Geopolymer　has　been　applied　in　road　engineering　as　an　environmentally　friendly　material.　This　study　prepared　geopolymer　road　grouting　pastes　in　different　mixture　ratios　of　volcanic　ash　(VA)　and　metakaolin　(MK).　The　mechanical　properties,　setting　time,　bleeding　and　expansion　ratio,　fluidity　and　expansion　ratio,　time-dependent　rheological　analysis　were　systematically　evaluated.　Finally,　the　microscopic　experiments,　including　X-Ray　Diffraction,　Fourier　Transform　Infrared　Spectroscopy　and　Scanning　Electron　Microscopy　with　Energy　Dispersive　Spectrometer　(SEM-EDS),　were　conducted　to　investigate　the　mechanism　of　geopolymerization　based　on　VA　and　MK.　The　results　showed　that　the　mechanical　strength　increased　with　the　content　of　MK.　The　flow　curve　of　all　pastes　fitted　the　Bingham　model.　With　the　increase　of　MK　content,　the　yield　stress　and　plastic　viscosity　coefficient　increased,　which　is　because　the　stacked　multilayer　gullies　microstructure　aggravated　the　internal　friction　of　paste　particles,　which　led　to　decreased　expansibility　and　pumpability.　When　the　mass　ratio　of　VA/MK　was　1:0.33,　the　paste　achieved　the　balance　of　mechanical　strength　and　rheological　properties　with　superior　water　retention　and　deformation　resistance.　The　microscopic　experiments　showed　that　MK＇s　mechanism　enhanced　the　mechanical　strength　of　geopolymer　due　to　its　high　content　of　amorphous　phases,　smaller　average　particle　size,　and　rich　content　of　Al　element.　The　SEM-EDS　indicated　that　the　MK　improved　the　mechanical　strength　also　by　the　improvement　of　nucleation　effect.　VA　and　MK　complement　each　other　in　mechanical　strength　development　under　room　temperature　and　fluidity,　which　are　expected　to　be　an　alternative　for　cement　as　an　eco-friendly　road　grouting　material.