Design,preparation And Performance Study Of EPS Concrete Modified By Foam Particles

Expanded polystyrene(EPS)concrete is an ideal wall insulation material It has low density,water absorption ability,and thermal conductivity.Compared to ordinary concrete,the strength of EPS concrete is relatively low.It is mainly used for functional materials.At present,most buildings waste a lot of energy because of the poor thermal insulation of the exterior wall.In order to reduce building energy consumption,the thermal performance of exterior wall must be improved.The exterior wall should have the character of good thermal insulation,as well as sufficient load-bearing ability.In order to reduce the building energy consumption,it is particularly necessary to extend EPS concrete into structural materials;therefore,the strength of EPS concrete needs to be improved.The main research work and findings of this study are as follows.(1)A new type of EPS beads strengthening technology is proposed in this study.EPS beads were wrapped on the surface by magnesium phosphate cement(MPC),ultra-high performance concrete(UHPC),and waterborne polyurethane(WPU),the test results show that the wrapping material form a shell structure on the surface of EPS beads;the hydrophilic property of the wrapped EPS beads have been significantly improved;the EPS beads are in close contact with the wrapped materials.(2)The uniformity of EPS concrete is qualitatively evaluated by slice method,EPS area distribution method and PVC quality test method is used to quantitatively evaluate the uniformity of EPS concrete.The workability and uniformity of concrete with EPS beads wrapped have been significantly improved.The floating problem of EPS beads has been resolved.(3)The cube compression test,prism bending test and prism uniaxial compression test of fo ur groups of EPS concrete were completed respectively,the failure characteristics of the specimen was analyzed.The uniaxial compression performance of each group of specimens was systematically studied,and the complete stress-strain curve equation is proposed.The cube compressive strength of concrete is increased by 80-110%,the flexural strength of concrete is increased by 40-90%,the axial compressive strength of concrete with EPS beads wrapped is increased by 50%to 75%compared with unwrapped ones.The concrete with EPS beads wrapped by MPC and WPU showed obvious brittleness.The concrete with EPS beads wrapped by UHPC has axial compressive strength close to that of EPS concrete wrapped with MPC and WPU,but has larger ductility coefficient(150%),a larger toughness coefficient(50-90%larger),a higher energy dissipation coefficient(40%larger),and larger residual stress.It is more suitable for structural materials.The proposed stress-strain model is in good agreement with the experimental results,which can accurately describe the stress and deformation characteristics of EPS concrete under uniaxial compression and has good applicability.The discovery of this study provides background knowledge for structural analysis and design with this type of concrete;it provides a basis for using EPS concrete as structural materials.(4)The concrete with EPS beads wrapped and unwrapped was tested by scanning electron microscope(SEM)and acoustic emission(AE).The SEM test shows that the wrapped EPS beads are in close contact with the cement base,the gap width in the ITZ is much smaller than that of the unwrapped EPS beads.The results of acoustic emission test show that comparing with EPS unwrapped,the concrete with EPS wrapped has characteristics of more impact counts,high cumulative energy,large amplitude and wide high-frequency distribution,which showed stronger energy consumption and bearing capacity.Test results of scanning electron microscope and acoustic emission explained the macro mechanical behavior of the concrete with EPS beads wrapped from the micro level.(5)The carbonation resistance,frost resistance and shrinkage behavior of four groups of EPS concrete were tested.Combined with SEM test,the mechanism of durability enhancement of concrete with EPS beads wrapped was explained.In this study,the frost resistance of EPS concrete was emphatically analyzed,the frost resistance criterion of EPS concrete was revealed.Besides,it take the relative dynamic elastic modulus as the damage variable and the freeze-thaw damage model of EPS concrete is established.According to the freeze-thaw damage test results,the EPS concrete freeze-thaw damage model is fitted and the attenuation equation of relative dynamic elastic modulus of EPS concrete is proposed.Based on the results of frost resistance test,the frost resistance life of these four type of EPS concrete is predicted.(6)The finite element model of modified EPS concrete was established,and their analysis results for EPS beads wrapped and unwrapped were compared.The influence of EPS beads coating on the mechanical properties of concrete was analyzed,it was found that EPS beads coating can significantly improve the mechanical properties of EPS concrete.Beside,the effects of different wrapping materials on the mechanical properties of EPS concrete was analyzed,it was found that the stronger the wrapping material of EPS beads,the stronger the concrete.Based on the finite element test results,a micro mechanical model of concrete with EPS wrapped is proposed and the strengthening mechanism of EPS concrete by wrapping layer is explained.The research results of this study are of great significance for EPS concrete used in structural material and fabricated lightweight wallboard.It is significant to promote low-carbon buildings and reduce building energy consumption.