Influence of synthetic waste fibres on drying shrinkage cracking and mechanical properties of adobe materials

Earthen construction materials are often vulnerable to cracking due to excessive drying shrinkage deformations because of the high content of fine particles. Thus, fibrous materials can beneficially be added, not only to reduce such crack formation but also to improve the mechanical performance. In this study, recycled polyethylene fibres (R-PE) obtained from discarded fishing nets are added to adobe bricks in different fractions (1–5% by weight). Besides a chemical and geotechnical characterization of the raw materials used for the adobe production (Fine-grained Greenlandic sediments (GP) and a coarser gravel fraction (KG)), the investigation described in this paper includes the mechanical properties and restrained drying shrinkage deformations in manufactured, laboratory-scale adobe specimens. The crack formation due to restrained shrinkage is analysed using a digital image correlation (DIC) technique, which allows detailed, continuous monitoring and quantification of surface deformations. The results show that the evaluated adobe material can provide adequate mechanical properties, which makes the raw materials suitable for adobe brick production. From the mechanical tests, the addition of R-PE fibres resulted in improved flexural toughness, flexural strength and compressive strength. A detailed analysis using the DIC technique revealed that the addition of R-PE fibres significantly and quantitatively reduces the degree of shrinkage cracking.