Reinforcement simulation of water-rich and broken rock with Portland cement-based grout

To explore solutions for water plugging and reinforcement problems of water-rich and broken rock mass in underground engineering, it is necessary to study the performance of cement-based grout and its reinforcement effect. In this study, Portland cement-based grouts with high amounts (70%) of granulated blast-furnace slag (GBFS) (30%) and Class C fly ash (FA) (40%) were prepared. The superplasticizer (SP) and anti-washout agent (AWA) were formulated to improve flowability and stability of single slurries. A new self-developed experimental device was designed for the grouting simulation. The fresh-state properties of cementitious single slurry i.e., flowability, mini-slump, stability, effective W/S and initial/final setting time; flexural and compressive strengths of grout stone bodies were studied. Meanwhile, the grouting reinforcement effect; mechanical performance of reinforcement sample i.e., unconfined compressive strength (UCS), failure mode, process and key parameters were evaluated. The results show that the performance and grouting effects of cement-based grouts with high amounts of GBFS and FA were generally acceptable. The addition of SP + AWA enhanced the stability and was beneficial to the grouting effectiveness especially at higher (0.8–1.2) water-solid (W/S) ratios. The diffusion or setting time of this type grout should be shortened appropriately in practice. The rupture interface and tensile fracture of grout were two main failure modes of reinforcement samples. The variations of key parameters corresponding to different failure modes were analyzed.