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| Microstructural mechanisms of strength development in solidified dredged sludge using industrial by-products |
| WANG Liujiang1, ZANG Yaohui1, JIANG Hougen1, YU Yongxue2, CUI Hongbin3, LIU Sihong1 |
(1. College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, Jiangsu 210098, China; 2. PowerChina STECOL Corporation, Tianjin 300384, China; 3. Shanghai Soil Environmental Technical Inc., Shanghai 200051, China)
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Abstract Dredged sludge can be synergistically solidified using ground granulated blast-furnace slag (GGBS), carbide slag (CS), and phosphogypsum (PG). To investigate the strength-deformation characteristics, water transformation behavior, and microstructural evolution of GGBS-CS-PG (GCP) solidified dredged sludge under varying dosages of curing agents and curing durations, a series of unconfined compressive strength tests, scanning electron microscopy (SEM) observations, and low-field nuclear magnetic resonance (LF-NMR) analyses were conducted. Furthermore, the microstructural mechanisms underpinning the strength development of the GCP solidified sludge were explored. The results indicated that the early strength development of GCP solidified sludge occurred rapidly, with the unconfined compressive strength increasing logarithmically as curing age progressed. This behavior was primarily attributed to the synergistic interactions among GGBS, CS, and PG, which facilitated the rapid generation of a substantial amount of ettringite (AFt). The produced AFt effectively filled the pores and enhanced structural density through interactions with C-(A)-S-H gels. Moreover, the formation of AFt promoted the conversion of free water in the pores into bound water, resulting in a logarithmic increase in bound water content as curing age advanced. The pore size distribution primarily ranged from 0.003 to 0.11 μm. As the dosage of GCP increased, both the amount of bound water and the number of micropores significantly rose. Additionally, a quantitative relationship was established between microstructural parameters and macroscopic mechanical properties. The unconfined compressive strength and deformation modulus exhibited power function growth corresponding to increases in bound water content and micropore quantity.
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2025, Vol. 44 
