Natural hydraulic limes (NHL) differ from non-hydraulic limes in their chemical composition and carbonation process.
Natural Hydraulic Lime (NHL)
Natural hydraulic limes (NHL) undergo both chemical setting and carbonation. The limestone used naturally contains silica and alumina, which create hydraulic properties when heated. The calcination process produces calcium oxide, calcium silicates, and calcium aluminates, which are then ground, hydrated, and packaged.
On-site, NHL is mixed with aggregates using a mortar mixer to create compatible, flexible, breathable plasters and mortars. Its hydraulic properties provide strength and durability.
Three different strength grades of NHL
(1) NHL 2 - Weakly Hydraulic Lime:For sheltered interior/exterior walls, pointing, and backing coats.
(2) NHL 3.5 - Moderately Hydraulic Lime:Most common grade for normal exposure conditions.
(3) NHL 5 - Strongly Hydraulic Lime:For extreme exposure like sea walls and lime concrete.
Raw materials for natural hydraulic lime (NHL) mortar
(1) Binder: NHL vs. Other Options
Natural cement is used for stucco, casting, and underwater work. Hydraulic lime (HL) contains additives that modify its properties. NHL sets faster and stronger than lime putty. It differs from hydraulic lime (HL), which may contain undisclosed additives. A mortar mixer ensures consistent NHL mortar quality.
(2) Sand
Sand is crucial for mortar properties. High-quality sand should be clean, sharp, and well-graded. Avoid soft, silty, or single-sized sands. The sand used should be well-graded with a range of particle sizes, typically from 5 mm to 75 μm for most plastering, rendering, and mortar applications. When mixing, add sand to the mortar mixer in controlled proportions for consistency.
(3) Water
Use clean water in minimal amounts. Add water gradually in the mortar mixer until reaching a workable consistency, avoiding excess water that causes shrinkage.
(4) Mixing Process with a Mortar Mixer
The mortar mixer ensures consistent quality and workability. Follow these steps:
1. Prepare : Gather NHL, well-graded sand, and clean water.
2. Dry Mix : Add NHL and sand to the mortar mixer and blend until uniform.
3. Add Water : Gradually add water while mixing until the desired consistency is reached.
4. Final Mix : Allow the mortar mixer to run for a few minutes to ensure all ingredients are fully incorporated.
5. Test : Check the mortar's consistency before use.
Proper mixing with a mortar mixer is essential to achieve the desired strength, durability, and aesthetic qualities of NHL mortar.
