Lime-based construction materials: effect of novel additives on physical and chemical properties

Abstract

A lower environmental impact and the realisation that modern cementitious materials are incompatible with older buildings has led to a revival in the use of lime over the last 40 years, for both conservation and new build.
This research investigated the use of novel additive materials that have the potential to improve the physical properties of lime based construction materials, reduce their environmental impact and promote their use.
Five experimental lime based mixes were prepared: an insulating lime plaster incorporating aerogel granules and polypropylene monofilament fibres, mortar containing olivine sand aggregate, ‘hot lime’ mortars with slate and granite aggregate, lime putty and sand mortar with nanosilica and nanolime with graphene oxide. Physical and chemical properties of the mixes containing novel additives were compared with lime containing standard sand as a reference.
The insulating plaster achieved thermal conductivity approximately 75% lower than gypsum plasters, and the addition of fibres imparted a high degree of flexibility. The use of olivine aggregate increased the level of carbonation by 10.4%, which also had the effect of increasing compressive strength. The investigation of ‘hot lime’ mixes did not discover any significant difference compared with lime putty binder, but the use of slate and granite aggregate was found to improve the interconnectedness of the pore structure and increase 91 day compressive strength by 45.7%. compared with silica sand. The addition of nanosilica to the lime putty and sand mortar had the unexpected effect of significantly reducing compressive strength. The effect of graphene oxide appeared to have a positive effect on early carbonation but the evidence was inconclusive.
This work has demonstrated there is significant potential for improving the properties of lime-based construction materials and to reduce the environmental impact associated with their use; however, there is still much further research that should be carried out.

Date of Award	1 May 2020
Original language	English
Awarding Institution	University of Bath
Supervisor	Richard Ball (Supervisor) & Kevin Paine (Supervisor)