Dynamic Fracture Toughness of Sandstone Masonry Beams Bound with Fiber-Reinforced Mortars

This paper reports the fracture parameters of bond in stone masonry beams bound with plain and fiber-reinforced mortar. Sandstone blocks were joined together with a modern Type S mortar conforming to the Canadian standard. A companion series was examined employing a hydraulic lime mortar, typically used in the restoration of historical masonry. Based on a previous study, polypropylene microfibers were incorporated at up to 0.50% by volume to achieve superior crack growth resistance. This study evaluated the critical stress intensity factor, the critical effective crack length, and the critical crack mouth opening displacements. The masonry beams were subjected to quasi-static flexure as per ASTM and dynamic bending through a drop weight impact machine that generated stress rates up to 107kPa/s. The study reveals that there is an improvement in the bond strength due to fibers but a difference in the fracture performance between the Type S and hydraulic lime mortars. Whereas with Type S mortar, fibers promote failure through fracture in the stone block especially under dynamic loading, in the hydraulic lime mortar fiber reinforcement moves the failure plane from the interface to within the bulk mortar.