of industry in recent years makes it all the more important to manage trash effectively and lessen its impact on the natural world and on people’s health. The annual production of ground- granulated blast-furnace slag (GGBFS) as a solid waste material from the iron melting process is very high. Reusing trash to make new building supplies or synthetic exaggerate (like fly ash, a byproduct of thermal power plants) is supported by research,[1,2] sewage sludge,[3,4] quartz powder,[5] and different types of ashes[6] which were studied. Cold bonding (cement-based pelletization) and sintering processes[7] are the most common methods in aggregate production. Although the properties of sintered aggregate are better than those of cold-bonded aggregate in terms of strength, it is a costly and energy-consuming method when compared to the cold-bonded process. The disadvantage of the cold bonding process is the time that the pellets need to gain the required strength,[8] in contrast to the sintering method, in which the pellets gain strength and are ready to use immediately after the sintering is completed.[9] Utilizing cold-bonded and sintered artificial aggregates in concrete production has been investigated in the literature. Some studies have shown that 30% replacement of artificial aggregate with natural aggregate could result in comparable properties to normal concrete.[10,11] Sintered fly ash artificial aggregate as a replacement for fine aggregate improved the mechanical properties and fracture strength of concrete.[12] A compressive strength of concrete between 20 MPa and 80 MPa could be achieved using artificial aggregate. The axial strength of the concrete increased with the use of 10% of fly ash artificial aggregate as a replacement for natural coarse aggregate.[13] In addition to the mechanical properties, the workability can also be improved when using artificial aggregate due to its spherical shape.[14] Although some studies resulted in the lower mechanical properties of artificial aggregate concrete compared to normal concrete, artificial aggregate concrete has advantages such as being low-cost, eco-friendly, and lower in dead load.[15-17] The cost of concrete produced with artificial aggregate reduces by 13–15% compared to the cost of normal concrete.[18] There are few studies on the use of GGBFS in the production of lightweight aggregate. Therefore, the aim of this study is to propose a new idea of utilizing the large amount of such waste materials in the production of the frequently and in Cihan University-Erbil Scientific Journal (CUESJ) Corresponding Author: Mais A. Ibrahim, Department of Civil Engineering, Cihan University-Erbil, Kurdistan Region, Erbil, 44001, Iraq. E-mail: mais.ibrahim@cihanuniversity.edu.iq Received: March 23, 2023 Accepted: August 07, 2023 Published: August 25, 2023 DOI: 10.24086/cuesj.v7n2y2023.pp26-30 Copyright © 2023 Mais A. Ibrahim, Nihat Atmaca, Adem Atmaca. This is an open-access article distributed under the Creative Commons Attribution License (CC BY-NC-ND 4.0). Ibrahim, et al.: Production of artificial aggregate using waste material 27 http://journals.cihanuniversity.edu.iq/index.php/cuesj CUESJ 2023, 7 (2): 26-30 large quantities used material, which is aggregate. Thus, this investigation concentrated on the possibility of manufacturing artificial aggregate using GGBFS and optimizing the amount of GGBFS that would result in physical and mechanical properties of aggregate that can be compared with those of natural aggregate. MATERIALS AND METHODOLOGY In this experimental study, ordinary Portland cement (OPC) of grades CEMI 42.5 R and GGBFS from the local markets was used to manufacture the cold-bonded and sintered aggregates. The GGBFS was oven-dried for 24 h at 105°C before being used followed by grinding into powder. The major components of GGBFS are CaO, SiO2, and Al2O3. Table 1 shows the physical and chemical compositions of OPC and GGBFS. Manufacturing of Aggregate To produce the cold-bonded aggregate, GGBFS was mixed with cement in proportions of 20, 30, and 50%, as shown in Table 2. The proportions were selected after trials to get the appropriate pellets in terms of shape and size. The ratio of GGBFS above 50% showed difficulty in forming rounded pellets, and the loss