| Sulphate aluminium cement(SAC)is a kind of environmental cement with low carbon content developed independently by our country.It has the advantages of early strength,high strength and good sulfate-resistant property.Therefore,it has been widely used in ocean engineering in recent years.Since river sand is in great shortage in island and coastal areas,marine sand has become the only choice for concrete engineering.However,there are few literatures about the performance of marine sand SAC under carbon-chlorine coupling erosion as well as the corrosion performance of the steel bar in SAC cement after employing marine sand,which have restrained the promotion and application of marine sand SAC cement in ocean engineering.This paper conducts carbonization and carbon-chlorine experiments by varying the dosage of the kaolinic as well as corrosion experiments of the steel bar by varying the types of the corrosion inhibitors(triethanolamine and so on),dosage and admixture(coal ash,mineral powder and so on).Furthermore,it also studies the carbon-chlorine coupling performance of marine sand SAC cement and the corrosion resistance performance through combining the structure of nitrogen adsorption,XRD,FSEM and other microcosmic experiments,thus revealing its mechanism.The result of the research indicates that:1.When accelerating carbonation,carbonation depth of marine sand SAC concrete carbonation 14d is lower than marine sand OPC concrete.However,when carbonizing 70d,compared with the marine sand OPC concrete,by reason of carbonation will increase average pore size and total pore volume of the marine sand SAC concrete,the depth of carbonation increased 6.8mm.Compared with the standard at the same age stage,the ratio of compressive strength is 0.818,Cl" curing rate ratio of 0.622.And added 20%metakaolin can reduce the carbonation depth of marine sand SAC concrete,as well as reduce the curing rate of Cl-decrease amplitude,but improve the compressive strength reduction effect is not obvious.2.When soak NaCl solution and NaCl solution dry-wet circulation,the free chloride ion erosion depth ratio of marine sand SAC and marine sand OPC concrete is 0.545 and 0.667.And added metakaolin can reduce the erosion depth of free Cl-,the best effect dosage is 20%.3.During carbon-chlorine coupling,with the age of corrosion increase,marine sand SAC of concrete carbonation depth gradually accelerated along with age increase,112 d up to 13.7 mm.Carbon-chlorine coupling increases slightly before compressive strength under 28 d,then decreased,Compared with the standard at the same age stage,the strength decreased by 9.9%.Compared with accelerated carbonation,due to the NaCl may crystal in the pore,marine sand SAC concrete average aperture and cumulative pore volume are smaller under the action of carbon-chlorine coupling.When carbon-chlorine coupling 112 d,the depth of marine sand SAC concrete chloride ion erosion is up to 20 mm.compared to marine sand SAC concrete under NaCl solution soaking and NaCl solution with dry-wet circulation,respectively increased by 10 mm and 4 mm.Adding Metakaolin can reduce carbonation depth of carbon-chlorine coupling of the marine sand SAC concrete.4.In marine sand SAC concrete,added moderate amount of rust and corrosion inhibitor can effectively reduce the polarization potential,delay corrosion of rebar.Three kinds of rust inhibitors corrosion effect were,in order,triethanolamine>single fluorine sodium phosphate>nitrous acid lithium.When added double 1.5%triethanolamine and 20%of metakaolin,its polarization is close to SAC river sand concrete,that is to say that combination of the two can effectively improve the reinforced protection performance of the marine sand SAC concrete. |
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