Bio-based building solutions using corn and sunflower stalks. Thermal, acoustic and durability analysis

Abstract

This work has been carried out within the framework of the SAVASCO project, which aims to valorize agricultural by-products, specifically corn and sunflower stalks, by incorporating them into construction materials. This Master's thesis consists of a first part of an experimental type, referring to the thermal and acoustic characterization of some of the materials obtained in the project, and a second part of simulation using Design Builder software. Firstly, the properties of small-scale clay blocks were analyzed. They were developed using sunflower, corn, and hemp as aggregates to lighten and improve their thermal properties. It was found that acoustic absorption and thermal conductivity properties of corn and sunflower blocks were better than hemp blocks. Next, blocks of medium scale were made from clay and sunflower aggregates using a block making machine. Compared to the small blocks, these have a higher density and, consequently, lower sound absorption and higher thermal conductivity were obtained. In addition, insulating panels were developed with the inner part of sunflower stalks (pith) and a natural binder (alginate). Panels had much lower thermal conductivity as compared to blocks. Within the SAVASCO project, a full-scale prototype was designed and built, using the medium blocks and sunflower stalk panels previously characterized. It had four different corners. In the first corner, medium sized blocks were used with an external lime render. In the second corner prefabricated rammed earth panels were installed. In the third corner, conventional brick wall was constructed, on which later the insulation panels were fixed, and lime render applied. In the fourth corner, OSB cavity wall was developed which was later filled with corn stalk aggregate. This Master's thesis was focused on simulating the protype in design builder to determine the best composition of wall. Lime render was also applied on the panel and tested for water absorption using Karsten Tube test. The rendering material was applied in two different thicknesses which were 1cm and 0.5cm respectively. The lesser thickness render had lesser absorption due to its uniformity on the surface.