Physical and mechanical properties of plasters incorporating aerogel granules and polypropylene monofilament fibres

- Experimental insulating plasters comprising lime, aerogel particles and polypropylene monofilament fibres are investigated.
- Replacing sand aggregate with aerogel significantly reduces both thermal conductivity and strength.
- Incorporating polypropylene fibres greatly improves flexibility and toughness.
- Incorporating aerogel granules in a plaster mix significantly improves vapour permeability.

Growing concern over global warming in recent years has required buildings to become significantly more energy efficient. One of the main ways of achieving this aim has been through the use of innovative materials to facilitate improvements in levels of building insulation. This paper describes the use of aerogel granules as an additive material for lime-based plasters, with the objective of improving the thermal efficiency of buildings whilst maintaining or improving vapour permeability.Five experimental lime composite mixes were prepared, with lime putty as the binder material and aggregate comprising differing proportions of standard sand and aerogel granules. Previous work had already confirmed very low strengths for plaster mixes containing aerogel granules alone as the aggregate material; therefore, polypropylene fibres were incorporated as a secondary additive material to improve the mechanical properties and reduce strength loss attributed to shrinkage and cracking.The flexural strength, compressive strength, thermal conductivity and water vapour permeability of lime composite mortars containing different volume fractions of aerogel were determined. Microstructures were examined using scanning electron microscopy and transmission electron microscopy. The results showed that aerogel granules can be successfully incorporated into lime plasters to improve thermal efficiency. The addition of aerogel was also found to improve moisture vapour permeability. The inclusion of polypropylene fibres in aerogel plasters was effective in reducing shrinkage and cracking to acceptable levels. Experimental mixes exhibited a slight reduction in strength compared to standard plaster mixes, although this was compensated for by a high level of flexibility and toughness.This work provides innovative information on utilising aerogel granules as an insulating plaster additive by addressing the issues of strength and flexibility, properties that are not normally associated with aerogel but which are of importance in a functional plaster material.