Restoration of existing historic concrete structures with PE fiber strain hardening cementitious composites

Abstract

Important historic buildings of the 20th century located in the seismogenic zones of the Mediterranean have been designed without the provisions of Eurocode 8; thus, they require strengthening to account for seismic excitations and to be rendered safe for use by future generations. A common disadvantage in historic concrete buildings is the insufficient or even null reinforcement in shear, which usually results in brittle shear failures. This research focuses on the use of a self-compacting, fiber reinforced cementitious composite, which can be applied as cover replacement, or in a thin layer around the perimeter of an existing column, thus providing confinement to the original core and increasing the shear strength of the structural member. Different mix designs prepared in various countries have been examined, all incorporating the use of industrial by-products, such as silica fume or fly ash. The aforementioned mixtures were replicated with the use of locally available raw materials at the laboratories of the University of Cyprus. Polyethylene (PE) fibers, with or without coating, measuring 12 and 18 mm in length were also included in the various mix designs. The mechanical properties of the hardened specimens were compared through compression, tension and flexure tests at 28 and 90 days of curing. Based on the results, a self-compacting mixture, presenting particularly high strengths in direct tension and bending, was eventually chosen to investigate the strengthening of existing historic concrete members.