Effect Of Nanoparticle On Mechanical Properties Of Cement-based Materials And Its Mechanism

Nanoparticles such as nano-silica(NS) and nano-titanium(NT) have been utilized to improve the mechanical properties of cementitious materials in the last one decade. The effect of nano-silica and nano-titanium on the mechanical properties of cement-based materials may be different as nano-silica has pozzolanic activity while nano-titanium is not a pozzolanic material. The purpose of this study was to experimentally study the influence of particle size and dosage of nanoparticles with different pozzolanic activities on the mechanical behavior and microstructure of cement paste and mortar, which will be meaningful for the application of nano cement-based materials in practical project. The main research contents in this study are outlined as follows:Firstly, the dispersion state of nanoparticles in cement-based materials using different dispersion methods was studied. After that, the effect of particles size and content of nano-silica and nano-titanium on the fluidity, flexural strength, compressive strength and fracture energy of cement paste was experimentally investigated. Experimental results demonstrated that cement paste incorporating silica nanoparticle showed a greater compressive strength, especially the 3d compressive strength, in comparison with nano-titanium containing cement paste. The smaller the particle size of nano particles, the better compressive strength of cement paste, similarly, the compressive strength will increase when improving the content of nanoparticles in cement paste. The fracture energy of titanium dioxide nanoparticles incorporated paste was greater than that of paste containing nano-silica.Secondly, the influence of nano-sized silica and titanium on the fluidity, flexural strength, compressive strength and fracture energy of cement mortar was investigated. The fluidity of mortar with a larger dosage of nanoparticles was much worse so superplasticizer was used to improve the workability of mortar. The effect of nanoparticles on the mechanical properties of cement mortar with different fluidities was also analyzed, at the same time, the mechanical properties of nanoparticles incorporating cement paste and mortar was compared. Test results demonstrated that nanoparticles can also improve the mechanical properties of cement mortar, compared to cement paste, the impact of nano-silica and nano-titanium on the mechanical behavior of cement mortar was less than that of cement paste.Lastly, the effect of nano-scale silica and titanium on the composition, degree of hydration, pore structure and morphology of hardened cement paste was experimentally studied. After adding nanoparticles to cementitious materials, the degree of hydration of hardened paste was improved and the porosity of hardened paste was decreased. The proportion of pores with pore size less 50 nm was greatly improved. At the same time, Nanoparticles can help to form a denser and compact microstructure. Bsed on the experimental results, accelerating the hydration of cement was the most important effect of nanoparticles on cementitous materials.