Konstantinos Zavliaris M Sc. Ph.D C.E

In many instances concrete structures need to be either repaired because of degradation or strengthened for upgrading. There is a variety of available repair methods involving techniques for restoring the initial load bearing capacity such as different types of injections and patching and strengthening techniques which aim at increasing the load bearing capacity and the stiffness of the structural members, among which jacketing by means of cast in place concrete, shotcrete and placement of external steel glued plates or epoxy bonded FRPs.

Polymer modified high performance concrete (PMHPC) and mortar (PMHPM) can be used as repair and strengthening materials as is stated and discussed in this paper.
PMHPC and PMHPM have mechanical properties superior to that of normal concrete, controlled workability, high adhesion to normal concrete substrates and high durability.

These properties are further enhanced by the addition of reinforcing fibers of different types (steel, carbon, glass, mineral, PVA-Polyvinyl Alcohol-polypropylene) and in different forms (chopped fibers, mats, meshes).

From the point of view of constructability PMHPC and PMHPM are treated in the same way as that of normal concrete, thus contributing to reliable and cost effective application.

The structural performance of PMHPC and PMHPM is controlled by the cement type, the presence of pozzolans in the mix, the type and size of aggregates, the W/C ratio, the type and the content of Polymer and the type and content of fibers.

From design considerations point of view the shear transfer and slip across the interface, the effect of shrinkage, and the combined action of steel bars and fibers are important and discussed.

Finally a comparison of PMHPC, HPC, normal cement concrete and shotcrete in terms of mechanical resistance, durability, bond across the interface and cost is made which can serve as selection guide for the repair materials and techniques.