Preparation Of Graphene Oxide And Nano-belite Cement Based On Modified Method And Their Influence On The Properties Of Cementitious Materials

Cementitious materials are the most widely used construction materials in today’s society,but they will be damaged and cracked during use.The resulting consequences of insufficient durability of concrete structures are very serious and can cause huge economic losses.In order to achieve the purpose of strengthening and toughening cementitious materials,we have prepared Graphene Oxide(GO)and Nano-belite Cement(NC),and use them to form composite materials for use in cementitious materials to improve their pore distribution and mechanical properties.Specifically,the mechanism of preparing GO by electrochemical method is firstly clarified.GO is fully characterized and combined with Graphene(GR)to form a composite material(GO/GR)into the cementitious material,thereby improve the dispersion of GR in cement and bring it better mechanical properties.NC materials have been prepared by the combustion method,and the production process has been optimized.The prepared GO is combined with NC to make GO/NC composite materials,and the possibility of improving the interface between GO and cementitious materials through NC to better enhance the toughening effect was initially discussed.The results show that the electrochemical preparation of GO is the result of the deterioration of the Carbon Fiber(CF)anode.When energized,the oxygen generated by the anode enters the CF anode,which oxidizes the CF.The morphology shows that some fibers of the CF cloth shed,and the composition shows that a large number of C-C bonds are converted into C=O bonds.The shed fibers enter the electrolyte and become GO.After characterization,it was found that the electrochemically prepared GO has a typical 2D film-like structure with 1 to 3 layers and rich oxygen-containing functional groups.In addition to simple filtration,the entire preparation process does not require complicated purification treatment,and the composition does not contain substances harmful to cementitious materials and the environment,which is a simple,stable and environmentally friendly preparation methodThe presence of oxidized functional groups in GO makes the mechanical properties of GO decrease while compared to GR,but the dispersion effect in water is improved.Therefore,the combined use of GO and GR,on the one hand,can make up for the lack of GO’s mechanical properties,on the other hand,it can strengthen the dispersion effect of GR,so as to achieve better enhancement of cementitious materials.When the total amount of GO and GR is unchanged,the two are mixed and added to the cement mortar,the mechanical properties are improved compared to the use of GO or GR alone.Compared with the reference sample without admixture,when the ratio of GO:GR is 3:1,the flexural strength of 3-day samples is increased by 22.88%,and the compressive strength is increased by 38.13%.When the ratio of GO:GR is 1:1,the flexural strength of 28-day samples increased by 30.73%,and the compressive strength increased by 19.50%.For the preparation of NC materials,when the calcium carbonate and micro silicon powder are mixed at a mass ratio of 3:1 and calcined at a high temperature of 1150 ℃ for 120 min,BC material with an active ingredient Ca2 Si O4 content of up to 95.8% is prepared.The foaming agent is combined with the BC(pressure of 6k N)and then calcined again,which can synthesize NC material with high specific surface area(2.2 times of BC material).The obtained NC surface particles have obvious refining effect,and the particle size has reached about 100 nm.As an admixture,NC shows higher activity than BC materials,which makes up for the shortcoming of BC materials that it’s early hydration speed is too slow,and can enhance the cement mortar on flexural and compressive strength after curing for 28 days and more.GO can reunite with NC in water,which can increase the dispersion of NC in water.After immersing NC in GO solution for 180 d,a large amount of C-S-H gel and Ca CO3 with a particle size ranging from 16 to 31 μm can be generated.The large-scale generation of C-S-H gel can ensure the seamless connection between GO and concrete.The suitable particle size of GO/NC composite,right between the nano-level GO and the micron or even millimeter-level cement particles,bring it the ability of playing a transition role,thereby making the GO surface functional groups fully utilized.The synergy of GO and NC shows its potential as a seed crystal to improve the performance of cementitious materials.