Substitute materials have long since been used instead of volcanic ash, hence any burnt clay that reacts with pure limes to create a hydraulic lime set is referred to as a Pozzolan or Pozzolanic after the original discovery. If lime putty is kept moist and free from Pozzolans, it will last indefinitely and actually improve with age reducing wastage.
So the original hydraulic lime was in fact a combination of pure lime putty and a Pozzolan that can still be replicated and is usually used these days in the UK to render and point externally or internally on to walls that are inherently damp and require the chemical set.
We are a leading supplier of lime plasters, mortars, putty and ancillaries in the UK and offer easy to use, efficient building materials that are eco-friendly. Get in touch and see how we can help you and your building project. Subscribe to the Ecomerchant mailing list to receive updates on new arrivals, special offers and other discount information. Email us: info ecomerchant. Email us Request a call back.
By absorbing moisture, lime mortar is keeping the masonry dryer and lessening the risk of spalling At Ecomerchant we stock a wide range of high quality, easy to use lime plaster and lime mortar products, including bagged and premixed lime , lime putty and natural hydraulic lime.
To enquire about all orders, including bulk, call Lime use in buildings Up to the 20th century Up to the 20th Century building techniques and materials were very different from those employed today. Working on historic buildings today If work is being undertaken to a historic structure, it is important to establish what sort of mortar was used in its original construction or what sort of mortar predominates in the existing construction. Modern lime renders and putties Lime is most often used in traditional buildings but modern lime renders and putties are now emerging as viable performance options over cement-based products.
To a large degree, the type of lime and sand and the need to obtain a workable mix determined these ratios. With the lime revival of the past 25 years which for many years was primarily based on the use of pure, non-hydraulic lime prepared as a putty mixed with a well-graded aggregate it is interesting to note that there has been an emphasis on the common use of a lime:sand ratio based essentially on a measurement of the 'voids by volume' within a measure of dry sand.
It is generally accepted that this measurement provides a good indication of the volume of lime binder required to ensure a coating of lime around every grain of sand, and technically it is quite correct. The method used to measure the voids involves half-filling a graduated laboratory flask with an oven-dried sample of the specified sand, and then carefully pouring clean potable water into it from another identical graduated flask until all the voids are filled and the surface of the water rises level with the surface of the sand.
The volume of water required to fill all the voids in this volume of sand can then be calculated by subtracting the volume of water left in the water flask from the volume it contained at the start, this being determined as the minimum volume of lime binder required for producing a good mortar. Typically this is found to be one-third of the original volume of the water and hence the ratio is determined as But it is not correct to believe that this provides all the answers, and nor does it reflect the reasoning by which the ratio was historically specified.
It is vital to understand that, until the Second World War, a majority of limes were still prepared from freshly burnt quicklime delivered to site, as opposed to ready-to-use slaked putties, which would have been extremely heavy to transport, or bagged dry-hydrates. For general mortars the quicklime was then usually slaked to a crude powder technically, a dry-hydrate on site. One of the most popular methods to achieve this was to place a one-third measure of quicklime broken down to the size of nutmegs within a cubic yard of ringed sand, and then apply the minimum of water necessary to slake it, before quickly drawing the sand over it as it both heated and broke down in slaking.
After slaking was completed the pile would be turned over dry to fully integrate the sand and lime. One option was then to add extra water to bring it to the working consistency of mortar ready for immediate use. The important thing to note here is that the lime used in the ratio of was not prepared slaked lime calcium hydroxide but unslaked quicklime calcium oxide , a fundamentally different substance in several respects, including volume.
This vital point has frequently been overlooked and has led to misinterpretation of a great many historical mortar mixes based on original documents recording mortar ratios, or on those recorded within old craft books. A simple but very good example of this is to be found in an architect's private site book, for an entry dated on preparing lime mortar as follows: 'Mortar: Lime 1, Sand 3. Lime: slack [slake] with water and then cover with sand. Today, lime is still used as the primary binder in many mixes, usually in the form of lime putty or Hydraulic lime.
Hydrated lime is used in modern cement based mortars mainly for its properties as a plasticiser. Pure lime mortars behave as if they are flexible and lime cement mortars are slower hardening and remain more flexible than cement sand mortars. Lime, therefore, enhances the ability of the brickwork to accommodate stresses caused by building movement and cyclical changes without excessive cracking.
Lime improves the plasticity and workability of mortar, while providing a high degree of cohesiveness it also spreads easily under the trowel. Lime mortars have high water retention, creating an improved bond as there is more contact between unit and mortar. Retention of water in mortar improves carbonation in pure lime mortars and results in best conditions for early hydration of cement lime mortars — thus reducing cracking and water penetration into hardened mortar joints.
The use of lime in mortar reduces the compressive and flexural strength of the hardened mortar. In situations where structural movement takes place, lime mortars can better accommodate this movement. Not only does lime mortar reduce the risk of water ingress, vapour permeability allows any moisture to evaporate, thus reducing the risk of freeze thaw deterioration.
Vapour permeability of mortar improves with increasing lime content. We manufacture our own lime putty using lime from Singleton Birch in Lincolnshire and have supplied construction products to major building works including those on Wells Cathedral, Westminster Abbey and Salisbury Cathedral. The History of Lime Mortar. First traces of mortar Lime, on its own, has been used within the construction industry for over years.
Key points for lime mortar throughout history — BCE — The first mortars contained no lime and were found to mainly contain a mix of mud, clay or sand. Benefits of lime mortar Although technology has developed new construction products, lime mortar is still widely used. These include: Workability — Lime mortar has a great plasticity. This makes it easy to work with and suitable for shaping into decorative settings.
Adding water to lime activates the calcium oxide but does not turn it into a putty or a paste. This prevents the mortar from crumbling away over time, ensuring it can withstand the elements. Damp ingress protection — Lime is excellent at protecting your home against damp ingress.
This is because lime can take on and release moisture rather than being fully waterproof such as cement based mortars. Minimised shrink cracking — Other cement based mortars expand and shrink with temperature, causing the surface to crack.
0コメント