What is hydraulic lime mortar?
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.
Why is lime mortar no longer used?
With the introduction of Portland cement during the 19th century, the use of lime mortar in new constructions gradually declined. This was largely due to the ease of use of Portland cement, its quick setting, and high compressive strength.
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 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. Easy to use, powdered lime.
What do you use hydraulic lime 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 mortar set?
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.
What are the disadvantages of lime mortar?
DISADVANTAGES
- the rapid setting time limits the time available to the user in which to work with the gauged mortar.
- some cements contain appreciable amounts of soluble salts, in particular potassium sulphate, which may become a source of salt damage to stonework.
How many years does lime mortar last?
Most bagged, hydrated lime has a shelf life of 12 months once kept dry and sealed. Once opened bags should be used straight away or resealed so as to be airtight. Some premixed lime mortars with additives may have a shorter shelf life. Lime putty will last indefinitely once kept underwater and airtight.
How long does hydraulic lime last?
4-12 months
Hydraulic 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.
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.
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.
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.
Why is my lime mortar crumbling?
Lack of carbonation can be caused by exposure to freezing temperatures causing expansion of the lime as it is absorbing CO2 and prohibiting a coherent mortar being formed. It can also be caused by the mortar drying too fast by either not wetting the background or lack of tending and protection afterwards.
Can you add cement to hydraulic lime?
A non hydraulic lime can be made to set much more rapidly by the addition of an hydraulic or ‘pozzolanic’ additive. This practice is known as ‘gauging’. The additives include finely crushed brick powder, PFA, HTI, pozzolana, trass or cement (white or OPC).
Is lime mortar better than cement?
Lime mortar has better properties than straight concrete mortar. These qualities help structures withstand weathering and aging better than before. If your stonework has an ordinary concrete mortar between the stones, you will have probably noticed cracking, pitting and crumbling.
Why does lime mortar crumble?
Crumbling or failing mortar can be caused by a number of reasons: Failing mortar can usually be attributed to a lack of carbonation of the lime within the mortar meaning that the mortar will have little if any, strength.