Assessment of the long term performance of repaired reinforced concrete.

Rational decisions about cost-effective maintenance and structural repair are hampered by the absence of comprehensive data on structural performance of generic repair materials acting compositely with deteriorated concrete elements. In the present climate of durability problems in concrete construction such information is of critical importance. In order to assess long-term structural performance of repaired elements, basic short and long-term properties of generic repair materials are required under various exposure conditions. The principle requirements to ensure satisfactory long-term performance of the repair have always been high dimensional stability and relatively high early bond strength of the repair material with the substrate concrete. As part of a "Brite Euram" project, sponsored by E.E.C., the author has obtained considerable experimental data on properties of three commercially available generic repair materials, which are significant to the subsequent structural behaviour of repaired concrete members. A comparison is also made between the performance of these repair materials with a plain concrete mix of similar strength and stiffness. The following generic repair materials were used: a high performance non-shrinkable concrete, a mineral based cementitious material with no additives and no coarse aggregate size particles, and a cementitious mortar which contains styrene acrylic copolymer with fibre additives. The repair materials are supplied as single component systems by their manufacturers, ready for on-site mixing and use, and require only the addition of clean water. Data on strength, stiffness, post peak-load ductility under compression, swelling, shrinkage and creep deformations under various curing conditions are presented in this thesis. In addition water permeability coefficients and chloride penetration profiles of the materials at various ages of exposure have been determined. A comprehensive compilation of chloride diffusion data is made and an empirical expression is derived for the prediction of long-term chloride penetration profiles based on data obtained at relatively early ages. Application of this prediction model to the field data of some Arabian Gulf structures is made. The influence of repair materials on the performance of reinforced concrete compression members has been studied. A theoretical model is also derived to predict the long-term structural interaction between a repair patch and substrate concrete in short compression members of reinforced concrete. The model is based on the basic properties of materials, such as creep deformation, drying shrinkage and modulus of elasticity. The validity of the model is established on the basis of the experimental data obtained in this study.At the end of the thesis, conclusions and recommendations for future research are made.