The effects of Cr2O3 nanoparticles on strength assessments and water permeability of concrete in different curing media

In this study, the effect of limewater on strength assessments and percentage of water absorption of concrete incorporating Cr2O3 nanoparticles has been investigated. Portland cement was partially replaced by Cr2O3 nanoparticles with the average particle size of 15 nm and the specimens were cured in water and saturated limewater for specific ages. The results indicate that Cr2O3 nanoparticles up to 2.0 wt% 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. Although the limewater reduces the strength of concrete without nanoparticles when compared with the specimens cured in water, curing the specimens bearing Cr2O3 nanoparticles in saturated limewater results in more strengthening gel formation around nanoparticles causing improved permeability together with high strength. In addition, Cr2O3 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 Cr2O3 nanoparticles could improve mechanical and physical properties of the specimens. (C) 2010 Elsevier B.V. All rights reserved.