Lime Materials
(1 Product)For centuries, lime has been used as a binding agent in mortars and renders. Often combined with additional binder materials to achieve faster setting times and increased strength gains, lime stands out for its efficacy and longevity. Lime mortar is a mixture of lime, aggregate such as sand or grit, and water. It can be either hydraulic or non-hydraulic.
What Is Building Lime?
Building lime is a traditional material with a wide range of applications in construction and environmental management.
Its benefits in terms of workability, breathability, and environmental impact make it a valuable choice, especially in the restoration of historic structures and sustainable building practices.
Uses of Building Lime in Construction
- In steel production, building lime is used to eliminate any pollutants or contaminants, creating a high-quality product.
- When creating roads, airfields and foundations for buildings, soil stabilisation requires a substantial amount of lime.
- As a unifying adhesive, lime slurry is essential for masonry construction and plastering.
- Asphalt is enhanced with the addition of lime, leading to a better cohesive property and increased resistance against stripping and ageing.
Lime Cement Vs Traditional Cement Mortars
Lime mortar has been used for centuries to bind and point between bricks. It is softer than brick itself, allowing airflow as well as moisture permeability - meaning that it gets wet and then quickly dries again.
Portland cement does not allow for this same breathability. If an old brick wall is repointed with Portland cement, the moisture content of the bricks will rise significantly – leading to spalling (where pieces break off).
Natural hydraulic lime mortar's effectiveness reigns supreme against Portland cement in natural stone and soft brick applications, as it provides excellent plasticity while still maintaining the solidity of your structure. Plus, its strength can reduce shrinkage significantly compared to other options.
Types of Lime
Lime products are commonly used in construction, particularly for mortar, plaster, and other building materials. There are different types of building lime, each with specific properties and applications.
Blue Circle Hydralime
Hydralime is designed to boost the cohesion, workability, plasticity and durability of mortars and renders when combined with Procem, Mastercrete, General Purpose Cement, Snowcrete or Sulfacrete.
However please be aware that due to its non-hydraulic nature, Hydralime cannot be used by itself in a mortar or render mix, it should always be used alongside Portland cement mortar.
- For use in cement, sand and lime mortars and renders
- Fine dry white powder that lightens mortars
- Eases floating renders and pointing mortars
- High calcium
- Suitable for both interior and exterior use
- Compatible with Portland cement
- Conforms to BS EN 459-1 and CL 90-S
Hydraulic Lime
Hydraulic limes are made from impure limestone and set via a hydrolysis reaction caused by water. As a powdered material, hydraulic lime sets more rapidly than traditional non-hydraulic lime and carries with it higher strength attributes but reduced permeability.
Conservators prefer to use natural hydraulic lime as a binder in mortar and plaster because it has the capacity to both set and harden under damp conditions, while also building reliable mechanical strength.
Hydraulic lime products can be either sourced from natural rock (Natural Hydraulic Lime or NHL) or produced by mixing hydrated lime and reactive binder components (Formulated Lime or FL).
Non-Hydraulic Lime
Non-hydraulic lime, often referred to as fat lime putty, is created with pure limestone and calcium carbonate. Unlike hydraulic lime, fat lime putty doesn't react when exposed to water; rather, it reacts with carbon dioxide in the atmosphere in a process called carbonatation; hence why non-hydraulic lime materials are often called 'air lime' products.
Lime putty mortar hardens as a by-product of calcium hydroxide reacting with carbon dioxide. It's softer than hydraulic and cures more slowly than NHL mortar while remaining malleable for longer periods.
Non-hydraulic limes take longer to set compared to other limes since they require specific environmental conditions in order for them to absorb CO2 from the atmosphere. The suppleness of non-hydraulic lime makes it ideal for plasters and renders.
Lime-Sand Mortar
Lime-sand mortars are a convenient and ready-made mixture of damp sand, hydrated lime, cement, additives, and water that you simply mix in a mixer before application.
Frequently Asked Lime Questions
How Does Lime Enhance Portland Cement Mortar?
Adding the correct amount of hydrated lime to a cement-based mortar mix increases workability, making it smoother to handle with a trowel. It also boosts water retention, resulting in better contact and adhesion between components.
What Would Happen If I Applied Modern Mortar On A Building Originally Pointed With Lime Mortar?
Utilising cement mortar in a historic building that was originally pointed with lime can be incredibly destructive to its structural integrity. The construction of historic buildings often uses soft brick or stone that is prone to a certain amount of movement. This movement will cause the weakest portion of walls, most commonly masonry with Portland cement mortar, to crack and separate.
By employing lime-based mortar in historic buildings, we are not only upholding the traditional technology but also affording a repair material that is compatible with softer building materials such as porous masonry bricks and stones.
The soft and porous properties of lime mortar ensure that it becomes the weaker element in the structure allowing for less damage overall. Essentially lime mortar serves as a defensive barrier for substrates, safeguarding them from deterioration due to external agents such as frost and salt.
The abundance of long-lasting monuments built using this very same material serves as clear evidence that hydraulic lime mortar is an incredibly resilient product.
Does Lime Mortar Prevent Damp?
The unique characteristics of lime mortar create a breathable environment within brick walls; allowing airborne moisture to penetrate and be released in order to prevent damp.
For structures with bricks that are less porous, this is an incredibly beneficial way for humidity levels to remain balanced throughout the building structure.
What is The Difference Between Natural & Artificial Hydraulic Lime?
Natural hydraulic lime (NHL) mortars are derived from limestone that is naturally rich in silica and/or alumina.
Artificial hydraulic lime (AHL) or artificial lime (AL) can be transformed into its hydro-reactive state through the addition of pozzolan materials either before or after burning it in a kiln.
