Compression Index and Small Strain Stiffness of Six Coal Bottom Ashes in South Korea
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pISSN 1226-7988, eISSN 1976-3808 www.springer.com/12205
DOI 10.1007/s12205-020-1608-7
Geotechnical Engineering
Compression Index and Small Strain Stiffness of Six Coal Bottom Ashes in South Korea Hyunwook Chooa, Linh Van Ngob,c, Taeki Kimd,e, Youngsang Kimf, and Changho Leeg aMember,
Dept. of Civil Engineering, Kyung Hee University, Yongin 17104, Korea of Civil Engineering, Thuyloi University, Hanoi 100000, Vietnam cDept. of Architectural and Civil Engineering, Chonnam National University, Gwangju 61186, Korea dHyein E&C, Seoul 07547, Korea eDept. of Civil and Environmental Engineering, Chonnam National University, Yeosu 59626, Korea fDept. of Civil Engineering, Chonnam National University, Gwangju 61186, Korea gMember, Dept. of Civil Engineering, Chonnam National University, Gwangju 61186, Korea bFaculty
ARTICLE HISTORY
ABSTRACT
Received 11 December 2019 Revised 28 May 2020 Accepted 13 July 2020 Published Online 2 October 2020
This study investigates the small strain stiffness (Gmax) of six coal bottom ashes in South Korea. One-dimensional compression tests using an instrumented oedometer cell were performed to measure the shear wave velocity (Vs), and the compression indices (Cc) of the six different bottom ashes were also explored in this study. The results demonstrate that, at low confinement, the Cc of bottom ashes are comparable to that of sand under a similar void ratio. However, at high confinement, the bottom ash shows very high Cc compared to sand due to the crushability of the weak and porous bottom ash particles upon confinement. The variations of α and β, which are Vs parameters (i.e., Vs = α (σ´m /1 kPa)β ), with different Cc values of the tested bottom ashes are consistent with the existing empirical relationship. The Gmax of tested bottom ashes can be adequately captured by the existing Gmax estimating formula for angular sand, indicating that the Gmax of bottom ash is highly comparable to that of sand with a similar void ratio and confining stress.
KEYWORDS Bottom ash Crushability Compression index Shear wave velocity Small strain shear stiffness
1. Introduction Coal ashes are granular solid residues generated when burning coal for electricity generation. Because coal is the main energy source for electricity generation in many countries, including the United States (American Coal Ash Association, 2013), it is important to find strategies to manage and recycle coal ash (Torkittikul et al., 2017). Coal ash is generally composed of fly and bottom ashes. Large amounts of fly ash have been recycled in various engineering applications (Bakharev, 2005) as cement additives (Helmuth, 1987; Xu and Sarkar, 1994; Lam et al., 2000; Kumar et al., 2007), road base materials (Arora and Aydilek, 2005; Lav et al., 2006; Shen et al., 2009), barrier materials (Nhan et al., 1996; Czurda and Haus, 2002), lightweight aggregates (Bijen, 1986; Kayali, 2008), and raw materials for geopolymer (Swanepoel and Strydom, 2002; Chindaprasirt et al., 2007). However, more research is needed into the recycling of bottom as
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