Optimized Design Of ECC Based On Local Materials In Kunming,Yunnan

High-performance engineered cementitious composites(ECC)have a high ultimate tensile strain compared with the normal concrete.The mechanical properties of ECC strongly depended on the raw material properties.Meanwhile,based on the same raw materials,ECC perfomance is control led by its mix propotion,which is of crucial importance.This study is based on local materials and industrial wastes in Kunming,Yunnan.Two proportion design methods,Micro-Mechanics and Fracture Mechanics(MMFM)mix proportion design method and the Uni form Design Experiment Method(UDEM)together with Alternating Conditional Expectations(ACE)which is a type of Non-Parametric Regression Analysis(NPRA)are used to design the ECC proportion respectively.Compared with the current widely used material proportion design methods such as rough mix proportion list method,absolute volume method,comprehensive test design method and orthogonal test method,the MMFM method and UDEM-ACE method performes more theoretically and scientificly.Although the MMFM mix proportion design method has better theoretical basis and scientificity for choosing the cement matrix and fiber parameters,MMFM mix proportion design method has more requirements for test instruments,test procedures and the number of test samples,and th is method can only be based on ECC intended test targets for the mix proportion design.Furthermore,MMFM method cannot optimize the ECC design based on specific local materials in a certain area.In order to achieve ECC optimization mix design based on the loacal materials in Kunming,Yunnan,UDEM-ACE mix proportion design method is prefered.UDEM-ACE mix proportion design method can achieve an optimal ECC mix proportion design with design goals.It also improves test efficiency and reduces test cost under the same test conditions.Based on the UDEM-ACE mix proportion design method,this study analyzes and obtains the optimal mix proportion range of ECC based on the local materials in Kunming.The W/B is 0.35 to 0.42,S/B is 0.25 to 0.3,and F/B is around 0.02.Then the axial compression test,axial tensile test and thin plate four-point bending test are conducted for ECC optimal mix proportion verification in the range.The ultimate tensile strain of ECC can reach about 3.8%~6.7%,which is 300~600 times more than that,compared with the normal concrete ultimate tensile strain which is about 0.01%.The ECC fracture energy is 2546.78~5980.43 N/m,which is about 10 ~20 times more than that of the normal concrete fracture energy which is 200~300 N/m.A scanning electron microscope instrument was used to randomly detect fiber dispersion in the tested ECC specimens.It verifies that the ECC and the mixing process have good feasibility.The suggested ECC mix proportionsand the ECC mixing process based on the local materials in Kunming are provided in this study.Also,the application of optimized design of a mix proportion based on UDEM-ACE method can provide theoretical and practical guidance for ECC mix proportion or other cement-based material design in different regions.