Date

2022-12-15

Author

Pedergnana, Matthieu Joseph

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Traditional earth plasters and renders have a long history of usage adapted to the climate history and culture of the population. They procure aesthetics, protection and comfort in the building they are applied on and they are made of local materials and with local workmanship reducing the environmental footprint of the construction and enhancing the social responsibility of the owner. However, earth plasters need to be upgraded to the standard of the construction industry and they need to fulfil the expectations of the users by becoming a strong and long-lasting material while retaining its ease to use, low environmental impact and comfort procuring properties. Thus, the improvement of plasters should be made with materials which will allow the former properties to be conserved while dealing with the issues of strength improvement, water resistance and cohesion enhancement. This research explores the traditional knowledge on earth plaster and investigates the state-of-art of earth mortar stabilization through the usage of natural and local materials and their adaptation to modern construction standards. Accordingly, a type of soil, known to be used for the production of traditional earth mortar was selected and ten types of sands, eleven types of fibres and thirteen types of biopolymers were chosen amongst the diversity of the material available according to their known or expected beneficial impacts on earth mortars. A reference mortar corresponding to the minimum requirements of the existing standards on earth plaster was produced and after that, the traditionally used sand and fibre were substituted with alternative ones in similar quantities or biopolymers such as molasses, linseed oil or egg white were added in different quantities to the earth mortar. Once fully dried, all specimens were tested for their physical, mechanical, durability, hydric and hygric properties to determine the impact of the changes in the mix on the plaster properties and the possibility to use the selected additives for the production of up-to-standard plasters. Mechanical properties obtained from flexural and compressive tests, water resistance properties obtained from erosion and immersion tests and cohesion properties obtained from abrasion tests were improved by the substitution of sands and fibres with alternative ones but even better results were obtained by the addition of biopolymers such as linseed oil, flour paste, cow dung or casein. Such improvements were obtained without impacting the hygric, properties found from the vapour permeability and vapour sorption tests for flour paste or liquid from the decomposition of hay or casein. In conclusion, it was determined that it is possible to improve the properties of earth plasters and increase their resistance and strength without decreasing their high vapour sorption property. It should be noted that, the results obtained here are only valid for the specific soil chosen with the specific additives tested and more work is necessary to understand the principles behind the improvement of the properties in order to generalize the conclusions of this study for all kinds of earthen materials.

Subject Keywords

Earth Plaster, Earth Construction, Natural materials, Natural Additives, Natural Fibres

URI

https://hdl.handle.net/11511/101853

Collections

Graduate School of Natural and Applied Sciences, Thesis