Structural Investigation of an Alternative Cordwood Binder

Abstract

Cordwood masonry is a vernacular building technique that utilizes short pieces of wood in a binder matrix. The binder matrix used today is usually cement, lime-mortar or clay all with various downsides including thermal bridging, high environmental impact or difficulties of separating the materials at end of life. A novel binder made of a mixture of starch-based glue, lignin and saw dust is investigated to determine if the mechanical properties make it suitable to serve as an alternative. Samples of the binder are tested experimentally to find how it reacts to an outdoor environment and compressive strength. The parameters are used to develop a model of a wall element for FE-analysis that is compared with calculations based on Eurocode to verify the suitability of the material. This thesis found the best binder candidate to be one with two parts lignin and one part saw dust. This binder has a compressive strength of 0.4 N/mm2 and a modulus of elasticity of 13.7 N/mm2. This is sufficient for walls in a one-story building according to both the Eurocode calculations and the FE-model. This binder candidate withstood the weather during the three-month trial with only little damage while other candidates partially dissolved after 30-40 days in an exposed environment. The binder performed even better in a semi-sheltered environment, with little to no visible damage.