Full Scale Tests on Hollow Brick Masonry Walls Repaired with Steel Fiber Reinforced Mortar Coating

An experimental study on 3 m long and 2 m high Unreinforced Masonry (URM) walls repaired or strengthened with thin Steel Fiber Reinforced Mortar (SFRM) coating is presented. The samples are made with hollow-clay brick masonry having mechanical properties typical of existing masonry buildings constructed in Italy between the ‘50s and ‘70s of the 20th century. The walls are subjected to a constant vertical load combined with a lateral reverse cyclic quasi-static load. Unlike traditional strengthening coating techniques, the one herein proposed adopts a thinner thickness (25 mm) and high strength short steel fibers as a reinforcement uniformly spread within the mortar matrix. The SFRM overlay is anchored to the masonry surface by nylon wall plugs with steel screws (~9 connectors/m2) drilled into masonry units. The study includes a total of four tests: two on unstrengthened walls and two on the previous specimens, repaired and reinforced with SFRM coating on both sides. A novel feature is represented by a series of steel rebars placed along the wall base to anchor the SFRM coating to the wall foundation. The experimental results show the strength and stiffness improvement provided by the proposed technique. Moreover, a critical discussion on the effectiveness of the coating-to-foundation connection is reported.