Study On Preparation Of Electrical Conductive Additive And Its Performance In Cement-based Materials

Pyrite cinders, which are the waste slags of sulphuric acid manufacturingplants, contain higher iron oxide (29.8%Fe2O3) and active siliceous andaluminium components from chainotte. In this study, the electrical conductiveadditives (ECA) with lower resistivity and supplementary cementitiousproperty using pyrite cinder as raw material were prepared under hightemperature in reducing atmosphere. The conductivity and resistivity stabilityof electrical conductive additive (ECA), and its conductivity and mechanicalproperty of potential use in cement-based materials were discussed. Toimprove conductivity and mechanical strength of the conductive cement-basedmaterials with electrical conductive additive (ECA), electrical conductiveceramics were manufactured from pyrite cinder and replaced ordinary sandwith it in the cement-based materials. The conductivity and mechanicalstrength of the conductive cement-based materials with electrical conductiveaggregate were also investigated.The main research results were obtained. Electrical conductive additive(ECA) with lower resistivity was obtained using low-grade pyrite cinder andfew reducing agent such as coal powder, through a simple process.The optimalprocess of manufacture that when0.1of mass ratio of coal powder to pyritecinder, molding of5MPa after milling mixture for60seconds(d(0.5)=17.5μm)and roasting at800℃for60minutes were adopted, electrical conductiveadditive(ECA) with resistivity of2.02·m can be prepared in the laboratoryscale.Resistivity of the electrical conductive additive (ECA) in five differentconditions, such as water, standard curing, natural curing, alkali and acidsolution increased with reduction of its FeO/TFe ratio. However it will tend tobe stable after30days. Research showed that in acid solution and waterresistivity growth is biggest, in standard curing next and resistivity minimumin alkali solution. Electrical conductive additive(ECA) in alkalineenvironment, the magnetite of which was oxidized to2:1of molar ratio ofFe3+to Fe2+,which would generate Fe3O4to stop generation of fartheroxidation. The results showed that the electrical conductive additive (ECA) can be applied in alkaline cement-based materialsThe resistivity of cement-based materials with electrical conductiveadditive (ECA) can be significantly reduction. but the mechanicalperformances, such as rupture of modulus and compressive strength wereobviously reduced. Filtration threshold in cement paste with electricalconductive additive (ECA) is40%(FeO is6.3%) or so, and in the mortar is40%~60%(FeO is6.3%~9.5%). Resistivity of composite conductivecement-based materials increases with the increase of age, and reach stabilityof the time required for long.Conductive ceramics with resistivity of10·m were prepared at1250℃~1450℃through pulverized coal and pyrite cinder with mass ratio of0.1,and mixed with a small amount of mineralization agent,such as fluorite orsodium bicarbonate, and then calcining at the temperature mentioned above.Electrical conductivity ceramic products with resistivity of0.58·m andcompressive strength of87MPa were obtained in lab scale at1400℃for60min under5.4%dosage of fluorspar, moreover, the resistivity and strengthattained to0.88·m and84MPa respectively when the dosage of Na2O was4%.Conductive ceramic as fine aggregate replacing sand in mortar, can not onlysignificantly reduce the conductivity, and can improve rupture andcompressive strength of the mortar.