Effect Of Nano TiN And Nano Boehmite On Portland Cement-based Materials

With increasing technical requirements of cement-based materials and continuous development of nanotechnology,the research of modifying cement-based materials by nanomaterials has become a hot topic.This paper studied the effect of nano-TiN and nano-Boehmite on reference cement and fly ash cement,the mechanical property of which was compared by testing,and then some measurements including X-ray diffraction,scanning electron,pore structure,differential thermal analysis,heat of hydration were combined to analyze the mechanism that nanomaterial influenced cement-based material.On the basis of experimental analysis,the following conclusions were obtained:(1)The optimum dosage of nano-TiN added to reference cement and fly ash cement is respectively 0.05% and 1%,resulting in 17% and 21.3% rise of 28 d compressive strength of responding specimen.However,the species of hydration products in specimen is unchanged,nano-TiN only plays a part of crystal nucleus in crystal growth process and enhances the density of cement products,leading to increase of compressive strength of portland cement,the result of hydration heat indicates that nano-TiN can accelerate hydration process of reference cement and fly ash cement.(2)The optimum dosage of nano-Boehmite added to reference cement and fly ash cement is separately 1% and 1.5%,giving rise to augment of 20.1% and 10.3% of 28 d compressive strength of corresponing specimen,the density of hydrated products can be enhanced by appropriate dosage of nano-Boehmite,which also takes participation in hydration of cement,resulting in the increase of ettringite product,so the compressive strength of cement is improved.However,excess dosage of nano-Boehmite makes hydration excessively fast,which leads to disorder overlaping joint of much hydrated product,and porosity of harden cement paste increases in later period of hydration,thus the compressive strength of harden cement paste is reduced.Due to nano-Boehmite involving in hydration process,the effective amount of nano-Boehmite that plays other role is declined,thus under the same effect the dosage of nano-boehmite will be larger compared to nano-TiN.(3)The optimum dosage of combined nanomaterials added to reference cement and fly ash cement is 0.5% and 0.5%,which makes 28 d compressive strength of responding specimen increase by 26.5% and 16.3% respectively.The hydration rate is advanced by addition of combined nanomaterials,which is particularly obvious in fly ash cement,because the micro-aggregate effect of nanomaterials makes fly ash particles and cement particles disperse more evenly.However,the principal effect of combined nanomaterials in cement is still nucleation effect.(4)Through contrastive analysis,the mechanism that nano-TiN and nano-Boehmite influence portland cement-based material is unvaried under the condition of adding combined nanomaterials,but the overall effect of two kinds of nanomaterials is more evident on account of synergistic effect of two nanomaterials under dosage of combined nanomaterials.