This study evaluated the performance of cement-based grouts in compaction grouting. In the experimental study carried out, the simultaneous effects of fly ash (FA) and nano-silica (NS) on rheological and fresh-state as well as strength performances were investigated. In this context, 16 samples were prepared using 0%, 10%, 20%, and 30% FA replacement levels and 0%, 1%, 2%, and 3% NS content ratios at w/b = 0.75. Rheological characteristics and behavioral performance were defined with shear stress, apparent viscosity, yield stress, and plastic viscosity. Fresh-state performances, flow time with mini-slump, stability capacity with bleeding, and hardening periods with setting time were determined. In terms of mechanical performance, 28-day unconfined compressive strength (UCS) tests were carried out on grout samples. After the tests, the correlation relationship between them was examined using experimental data. The experimental results were performed with statistical analysis, and then, the contribution and impact levels of important parameters were evaluated. Test results showed that the simultaneous FA and NS influence resulted in reasonable outcomes in both the rheological and fluidity properties and caused a visible enhancement in the strength features., Statistically, NS content was dominant in rheological and fresh-state performance, while FA replacement was effective in strength features.