Characterization of the Clay and Fibres for Hygrothermal Modelling

Abstract

Ecomaterials used in traditional construction are experiencing renewed interest for their low environmental impact. However, the lack of reference values for the hygrothermal behaviour of some composite ecomaterials with a low carbon footprint prevents the overall analysis of the structures of buildings designed with these materials. The wood-clay construction system is an ecological and sustainable building system. These materials have great potential for applications in places where housing needs are high, in rural areas of Africa, and have been used for hundreds of years in Europe. The plant fibres improves the hygrothermal, mechanical and weather resistance performance of clay materials. This study determines the water content absorbed by the wheat and corn stalk fibres that will allow the water/clay ratio to be adjusted. For the characterization of red and white clay, the results obtained by the pycnometer method show that the bulk density of the clay is 2.80 and 2.73 with an absolute density of 2.79 g/ml and 2.72 g/ml. The results of the characterization of wheat and corn fibres show that they have the capacity to absorb more than 200% and 120% water by weight in only 25 minutes respectively at 23℃. The water absorption of fibres increases with increasing temperature. This increase contributes to the improvement of the hygrothermal performance of the materials by the restitution of the absorbed humidity, providing a very good feeling of comfort. Samples formulated with 0% to 3% wheat fibre have shown that the addition of fibre reduces the shrinkage of clay materials by 6.35 to 1.53%.

The Impact of Vegetable Fibres on the Shrinkage and Mechanical Properties of Cob Materials

“…The density of the two clays was determined by means of the pycnometer method. For this, a 200 g mass of each clay was taken directly from bags and dried in an oven for 24 h at 110 • C. After drying, each clay quantity collected was separated into four 50 g parts after drying, and three parts of each type of clay were used for testing [40]. Tests were carried out following the ASTM D854 guidelines [41].…”

“…To determine the fibre absorption coefficient, tests were carried out following ASTM D2654 guidelines [42]. The value of the water absorption coefficient, obtained after immersing the fibres in distilled water for 25 min, was used as the water-to-fibre ratio for wetting the fibres before manufacturing the test samples [40].…”