What is natural hydraulic lime?
Saint-Astier® Natural Hydraulic Lime (NHL) is an industry-standard used for historic restoration mortar, stucco, and Plaster with no harmful portland cement present or required. Saint-Astier® NHL is pure and natural, free of additives, and has been in use throughout the world for over 150 years.
What is the difference between feebly and hydraulic lime?
Feebly Hydraulic lime is used where the highest amount of “free lime” is desired along with the greatest modulus of elasticity, low strength or high vapor exchange. It sets with air and water and cures in about four days Moderately Hydraulic lime is recommended for use when moderate strengths and better freeze-thaw resistance is required.
Is hydraulic lime harder than cement?
For those of you who are new to the European standards, what this means is: if you use a high strength Hydraulic lime you could end up with a product nearly as hard as cement! Another point to remember is that the sand you use is as important as the lime itself; it must be sharp with equal parts of each aggregate size eg, 1mm, 2mm, 3mm, 4mm, 5mm.
What is the ratio of hydraulic lime to sand?
Natural Hydraulic Lime (NHL) 3.5 comes dry in 55 pound bags with no artificial additives. Mix with sharp sand at a ratio of 2 1/2 parts of Mason’s sand to 1 part NHL measured by VOLUME.
What's the difference between hydraulic lime and hydrated lime?
Hydraulic limes (so called because they set under water) are made in the same way as non-hydraulic lime but using different limestone. They are sold as hydrated lime and have an initial set when water is added, followed by hardening while they absorb carbon dioxide.
What is hydraulic lime used for?
Hydraulic lime is a type of lime, or calcium carbonate, which is used to make mortar and plaster products. The lime is heated, then mixed with an aggregate material like sand or stone. Once this mixture is blended with water to form mortar, it can be used in many types of masonry construction projects.
How long does hydraulic lime keep?
4-12 monthsHydraulic lime mortars have a shelf life and should be stored dry and sealed from the atmosphere to prolong its life. If stored correctly, the bags of dry powder could last anything from 4-12 months from manufacture.
Should I use hydraulic or non-hydraulic lime?
Hydraulic lime is made from an impure limestone and sets through hydrolysis, a reaction caused by water. Hydraulic lime provides a faster initial set and greater compressive strength compared to non-hydraulic lime and will set in more extreme conditions including under water.
Can you mix hydraulic lime with cement?
Mixing Hydraulic Lime. A conventional cement mixer can be used to mix hydraulic lime plasters. However, for larger projects a roller-pan or paddle-mixer is preferable.
Is hydraulic lime waterproof?
Therefore, the use of hydraulic lime mortars of medium aggregates impregnated with siloxane can be considered as a compatible system for waterproofing historic masonry.
How long does hydraulic lime take to dry?
Properly mixed, placed and cured, they have great versatility, but should not be used in very demanding exposures such as copings, chimneys and pavings. Their initial setting time varies between four and 12 hours. Moderately to eminently hydraulic limes are not currently manufactured in the UK.
How do you make hydraulic lime mortar?
We recommend the following procedure:Start with an empty mixer.Add 1 part sand.Mix in 1 part lime.Followed by 1.5 parts sand.Mix dry for at least 5 minutes.After 5 minutes slowly add water until the desired consistency is reached, it is very important not to drown the mix by adding too much water.More items...
Why is lime plaster no longer commonly used?
The promotion of modern gypsum-based plasters has led to the almost complete demise of lime plastering, and of many of the traditional skills associated with the craft. This has been exacerbated by the plastering trade being divided into flat and decorative work, with new 'fibrous plasterwork' being made in workshops.
What does NHL stand for lime?
Natural hydraulic limesNatural hydraulic limes (NHL's) are classified by British Standard according to their compressive strength. These grades are associated with the terms: feebly hydraulic (NHL2) moderately hydraulic (NHL 3.5) eminently hydraulic (NHL5)
What kind of lime do you use for pointing?
natural hydraulic limeLime pointing of traditional masonry using lime mortar based on lime putty or natural hydraulic lime (NHL) offers many advantages over cement based mortars.
Can you use hydraulic lime for Limewash?
