The interest in bio-composites has grown considerably in recent years due to good mechanical properties, recyclability opportunities and also thank to the need of minimum energy for their production, in line with recent headlines for low emission of carbon dioxide during manufacturing process. Overall biocomposites have become very attractive for retrofitting masonry/timber structures and in general any type of structure that present low or poor quality materials, that do not require the need of high performance (strength and modulus) fibers.

Among the countless bio-fibers, the ones that are of particular interest are flax and hemp fibers for strengthening and retrofitting historical and civil structures. Like all vegetable fibers, they have an extremely complex molecular structure consisting of a variety of biopolymers (lignin, crystalline cellulose, pectin..etc) and nano-structured architecture that give these fibers excellent mechanical properties.

The main characteristics of flax and hemp fibers are:

• relatively high ultimate tensile strength and deformation;
• low acoustic, electrical and thermal conductivity;
• recyclability;
• ideal for matrices of resin as well as mortars.

Thanks to their mechanical properties, biocomposites are ideal for strengthening masonry elements such as vaults, arches, etc. and structural elements with low property substrates. Bio-composites are available both as unidirectional as well as grids with density and strength of fiber properly engineered to meet high quality standards. Upon request, Fidia's engineers are able the necessary support to meet any client's needs.

According to the CNR-DT 200/2004 design guidelines, "Guide for the Design and Construction of Externally Bonded FRP Systems for Strengthening Existing Structures" FRP basalt composite materials supplied by FIDIA S.r.l. have the following nomenclature:

• FIDFLAX or FIDHEMP indicating the fibers typology (flax or hemp);
• UNI, BID, QUADRI corresponding to the direction of fibers arrangement (unidirectional, bidirectional and quadric-axial);
• the number following the above-mentioned name (200, 300, 320, 400 etc.) explains the sheet weight, generally expressed in g/m2;
• the nomenclature HS represent the acronym of High Strength;
• the last number (40 or 50.) corresponds to the elastic modulus of the material and is expressed in Gpa.