Experimental Study On Influence Mechanism Of Nano-particles On Abrasion Resistance Of High Performance Cement-based Composites

As a large water conservancy country,China has built water conservancy facilities all over the country,and one of the serious problems faced by hydraulic structures is the erosion and damage of hydraulic structures under the action of high-speed water flow and sediment.In order to improve the abrasion resistance of hydraulic structures and increase their durability,it is necessary to design an appropriate concrete that has good abrasion resistance when the hydraulic structures are cast and formed.In this paper,the impact and mechanism of nano-particles on the impact and abrasion resistance of concrete are studied,and the impact and abrasion resistance of concrete is evaluated by"underwater steel ball method"impact and abrasion test method.By means of XRD,SEM,hydration heat release test and TG analysis the influence of nano-particles on cement hydration is studied,and then the mechanism of its influence on the abrasion resistance of concrete is discussed and the correlation between nano-particles,microstructure of cement paste and abrasion resistance is established.The theoretical and technical support is provided by analyzing the selection of aggregate and nano-particles admixture in anti-abrasion concrete.The main research conclusions are as follows:1.The impact mechanism of nano-CaCO₃ on the abrasion resistance of concrete is analyzed by studying the abrasion resistance of concrete mixed with nano-CaCO₃ and combining with a series of microscopic test results on the microstructure of cement paste and slurry-aggregate interface.Only 0.5%,1.5%and 2%nano-CaCO₃ can improve the mechanical properties and abrasion resistance of concrete.In this test,when the content of nano-CaCO₃ is 1.5%,the effect of abrasion resistance improvement is the best,with an increase of 116.66%.The addition of nano-CaCO₃ promotes the hydration reaction and generates more C-S-H.The amount of AFt is reduced while calcium carboaluminate hydrate is generated,and the bonding degree at the slurry-aggregate interface is improved,thus improving the impact and abrasion resistance of concrete.2.By studying the impact and abrasion resistance of concrete mixed with nano-SiO₂,combining the hydration exothermic process and the composition of hydration product phase,the mechanism of the impact of nano-SiO₂ on the abrasion resistance of concrete is analyzed.With the addition of nano-SiO₂ increasing by 1.5%,3%and 5%,the mechanical properties and abrasion resistance of concrete also gradually improve.When the addition of nano-SiO₂ is 5%,the abrasion resistance of concrete increases by 183.36%.The addition of nano-SiO₂ accelerates the hydration reaction rate,increases the total heat release,consumes Ca?OH?₂ at the slurry-aggregate interface,refines the size of Ca?OH?₂,and generates more C-S-H.Due to the increase of C-S-H content,the bonding performance at the interface is improved,and the microstructure of cement paste is also improved,which refines pores and reduces porosity,thus improving the abrasion resistance of concrete.3.By studying the abrasion resistance of concrete mixed with nano-CaCO₃ and nano-SiO₂,and comparing the test results of two groups of single mixed nano-particles,the mechanism of the impact of mixed nano-particles on the abrasion resistance of concrete is analyzed.The influence trend of mixing two kinds of nano-particles on the mechanical properties and abrasion resistance of concrete is consistent with that of mixing nano-SiO₂ alone.The two kinds of nano-particles play their own roles4.separately to jointly promote the hydration reaction of cement,to advance the occurrence time of hydration exothermic peak,and to reduce the total amount of heat released in the initial stage of hydration to a certain extent.The content of Ca?OH?₂ at the interface between slurry and aggregate is greatly reduced,the formation of C-S-H is increased,the compactness of concrete is improved,and the impact and abrasion resistance of concrete is enhanced.