Efficient utilization of waste drilling mud to prepare material stabilized with fly ash/slag based geopolymer for subgrade engineering.

The usage of industrial waste drilling mud in construction materials provides an approach for relieving environmental issues as well as resource utilization. Geopolymer as a new green binder is a promising stabilizer for the waste drilling mud solidification. In this study, environmentally friendly road base materials were prepared using waste drilling mud stabilized with fly ash/slag based geopolymer. The compression tests, bending and fracture tests was performed to evaluate mechanical properties of geopolymer stabilized waste drilling mud. Results revealed that the unconfined compression strength, flexural strength, fracture energy, and fracture toughness of geopolymer stabilized waste drilling mud were enhanced with slag powder content in precursor increasing. Compared to geopolymer stabilized waste drilling mud with 60% slag powder content, the unconfined compression strength, flexural strength, fracture energy, initial fracture toughness, and unstable fracture toughness of geopolymer stabilized waste drilling mud with 100% slag powder content increased by 80.8%, 59.1%, 369.5%, 49.4%, and 28.1%, respectively. Conversely, the durability of geopolymer stabilized waste drilling mud like water stability and drying-wetting cycle resistance was descended with the growing slag powder proportion. As the content of slag powder increased from 60% to 100%, the water stability coefficient after soaking for 14 days and drying-wetting cycle coefficient were decreased by 10.8% and 4.3%, respectively. Nevertheless, all groups met the durability requirement of the pavement design standard. Microstructure results showed that the amorphous hydrated gels were mounted up with the slag powder content increasing, which filled pores and micro cracks of geopolymer stabilized waste drilling mud and compacted the matrix. The findings suggested that geopolymer was practicable to stabilize the waste drilling mud to employ in the road base, which can achieve the resource utilization and reduce the environmental pollution.