The “NatuRALiMe ” project: new insights into the study of hempbased mortars for new construction and heritage conservation

Abstract

NatuRALiMe (acronym standing for: “Naturally durable: Developing and testing the Resilience of innovative natural Additives for Lime-based conservation Mortars”) is a two-year project (2013- 2015) funded by the European Union's Seventh Framework Programme (FP7/2007-2013) and being developed at the University of Oxford (UK). The overall aim of this research project is to design suitable and durable mortars made with lime and natural additives (i.e. derivatives of the vegetable and animal world). Interest in studying and using these additives is clearly linked to the need to use sustainable building materials and adopt processes that entail reduced pollution, CO2 emissions and energy consumption. The first part of this project has been especially focused on the study of hemp-based mortars. Hemp is one of the 10 major primary plants grown as a source of bast fibres and hurds, used for various industrial purposes, such as: textiles, cordage, panelling, biofuel, paper, plastic composites and building materials. The use of hemp hurds in mortars involves important modifications to textural, physical-mechanical and hygrothermal properties compared to those of a typical mortar made with a limestone aggregate. This research project aims to investigate all these inter-related aspects to gain an exhaustive knowledge into this peculiar biomaterial. In particular, new durability tests that consider at the same time temperature and humidity changes, rainfall, salt attack and microbiological growth have been designed to study the resilience of hemp-based mortars under different climatic conditions. The research so far demonstrates the importance of bio-receptivity to hemp mortar durability, something that has not to our knowledge been taken adequately into consideration before. This paper introduces the research work undertaken so far on hemp-based mortars under the NatuRALiMe project, aiming to contribute to the knowledge and development of sustainable plant-based building materials.