Research On Preparation And Mechanism Of Graphene Modified Cement

Cement and concrete are the most popular building materials in the world.Therefore,it is of great practical significance to study the performance improvement of cement.With the development of nanotechnology,many researchers pay attention to improving the properties of cement with nano-materials,which have achieved promising results.Graphene,a new class of two-dimensional nanostructure,has attracted much interest due to its extraordinary properties.This paper presents the effect of graphene and graphene oxide on the hydration process and hydration degree of cement.On this basis,the flocculation procedure of graphene oxide in alkaline environment of cement is also analyzed.On the other hand,graphene is dispersed in the cement matrix by ball milling method in order to prepare the modified cement material with good performance.Firstly,graphene oxide is synthesized by modified Hummers method.The surface of graphene oxide is wrinkled.What's more,graphene oxide contains a large number of functional groups such as-OH ?-O-and-COOH.In this study,the influence of graphene/graphene oxide on the hydration process and hydration degree of cement is investigated by the isothermal calorimetry and TG-DSC methods.No major differences could be seen in the normalized hydration heat flow and the cumulated hydration heat evolution of the different cement paste with and without graphene/graphene oxide.Meanwhile,the addition of graphene/graphene oxide does not significantly change the dosages of calcium hydroxide(CH)and non-evaporable water.Considering to SEM analysis,it is indicated that graphene/graphene oxide are only physically dispersed in cement matrix.The flocculation procedure of graphene oxide in cement paste is studied.To emulate the alkaline environment generated during cement hydration,CH is uesd.The flocculation process of graphene oxide is explored systematically by the UV-Vis spectrum and zeta potential.In addition,the author tries to improve this phenomenon.The results show that a small dosage of CH(30 mg/L)can lead to the flocculation of graphene oxide.What' more,polycarboxylate superplasticizer(PC)can effectively control the flocculation of graphene oxide and there is no interation between graphene oxide and PC.The dispersed mechanism of graphene oxide by PC is developed in terms of the functional groups: Compared with-OH,-COOH functional group is more effective in inhibiting flocculation of graphene oxide.At the same time,the special molecular structure of PC has steric hindrance effect on the dispersion of graphene oxide.Cement composites have been successfully prepared by the ball milling method and the effect of graphene on reinforcing cement is studied.The results exhibit that the introduction of 0.03 wt% graphene strengthens the compressive strength by approximately 9%.The morphology and size of graphene does not be changed after ball milling and the addition of graphene does not induce the formation of new hydration products.