Abstract:

To address the engineering challenges posed by organic-rich soils and industrial solid waste and to promote their resource utilization in geotechnical engineering, this study adopts a solidification method using alkaline solid waste combined with cement. Through unconfined compressive strength, flowability and shrinkage tests, as well as microscopic charaterization techniques including X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), nuclear magnetic resonance (NMR), and scanning electron microscopy (SEM), the mechanical properties, microstructural evolution, and chemical reaction mechanisms of alkaline solid waste-reinforced cementitious flowable solidification in organic-rich soils are investigated. The results indicate that as the fulvic acid content in soil increases, the strength of the stabilized soil gradually decreases while its fluidity continuously increases. In contrast, the fluidity of stabilized soil initially increases and then decreases with rising humic acid content. Incorporating alkaline solid waste significantly enhances strength and reduces volumetric shrinkage. During the 28 day curing period, the strength influence hierarchy was: alkali residue ≥cement ≥naphthalene-based superplasticizer ≥fly ash ≥red mud ≥carbide slagging. In the 60 day curing period, the hierarchy changed to: cement ≥alkali residue ≥naphthalene-based superplasticizer ≥red mud ≥fly ash ≥carbide slagging. Microstructural analyses confirm that hydroxide ions (OH⁻) from alkaline wastes neutralize hydrogen ions (H⁺) released from organic matter, promoting the formation of C-S-H and C-A-H gels. This process improves soil particle cementation and refines pore structure. A novel microscopic mechanism model to elucidates the interactions between organic matter and alkaline waste is established. This model provides theoretical foundations for the sustainable recycling of problematic soils and industrial solid wastes.

Key words: alkaline solid waste, fulvic acid, humic acid, strength, microstructure