Applicability of granulated blast furnace slag as a geo-material in vietnam

Kỷ yếu Hội nghị: Nghiên cứu cơ bản trong “Khoa học Trái đất và Môi trường” DOI: 10.15625/vap.2019.000103 132 APPLICABILITY OF GRANULATED BLAST FURNACE SLAG AS A GEO-MATERIAL IN VIETNAM Tran Thanh Nhan 1 , Nguyen Van Hop 1 , Takeshi Katsumi 2 , Nguyen Hai Cuong 1 Hiroshi Matsuda 3 , Ho Trung Thanh 1 , Duong Phuoc Huy 1 , Nguyen Van Thien 1 1 University of Sciences, Hue University, Email: ttnhan@hueuni.edu.vn 2 Graduate School of Global Environmental Studies (GSGES), Kyoto University Email: katsumi.takeshi.6v@kyoto-u.ac.jp 3 Graduate School of Science and Technology for Innovation, Yamaguchi University Email: hmatsuda@yamaguchi-u.ac.jp ABSTRACT Blast Furnace Slag (BF slag) is produced when iron ore is melted together with auxiliary materials including lime stone and coke in the blast furnace and the amount of BF slag is roughly 300 kg per ton of pig iron. In Vietnam, mostly more than 95 % of BF slag is used for producing Granulated Blast Furnace Slag (GBFS) and the annual production is predicted to exceed 7 million tons in 2020. In this study, physico-mechanical and chemical properties of GBFS produced by Formosa steel plant in Vietnam (named as Formosa GBFS) were observed and compared with those of GBFS produced in Japan. Such comparisons were also performed with a granite rock-crushed sand which is widely applied as an alternative construction material to natural sand in Thua Thien Hue province. Based on these observations, the applicability of Formosa GBFS as a geo-material in construction was then clarified. Keywords: Construction, geo-material, granulated blast furnace slag, geotechnical property. 1. INTRODUCTION In Vietnam, steel industry has developed rapidly resulting in considerable production of iron and steel slag and the annual production is predicted to exceed 12 million tons in 2020 [1]. On the other hand, the operation of two biggest steel plants throughout Vietnam (Formosa plant and Hoa Phat Dung Quat plant which are located in the Central region of Vietnam) will produce about 7 million tons of BF slag per year. Due to the huge amount of production and chemical stability under environmental conditions, BF slag has been utilized in different fields such as raw material for cement industry, material for construction - civil works and as a fertilizer in agriculture. Furthermore, GBFS has a similar particle size to those of river sand and the geotechnical properties of GBFS have been confirmed to be more advantageous than those of natural sand [2]. Therefore, GBFS has been widely used as an alternative material to natural sand in the port and harbor construction in Japan. Since GBFS is produced by rapid quenching the molten slag (at 1500 C), the mineral structure of particles is therefore unstable resulting in its latent hydraulic property by which GBFS starts to solidify and its shear strength increases gradually with time under natural wet conditions without any additives [3]. This hydraulic property of GBFS and the effects on environment should be clarified when promoting the usage of GBFS as a geo-material. Vietnam has been facing to serious shortage of natural sand in construction for a decade meanwhile the natural sand for construction (river sand) will be exhausted after 10-15 years. In order to solve this problem and also to protect the environment, controlled exploitation of natural sand and the utilization of alternative materials have been issued by National Government and the Ministry of Construction (MOC). Although since 2007, MOC has provided 7 technical standards and guideline for the usage of iron and steel slag in Vietnam, these standards focus mainly on the quality of slag for the usage as a raw materials and additives for cement, concrete and mortar. Due Kỷ yếu Hội nghị: Nghiên cứu cơ bản trong “Khoa học Trái đất và Môi trường” 133 to the lack of technical standards and research works, iron and steel slag including GBFS have not been widely used in the construction site in Vietnam. 2. RESULTS AND DISCUSSION ON THE APPLICABILITY OF GBFS AS A GEO- MATERIAL 2.1. Chemical characteristics The chemical components of GBFS produced in the steel plants in Vietnam and in Japan are typically shown in Table 1. The results indicate that the chemical components of GBFS produced in Vietnam are similar to those of Japanese products which have been confirmed to satisfy the environmental requirements in Japan [2]. Therefore, the concentrations of environmentally hazardous constituents in Formosa GBFS and in different leaching solutions due to its latent hydraulic property should be clarified when promoting the applicability as a geo-material at the construction site in Vietnam. Table 1. Chemical components (%) of GBFS produced in Vietnam and Japan (*) GBFS samples CaO SiO2 Al2O3 MgO T-S FeO MnO P2O5 IL Total GBFS-A [4] 43.45 34.02 14.36 5.95 0.7 0.56 0.12 - 0.537 99.70 GBFS-B [4] 42.65 34.23 14.54 6.46 0.9 0.43 0.27 - 0.092 99.57 GBFS-C [4] 40.06 37.28 15.04 5.48 0.9 0.49 0.25 - 0.085 99.59 GBFS [5] 41.7 33.8 13.4 7.4 0.8 0.40 0.3 0.1 - 97.90 Hoa Phat GBFS [6] 41.0 35.5 11.0 9.2 0.6 0.7 - - - 98.00 Thai Nguyen GBFS [6] 37.7 36.1 12.7 8.2 0.7 2.4 - - - 97.80 Formosa GBFS 41.09 34.72 13.15 7.37 0.6 0.40 - - 0.140 97.47 (*) T-S: total sulphide; IL: ignition loss; GBFS-A, GBFS-B, GBFS-C and GBFS are produced in Japan; Hoa Phat GBFS and Thai Nguyen GBFS are produced in Vietnam; the data of Formosa GBFS was obtained from the samples used for this study. 