Study on Macroscopic Mechanical Properties and Microscopic Mechanism of Drilling Cuttings Solidified by Alkali-Activated Furnace Ash

To promote the resource utilization of oilfield solid waste and facilitate the green and low-carbon transformation of transportation infrastructure, this study employed drilling cuttings from the Maye area of the Xinjiang oilfield and coal-fired furnace ash as primary raw materials. NaOH, Na2O·nSiO2, and Ca(OH)2 were used as alkali activators to prepare alkali-activated solidification materials for oilfield road base applications. The optimal curing system identified in this study (4 wt.% NaOH + 20 wt.% furnace ash) falls within the commonly reported dosage ranges for alkali-activated solid-waste materials, where NaOH contents are typically 3%–8% and furnace ash contents 15%–30%. Considering the distinct chemical characteristics of the Xinjiang oilfield solid wastes, a targeted optimization strategy was adopted to achieve a balance between mechanical performance and economic feasibility. Based on mix-proportion experiments, macroscopic mechanical properties were evaluated. In combination with X-ray diffraction (XRD), laser particle size analysis, simultaneous thermal analysis (TG–DSC), and scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM–EDS), the influence of activator type on both mechanical performance and microstructural evolution was systematically investigated. The results indicate that the system containing 4 wt.% NaOH + 20 wt.% furnace ash exhibits the best overall performance, achieving a 28-day compressive strength of 4.81 MPa and a splitting tensile strength of 0.41 MPa, which are significantly higher than those of the Na2O·nSiO2 system (3 wt.% Na2O·nSiO2 + 20 wt.% furnace ash) and the Ca(OH)2 system (4 wt.% Ca(OH)2 + 15 wt.% furnace ash). The primary hydration products were identified as C-(N)-A-S-H and C-S-H gels. The type of alkali activator plays a decisive role in regulating hydration reaction kinetics and the spatial distribution of Ca and Si elements, thereby governing the hierarchical differences in macroscopic mechanical properties. In particular, NaOH generates a highly alkaline environment that promotes the dissolution of active Si/Al components in both drilling cuttings and furnace ash, enhances gel polymerization, and results in a denser microstructure. This study provides theoretical and technical support for the high-value utilization of oilfield solid wastes in highway base engineering.