The compressive strength of lignosulphonate stabilised extruded earth masonry units

Earthen (unfired clay) bricks offer several distinct advantages over conventional fired clay bricks and other high energy masonry units. Most notably there is significantly lower environmental impact, including carbon emissions during manufacture, than comparable products, with unfired clay bricks having an estimated 14% of the energy of fired bricks and 25% of concrete blocks. Earth construction is able to provide passive environmental controls; including the regulation of temperature and humidity which can be utilized in unfired clay masonry to improve internal levels of comfort. The commercialisation of unfired clay masonry as a structural material is dependent on several factors. Modern earthen construction methods need to fit in with demands of contemporary construction, compete commercially and provide a high quality consistent performance. To ensure that thin walled unfired clay masonry can be used in a load bearing application, it is important to consider the effect high moisture content, due to accidental and intentional wetting, has on the strength of the material as well as the building unit. The proposed paper presents initial findings from an investigation into the development of low impact alternative stabilisers. Cement and lime are widely used in some countries, but both have an associated embodied energy and carbon emissions that may hinder the benefits of unfired clay as a mainstream building material. The use of lignosulphonate was chosen as a way of minimizing the adverse environmental impacts whilst improving water resilience, an essential requirement for thin walled loadbearing masonry using earth. Unconfined compressive strength of extruded soil samples that have been stabilized by three types of lignosulphonate. Specimens were tested both dry and wet as a basis for comparing loss of strength due to exposure to a wet environment.