Durability of textile reinforced mortar (TRM) systems

Textile Reinforced Mortar (TRM) materials represent an innovative strengthening technique particularly used in the retrofitting of masonry structures. These systems are composed of a fiber net embedded in an inorganic matrix (lime or cementitious mortar) sometimes enriched with short fibers. The knowledge of the durability of these composite materials is of primary importance in order to calibrate design guidelines and to evaluate the design life of the strengthened structure. In the literature, only few experimental works are available, and only a limited number of systems and aggressive environments are considered. In this paper, the preliminary results of an ongoing extensive experimental campaign at the Material Testing Laboratory of the Politecnico di Milano are described. A series of TRM (also pre-cracked) coupons were subjected to freeze and thaw cycles. After the conditioning, the samples were subjected to tensile tests and the results were compared with those obtained by tests performed on control specimens. In particular, the slopes of the different phases of the stress-strain curves and the stress reached at the onset of cracking and at collapse are compared. Different materials were analyzed, composed of lime or cementitious mortars and glass, PBO, and carbon fibers. The experimental results obtained and the analysis reported could represent an important contribution in the calibration of environmental coefficient for design procedures.