The Preparation And Optimization Design Of High Performance Fiber Cement-Based Composites

The preparation and optimization design of a preparation optimization design of a high performance fiber cement-based composites materiel named Engineering Cementitious Composites (ECC) was studied, aiming to use ECC for bridge strengthening. Firstly, Specimens were prepared with ECC of different fiber type, fiber content, water-binder ratio, sand-binder ratio, cement to fly ash ratio, and mixed fiber. And we got the basic mechanical properties such as flexural properties, tensile properties, compressive properties and flowability of the ECC specimens by four-point bending, direct tensile, cube compression and jumping table tests.Secondly, the effects of the water-binder ratio, sand-binder ratio and cement to fly ash ratio to spray ECC were tested using shotcrete machine. Spary performance such as resilience, patency, smoothness and max thickness were investigated. Meanwhile, ECC specimens with the same mix proportion were made by spraying and casting, and four-point bending and cube compression tests were conducted. So flexural properties and compressive properties of spraying and casting specimens were compared.Lastly, the bearing capacity and cost advantages of using ECC to strengthen bridge were discussed, which were classified by flexural bearing capacity strengthening, shear bearing capacity strengthening and compressive bearing capacity strengthening. Analyses around these tests are as follow:(1) We analyzed the load displacement curve figure from ECC four-point bending test; And the equivalent tensile strength, equivalent ultimate strain and ASTM toughness indexes were extracted from these figures; So the effects of fiber type, fiber content, water-binder ratio, sand-binder ratio, cement to fly ash ratio, and mixed fiber to the ECC bending performance were concluded.(2) We analyzed the effects of water-binder ratio, sand-binder ratio, cement to fly ash ratio to the resilience, patency, smoothness and max thickness performance of spray ECC; And concluded how to prepare spray ECC with a mix proportion based on cast ECC, but different from cast ECC.(3) The bending, shear and compressive bearing capacity strengthening desgin of casting FRP grid reinforced ECC, pasting FRP and enlarging cross section were performed. What’s more, on the basis of considering the service life of each strengthening way, we put forward the’cost of strengthening in whole life cycle’ concept. And then, cost of single strengthening and whole life cycle, were calculated for each strengthening way to achieve the same bending, shear and compressive bearing capacity.