Bio-Stabilised Earthen Blocks: A Critical Study on Compression Tests of Immersed Samples: Fid-Bau Portal

Bio-Stabilised Earthen Blocks: A Critical Study on Compression Tests of Immersed Samples

Guihéneuf, Simon / Perrot, Arnaud / Rangeard, Damien / Cocheteux, Mathilde

Currently, much consideration is given to earthen building materials regarding their highly sustainable properties. Numerous studies have highlighted their structural ability but their water sensitivity is still limiting a potentially more spread use. To limit this sensitivity several studies have recently brought out the positive effects of bio-stabilisers such as linseed oil or xanthan gum. These recent developments allow bio-stabilized earthen materials to be resistant to immersion in water. Also, a French experimental standard (XP P 13-901) for compressed earth blocks already asks for a minimal compressive strength after a two-hour immersion that is overly severe and is difficult to satisfy without the addition of high contents of hydraulic binders. In this paper, a critical study of this compressive test after immersion is conducted on bio-stabilized (linseed oil and xanthan gum) samples of different Breton earths. Some testing adjustments are suggested and the water-diffusion in the samples is followed and linked to previously obtained capillary absorption coefficients. It is shown that the effect of immersion on the mechanical strength depends on the sample size and that an equivalence between size and immersion time can be made based on an equivalent penetration depth. Linseed oil and xanthan gum help to significantly increase the compressive strength of the earthen materials after immersion and allow to avoid the addition of hydraulic binders in earthen blocks to obtained a strong water resistance. The water diffusion in the sample during the immersion can be linked to capillary absorption behaviour, thus a water content and a compressive strength after a given time of immersion could be easily predicted.