Department of Architecture and Civil Engineering

Movement characteristics of lime mortared masonry

At a glance

Funding body: Lhoist Research and Development, University of Bath
Principal investigator: Pete Walker
Co-investigator: Richard Ball
Researcher: Stella Kioy (PhD student)
Industry partners: Lhoist Research and Development
Dates: 2010-2013

Abstract

Until the mid-twentieth century lime was the primary binder for mortars in brickwork and other masonry construction. Cement replaced lime in mortars through its faster setting time, higher final strength and greater consistency of performance. However, many of the beneficial qualities of using a low strength ductile mortar were also lost. Lime mortars have a well known reputation for a greater ability to accommodate movements arising from environmental and structural loadings, including ground settlements and even possibly seismic actions. Movement joints have become common place in higher strength and more brittle cement mortared masonry walls, impairing aesthetic qualities and complicating construction.

Lime mortars, formed through the calcination of calcium carbonate and slaking of resultant calcium oxide have gained increasingly popularity in recent years. The presence or addition of pozzolanic materials provides hydraulic limes capable of faster strength gain and setting under water. Conservation sector has provided the route back into new construction market for lime materials. Further benefits of lime mortars include ease of masonry recycling on building demolition, lower embodied carbon (following carbonation) and improved aesthetic qualities. Delivery of high quality consistent silo mixed lime mortars has supported this reintroduction. However, market share for lime mortars remains at only 1-2%, partly through higher initial cost of manufacture and reticence of a construction industry to change.

This project aims to develop understanding of the movement properties of lime mortars and lime mortared brickwork subject to environmental actions (stress, moisture and temperature changes). This will require developed knowledge of the influence of initial interaction between mortar and brick during initial construction and subsequent actions. The PhD project will combine apply experimental methodologies of material performance, combined with chemical and micro-structural analysis.