This　work　investigated　the　influence　of　graphene　oxide　(GO)　suspension　as　a　surface　sealer　on　the　properties　of　two　types　of　cementitious　mortars　(Portland　cement　mortar　and　high-volume　fly　ash　(HVFA)　mortar)　under　two　curing　conditions　(wet　curing　and　dry　curing).　Experimental　results　showed　that　GO　surface　treatment　slightly　improved　compressive　strength　of　wet　cured　HVFA　mortar　and　dry　cured　cement　mortar　while　it　significantly　reduced　the　water　absorption　of　wet　cured　HVFA　mortar　and　the　gas　permeability　of　both　wet　cured　and　dry　cured　cement　mortars.　Scanning　electron　microscopy　(SEM)　analysis　suggested　that　the　GO　surface　treatment　facilitated　the　hydration　process　and　densified　the　microstructure　of　both　types　of　mortars.　X-ray　diffraction　and　Thermogravimetry　results　revealed　the　formation　of　hydroxyl　grafted　AFm　phase　at　the　interface　of　GO/HVFA　mortar.　Moreover,　the　GO　surface　treatment　was　found　to　decrease　the　carbonation　of　HVFA　mortar　but　increase　that　of　cement　mortar.　(C)　2017　Elsevier　Ltd.　All　rights　reserved.