Study On The Effect Of Nanomaterials On The Mechanical Properties Of Concrete

The incorporation of nanomaterials into concrete can enhance the hydration effect of cement,improve the microstructure of concrete,and thus improve the mechanical properties of concrete.In this paper,the influence of nano-SiO2 and nano-Fe2O3 on the mechanical properties of concrete is studied.When nano-SiO2 and nano-Fe2O3 are singly mixed,four mixing amounts of 0.5%,1.0%,1.5%and 2.0%are set.When nano-SiO2 and nano-Fe2O3 are mixed,the total mixing amount is set to 1.0%,1.5%and 2.0%.By analyzing the mechanical properties of nanomaterial modified concrete and the macro and micro failure modes after uniaxial compression,the influence law and promotion effect of nanomaterial on the mechanical properties of concrete are obtained,and the relative optimal mixing amount of nanomaterial is determined,which provides reference for the application of nanomaterial in practical engineering.The main research contents of this paper are as follows:(1)The effects of nano-SiO2 and nano-Fe2O3 on the mechanical properties of concrete were studied through 7d and 28d compressive strength and flexural strength tests of nano-modified concrete.The experimental results show that when the content is 0～2.0%,nano-SiO2 and nano-Fe2O3 can both improve the compressive strength and flexural strength of concrete,and the optimal content of both is 1.0%.At the same dosage,the effect of nano-SiO2 on the mechanical properties of concrete is obvious in nano-Fe2O3.When the content of nanomaterials is 1.5%,the mechanical properties of concrete can be improved better by adding 1.0%nano-SiO2 and 0.5%nano-Fe2O3.When the content of nanomaterials is 2.0%,the addition of 0.5%nano-SiO2 and 1.5%nano-Fe2O3 can improve the mechanical properties of concrete better.(2)The numerical model is established by PFC3D software,servo load of uniaxial compression is carried out and mesoscopic parameters calibration,and on the basis of the research on its stress strain curve particle displacements of five different stages and the contact force between particles,particles,crack development,cracking status to analyze nano modified concrete mesoscopic failure process under uniaxial compression.(3)Cold-field emission scanning electron microscopy(SEM)and energy dispersion spectrometer(EDS)were used to observe the micro structure of nano-modified concrete and analyze its chemical composition.The experimental results show that the addition of nano-SiO2 can produce acicular and coral-like hydration products,make the internal structure of concrete compact and uniform,and hinder the generation and development of micro-cracks.The incorporation of nano-Fe2O3 causes the formation of tightly arranged spherical hydration products,which plays a filling role.In the nano-modified concrete mixed with nanometer 1.0%SiO2 and 0.5%nanometer Fe2O3,the improvement effect of the modification of the two nanomaterials on the mechanical properties of concrete is better than that of the concrete mixed with nanomaterials alone.Adding nanomaterials into concrete will generate more hydration products,filling the holes and voids inside the concrete,making the concrete interface more rough and compact,thus improving the mechanical properties of concrete.