Research On The Properties Of Cement-based Materials With Lamellar Graphite

As a product from natural graphite flake peeling,Lamellar graphite belonging to nano-carbon material who has distinct sheet structure,it usually composed of a single layer,less or more layers graphene sheets.In broad terms,graphene is also a lamellar graphite.Lamellar graphite is generally obtained in the process of acquiring graphene,and having a graphene-like structure and physicochemical properties.It have a wide range of applications because of its large specific surface area and excellent thermal conductivity,acid corrosion and strong mechanical properties.This paper was prepared lamellar graphite according to the invention patent CN 104889411 A,and added into cement system to explore the impact of lamellar graphite on the properties of cement-based materials.In order to ensure that lamellar graphite is uniformly dispersed in the cement system,experiment need to determine a surfactant that could disperse lamellar graphite stably,and formed a stable suspension of lamellar graphite in aqueous phase,and then mixed with cement in different proportions.By measuring the mechanical properties and electrical properties of cement specimens to evaluate the impact of lamellar graphite on cement-based materials.Selected a effective surfactant to obtain uniform dispersion of lamellar graphite.Eight kinds of cationic,anionic and nonionic surfactants were choosed,including CTAB?SDBS?PCE?PEG1000?PEG6000?PVA1788?PVP-K30?Tween80.The lamellar graphite stable aqueous suspension was gained through surfactant assisted sonication.Then preferred surfactant and determined its dosage by observing the sedimentation and testing on the absorbance of lamellar graphite dispersion.PVP-K30 is the effective surfactant to disperse lamellar graphite,and its dosage is 7% of lamellar graphite weight.The impact of lamellar graphite on the standard consistency water?setting time of fresh cement paste,and fluidity of cement mortar.A lamellar graphite suspension was prepared with PVP-K30 whose content was 7% based on lamellar graphite weight.Lamellar graphite suspension was mixed with cement mortar in accordance with dosage of 0.6%,1%,1.5%,2%,and formed lamellar graphite cement paste and cement mortar,also two blank groups that is reference cement and cement mixed with 0.14%PVP-K30(based on cement weight).Standard consistency water and setting time of six groups cement paste were measured,and also determinated the fluidity of six groups cement mortars.The results shows,lamellar graphite was added to increase the water content of cement system.Under the same water-cement ratio,the participation of lamellar graphite will reduce the liquidity of cement system.It extended setting time of cement as well,it means that lamellar graphite have the effect of retarding.In general,the water content of cement system was increasing with the lamellar graphite content,and the setting time also increased linearly with lamellar graphite dosage.Effects of lamellar graphite on the water absorption?bulk density and mechanical properties of cement mortar.Lamellar graphite suspension was mixed with cement mortar in accordance with dosage of 0.6%,1%,1.5%,2%,and prepare lamellar graphitecement mortar and also blank groups,and test the flexural and compressive strength of those cement mortars of 3d and 28 d age.Each cement mortar group under standard curing after 28 d,the standard cement mortar and four groups of lamellar graphite cement mortar were placed in a drying oven with 105? for 48 h,and then cool to room temperature.Bulk densities of five cement mortar groups were measured,and according to the change of mass before and after drying,water absorption of five groups mortar were calculated.The results show that lamellar graphite was added to increase the water absorption of cement mortar,and show a growing trend with the increase of lamellar graphite content;At the same time,lamellar graphite was added to reduce the density of cement mortar to a certain extent,mainly because of lamellar graphite was added to the cement mortar,it adsorbed and isolated a portion of water,which lead to a greatly reduced of mixing water,so that mortar fluidity is reduced,and internal porosity of cement mortar test block was increased,density decrease.The results also show that the participation of lamellar graphite could increasing the mechanical strength,and has more promotion on compressive strength.The growth rate of mechanical strength of cement mortars showed the trend of increasing first and then decreasing with the change of lamellar graphite content.In this experiment,there was best lamellar graphite dosage to improve the mechanical strength of the cement mortar,it is 1% of cement content.The influence of lamellar graphite on the conductive properties of cement mortar.Prepare conductive cement mortar with lamellar graphite content of 0.6%,1%,1.5%,2% and a reference group.Measured the resistance at different ages of 3d,7d,14 d,21d,28 d of those conductive mortars,and the results show that lamellar graphite didn't have a obvious enhancement on cement mortar at Early cement hydration,but have a good improvement at late hydration.And the cement mortar conductivity was decreased after the first growth with the increase of lamellar graphite dosage.Those test results show that lamellar graphite was added to delayed the coagulation of cement-based materials in a certain degree,increased the water absorption of cement-based materials,which means the water consumption of cement system was increased.Under the same conditions of water-cement ratio,the fluidity of cement-based materials was reduced,and its internal porosity was increased.However,due to the excellent properties of lamellar graphite,it good to make up for the defects caused due to increasing water absorption.To a certain extent,it increased the mechanical strength of the cement-based material.Furthermore,since the lamellar graphite has large specific surface area and high electrical conductivity,It is incorporated into the cement-based materials to reduce the resistivity of the cement-based material effectively,and made its conductive performance greatly improved.