RETRACTED: The effects of zinc dioxide nanoparticles on flexural strength of self-compacting concrete

Abstract

Abstract In the present study, flexural strength of self-compacting concrete with different amount of ZnO 2 nanoparticles has been investigated. ZnO 2 nanoparticles with the average particle size of 15 nm were added partially to self-compacting concrete and flexural strength of the specimens has been measured. The results indicate that ZnO 2 nanoparticles are able to improve the flexural strength of self-compacting concrete and recover the negative effects of polycarboxylate superplasticizer on flexural strength. ZnO 2 nanoparticle as a partial replacement of cement up to 4 wt.% could accelerate C–S–H gel formation as a result of increased crystalline Ca(OH) 2 amount at the early ages of hydration. The increased the ZnO 2 nanoparticles’ content more than 4 wt.%, causes the reduced the flexural strength because of unsuitable dispersion of nanoparticles in the concrete matrix. Accelerated peak appearance in conduction calorimetry tests, more weight loss in thermogravimetric analysis and more rapid appearance of related peaks to hydrated products in X-ray diffraction results all also indicate that ZnO 2 nanoparticles up to 4 wt.% could improve the mechanical and physical properties of the specimens. Finally, ZnO 2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.