Significance of property mismatch in the patch repair of structural concrete Part 2: Axially loaded reinforced concrete members

Approximately £500 m is spent in the UK each year on the repair of concrete members. Despite the existence of this large and expanding market, little fundamental attention has been paid to the structural implications of property mismatch between patch repair materials and the substrate reinforced concrete. Part 1 of this Paper has discussed the measurement of mechanical and physical properties of repair systems considered relevant to the subsequent structural performance of a repaired member. Using the range of material properties determined for nine generically different systems, two- and three-dimensional linear elastic finite element techniques have been used to elucidate axial load transfer through simple patch repairs in reinforced concrete members. Areas of localized concentrated stress and requirements for especially high values of adhesion become apparent when the modulus of the repair material differs significantly from that of the concrete substrate. Comparison of the finite element results with those from identical experimental prisms repaired with the nine selected systems showed good agreement within the elastic range, provided that there were no interfacial adhesion failures. Such failures occurred with polyester resin mortars and unmodified cementitious mortars due to early shrinkage.