Effect of basalt fiber length on the behavior of natural hydraulic lime-based mortars

The number of studies aimed at the characterization of reinforced lime-based mortars for use in the rehabilitation of historic buildings is still very small. This fact contrasts with the growing interest of the industry in these products as substitutes for cement mortars, both for their constructive advantages (compatibility requirements) and their lower cost (economic and environmental). For this reason, this study investigates the effect of basalt fiber length on the physical, mechanical, and durability properties of reinforced natural hydraulic lime mortars and provides criteria for selecting optical blends to meet the various performance requirements for their use as building materials for traditional and contemporary structures. Specimens with 1% volume of basalt fibers and lengths of 6, 12, 18, and 24 mm have been tested. The results in fresh mortar show that increasing the fiber length decreases the consistency and bulk density, as well as increases the air content. Regarding the durability properties of hardened mortar, no direct relationship is observed between fiber length and the decrease in the water absorption coefficient of reinforced mortars. Nor is there a clear relationship between fiber length and the increase in Shore hardness and the decrease in adhesive strength in the reinforced mortars. On the contrary, for small lengths (up to 12 mm), there is a direct relationship between fiber length and the increase in other fundamental mechanical properties such as flexural and compressive strength. Based on the results obtained, a predictive model is proposed to determine the amplification factor of flexural and compressive strength as a function of fiber length.