Experimental Research On Physical And Mechanical Properties Of High Toughness Fiber Reinforced Cementitious Composites

Ordinary concrete is a kind of brittle material with high compressive strength, low tensile strength and poor deformability, which causes far more serious problems to the service life of concrete structures. Meanwhile, cracked concrete structures need frequently maintaining and lead to enormous economic waste and security risk. From two aspects on the basic principle of micromechanics and fracture mechanics, High toughness fiber reinforced cementitious composites with lightweight, high tensile strength, superior tensile and flexural ability are worked out by incorporating polyvinyl alcohol(PVA) fiber with high elastic modulus into cement mortar matrix. As a new material, Neither do PVA fiber reinforced cementitious composites(PVA-ECC) have an exclusive norm and methods to test the physical and mechanical properties of PVA-ECC nor have a unified standard to evaluate the physical and mechanical properties of PVA-ECC. According to the problems above, the main contents of this dissertation are as follow.First, referring to the study of the ingredients of PVA-ECC and two aspects on the basic principle of micromechanics and fracture mechanics, it is found out that the main factors influencing the physical and mechanical properties of PVA-ECC are fly ash content, sand-cement ratio, water-cement ratio and PVA fiber content. They play different roles when PVA-ECC bears load.Next, 25 different mixture ratio groups of PVA-ECC are schemed out after determining the actual range of every factor based on considerable references and with the help of orthogonal experimental theory. After that, by adjusting the test method in Test Method for Fluidity of Cement Mortar(GBT 2419-2005) to PVA-ECC, the experiment on workability of 25 different mixture ratio groups of PVA-ECC are proceeded to guarantee the feasibility of the subsequent experiments on physical and mechanical properties of PVA-ECC.Then, referring to Standard for Test Method of Mechanical Properties on Ordinary Concrete(GB/T50081-2002), the mechanical indexes reflecting the compressive, flexural and tensile performance of PVA-ECC are extracted from the mechanical test results. The influence of four factors such as fly ash content, sand-cement ratio, water-cement ratio and PVA fiber content on the physical and mechanical properties of PVA-ECC are acquired.Finally, optimization in mix proportion of PVA-ECC for bridge deck pavement, bridge connecting plate and bridge surface expansion joint will be provided through the comprehensive analysis on all the conclusions of PVA-ECC experiments.