Mixture Proportion Optimization,FRP Reinforcement And Ballistic Performance Of Concrete Canvas

In rencent decade,Concrete canvas(CC)has shown a promising future in the field of civil and military engineering due to its unique properties and molding method..Like soft cloth,CC can closely cover the surface of arbitrary structure or element during construction,without the needs of mixing equipment.Then just add water to the solid surface of CC or soak in watrer,that hardens to form a thin,durable,waterproof and fire resistant concrete layer.Due to the characterization of fast construction and quick setting and hardening of CC,CC has low labor,equipment and time cost.Currently applications of CC are cover of prefabricated shelter,slope protection,a trackway for vehicles,pedestrians or protection layer for pipe and lining,and defense sector.However,compared with the casting,compacting and finishing processes of conventional plain concrete or fiber/textile reinforced concrete,the impregnation process of dry cement powder into 3D spacer fabric leads to a relative lower initial apparent density of CC,and after spaying water,the final apparent density of hardened CC product is only 70～80%of that for ordinary concrete.Consequently,there is a greater likelihood of producing a hardened matrix with high porosity.Moreover,the 3D spacer fabric is a loose woven material.Therefore,the tensile and flexural strength of CC is low.Apparently,the low tensile and flexural strength significantly limit the application of CC.Consequently,the possibility of improving the mechanical strength of CC has been studied by mixture proportion optimization,and adjusting the geometric pattern of 3D spacer fabric.Unfortunately,the increase in tensile and flexural strength is slightly.However,CC as the thin layer of material usually in application of large-format,besides the compressive strength,tensile,flexural,shear and dimensionl stability of CC in air condition and water condition have more infulence on the CC’s application performance but little work concentrated on the improvement of this mechanical behavior of CC.In addition,CC have been used in military defense sector.while the ballistic performance of CC have not been investigated.Thus,aiming to meet the requirements of CC application,improve its performance and expand its application in the field of engineering.This paper will study on mixture proportion optimization,FRP reinforcement and ballistic performance of concrete canvas,as follows:Start with the mixture proportion optimization of CC,the CAC based cements matrix with gypsum are studied with different mineralogical composition CAC and different dosage of gypsum.The results indicate that the Ternal,Fondu and PP127 CAC with suitable dosage hemihydrate systems have higher compressive strength compared with current CC products and CSA system.The mineralogical composition of the CAC cements have significantly influence on the hydration and compressive development of CAC+gypsum systems.If a little calcium hydroxide is present,the Fondu CAC+gypsum system appears macro-cracks after expansion due to excessive ettringite form.PP127(C12A7 as main mineral phase)system shows excellent formula designability and faster setting time compared with Ternal and fondu CAC(CA as main mineral phase)systems.As focussed on long-term dimensional stability the preferred PP127CAC+heimihydrate system,considering the influence of curing conditions(Air/water curing),dimensional changes are measured from 24 h to 180 d.The results show,CAC system has more excellent drying shrinkage restraint than the current CSA system,shrinkage of air curing samples decrease with the increase of hemihydrate content,while expansion of water curing samples is decrease with the increase of hemihydrate content(below 20%)and increase with the increase of hemihydrate content(beyond 30%),expansion increases with the hemihydrate content exceed or equal to 40%appear macro-craks due to the deformation of Aft.Suitable deformation of Aft can improve the dimensional stability of CC.To improve mechanical properties and retain the advantages of CC at the same time,inspired by strengthening efficiency of structural concrete elements by externally bonded fiber sheet reinforced polymer(EB-FRP),we want to explore the possibility of application FRP reinforcement into CC system.Firstly,a design method is proposed for estimating the ultimate bending moment of the FRP reinforced CC panel.Then mechanical properties(bond,tensile,flexural and shear)of CC and FRP reinforced CC is studied.In which the bond behavior of CC-FRP joint is analysised by test and theoroty to support the design method and explain the reinforcing mechanic;The caculation and test results indicate that the tensile,flexural and shear stength are significantly improved.The performances of targets prepared by CC and FRP reinforced CC under ballistic impact were studied through ballistic impact tests and failure modes analysis.Due to confinement and plastic deformation,the ballistic performance of CC was largely improved by increase the number of layers.It was also found that FRP reinforcement significantly improves the ballistic performance of CC.In addition,all the targets being impacted on the solid surface showed better ballistic resistance than that impacted on the mesh surface.Furthermore,the damage was localized around the projectile trajectory in all cases.This thesis investigated the composite performance enhancement study on concrete canvas and its mechanisms which provide a technical support and theoretical design method to its engineering applications.