| Due to the availability of a wide variety of repair materials in the concrete repair industry, with a wide range of physical and mechanical properties, selection of repair material for a particular repair of concrete is challenging. Previous studies and the available literature indicate that the failure of concrete repairs is mainly due to improper selection of repair material based on repair material properties, without investigating compatibility between repair material and substrate concrete. The compatibility between repair material and substrate concrete exists when the composite section of repair material and substrate concrete withstands all stresses induced by applied load under different environmental conditions without experiencing distress and deterioration over a designed period of time.; In this dissertation the compatibility between eight repair materials and substrate concrete was investigated in three stages. First, individual properties of the repair materials such as setting time, flow, compressive strength, flexural strength, split tensile strength, bond strength, drying shrinkage, freeze-thaw resistance, and permeability, were determined using standard ASTM test procedures. Second, the compatibility was investigated using a composite beam of repair material and substrate concrete under third point loading. Third, the correlation of repair material properties with the compatibility was investigated to predict the durability of the concrete repair. Based on these studies, a compatibility test method is proposed to examine the compatibility between repair material and substrate concrete.; In the first stage of this research, many variations in the material properties were observed among the eight repair materials. While determining the slant shear bond strength of the repair materials, it was observed that the failures of the composite cylinder specimens did not occur on the slant surface for all repair materials as selected. Those types of failure lead to different values of the bond strength for the same repair materials. Slant shear bond strength test method of ASTM C 882 is widely employed, wherein a composite cylinder prepared with repair material and substrate mortar was tested under compression. In this research the potential reasons behind the different failure patterns as observed were analyzed using experimental and finite element methods. It was observed that the bond strength of the repair materials and the mode of failures depended on the mechanical properties of repair material relative to the properties of substrate mortar. Also, the surface texture of the substrate mortar and the type of curing influenced the bond strength. Based on these findings, suggestions were made to improve the ASTM C928 specification.; In the second stage of this research, composite beams of repair material and substrate concrete were prepared and tested in flexure to simulate tensile stresses in the repaired section. Tensile stresses are generally observed at the joints and in the tension areas in a concrete structure, where the tension in the concrete repair is induced by imposed loads or due to environmental conditions. In this study the flexural strength, failure patterns, and load-deflection curves of the composite beam specimens were compared with the similar results of a control beam to assess the compatibility. In addition, the influence of three curing conditions was evaluated to determine the effect on the compatibility. Compressive strength, flexural strength, split tensile strength, and drying shrinkage of the repair materials and substrate concrete were investigated to aid in the analysis of the compatibility. In this study incompatibility of repair material and substrate concrete refers to a combination of factors such as (i) flexural strength of composite beam as compared to control, (ii) failure patterns (de-bonding and edge cracking), and (iii) behavior of load-deflection curves. It was observed that si... |
