In the present study, the effect of limewater on strength and percentage of water absorption of Al2O3 nanoparticles blended concrete has been investigated. Portland cement was partially replaced by Al2O3 nanoparticles with the average particle size of 15 nm with different amount and the specimens were cured in water and saturated limewater for specific ages. Utilizing up to 2.0 wt% Al2O3 nanoparticles could produce concrete with improved strength and water permeability when the specimens cured in saturated limewater while this content is 1.0 wt% for the specimens cured in tap water. The high action of fine nanoparticles substantially increases the quantity of C-S-H gel. Although the limewater reduces the strength of concrete without nanoparticles when compared with that cured in water, curing the specimens in saturated limewater results in more strengthening gel formation around Al2O3 nanoparticles and causes improved permeability together with high strength. In addition, Al2O3 nanoparticles are able to act as nanofillers and recover the pore structure of the specimens by decreasing harmful pores. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of peaks related to hydrated products in X-ray diffraction results, all indicate that Al2O3 nanoparticles could improve mechanical and physical properties of the specimens. (C) 2011 Elsevier B.V. All rights reserved.