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

In the present study, flexural strength of self-compacting concrete with different amount of ZnO2 nanoparticles has been investigated. ZnO2 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 ZnO2 nanoparticles are able to improve the flexural strength of self-compacting concrete and recover the negative effects of polycarboxylate superplasticizer on flexural strength. ZnO2 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 ZnO2 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 ZnO2 nanoparticles up to 4 wt.% could improve the mechanical and physical properties of the specimens. Finally, ZnO2 nanoparticles could improve the pore structure of concrete and shift the distributed pores to harmless and few-harm pores.