The Study Of Mixing Methods Of Engineered Cementitious Composites

ECC,short for Engineered Cementitious Composites,is an ultra ductile mortar based composite reinforced with short random fibers.ECC,unlike common fiber reinforced concrete, is a micromechanically designed material.This means that the mechanical interactions between fiber,matrix and interface are taken into account by a micromechanical model which relates these constituent properties to composite response.As a result,guidelines for selection of fiber, matrix and interface characteristics advantageous for composite properties are made available. Macroscopically,the most significant characteristics of ECC is its tensile strain-hardening behavior with strain capacity in the range of 3-7%,yet the fiber content is typically less than 2% by volume.The ultra high-ductility is achieved by optimizing the microstructure of the composite employing micromechanical models.During strain-hardening,multiple micro cracks limited to about 60μm in crack-width form along the length of the tensile specimen.ECC may be regarded as an optimized high performance fiber reinforced cementitious composite (HPFRC).Mixing method has an important affect on the performance of ECC,the dosage of admixture and mixing methods of Polyvinyl Alcohol fiber reinforced Engineered Cementitious Composites were investigated based on the mixing methods of fiber reinforced concrete and research findings at home and abroad.The specifics are as follows:(1) By slump-flow experiments of PVA-ECC mixture,the influence of mixing methods of HPMC,the mixing batch of fiber,mixing procedure and the time of mixing on the liquidity of PVA-ECC mixture were studied,the mixing methods which is in favor of PVA-ECC mixture liquidity is put forward.(2) The influence of mixing methods of HPMC,the mixing batch of fiber,mixing procedure and the time of mixing on the bending resistance performance,bending property and other mechanical property of PVA-ECC were studied by four-point-bend experiments of PVA-ECC sheet and beam and experiments of compressive strength.The best mixing method of PVA-ECC was proposed by combing with the results of experiments of mixture liquidity.(3) By experiments of slump-flow of PVA-ECC mixture,flow test,V-funnel test, U-channel test,the influence of various dosage of super plasticizer admixture and HPMC on the workability of PVA-ECC mixture was investigated,the proportion of self compacting PVA-ECC was obtained.(4) Through four-point bending test for sheets and beams of PVA-ECC,it was studied the effect in different dosage of super plasticizer and HPMC.In addition,it modified the proportion of admixture of self-compacting PVA-ECC through the mechanical properties. The contents and achievements of this research can play a guiding role in mixing method and admixture of self-compacting PVA-ECC.