Effect of chloride attack in combination with mechanical loading on durability of fiber reinforced lightweight waste aggregate concrete

Abstract

The dissertation thesis explores the mechanical properties, durability, and service life estimations of lightweight concrete made from waste red ceramic fine aggregate, reinforced with copper-coated crimped steel fibers. The research encompasses a literature review focusing on the characteristics of lightweight concrete, theoretical modeling of chloride ingress, and service life predictions. The key objectives were to create a mixture from waste material, evaluate its resistance to chloride ions, model chloride ingress into solid and damaged concrete, and predict service life and residual strength under simultaneous mechanical and environmental loading. The thesis incorporates selected mathematical chloride ingress models in concrete, ranging from analytical equations to finite element method simulations, and more precise tensile characteristics obtained through inverse analysis of a three-point bending test. Although the proposed concrete does not reach the strength and durability of normal concrete, it has been found that in its integral state, it can reach a service life of 50 years with a greater thickness of cover and in a less aggressive environment defined by selected boundary conditions. Research suggests that fibers, without considering their corrosion potential, reduce crack formation and increase residual strength. The optimum level of fiber reinforcement appears to be 1 % of the concrete volume. A higher percentage of fiber reinforcement resulted in poorer results; however, this might be caused by a lack of data from three-point bending tests. The appendices include a literature review on test methods related to chloride ingress into concrete, an overview of the used analytical models, thermal properties of the designed concrete, figures from the APIS iteration process, and images related to the modeled case study in ATENA. The thesis investigates the use of waste material for concrete production and provides insights into the estimation of the service life of concrete structures under mechanical and environmental loading, with a focus on the effect of fiber reinforcement.