Engineering with lime
27 November 2002
Lime mortar has been used in building construction for thousands of years. But despite this long history, little is understood about how it behaves.
Lime mortar has been used in building construction for thousands of years. If your home was built before 1900, the chances are it is lime mortar which bonds the stone or bricks. But despite this long history, little is understood about how it behaves.
Lime mortars are slow-hardening mixtures of lime and sand, necessitating the use of skilled labour and extended build times. So development of Portland cement in the 1800s, which was more consistent and set rapidly, resulted in cement mortars becoming the mainstay of all building work. More recently, however, building conservation has led to a resurgence in the manufacture of lime mortar and architects have begun to realise its suitability for new buildings.
Many environmental benefits accrue by increasing the use of lime in modern buildings. Less energy is used in manufacture and CO2 levels in the atmosphere are reduced as it is absorbed during setting. Because lime mortar is softer than the masonry around it, it can accommodate movement and prevent masonry from cracking while using fewer expansion joints, the bane of many architects’ lives. Despite these clear advantages, the construction industry lacks information on how best to use lime mortars. Therefore, over the last three years, a team which included the University’s Interface Analysis Centre, has fully characterised lime mortars for their physical properties, chemical resistivity and microstructural behaviour. This has resulted in development of a Code of Best Practice.
Following the success of the first phase of this project, the DTI has awarded the group a further £400,000 to look at the engineering properties of these materials, and their associated environmental gains, so that a greater understanding can be gained of how large and how fast buildings could be constructed using them. Completion of this phase will provide the construction industry with the necessary specifications for the application of these products.