2.2. Grain size and physico-mechanical properties Photos and typical geotechnical properties of Japanese GBFS, Formosa GBFS and a crushed sand are shown in Figure 1 and Table 2, respectively. In Thua Thien Hue province, the natural sand for construction has been exhausting for recent years. This problem has become more serious since last year leading to a considerable increase in the price of sand. Consequently, crushed sand is currently permitted to produce and use as an alternative material to natural sand in construction. Therefore, comparison of the geotechnical properties between GBFS and crushed sand should be done when the wide application of these materials is under promotion. Matsuda [2] confirmed that GBFS shows more advantageous geotechnical properties than those of natural sand due to such as high permeability, light weight and the latent hydraulic properties. The grain size distribution curve on Formosa GBFS is shown together with those of GBFS-A, GBFS-B, GBFS-C and the crushed sand in Figure 2(a) and the compaction curves of these materials are shown in Figure 2(b). The grain size distribution curve of Formosa GBFS shows inside the range which were issued by TCVN 7570:2006 [7] and therefore, this material is adopted as a fine aggregate for concrete and mortar following Vietnamese standard. The compaction curves in Figure 2(b) indicate that the dry densities of GBFS are mostly independent of the water content and that the densities of GBFS are smaller than those of natural sand and crushed sand. These observations suggest that the compaction management at the construction site becomes easier when using GBFS as an alternative material to natural sand and crushed sand. Hồ Chí Minh, tháng 11 năm 2019 134 Figure 1. Photos of (a) GBFS produced in Japan, (b) Formosa GBFS and (c) a crushed sand produced from granite rock in Thua Thien Hue province. Table 2. Typical geotechnical properties of GBFS and crushed sand (*) Samples s (g/cm 3 ) emax emin k 10 -4 (m/s) at Dr = 80% GBFS-A [4] 2.730 1.378 0.807 7.91 GBFS-B [4] 2.680 1.571 0.967 9.22 GBFS-C [4] 2.755 1.402 1.044 8.26 Formosa GBFS 2.790 1.398 0.881 28.60 Crushed sand 2.655 0.977 0.490 6.73 (*) GBFS-A, GBFS-B, GBFS-C, Formosa GBFS and crushed sand as in Table 1. Figure 2. (a) Grain size distribution curves and (b) typical compaction curves of Japanese GBFS, Formosa GBFS and crushed sand (GBFS-A, GBFS-B, GBFS-C, Formosa GBFS and crushed sand as in Table 1). 3. CONCLUSIONS In order to clarify the applicability of GBFS produced in Vietnam as an alternative geo- material to natural sand, samples of Formosa GBFS and a crushed sand in Thua Thien Hue province were collected and used for chemical and physico-mechanical tests. The experimental results suggest that the chemical components of Formosa GBFS are similar to those of Japanese products. In addition, the grain size and geotechnical properties of Formosa GBFS show more advantageous than those of natural sand and also crushed sand when using as a geo-material. However, in order to confirm the applicability of Formosa GBFS in practice under tropical climate conditions in Vietnam, further studies should be done. Acknowledgement This research is funded by Ha Tinh Department of Science and Technology under Contract number 681/HĐ-SKHCN and GSGES Seeds Research Funding for Construction of Global 10 mm (a) (b) (c) 0 100 0.01 0.1 1 10 GBFS-A [4] GBFS-B [4] GBFS-C [4] Formosa GBFS Crushed sand 1.2 2.0 0.0 30.0 Grain size (mm) P er ce n t fi n er b y w ei g h t (% ) Moisture content, w (%) D ry d en si ty , d (g /c m 3 ) Crushed sand GBFS produced in Japan [2] Formosa GBFS Seabed sand in Japan [2] Upper and lower boundaries of fine aggregate for concrete and motar [7] (a) (b) Kỷ yếu Hội nghị: Nghiên cứu cơ bản trong “Khoa học Trái đất và Môi trường” 135 Environmental Study Basis (Year 2019-2020). The authors would like to express their gratitude to these supports. REFERENCES [1]. Le Viet Hung (2016). Current situation of the regulations and standards respect to slag application in Vietnam. Conference on Application of Iron/Steel Slag in Construction Industry for Sustainable Development, Hanoi, 41-52. 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