What does NHL stand for in lime mortar?
Natural Hydraulic Lime
The NHL stands for Natural Hydraulic Lime. The number relates to compressive strength in MPa (Megapascals) or N/mm² (Newtons per square millimetre) at 28 days under the current British Standard.
What is NHL 3.5 lime mortar?
Secil Natural Lime NHL 3.5 is a moderately hydraulic lime, causing a medium set. It’s the most popular NHL and suitable for most applications including brickwork, repointing and rendering. Suitable for masonry and external plaster works and for new build work.
Is hydrated lime the same as NHL?
They are sold as hydrated lime and have an initial set when water is added, followed by hardening while they absorb carbon dioxide. The more hydraulic a lime is the faster it sets and the higher it’s final strength, but this means that it is less breathable and flexible. NHL5 is the most hydraulic, then NHL3.
Should I use hydraulic or non hydraulic lime mortar?
Non-hydraulic lime is softer and sets much more slowly. The carbonation process is very slow and the material remains soft and flexible. This of course, can be extremely advantageous if that’s what is required. The hydraulic lime is available in degrees of strength, is faster setting and more durable.
How do you mix NHL lime?
Mixing Hydraulic Lime
- Start with an empty mixer.
- Add one part sand.
- Followed by one part lime.
- Followed by two parts sand.
- Mix dry for at least five minutes.
- After five minutes slowly add water until the desired consistency is reached, it is very important not to drown the mix by adding too much water.
What is the difference between NHL 3.5 and NHL 5?
NHL 2 and NHL 3.5 are frequently used for internal, as well as external works. NHL 5 is generally used for external works in exposed and more extreme conditions but is less ‘breathable’ and much less flexible.
Does NHL lime go off?
Hydraulic lime mortars have a shelf life and should be stored dry and sealed from the atmosphere to prolong its life.
Do I add cement to lime mortar?
The addition of cement to lime mortars is a widespread, almost traditional practice, but few consider why it is done or the consequences. There is also confusion over the substances and chemistry involved.
What is the difference between quick lime and hydraulic lime?
The key difference between quicklime and hydrated lime is that the quicklime contains calcium oxide whereas the hydrated lime contains calcium hydroxide.
What is the difference between fat lime and hydraulic lime?
The main difference between the two is the way is which they set. Hydraulic limes set by hydrolysis, a reaction caused by water. Non Hydraulic Limes have various names such as Fat Lime, Lime Putty, Air Lime and set by carbonation. This causes a much slower set and the lime remains softer and more breathable.
What are natural hydraulic limes (NHL)?
Saint Astier® pure and natural hydraulic limes (NHL) have been in production for over 150 years. The characteristics of the raw materials are unique and consist of an undisturbed layer of calcareous rock infiltrated mainly by silica with only traces of other minerals.
What is the difference between lime putty and NHL mortar?
While a NHL based mortar also requires a sharp, washed, well graded sand, the sand is often slightly less coarse than that used for a lime putty based mortar. You always need to be mindful when using less coarse sands that they may need to be applied in slightly thinner coats to avoid the risks of shrinkage cracks.
What are the different grades of hydraulic lime?
Hydraulic lime is available in three different grades; NHL 2, NHL 3.5 and NHL 5 . The NHL stands for Natural Hydraulic Lime . The number relates to compressive strength in MPa (Megapascals) or N/mm² (Newtons per square millimetre) at 28 days under the current British Standard.
What is hydraulic lime mortar used for?
A softer hydraulic lime mortar will absorb and evaporate the moisture from the surrounding masonry, thus allowing it to breathe . It will also accommodate movement and thermal expansion and will not damage the masonry by wearing it away over time.