Effect Of Graphene Oxide On Strength And Corrosion-Resistance Of High Blite Cement-Based Materials

High belite cement?HBC?could decrease the amount of temperature cracks with its unique mineral composition which the content of C₂S was greater than 40%.Meanwhile,it had the characteristics of low hydration heat and less water-demand.HBC could be used in mass concrete engineering,seaport and water conservancy,underground,tunnel,diversion,road and bridge,those infrastructures which are corroded by sulphate and so on.Graphene oxide?GO?was a kind of carbon nanomaterials composed of carbon atom mon-ayer and two-dimensional planar honeycomb lattice structure.GO had abundant oxygen-c-ontaining functional groups on the surface and was easily soluble in water.It was conveni-ent to add into cement composite material and play a role.Therefore,in this article,the fluidity,strength,hydration heat and corrosion resistance of the HBC composite materials were investigated by adding GO.The first,the dispersion of GO in the cement was improved by adding polycarboxylate superplasticizer?PC?in the experiment.The effect of GO on the working and mechanical properties of HBC materials was studied.The results showed that the fluidity of cement mortar decreased with the increase of GO content.The strengthening effect of GO alone was not obvious for the strength of each age of the specimen,but the strength of each age of the specimen could be obviously increased by adding PC/GO,and the flexural strength and compressive strength of each age of the specimen reached the best when the addition of GO was 0.05%.Compared with the standard specimen,the flexural strength and compressive strength of the curing age of 3 days,7 days and 28 days were increased by27%,21%and 12%and 23%,18%and 8%,respectively.At the same time,under the function of PC,when the addition of GO was 0.02%,compared with the standard specimen,the hydration heat of the curing age of 3 days,7 days and 28 days of specimens were reduced by 14.4%,11.3%and 4.8%.It showed that GO could also reduce the hydration heat of HBC materials at different ages.The results of X-Ray?XRD?and scanning electron microscopy?SEM?analysis showed that the addition of GO could promote the formation of hydration products calcium silcate hydrate gel?C-S-H?and alunite?AFt?and increase the density of the internal structure of cement materials so that the strength could be improved.The effects of GO incorporation on the corrosion resistance of HBC materials were studied in the presence of sodium sulfate,sodium chloride and composite solution?including sodium sulfate and sodium chloride?.The results showed that the addition of GO could improve the flexural strength,compressive strength and corrosion resistance of cement mortar specimens under the condition of three kinds of salt solution erosion,and the improvement effect was better when the content of GO was 0.05%.Furthermore,when the corrosion age was 90 days,the corrosion resistance coefficient of compressive strength of the specimens with 0.05%GO were all greater than 1 at each erosion solution and showed the well corrosion resistance property.The microscopic analysis of the specimens showed that in the sodium sulfate solution,the main corrosion product generated by the specimens was AFt,in the sodium chloride solution,mainly hydrated calcium chloroaluminate?Friedel's salt?,and AFt and Friedel's salts were present in the composite solution.Because GO could promote the hydration process of the cement,the density of the internal structure of the cement materials can be improved in the early stage of curing,so that the eroded rate of sulfate ion and chloride ion erosion was limited,and the AFt and Friedel's salt produced by the partially-invasive attack ions and the cement hydration products Ca?OH?₂ could make the internal structure of cement reach the effect of density in some measure.Therefore,the corrosion resistance of HBC materials was improved under the action of full immersion in erosive solution.In addition,the flexural strength and compressive strength of the specimens mixed with GO at each erosion age were higher than those of the reference specimens under the action of semi-soaking in salt solution.By analyzing the microstructure of the unsoaking site,it could be seen that the diffraction peak intensity of the erosion product produced by this part was weaker than that under the full immersion.At the same time,under the action of semi-soaking sodium sulfate,the corrosion products formed in the unsoaking part were mainly AFt and CaSO₄,sodium chloride mainly Friedel's salt,compound sodium sulfate and sodium chloride mainly AFt,Friedel's salt and CaSO₄.Therefore,the addition of GO into the HBC material could improve the corrosion resistance of the cement composite materials under the full immersion and the strength development under the semi-soaking in the presence of sodium sulfate,sodium chloride and composite sodium sulfate and sodium chloride solution.The test results have a bright prospect for the application of high belite cement in those infrastructures which are corroded by sulphate and chloride and so on.