Title:
Multiscale Study of Strength Retrogression and Toughness Progression in Bentonite-Modified Concrete (Prepublished)
Author(s):
Bei Tang, Wei Cui, Zhi-an Jiang, Bao-zeng Zhang
Publication:
Materials Journal
Volume:
Issue:
Appears on pages(s):
Keywords:
bentonite; concrete; modification mechanism; multiscale investigation; strength; toughness
DOI:
10.14359/51749333
Date:
11/20/2025
Abstract:
Due to the excellent deformation coordination ability and permeability, bentonite has been widely introduced to modify concrete in underground geotechnical engineering. However, the underlying mechanism for bentonite modification remains unexplored. A series of experiments was performed to clarify the modification mechanism of bentonite. The results showed that all strengths decreased upon bentonite addition, while high toughness was achieved. The micro-test results revealed that bentonite promotes the dissolution of calcium hydroxide (CH) and the nucleation of calcium silicate hydrate (C-S-H) in the interfacial transition zone (ITZ). The hydration products produced by the reactive ions and ultrafine bentonite particles continuously reduced the porosity and Ca/Si ratio in ITZ, strengthened the interface bonding, and controlled the coalescence of microcracks. Inversely, bentonite particles tend to adsorb large amounts of water and hinder the available water from accessing cement grains, which results in an increased porosity and slower hydration progress of cement grains. The loose microstructure cannot be compensated for by reinforced interfacial bonding and inevitably results in the deterioration of mechanical performance in composites.