Mechanical properties and durability of biobased fabric-reinforced lime composites intended for strengthening historical masonry structures

Abstract

The use of lime-based composites reinforced with fabrics made of natural fibers, is a promising solution for the strengthening of historical masonry structures owing to its moderate mechanical strength, similar color and chemical compatibility, avoiding damage on the historical structure and contributing to crack-width control. In this study, a new lime-based composite reinforced with flax nonwoven fabrics is mechanically characterized to study its reinforcement potential in terms of strength, and stress distribution. To this end, laminate plates with lime/metakaolin matrix and four to six layers of fabric reinforcement were produced and totally carbonated in a CO2 chamber. Both the mechanical (flexural and tensile) and durability (against wet-dry cycles) properties of the composite were subsequently assessed. Furthermore, Digital Image Correlation (DIC) was carried out on tensile testing to study the stress distribution. The 6-layer composites displayed the best performance (with flexural and tensile strengths of approximately 5.3 MPa and 2.5 MPa, respectively), followed by the 5-layer and the 4-layer composites. The DIC analysis revealed a higher stress distribution in the 6-layer composites, with an increased number of cracks, although having a lower severity. As for durability, a decrease of 30–45% is observed in flexural strength, and of 6–18% in tensile strength, depending on the number of reinforcing layers. SEM analysis refers to fiber/matrix debonding as the cause of this decrease. No damage has been observed on the fiber surface, which retains its reinforcing capacity. All of the composites displayed strain-hardening behavior in both the unaged and aged conditions. Study outcomes are intended to serve as the basis for the creation of a future, compatible, reliable, and sustainable system given its potential application in the historical restoration of masonry structures.