Study On The Effect Of Nanomaterials On Cement Hydration

At present,there are many studies on the application of the nanomaterials in cement hydration,mostly focusing on the effects of nanomaterials on the micro-macro properties of cement-based materials.However,its mechanism of nucleation is still controversial.In this paper,the effects of nanomaterials on cement hydration are studied and their mechanisms are discussed.Six nanomaterials were studied,which were multi-walled carbon nanotubes（CNT）,graphene oxide（GO）,graphene（G）,nano-SiO₂,nano-CaCO₃and,nano-MgCO₃.First,the basic properties of nanomaterials were investigated using scanning electron microscopy,laser particle size measurement,and FTIR analysis.Second,simulated solutions of cement paste pore solutions were prepared.Zeta potential was applied to study the adsorption properties of nanomaterials for relevant ions in the simulated solutions.Then,SEM was used to study the effects of different nanomaterials on the morphology,content,and structure of hydration products.Next,the hydration kinetics of the nanomaterial cement paste system was simulated by the Krstulovic-Dabic model.Finally,based on the above results,the effect of different nanomaterials on cement hydration was analyzed and its mechanism was discussed.The results showed that:（1）The adsorption capacity of nanomaterials for Ca²⁺ionsis stronger than that of cement particles.The adsorption capacity of CNT,GO,and G particles for Ca²⁺ions is weaker than that for SO₄^2-ions.The adsorption capacity of nano-SiO₂,nano-CaCO₃,and nano-MgCO₃particles is stronger than that of SO₄^2-ions for Ca²⁺ions.（2）The strong adsorption of Ca²⁺ions by nanomaterials can promote the generation of hydration products.The C-S-H particles in the cement paste containing CNT,GO and G carbon-based nanomaterials are fine and regular.In contrast,the C-S-H particles in the cement pastes containing inorganic nanomaterials of nano-SiO₂,nano-CaCO₃,and nano-MgCO₃are coarse and irregularly shaped.（3）The incorporation of nanomaterials can promote the formation of CH.The incorporation of nanomaterials increased the degree of polymerization and the average chain length of hydration products.（4）The incorporation of nanomaterials in the hydration reaction increases the exothermic peak and total exothermic heat and shortens the length of the induction period and the exothermic peak.（5）The Krstulovic-Dabic model was used to simulate the hydration kinetics of the nanomaterial cement paste,showing that the hydration process is consistent with the NG-I-D process.In the NG process,nanomaterials can accelerate the hydration process,which makes the kinetic parameter reaction level（n）decrease and the reaction rate constant（K₁’）increase.In the I process,the migration of Ca²⁺ions becomes more and more difficult due to the continued increase of hydration products.This leads to a decrease in K₂’and hydration rate.In the D process,K₃’decreases rapidly.