Journal
CONSTRUCTION AND BUILDING MATERIALS
Volume 271, Issue -, Pages -Publisher
ELSEVIER SCI LTD
DOI: 10.1016/j.conbuildmat.2020.121890
Keywords
Mg0-activated GGBS; Cutoff wall; Hydration products; Engineering properties; Reaction mechanisms
Categories
Funding
- National Key R&D Program of China [2018YFC1803100]
- National Natural Science Foundation of China [41877248]
- Primary Research & Development Plan of Jiangsu Province [BE2017715]
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A new innovative cutoff wall backfill composed of reactive MgO, ground granulated blast furnace slag (GGBS), bentonite and local clayey sand (MSB) was developed for land remediation applications. The research investigated the engineering characteristics and reaction mechanisms of the backfills with different MgO-activated GGBS and bentonite contents. Results showed that UCS and dry density decreased with increasing bentonite content, while the opposite trend was observed with increasing binder content.
An innovative cutoff wall backfill consisting of reactive MgO, ground granulated blast furnace slag (GGBS), bentonite and local clayey sand (MSB) was developed recently for land remediation applications. This paper investigates the engineering characteristics (e.g. strength and permeability) and reaction mechanisms of the MSB backfills with various MgO-activated GGBS (i.e., the binder) and bentonite contents. A series of analytical techniques are employed to identify the hydration products in this complex system. The engineering properties are tested via the unconfined compressive strength (UCS) test and flexible-wall permeation test. Results show that UCS and dry density decrease with increasing bentonite content, while the opposite trends are observed when increasing the binder content. The UCS values increase with curing time and become plateaued after -90 days. Meanwhile, the hydraulic conductivity (k) decreases distinctly with the increase of the binder content and bentonite content. All backfills reach UCS of >100 kPa UCS and k <10(-8) m/s at 28 days while curing for 90 days leads to increase of UCS by >1.5 times and reduction of k by nearly one order of magnitude. The major hydration products of MSB backfills are identified as hydrotalcite-like phases (Ht), calcium silicate hydrates (C-S-H), monosulfate (AFm) and portlandite (CH). The hydration products, binding adjacent soil particles, filling pores, together with the swelling of bentonite, contribute to the mechanical performance and impermeability of the backfills. (C) 2020 Elsevier Ltd. All rights reserved.
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