9th International Conference on Fracture Mechanics of Concrete and Concrete Structures DEBILITIES AND STRENGTHS OF FEM-BASED CONSTITUTIVE MODELS FOR THE MATERIAL NONLINEAR ANALYSIS OF STEEL FIBER REINFORCED CONCRETE STRUCTURES

Abstract: During the last decades several improvements have been made on the numerical simulation of concrete type structures by modeling the relevant nonlinearities presented by concrete and reinforcements, as well as their interactions. With the advent of new cement based materials, such is the case of fiber reinforced concrete (FRC), new challenges and difficulties are placed to the computational mechanics community. This work discusses debilities and strengths of constitutive models implemented under the framework of the finite element method (FEM) for the simulation of FRC structures, and points out areas deserving further specific research for more reliable modelling strategies

9thInternational Conference on Fracture Mechanics of Concrete and Concrete Structures Effect of Non-uniform Corrosion on the mechanical properties of corroded steal bars

Abstract: In order to accurately study the mechanical performance of corroded steel bars, chlorine salt drying-wetting cycles experiment for pre-cracked concrete specimens is carried on for 4 years. Based on notch depth measurement and tensile test, the non-uniform coefficient and the mechanical of corroded reinforcement from cracked concrete specimens have been researched. Following conclusions can be concluded: (1) Significant localized corrosion can be observed for reinforcement around cracked areas, slight uniform corrosion occurs for reinforcement in sound concrete; (2) The non-uniform coefficient increases with the increase of corrosion rate as the corrosion rate between 3% to 5%; (3) Based on the existing literature data, mathematical model for 16 mm diameter steel bars has been built to predict corroded rebar mechanical properties; (4) Researching the impact of the corrosion nonuniformity on the ductility of steel bar, it is indicated that the main reason which cause the plasticity reduced and the yield platform disappeared is the nonuniformity of corrosion. It leads to the tensile with eccentricity and produce the additional bending moment, thus making for the brittle fracture of corroded reinforcement

9th International Conference on Fracture Mechanics of Concrete and Concrete Structures STUDY OF SHRINKAGE RESTRAINT EFFECTS AT EARLY-AGE IN ALKALI- ACTIVATED SLAG MORTARS

Abstract: Alkali-activated materials are being increasingly studied nowadays as hydraulic binders. In order to be enrolled in different civil engineering applications, several properties must be characterized. This study focuses on their cracking risk by shrinkage restraints. The current paper summarizes the experimental and numerical results of a project assessing the development of early age properties of an alkali-activated slag mortar. First, an experimental campaign was held in order to quantify hydration heat release and hydration kinetics, to determine the time evolution of the Young modulus and the tensile strength and to measure free shrinkage strains, all in autogenous conditions. Second, two modelling approaches for mechanical properties and shrinkage development were compared. The results showed that the classical approach to characterize the hydration kinetics based on semi-adiabatic calorimetry results isn't suitable for the studied binder because of slow hydration and low heat release. Numerical work was finally conducted in order to predict stress development of a massive structure of alkali-activated slag mortar subjected to internal (self) and external strains' restraints (at mesoscopic and macroscopic scales)