of materials started to increase. The combinations have been labeled by considering the ratio of cement and GGBFS; for example, 80C20G refers to pellets made with 80% of cement and 20% of GGBFS. The dry materials were fed into the pelletization disk with a diameter of 800 mm and a depth of 300 mm, as shown in Figure 1. The first stage of the cold bonding process is to mix the dry materials for 3–5 min to get a homogenous mixture followed by adding the water by way of spraying onto the materials while the rotating of the pelletization disk is continued. After 15–20 min, the pellets started to be formed in the size range of 8–16 mm. Figure 2 shows the cold bonding process, and Figure 3 shows the produced pellets. The pellets were then collected and kept in plastic bags to be cured at room temperature and humidity of 20°C and 95 %, respectively, for 28 days before being used as cold-bonded aggregates. On the other hand, a quantity of the produced pellets was taken once the pelletization process had been completed and exposed to a high temperature of 900°C for 2 h, as shown in Figure 4, to produce the sintered aggregates. The difference in appearance and color between cold-bonded and sintered aggregate is shown in Figure 5. Test Procedures To investigate the physical and mechanical properties of the produced pellets, tests of bulk density, specific gravity, and water absorption were carried out in accordance with ASTM 127,[19] and particle size distribution by sieve analysis procedures. Furthermore, the crushing strength value was measured as per BS 812 Part 110.[20] Table 1: Physical and chemical composition of the materials used in this study Composition (%) OPC GGBFS CaO 62.58 34.12 SiO2 20.25 36.41 Al2O3 5.31 10.39 Fe2O3 4.04 0.67 MgO 2.82 10.26 SO3 2.73 - K2O 0.92 0.97 Na2O 0.22 0.35 Loss on ignition 3.02 1.64 Specific gravity 3.15 2.79 Blaine fineness (m^2/kg) 326 418 OPC: Ordinary Portland cement, GGBFS: Ground-granulated blast-furnace slag Table 2: Mix proportions Mix ID OPC (%) GGBFS (%) 80C20G 80 20 70C30G 70 30 50C50G 50 50 OPC: Ordinary Portland cement, GGBFS: Ground-granulated blast-furnace slag Figure 1: The pelletization disk Figure 2: During the cold-bonding process Ibrahim, et al.: Production of artificial aggregate using waste material 28 http://journals.cihanuniversity.edu.iq/index.php/cuesj CUESJ 2023, 7 (2): 26-30 By measuring the pellets’ oven-dry weight (W1), pellets’ weight (W2) while submerged in water, and pellets’ saturated weight (W3) after 24 h in water, we were able to determine the pellets’ oven-dry (OD) relative density and water absorption. To do the math, we used these relationships:[19] Relative Density OD� � � � W W W 1 3 2 (1) Water absorption � � �W W W 3 1 1 100 (2) The pellets were tested individually for crushing strength by applying the aggregate particle between two parallel plates and applying a load of 28 KN until failure, as shown in Figure 6. The following equation[20] was used to determine the crushing strength after taking the average of ten pellets for each mix. Crushing�strength � � 2 8 2 . F d� (3) Where F is the maximum load at failure (N), and d is the diameter or the distance between the loading points (mm). RESULTS AND DISCUSSION The results of density, specific gravity, water absorption, and crushing strength values for the cold-bonded artificial aggregate are listed in Table 3 and graphically shown in Figures 7–9. It can be seen from the results that the addition of GGBFS improves the aggregate properties by increasing the specific gravity and density and reducing the water absorption capacity. The cold-bonded artificial aggregate can be considered lightweight aggregate as the densities are less than 2000 kg/m^3.