Study On Properties Of Cement Mortar Modified By Graphene Oxide Alone Or Combined With Nano Zinc Oxide

Cement-based materials are susceptible to microbial contamination when exposed to the natural environment.The propagation of microorganisms not only reduces the mechanical and durable properties of structures,but also has potential harm to human health.Although traditional antibacterial agents can make cement-based materials have antibacterial properties,they usually have adverse effects on mechanical properties and durability.Therefore,nano inorganic antibacterial agent has become a new choice for the preparation of high-performance antibacterial cement-based materials.In this paper,graphene oxide(GO)dispersion and two kinds of ratio(1:5 and 1:10)of GO/nano-Zn O composite dispersion are prepared by ultrasonic dispersion,and the effects of GO single or combined mixing with nano-Zn O on the fluidity,mechanical properties,drying shrinkage,frost resistance and antibacterial properties of cement mortar are studied.The microstructure and pore structure of cement mortar are analyzed by scanning electron microscope and mercury intrusion porosimetry.The main research results are as follows:(1)The blend of GO and nano-Zn O can promote dispersion of each.When the concentration of GO is constant,the dispersion degree of the solution increases with the increase of nano-Zn O concentration.(2)The fluidity of fresh cement mortar decreases with the increase of GO content.Only when the GO content is 0.01%,increasing the mixed nano-Zn O content can increase the fluidity of mortar;when the GO content is greater than 0.03%,the mixed nano-Zn O content can reduce the fluidity of mortar.(3)The early mechanical properties of mortar are improved by GO single doping,and the 28-day mechanical properties increased first and then decreased with the increase of single doping content,the optimum single content of GO is 0.05%,and the flexural strength and compressive strength are increased by 7.5% and 12.3%,respectively.The 28-day mechanical properties of mortar are significantly enhanced with the increase of the amount of GO/nano-Zn O,but the early mechanical properties are decreased due to the retarding effect of nano-Zn O.When the content of GO is constant,the flexural and compressive strength of 28 days can be improved by increasing the content of nano-Zn O..(4)The drying shrinkage of mortar can be significantly increased by GO single doping,and the drying shrinkage value reaches the maximum when GO content is0.05%.When GO/nano-Zn O are mixed,the drying shrinkage can be reduced only when the dosage of nano-Zn O is low,and the drying shrinkage value of the modified mortar is the lowest when GO was 0.03% and nano-Zno was 0.15%.(5)The frost resistance first increases and then decreases with the increase of GO single dosage,and the optimal dosage is 0.05%.When mixed with GO/nano-Zn O,its frost resistance has the same trend as that of GO single doping,and the frost resistance of the modified mortar is the best when the GO content is 0.05%.When the content of GO is certain and lower than 0.07%,the frost resistance of mortar increases after 100freezing-thawing cycles by increasing the content of nano-Zn O.When the content of GO is 0.07%,the increase of nano-Zn O content decreases the frost resistance.(6)The antibacterial activity of GO is low,while the antibacterial activity of nanoZn O and composite GO/nano-Zn O at two concentrations is good,and it increases with the increase of concentration.When the single dosage of GO is increased,the antibacterial properties of mortar first increase and then decrease,and the optimum dosage is 0.05%;GO/nano-Zn O compounding further improves the antibacterial properties of mortar,the antibacterial performance of 1:5 compound modified mortar is the best when GO is 0.05% and nano-Zn O is 0.25%,the 24-hour antibacterial performance of 1:10 compound modified mortar increases with the increase of compound content.With a certain amount of GO,the 24-hour antibacterial performance increases with the increase of nano-Zn O content.The modified mortar with GO monodoped or mixed with nano-Zn O affected the cell morphology of Staphylococcus aureus.With the increase of the dosage,the surface of the bacteria gradually shrank and deformed until it is destroyed and inactivated.(7)GO alone or mixed with nano-Zn O improves the microscopic morphology and pore structure of the cement mortar,so that the hydration products grow uniformly and densely and interlock with each other,reducing the porosity.When the amount of GO is constant,the porosity decreases with the increase of the amount of nano-Zn O.Single doping of GO can reduce the proportion of macropores and increase the proportion of capillary pores,and co-doping with nano-Zn O further reduces the proportion of capillary pores and increases the proportion of transition pores with smaller pore diameters.