Abstract
This paper investigated the effect of blast furnace slags (BFS) characteristics on the properties achievement after being alkali activated. The physical and chemical characteristics of BFS were determined by X-ray fluorescence (XRF), X-ray Diffraction (XRD) and laser granulometry. Multi-technical characterizations using calorimetry, XRD, Fourier Transform Infrared Spectroscopy (FTIR), Thermogravimetry (TG-DTG), scanning electron microscope (SEM), nitrogen sorption and uniaxial compressive strength (UCS) were applied to give an in-depth understanding of the relationship between the reaction products, microstructure and BFS characteristics. The test results show that the microstructure and mechanical properties of alkali activated blast furnace slags (BFS) highly depend on the characteristics of BFS. Although the higher content of basic oxide could accelerate the hydration process and result in higher mechanical properties, a poor thermal stabilization was observed. On the other hand, with a higher content of Fe, the hydration process in alkali activated BFS2 lasts for a longer time, contributing to a delayed compressive strength achievement.
Highlights
Blast furnace slag (BFS), which is an industrial by-product generated from the Fe and steel industry [1], has been thoroughly studied in the cement and concrete fields due to its high reactivity in alkali environments
The compressive strength of AAS highly depends on the amount of hydration product after the blast furnace slags (BFS) has been activated by the alkali solution
BFS1 contains a higher amount of basic oxides, such as CaO and MgO, which could react with water and generate Ca (OH)2 and Mg (OH)2, enhancing the amount of OH−
Summary
Blast furnace slag (BFS), which is an industrial by-product generated from the Fe and steel industry [1], has been thoroughly studied in the cement and concrete fields due to its high reactivity in alkali environments. 30% to up to 85%, could improve the durability and resistance to early-age cracking [2], produce high strength and performance concrete, and bring environmental and economic benefits together, such as resource conservation and energy savings [3,4]. Alkali activated materials (AAM), which have been widely discussed as a ‘sustainable cement binder’ [9], could be generated from a wide range of aluminosilicate precursors, such as BFS, fly ash or metakaolin. Compared with Portland cement, AAM enjoys a quick compressive strength development [10], lower permeability [11], and good resistance to acid and fire attacks [12]. Almost no SOx, NOx, or CO2 are generated in the process of AAM preparation [13], contributing to a great interest in the study and development of AAM worldwide
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