[21] The high porosity of artificial aggregate resulted in a higher water absorption capacity, which is not a desirable property when used in concrete because the aggregate will affect the water- cement ratio that affects the hydration process. However, in this type of artificial aggregate, the voids were reduced by Figure 3: The produced pellets Figure 4: Sintering the pellets at 900°C Figure 6: Test of crushing strength Figure 5: Difference in appearance between (left) cold bonded and (right) sintered pellets Ibrahim, et al.: Production of artificial aggregate using waste material 29 http://journals.cihanuniversity.edu.iq/index.php/cuesj CUESJ 2023, 7 (2): 26-30 Table 4: Physical and mechanical properties of sintered artificial aggregate at 900°C Mix ID Density (kg/m^3) Water absorption (%) Crushing strength (N) 80C20G 1299 15.85 690.8 70C30G 1324 14 858.5 50C50G 1337 11.15 1059.87 Table 3: Physical and mechanical properties of cold-bonded artificial aggregate. Mix ID Specific gravity Density (kg/m^3) Water absorption (%) Crushing strength (N) 80C20G 1.84 652.18 18.05 453.29 70C30G 1.80 750.00 17.20 541.78 50C50G 1.74 1114.42 16.27 1038.98 increasing the GGBFS dosage to 50%, and as a result, the minimum water absorption of 16.27 was achieved. In addition, the particle size distribution is shown in Figure 10 for the cold-bonded artificial aggregate at different ratios of GGBFS. Furthermore, the crushing strength results agree with the density and water absorption results, with the maximum crushing strength of 1038.98 N recorded at the mix with a maximum density of 1114.42 kg/m^3. This means that increasing the ratio of GGBFS could improve the physical and mechanical properties of artificial aggregate. The results of the sintered aggregate properties are shown in Table 4. The results indicated better performance when exposed to high temperatures by increasing the density and reducing the water absorption. The high temperature leads to a glassy texture inside the pellets, which, in turn, reduces water absorption. From the show results, the mixture of 50% of GGBFS can be considered the optimized mixture for producing the artificial lightweight aggregate, as it resulted in the best physical and strength properties. In the study of Kumar et al., 2016, the physical properties of an artificial aggregate made up with GGBFS were found to be similar to the results in this study, where the water absorption was found to be 18% and the specific gravity was 2.76.[22] CONCLUSION In this experimental study, GGBFS was selected to be utilized in the production of cold-bonded and sintered artificial aggregates. Due to the obtained results, the following conclusions are drawn: Figure 10: Particle size distribution of artificial aggregate Figure 7: Bulk density of artificial aggregate Figure 9: Crushing strength of artificial aggregate Figure 8: Water absorption of artificial aggregate Ibrahim, et al.: Production of artificial aggregate using waste material 30 http://journals.cihanuniversity.edu.iq/index.php/cuesj CUESJ 2023, 7 (2): 26-30 1. All of the produced aggregate can be considered lightweight aggregate since the densities are less than 2000 kg/m^3 in accordance with BS EN 13055-1 (2002). The highest density recorded at the artificial aggregate contains 50% of GGBFS in both cold-bonded and sintered aggregates, while the minimum is at 20% of GGBFS mixture. 2. The capacity of pellets to absorb water was found to be reduced by increasing the amount of GGBFS. The minimum water absorption obtained at 50% of GGBFS mixture. 3. It was found that the sintering temperature affects the water absorption and can reduce it to about 31% at a mix of 50% of GGBFS. This is due to the glassy texture that is obtained during the sintering process. 4. The artificial aggregate’s crushing strength increases as the percentage of GGBFS increases. Crushing strength increased by 56% when GGBFS was increased from 20% to 50%. The sintered artificial aggregate yielded similar results. Due to the properties obtained from the artificial aggregate, further studies are planned to be carried out to investigate the influence of the produced aggregate on the mechanical and durability aspects of concrete. REFERENCES 1. N. Atmaca, M. Ibrahim and A. Atmaca. Comparison of physical and mechanical properties of cold bonded and sintered lightweight artificial aggregates. Adıyaman Üniversitesi Mühendislik Bilimleri Dergisi, vol. 8, no. 15, pp. 560-570, 2021. 2. M. A. Ibrahim, N. Atmaca, A. A. Abdullah and A. Atmaca. Mechanical properties of concrete produced by light cement- based aggregates. Sustainability, vol. 14, no. 23, p. 15991, 2022. 3. S. H. Hu, S. C. Hu and Y. P. Fu. Recycling technology-artificial lightweight aggregates synthesized from sewage sludge and its ash at lowered comelting temperature. Environmental Progress and Sustainable Energy, vol. 32, no. 3, pp. 740-748, 2013. 