HYDRAULIC LIMEWASHES Another very interesting form of fine particle suspension limewash is achieved using hydraulic lime, the form of lime which sets on addition of water.
Otterbein NHL 2
Otterbein NHL 2 is a feebly hydraulic lime suitable for the production of plaster and mortar in ecological, biological building construction, in the restoration and preservation of historic buildings.
Roundtower NHL 3.5 White
Moderately Natural Hydraulic Lime - Another NHL 3.5 with the exception that it has a higher 'whiteness' and is useful when colour matching mortars.
Roundtower NHL 3.5 Lt Grey
Moderately Natural Hydraulic Lime - Used mainly for masonry and external plaster works. The most popular material for new build work.
Roundtower NHL 2
Feebly Natural Hydraulic Lime - Used for internal plastering and externally where the masonry is made up of a soft material.
Otterbein NHL 3.5
Otterbein NHL 3.5 is a moderately hydraulic lime suitable for the production of plaster and mortar in ecological, biological building construction, in the restoration and preservation of historic buildings.
Otterbein NHL 5
Otterbein NHL5 is an eminently hydraulic lime. For the production of plaster and mortar in ecological, biological building construction, in the restoration and preservation of historic buildings.
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Product description
This 55 pound bag of NHL 3.5 is perfect for old harder bricks and stone. Natural Hydraulic Lime comes with all the flexibility that comes with natural lime. Natural lime has higher permeability in general and allows for moisture to enter and freely escape, unlike Portland Mortar which locks in moisture and cracks over time.
What is hydraulic lime?
Both are hydraulic limes with either added pozzolans (PHL) or naturally occurring impurities (NHL). This means that the mortar will set in two stages: the first hydraulic set will occur when water is added so that the mortar gains limited strength quickly during its initial set.
How is PHL mortar made?
PHL mortar is manufactured domestically and made by adding a controlled quantity of hydraulic material, usually metakaolin, flyash, or slag to hydrated lime.
What is the ASTM C-141 for PHL mortar?
In the United States NHL and PHL mortars fall under ASTM C-141 “Standard Specifications for Hydrated Hydraulic Lime for Structural Purposes.” PHL mortars also fall under C1707 “Standard Specification for
Does lime help with final strength?
It will also contribute to final strength. Free lime provides some tolerance for initial structural movements and both sufficient strength and plasticity to accept slight load shifts. The higher the free lime the more accommodating the mortar: Hydraulic limes also facilitate vapor transmission, as seen in this graphic.
Pozzolan for Historic Restoration
PHL restoration mortar provides breathability, flexibility, and durability which is necessary for both historic masonry restoration Niagara PHL contains absolutely no Portland Cement, which helps reduce potential damage in historic applications where it was not originally used.
Our PHL Products
Pozzolan Lime Binder (PHL) is a manufactured lime product and its pozzolan impurities are added during its manufacturing. It is available as Moderately Hydraulic (PHL 3.5), and Eminently Hydraulic (PHL 5.0). PHL 5.0 works best for Chicago’s climate. It usually takes around 7 days to cure and achieve strength.
How to slake hydrated lime?
To slake hydrated lime, you must add the powder to water. NEVER add water to the lime, only add the lime to water. If you do this backwards, the chemical reaction that takes place can happen too quickly and the mix can explode. Be sure to wear goggles, a mask, and skin protection during this process.
What is lime putty?
The longer you leave the lime submerged the better the slaking job. When you are done and ready to use the material, it is called lime putty (Calcium Hydroxide). Do not expose the material to air once it has been rehydrated as it will start to harden and, once again, change its chemical makeup.
Is metakaolin expensive?
Metakaolin is still kind of expensive ( I seem to be finding 50 lbs. bags for around $45 online), but because of the final clay content in a mix, according to the NHL rating system, it may be possible to make a batch of AHL5 with 80% S-Type lime and 20% metakaolin. If anyone tries this out, let us all know.
Can you use lime putty out of a bag?
The dry, powder hydrate, most typically the form in which it is sold, can be used right out of the bag; however, it is best to slake it for a while in the form of a lime putty before use if you have the time and ability (More on Lime Putty in a minute)