Study On The Preparation Method And Properties Of Graphene Oxide Modified Limestone Calcined Clay Cement

Limestone calcined clay cement(LC~3)is mainly composed of calcined clay,limestone,clinker and gypsum in a certain proportion.Its principle is to form LC~3concrete with denser microstructure and excellent mechanical properties through the interaction between alumina of calcined clay and carbonate of limestone,pozzolanic reaction of calcined clay and filling effect of limestone.If calcined clay or limestone are used alone to replace clinker,in order to maintain mechanical properties similar to pure cement,they can only replace up to 25%and 15%.The influence of calcined clay on the working performance of LC~3 is the main factor,with limestone playing a major regulatory role.In addition,LC~3 is simpler to prepare than ordinary Portland cement,for example,the calcination temperature of calcined clay is lower than that of clinker,and limestone is easy to obtain and treat.However,due to the large BET of calcined clay,the early mechanical properties of LC~3 were poor.At present,the properties of cement-based materials reinforced by graphite oxide have been extensively studied.In this regard,the purpose of this paper is to improve the mechanical properties of limestone calcined clay cement through graphite oxide.First,according to the different addition order of raw materials and different dispersion methods of graphite oxide,the best preparation method of GO-LC~3 is preliminarily explored.Then,the influence of graphite oxide content on the mechanical properties of GO-LC~3 and its micromorphology is explored.Finally,the influence of graphite oxide on the durability of GO-LC~3 is analyzed,And analyze the economic and environmental benefits of GO-LC~3.The specific research work of this article is as follows:(1)By comparing the different addition sequences of raw materials,the variation of mechanical properties of the test block was analyzed to obtain the best test block preparation process.Experiments show that the best preparation process of GO-LC~3 is as follows:first,put the graphene oxide solution into the mixer;then the calcined clay was put into a mixer and stirred for 120s;the limestone was added to the mixer and stirred for 120s;finally,the cement is added to the mixer and stirred for 120s.At this time,the compressive strength of the prepared samples at 7d,14d and 28d reached33.85 MPa,40.42 MPa and 43.07 MPa,and the flexural strength reached 5.21 MPa,5.6 MPa and 6.28 MPa,which were higher than other preparation methods.This is because the preparation method can make GO more evenly distributed in the cement,effectively disperse the calcined clay,thereby improving its mechanical properties.The preparation method lays a foundation for subsequent experiments.(2)Three dispersion methods were designed to disperse GO.The results showed that under the same treatment time,GO could be better dispersed in aqueous solution by ultrasonic dispersion method.At the same time,the mechanical properties of the prepared GO-LC~3 samples were better than those of mechanical dispersion and mechanical combined ultrasonic dispersion.The compressive strength of 7d and 28d was 46.7%and 18.1%higher than that of the other two dispersion methods.This is because ultrasonic dispersion can more easily disperse GO in aqueous solution at the same time,thus improving the mechanical strength of GO-LC~3.(3)The effect of graphene oxide content on the macroscopic properties of GO-LC~3 was discussed.Five groups of experiments with different graphene oxide content were designed.The results of mechanical properties show that the incorporation of graphene oxide can improve the compressive strength of GO-LC~3samples compared with the control group.At the same time,with the increase of graphene oxide content,the compressive strength of GO-LC~3 samples increased first and then decreased.When the content of graphene oxide was 0.09 wt.%,the compressive strength of GO-LC~3 samples reached the best,and the compressive strength at 7d,14d and 28d ages increased by 25.6%,21.57%and 20.33%compared with the control group.(4)The GO-LC~3 test blocks were analyzed by XRD,SEM,FT-IR and TG-DTA.The results show that the incorporation of graphene oxide will not change the type of hydration products of LC~3,but graphene oxide will promote the production of hydration products(C-S-H,CH)of LC~3.When the content of graphene oxide is 0.09wt.%,the performance is the best,which improves the pore structure of GO-LC~3sample due to calcined clay,which is consistent with the results of mechanical analysis test.(5)Through three durability tests(frost resistance,sulfate resistance and permeability resistance),the influence of graphite oxide content on the durability of GO-LC~3 samples was analyzed.The results show that the durability,sulfate resistance,dry wet cycle and impermeability of GO-LC~3 can be improved by adding 0.09 wt.%graphite oxide.