The reaction between Ca 2+ from steel slag and granulated blast-furnace slag system: a unique perspective
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ORIGINAL PAPER
The reaction between Ca2+ from steel slag and granulated blast‑furnace slag system: a unique perspective Mengqi Wang1 · Binbin Qian2 · Jun Jiang1 · Huachen Liu1 · Qiang Cai1 · Bing Ma3 · Yueyang Hu1 · Luming Wang1 Received: 19 March 2020 / Accepted: 7 June 2020 © Institute of Chemistry, Slovak Academy of Sciences 2020
Abstract This paper proposes that Ca2+ in steel slag (SS) has a weak early hydration activity when SS and granulated blast-furnace slag (GBFS) are used as alkali-activated cementitious materials. Herein, alkaline activators and Ca(OH)2 are used as indicators of Ca2+ reaction in the SS and GBFS system. It is found that the 28-day compressive strength of the cementitious material with 2 wt% Ca(OH)2 addition increased by 25.9% compared with the blank. Hydration products and microstructures were characterized by XRD, SEM/EDS, FTIR and TG/DTA. Results show that the addition of Ca(OH)2 increased the content of active calcium ions in the reaction system, which promotes the reaction and the formation of C–S–H gel, resulting in an enhanced compressive strength ultimately. It can be also concluded that SS is not suitable as a sole precursor for the production of building materials on a large scale due to the weak early activity of Ca2+ in SS. Keywords Ca(OH)2 · Steel slag · C–S–H gel · Activity
Introduction Steel slag (SS) is an industry waste produced in the process of iron smelting. In China, the amount of SS is about 80 million tons (Wu et al. 1999; Li et al. 2011). The accumulation of SS results in serious environmental problems and social concerns (Huang et al. 2016). In this sense, the utilization of SS needs to be explored urgently (Li et al. 2013). Currently, steel slag is mainly used as road construction materials, building materials, agricultural fertilizers, etc. Most researchers are interested in the utilization of industry waste into construction field (Motz and Jens 2001; Altun and Yilmaz 2002; Shi and Qian 2000). The utilization of * Yueyang Hu [email protected] * Luming Wang [email protected] 1
College of Materials Science and Engineering, Yancheng Institute of Technology, No. 211 Jianjun Road, Tinghu District, Yancheng 224600, China
2
Department of Chemical Engineering, Monash University, Wellington Road, Clayton, VIC 3800, Australia
3
Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment of the People’s Republic of China, Nanjing 210042, China
SS in construction is an important way to reuse this waste as a high-value product, which will be able to bring huge economic benefits and reduce the cost of building materials. Further researches on the reaction mechanism of steel slag can improve the utilization rate of steel slag and reduce its environmental impacts. SS can be also used as a granular material in road base or subbase, which is another promising approach widely used in Europe (Netinger et al. 2011) for the several reasons: (1) a large amount of SS can be used without constraint conditions, (2) the process for granular use i
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