Residual Tensile Strength of Textile Reinforced Mortars After Have Been Exposed to Elevated Temperatures

The present paper demonstrates initial results from an ongoing experimental and analytical research programme on masonry structures confined with Textile Reinforced Mortars (TRMs). In the present experimental stage, three series of uniaxial tensile tests were conducted on TRM coupons having variables the types of fibres and the ambient temperature. The purpose of this experimental investigation is to examine the residual strength of Carbon, and Basalt fibre textiles, used for the preparation of TRMs, after having been exposed to elevated temperatures. Within the scope of the experimental programme, TRM coupons and single fibre yarns have been exposed to three different temperatures (100 ℃, 200 ℃ and 300 ℃) before tensile testing. Subsequently, parts of all specimens were subjected to Scanning Electron Microscopy (SEM) to assess any changes in the microstructure, both of the mortar and the fibres. Dogbone specimens were used to test the TRMs in tension, while prismatic specimens were used to assess the mortar’s flexural tensile and compressive strength. For each temperature group, additional tensile tests were conducted on bare fibre yarns to assess changes in their mechanical properties. A significant decrease in the compressive strength of mortar observed between 20 ℃ and 100 ℃, while there was a tendency for that value to increase gradually from 100 ℃ to 300 ℃. On the other hand, the flexural strength increased between 20 ℃ and 100 ℃ and gradually started to decrease as the temperature rose to 300 ℃. Overall, the residual strength of the TRMs, as the results indicated, decreased with temperature. Two main reasons are identified as responsible for that behaviour; loss of bonding between the fibres and the matrix and deterioration of the fibre’s and the mortar’s original strength. Moreover, changes in the porosity of the mortar and the fibre coating monitored with the use of Scan Electron Microscopy (SEM).