4. B. González-Corrochano, J. Alonso-Azcárate and M. Rodas. Production of lightweight aggregates from mining and industrial wastes. Journal of Environmental Management, vol. 90, no. 8, pp. 2801-2812, 2009. 5. M. A. Ibrahim and N. Atmaca. Cold bonded and low temperature sintered artificial aggregate production by using waste materials. Periodica Polytechnica Civil Engineering, vol. 67, no. 1, pp. 112- 122, 2022. 6. A. Białowiec, W. Janczukowicz, Z. M. Gusiatin, A. Thornton, J. Rodziewicz and M. Zielińska. Recycling potential of air pollution control residue from sewage sludge thermal treatment as artificial lightweight aggregates. Waste Management and Research, vol. 32, no. 3, pp. 221-227, 2014. 7. R. Cioffi, F. Colangelo, F. Montagnaro and L. Santoro. Manufacture of artificial aggregate using MSWI bottom ash. Waste Management, vol. 31, no. 2, pp. 281-288, 2011. 8. N. U. Kockal and T. Ozturan. Effects of lightweight fly ash aggregate properties on the behavior of lightweight concretes. Journal of Hazardous Materials, vol. 179, no. 1-3, pp. 954-965, 2010. 9. E. Güneyisi, M. Gesoǧlu, Ö. Pürsünlü and K. Mermerdaş. Durability aspect of concretes composed of cold bonded and sintered fly ash lightweight aggregates. Composites Part B: Engineering, vol. 53, pp. 258-266, 2013. 10. M. Limbachiya, M. S. Meddah and Y. Ouchagour. Use of recycled concrete aggregate in fly-ash concrete. Construction and Building Materials, vol. 27, no. 1, pp. 439-449, 2012. 11. A. Lotfy and M. Al-Fayez. Performance evaluation of structural concrete using controlled quality coarse and fine recycled concrete aggregate. Cement and Concrete Composites, vol. 61, pp. 36-43, 2015. 12. B. Basa, N. Pradhan and L. P. Parhi. Mechanical properties of concrete with sintered fly ash aggregate as substitute of natural fine aggregate. IOP Conference Series: Materials Science and Engineering, vol. 970, p. 012013, 2020. 13. A. N. Dabhade, S. R. Chaudari and A. R. Gajbhaye. Effect of flyash on recycle coarse aggregate concrete. International Journal of Civil Engineering Research, vol. 5, p. 35-42, 2014. 14. C. Lima, A. Caggiano, C. Faella, E. Martinelli, M. Pepe and R. Realfonzo. Physical properties and mechanical behaviour of concrete made with recycled aggregates and fly ash. Construction and Building Materials, vol. 47, pp. 547-559, 2013. 15. R. H. Faraj, A. F. H. Sherwani, L. H. Jafer and D. F. Ibrahim. Rheological behavior and fresh properties of self-compacting high strength concrete containing recycled PP particles with fly ash and silica fume blended. Journal of Building Engineering, vol. 34, p. 101667, 2021. 16. R. H. Faraj, H. F. Hama Ali, A. F. H. Sherwani, B. R. Hassan and H. Karim. Use of recycled plastic in self-compacting concrete: A comprehensive review on fresh and mechanical properties. Journal of Building Engineering, vol. 30, p. 101283, 2020. 17. R. H. Faraj, A. F. H. Sherwani and A. Daraei. Mechanical, fracture and durability properties of self-compacting high strength concrete containing recycled polypropylene plastic particles. Journal of Building Engineering, vol. 25, p. 100808. 18. A. Danish and M. A. Mosaberpanah. Formation mechanism and applications of cenospheres: A review. Journal of Materials Science, vol. 55, no. 11, pp. 4539-4557, 2020. 19. ASTM C127-07. Standard Test Method for Density, Relative Density (Specific Gravity), and Absorption of Coarse Aggregate. In: Annual Book of ASTM Standards. West Conshohocken. PA, 1994. 20. BSI. (British Standard Institution). Testing Aggregates-methods for Determination of Aggregate Crushing Value (ACV). British Standards Institution, London, 1990. 21. S. İpek, O. A. Ayodele and K. Mermerdaş. Influence of artificial aggregate on mechanical properties, fracture parameters and bond strength of concretes. Construction and Building Materials, vol. 238, p. 117756, 2020. 22. P. P. Kumar, S. Suhas, D. Ravikumar, S. Roopa, M. Keshavmurthy and S. Agarwal. Some physical and mechanical properties of concrete made from partial replacement of natural aggregates with artificially manufactured aggregates using ground granulated blast furnace slag (GGBS). International Journal of Research in Engineering and Technology, vol. 5, no. 14, pp. 47-52, 2016.