- News
- Magazine
- Awards
- CRC
- Legislation
- Housing
- Renewables
- Non-domestic
- Water
- Energy
- Waste & recyc..
- Refurbishment
- Innovation
- Materials
- Biodiversity
- Interiors
- Books
- Training
- Transport
- Links
- Events
Hydraulic lime mortar can now be used widely with modern masonry construction
http://www.greenbuildnews.co.uk/images/img/articles/297_198/Articles_262_1_1286260256.jpg
The market is currently awash with new innovative and green building products designed to help deliver lower energy buildings. At the same time, there is a growing niche market for lime-based materials, which are based on products first used centuries ago.
Yet, specifiers who think that lime mortars can only be used for the restoration of old and buildings should revaluate this view. Although cement replaced lime as a preferred mortar of choice in the 1950s, the development of hydraulic lime mortar means that this material can now be used widely with modern masonry construction techniques.
Hydraulic lime
Produced from limestone containing clay and impurities of silica and clay in the stone from which it is burnt, hydraulic lime hardens on contact with water. This makes it much quicker to use than non-hydraulic lime mortars and enables construction to proceed at a steady pace, as long as horizontal loading is not carried out too quickly.
The use of hydraulic lime as an alternative to cement offers a number of unique benefits. Firstly, hydraulic lime mortars are easily workable and, when dry, are less brittle and rigid than cement mortars, allowing the building fabric to accommodate slight movements with temperature change and settling. Crucially, this minimises the problems of cracks, increases the durability and strength of the building and removes the need for expansion joints, which can often be unsightly and expensive.
Increased durability
Secondly, hydraulic lime mortar is porous and permeable, unlike cement, which is impervious. This means that hydraulic lime mortar is able to take in and release air and water, allowing it escape by evaporation or transpiration. This is important for the control of moisture in buildings, reducing the chance of damp and humidity in the property and the risk of spalling.
The permeability of the lime can also increase the durability of the bricks, as water travels through the mortar instead of being forced through the brick. This process reduces the chance of the bricks eroding and also ensures that when temperatures drop below freezing, there is little water in the brick to freeze and expand, so they are less likely to crack.
The combined advantages of prolonging the lifetime of bricks and creating allowance for movement and settling improves the overall robustness of the building.
Evironmental advantages
There are other environmental benefits of using hydraulic lime that should be considered by those specifying mortars. Lime is both recyclable and biodegradable, and although the carbon advantage of lime over cement in manufacture is negligible, the use of hydraulic lime mortars ensure that bricks can be recycled when a building reaches the end of its lifetime. Bricks bonded with cement, which is stronger than the brick itself, cannot be easily recycled because the cement cannot be removed without causing damage to the brick. Currently, around two million bricks a year are being sent to landfill, demonstrating a clear need for hydraulic lime mortars to improve the long-term sustainability of masonry construction.
Advanced manufacturing
Advances in the development of hydraulic lime mortar means that the traditional benefits of lime are combined with up-to-date manufacturing and quality control. At Tarmac Buxton Lime, we have developed the White Peak Natural Lime (NHL) range of high-quality lime-based products to provide specifiers with a viable alternative to cement-based mortars.
The market for hydraulic lime in the UK is expanding, and although it is unlikely to assume cement mortar’s market dominance, it is becoming increasingly clear that this product has an important role to play in providing durability and strength in modern masonry construction.
Richard Givens is technical lime sales manager at Tarmac Buxton Lime.
Search related articles
