The potential of producing geopolymer (GP) composites using Jordanian oil shale ash (OSA) was investigated. Twelve GP mortar mixtures were prepared using OSA and different proportions of commercially available alkaline activator, composed of sodium silicate and sodium hydroxide. Prismatic specimens (40 × 40 × 160 mm), attained satisfactory workability, were left at laboratory air for 24 hr, then demolded and dry cured at different practical temperatures (60-100 C) for 24 and 48 hr before left in laboratory air and finally tested for strength and capillary porosity. Furthermore, SEM analysis was carried out on matured GP mortar samples to determine the extent of OSA polymerization and status of pore system. The results indicated the potential of producing GP mortar using OSA with strength grades of as high as 20 MPa. Dry curing at 60 C for 24 hr imparted the best mechanical and durability properties of OSA-based GP mortar. The internal pore structure showed excellent correlation with mechanical and durability properties of produced GP composites. K E Y W O R D S concrete, geopolymer, OSA, porosity, SEM, strength

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