The strength and permeability properties of various graded sand specimens grouted with superfine cement suspensions containing an additive of fine fly ash were experimentally investigated. To start with, such rheological properties as viscosity, bleeding, and setting time of superfine cement and fine fly ash mixture suspensions with various water-cement ratios (w/c) were determined. Then, the injectability tests with the mixtures were conducted on various graded sand samples. Finally, the unconfined compressive strength and the falling head permeability tests were run on the grouted specimens at different time intervals. The setting times and viscosities of superfine cement and fine fly ash mixture suspensions increased, but their bleedings were reduced. The addition of fine fly ash to superfine cement suspensions reduced the groutability of suspensions and hence increased the grouting pressure of sand specimens. The unconfined compressive strength of superfine cement grouted sand samples were increased and their permeabilities were reduced with the addition of fine fly ash. Moreover, the addition of fine fly ash to superfine cement grouts accelerated the grouted specimens' strength gain.