Study On Experiment And Constitutive Model Of EPS Concrete And Energy-saving Evaluation

EPS (Expanded Polystyrene) concrete is a new type of energy-savingbuilding materials. Due to the use of waste plastic foam as main parts of theconcrete aggregate to replace sand, EPS concrete has the characteristic of lightweight, thermal insulation, energy saving, waste recycling and environmentalprotection. Materials research and engineering application of EPS concrete havegradually become a research hotspot in the construction and environmentalscience about solid waste recycling. In this paper, based on domestic andinternational previous research work，aiming at the problems of high energyconsumption in northeast China, a kind of EPS concrete suitable for thenortheast area was presented through the profound study of material composition,structure and properties of EPS concrete on the grand, macro, sub-micro andmicro four levels. The mix proportion design and the properties of EPS concretewere researched experimentally, and the damage constitutive model of EPSconcrete was established as theoretical basis of the engineering application ofEPS concrete in the northeast. According to the climate environment of northeast,energy-saving evaluation index system for severe cold area of Northeast wasproposed as tool of building energy-saving assessment. This assessment indexsystem was favorable to promote the popularization and application of buildingenergy-saving technology and new type energy-saving building materials in thenortheast. The research of this paper has important significance for realization ofnational energy-saving and sustainable development.First of all, mechanical performance tests of EPS concrete with differentproportion had been carried out. Through regressive analysis of the test data，thefunction relationship between the compressive strength and the density of EPSconcrete was established. The influence of the components of EPS concrete onthe mechanical performance was studied respectively.The effect of EPS particleswith different size (2~3mm,3~6mm), different volume contents(56%,64%,67%)on the mechanical property of EPS concrete was analyzed; The influence ofdifferent content of silica fume (1%,10%,18%) on EPS concrete compressivestrength was investigated; The different dosage of polypropylene fiber added inEPS concrete was experimented, results showed that the optimal mixing contentof polypropylene fiber is1.3~2.0kg/m3. Based on analysis results of the effect ofdifferent water-cement ratio on compressive strength, the strength model of EPSconcrete applied to mix design was established. The stress-strain relationshipcharacteristics of EPS concrete with different uniaxial compressive strength wasanalyzed, the compression curve of EPS concrete with the lower strengthexhibited obviously three different phases: linear-elasticity, platform as result ofplastic buckling and collapse of cells, strain softening; The stress-strain curve ofEPS concrete with strength more than3MPa was summarized as elasticity, strengthening and softening stages. Microstructure characterization of EPSconcrete by scanning electron microscopy test revealed that the damagemechanism of EPS concrete and polypropylene fiber enhancement mechanism.The fast freeze-thaw and the moisture migration experiments were carried out fordurability of EPS concrete. The chemical composition of EPS concrete wasdetermined by X-ray diffraction method.Secondly, under the theory framework of the continuum damage mechanicsand the classic plastic mechanics，based on damage constitutive model ofconcrete, elastic-plastic damage constitutive model of EPS concrete was proposed.By determining the appropriate damage variable, establishing damageconstitutive equation based on the elastic Helmholtz free energy, defining yieldsurface in the effective stress space for considering plastic deformation, the basicformula of the elastic-plastic damage constitutive model was derived. Parametersof the model were determined according to the experimental data. The damageevolution equations, plastic deformation and the damage constitutive equations ofEPS concrete under uniaxial compressive and tensile was presented. The EPSconcrete elastic-plastic damage model is proved to be effective for describing theprocess of the damage evolution of EPS concrete by the test results.Thirdly, EPS concrete be considering as a two-phase composite material wasstudied on numerical simulation of Meso-level Structure. Two types model ofdifferent EPS aggregate distribution were established to analyze the effect of thedeformation and the relative position of the EPS aggregate on stress distributionof EPS concrete. The failure mechanism of EPS concrete under uniaxialcompression was revealed through analysis of numerical simulation andderivation of theoretical formula. According to the stress distribution of differenttime steps, crack mode of the EPS concrete in strengthening and softening stagewas analyzed.Finally, according to climate characteristics in northeast China,energy-saving evaluation index system for severe cold area of Northeast wasestablished by the fuzzy comprehensive evaluation method of system engineering,considering the impact of new energy-saving materials on modern buildingenergy efficiency, and maneuverability of it was verified through evaluation ofexisting building.