Durability of fibre reinforced cementitious composites: coupling mechanical and chloride environment loads

Abstract

Fibre reinforced cementitious composites (FRCC) may be characterized by their improved performance namely in terms of tensile ductility, accompanied by multiple cracking, and potentially lower permeability to liquid and gas in cracked state. Cracking, which is nearly inevitable, can occur due to applied structural loading, shrinkage, chemical attack, thermal deformations and restrained condition. Even though might not be a structural problem, cracking could be a durability issue, since it considerably modifies the transport properties of the cementitious composite and, as consequence, accelerates the deterioration process, which can significantly impair the long term service life of a structure or element. Literature indicates that, particularly for chloride penetration, the presence of cracks and/or load condition, causes a more deleterious attack compared to standard durability test on sound specimens composites. Contributing to that concern a methodology for accessing chloride attack in loaded and/or cracked FRCC is proposed. Cracking procedure and specimen geometry were selected, considering that cracks produced in laboratory should resemble those in structural elements (beams). Thus, FRCC specimens were firstly pre-loaded under four point bending up to a pre-defined crack width. The crack width was kept using special stainless steel frame. In addition, cracked but not loaded specimens were considered and sound specimens were used as reference. Then, specimens were exposed to wet-dry cycles in a chloride solution. It is argued that the chloride penetration is definitively influenced by the load and cracking conditions, which promoted a higher penetration depth leading to a severe fibres corrosion, which also compromised the mechanical performance of FRCC.