Study On Mechanical Properties Of Geopolymer Concrete With Steel Fiber At Room Temperature And After High Temperature

Using fly ash,slag and other industrial wastes instead of cement as cementing materials and using alkali solution to stimulate the preparation of geopolymer concrete has the advantages of reducing carbon dioxide emission and effectively utilizing waste materials,so it is a good substitute for ordinary concrete.By adding steel fiber into geopolymer concrete,the brittleness of geopolymer concrete can be improved,the overall performance of geopolymer concrete can be improved,and the new material can be better applied in practical engineering.Due to natural or man-made disasters,concrete structures may also suffer from high temperature.In order to promote the engineering application and research of steel fiber doped geopolymer concrete,it is necessary to determine its basic mechanical properties,constitutive relationship model and in-depth understanding of its microstructure.Therefore,this paper studies the mechanical properties of steel fiber doped geopolymer concrete at normal temperature and after high temperature.The main work is as follows:(1)144 cube blocks and 36 prism blocks were tested at room temperature,and the influences of steel fiber volume content(0,0.5%,1%,1.5% and 2%),age(7d and 28d)and water-binder ratio(0.45,0.5 and 0.55)on the properties of steel fiber geopolymer concrete were considered.The mechanical properties such as working performance,failure mode,compressive strength,splitting tensile strength,elastic modulus,peak strain,compressive stress-strain curve and toughness index were analyzed,and the relationship between the main mechanical properties and the characteristic content of steel fiber was obtained,and the uniaxial compression constitutive model of steel fiber doped geopolymer concrete was established at room temperature.(2)The experimental study of 144 cubes and 72 prismatic blocks was carried out at high temperature.Main test parameters for high temperature(20℃,200℃,400℃,600℃ and800℃),steel fiber volume content(0,1% and 2%),the cooling way(the natural cooling and spilt water cooling)and concrete type(Steel fiber-reinforced polymer concrete and Steel fiberreinforced ordinary concrete),mechanical properties such as apparent properties,failure forms,Compressive strength,Splitting tensile strength,Elastic modulus,Peak strain and Toughness indexes were analyzed.Based on the main mechanical index formula at normal temperature and the influence of high temperature temperature,the relationship between mechanical properties and high temperature after high temperature was obtained.Based on the uniaxial compression constitutive model at normal temperature,The uniaxial compression constitutive model of geopolymer concrete with steel fiber after high temperature is proposed.(3)Electron microscope scanning test(SEM)was conducted on 12 groups of geopolymer concrete and ordinary concrete doped with steel fiber at normal temperature and high temperature,and X-ray diffraction test(XRD)was conducted on 10 groups of specimens at normal temperature and high temperature.The microstructure,weak zone,interface transition zone between steel fiber and matrix,interface transition zone between aggregate and matrix,phase change and other microscopic mechanisms of steel fiber doped geopolymer concrete at normal temperature and high temperature were analyzed.The differences between the two types of concrete in microstructure were compared,and the deterioration mechanism of performance of the two types of concrete after high temperature action and the principle of interaction between matrix and steel fiber were revealed.