A Study On Mechanical Properties And Fracture Properties Of Engineering Geopolymer Composites

Professor Victor Li of the University of Michigan,USA,and others designed an ultra-high-performance fiber-reinforced cement-based material ECC(Engineered Cementitious Composites)for the first time based on the basic principles of micromechanics and fracture mechanics.Some scholars also call it strain hardening cement-based composite SHCC.The performance advantages of ECC make it have a broad space for development in civil engineering,but it still uses silicate series of cement to prepare substrates.Like other traditional Portland cement-based materials,it faces many resources and Environmental issues.Engineered Geopolymer Composites(EGC)not only have similar mechanical properties to ECC,but also its cementitious materials are derived from industrial waste.It is a green and environment-friendly building material.Due to the late appearance of EGC,at this stage,there is still much room for improvement in the study.Based on the preparation method of ECC and the geopolymer preparation technology,this paper prepared high ductility EGC materials with tensile properties dozens of times that of ordinary mortar and geopolymer mortar.In addition,the subject also analyzed the fracture properties and fiber pull-out properties of EGC.The main content are as follows:(1)The basic mechanical properties of the specimens were tested through compression test,bending test and tensile test.The results show that compared with geopolymer matrix,the tensile properties and bending properties of EGC are greatly improved.(2)The fracture energy of the specimens with different mix proportions were obtained through the three-point bending test of the notched beam,and the micro fracture energy and elastic modulus were obtained through the nanoindentation test.The study found that the EGC breaking energy in this test is 50-100 times that of the geopolymer substrate.The results of the nanoindentation test are similar to those obtained from the macro test.(3)The fracture toughness of the notched beam was also analyzed by the three-point bending test.EGC is significantly different from geopolymer matrix in that the unstable fracture toughness of EGC is much higher than the fracture toughness.EGC experienced obvious stable propagation deformation before starting unstable cracking,during which the crack length continued to expand.(4)Through the single fiber pull-out test,the bridging ability of the fiber was tested,and its related parameters were calculated.The results show that the chemical bonding force and interfacial friction of the EGC matrix and fiber increase with the increase of curing temperature.The slag is beneficial to enhance the fiber/matrix interface performance,but the excessively high interface performance is not conducive to the full play of the fiber bridging effect.