Insight to the effect of adding cow hair and pig bristles to lime mortars: Towards obtaining more sustainable construction products recycling waste animal byproducts.

The increase in demand for natural resources due to the growth of the world population is generating an unprecedented increase in waste, and the unsustainability of this situation has induced the change towards a more environmentally friendly economy, the so-called “Green Economy”. Through the new policies for waste management, its reuse in other industrial processes is being encouraged, favouring “Zero Waste” initiatives. This aims to minimize the emission of greenhouse gases that could accelerate climate change, as well as to the reduction of associated energy expenditure. In Spain, two of the sectors that generate the most waste are construction and agriculture, especially linked to animal by-products not intended for human consumption (SANDACH, by its Spanish acronym). In line with these new trends, new initiatives are required to promote the reuse of this waste and the development of more sustainable construction products that involve the reduction of the carbon footprint. Therefore, the main goal of this work is to better understand the effect of adding natural fibres of animal origin, in this case cow hair and pig bristles, to lime mortars for their use both in modern construction and its application in repair historical mortars. In this way, we aim to achieve a double goal: on the one hand, to obtain information about the quality of the result of combining these products; and on the other hand, to reduce CO₂ production by avoiding the incineration of animal by-products not usable in other sectors, finally producing a more sustainable mortar. The specific objectives proposed are: 1) to compare the quality of lime mortars considering the addition of hairs, bristles or with combined proportions of both fibres, with respect to control samples without fibres; 2) to evaluate if the speed and degree of carbonation are affected by the addition of fibres; 3) to identify deterioration processes that may reduce the quality of lime mortars due to aging in the laboratory and outdoors; and 4) to establish optimal production and handling conditions in collaboration with regional or national companies interested in the use of this product. To achieve these goals, in this first stage we will present the preliminary results comparing a mortar without fibres as control sample, with 3 sets of samples with different fibre proportions (containing 10 g or 20 g of cow hair or pig hair per 2 kg), as well as a mixture of both types of fibres (5+5 g and 10+10 g per 2 kg). Based on these results, it will be possible to consider the possibility of increasing the quantity of fibres until reaching an acceptable limit of workability and usefulness without compromising the quality of these mortars.

Acknowledgements: This study was financially supported by the Research Project TED2021-132417A-I00 funded by MCIN/AEI /10.13039/501100011033 and by the European Union NextGenerationEU/ PRTR and E. Molina-Piernas acknowledges co‑funding from the European Social Fund (D1113102E3) and Junta de Andalucía.