Study On The Effect Of GO On The Properties Of Chemical Shrinkage And Autogenous Shrinkage Of Cement-based Composites

Graphene oxide（GO）is a two-dimensional nanomaterial with lamellar structure.It has excellent properties such as ultra high strength,toughness and large specific surface area,which makes it have good application value in many fields.At present,the application research of GO in cement-based composites shows that GO has certain influence on the mechanical properties,durability,microstructure and hydration process of cement-based composites.Shrinkage is the main cause of the initial microcrack in cement-based composites,which has an important effect on their mechanical properties and durability.The shrinkage of cement-based composite materials mainly include chemical shrinkage,autogenous shrinkage,dry shrinkage and temperature shrinkage,shrinkage,carbonation of chemical shrinkage and autogenous shrinkage is caused by the cement base composite material internal cause of contraction,with the drying shrinkage,temperature shrinkage,carbonation occurred three contraction principle,the three contraction environment has great connection with the outside world,It can be controlled by controlling the external environment,and the occurrence of chemical shrinkage and self-contraction is not affected by the outside world.Under any environmental conditions,the chemical shrinkage and self-contraction of cement-based composites are inevitable.Because of graphene oxide cement base composite material all affect the microstructure and hydration process,so the graphene oxide could affect the chemical shrinkage,autogenous shrinkage,in order to study the graphene oxide chemical shrinkage and autogenous shrinkage of cement base composite material properties and the change rule of the specific impact,based on the graphene oxide content,water cement ratio,dosage of water reducing agent as a variable,The change rule of chemical shrinkage and autoshrinkage of cement-based composites is studied.The main research contents and relevant conclusions are as follows:（1）The basic performance of cement-based compositesThe effects of the content of GO on the fluidity,initial setting time and final setting time of cement-based composites were studied.The test results show that the addition of GO significantly reduces the fluidity of cement slurry,and the greater the amount of GO,the smaller the fluidity of cement slurry.The initial setting time and final setting time of net cement slurry decreased with the increase of GO content,and the influence on the final setting time was more obvious.When the content of GO was 0.05wt%,the initial setting time and final setting time decreased by 17.6%and 18.2%,respectively,compared with the control group without GO content.（2）Experimental study on chemical shrinkage of GO cement-based composites and establishment of prediction modelThe effects of water cement ratio,the amount of GO and the amount of water reducer on chemical shrinkage were studied.The results show that the chemical shrinkage increases with the increase of water-cement ratio.Under different water-cement ratios,GO can reduce the chemical shrinkage of cement slurry,and the reduction is proportional to the amount of GO.The water reducer can significantly increase the chemical shrinkage of cement paste.With the increase of the amount of water reducer,the increase range of the chemical shrinkage of cement paste is firstly large and then small,and GO can inhibit the increasing effect of water reducer on the chemical shrinkage of cement paste.In this paper,on the basis of Xiao Kaitao’s model,various parameters in the model were modified,and the function K（ξ,t）and P（λ,t）were introduced as influence factors respectively to consider the effect of the addition of GO and water reducer on the chemical shrinkage of cement-based materials.The prediction model obtained has a more accurate prediction of the chemical shrinkage of GO cement-based composites.（3）Experimental study on the self-shrinkage of GO cement-based composites and establishment of prediction modelThe effects of water cement ratio,the amount of GO and the amount of water reducer on autoshrinkage were studied.The results show that the self-shrinkage of cement slurry is directly proportional to the water-cement ratio.The reason for this result is that the self-shrinkage of cement slurry contains chemical shrinkage because the water-cement ratio is too large.When the water-cement ratio was 0.32,the effect of GO on the autoshrinkage of cement slurry increased and the autoshrinkage increased with the increase of the content,and the effect of GO on the increase of autoshrinkage weakened with the increase of the water-cement ratio.The effect of superplasticizer on the autoshrinkage of cement slurry was inhibited by GO.In this paper,on the basis of a large number of autogenous shrinkage test data,through the regression fitting method,A correction factorγ（ξ,t）,which takes into account the effect of GO content and time,is introduced,The correction coefficientγ（μ,t）,which takes into account the influence of water-cement ratio and time,the correction coefficientγ（λ,t）,which takes into account the influence of PC content and time,and the correction coefficientξ₁、ξ₂,which takes into account the influence of accidental factors on autoshrinkage in the test process,The self-shrinkage prediction model of GO cement-based materials is obtained,which has a higher degree of prediction compared with the existing experimental results.