Lime concrete is a composite blend comprising of lime as the binding agent, fine sand as the aggregate, and coarse gravel as the other aggregate, in the correct proportions. The lime concrete mix ratio may differ based on the construction requirements, but a typical ratio can be 1 part lime, 2 parts sand, and 3 parts coarse aggregate.
In the past, lime concrete had a vast range of uses in construction before the widespread use of cement as the primary binding agent. Lime concrete is still used in modern times as a capillary break, where it is placed on top of the vapor-permeable insulation base. By serving as a capillary break, lime concrete prevents the rise of moisture by capillary action through the porous insulation material.
By using lime concrete as a capillary break, moisture problems can be prevented, which can be particularly useful in areas with a high water table. Furthermore, lime concrete’s use helps in maintaining the historical architecture, as it was the preferred material used by the builders of the past. Lime concrete’s characteristics, such as durability and flexibility, make it an ideal material for use in construction projects.
This article will cover the process of proportioning, mixing, placing, and curing lime concrete, which involves the use of two types of lime: Class A and Class B.
Class A lime is eminently hydraulic and is typically used for structural purposes. On the other hand, Class B lime is semi-hydraulic and is commonly used for lime concrete.
Proper proportioning, mixing, placing, and curing are crucial steps in creating high-quality lime concrete. By understanding the differences between the two types of lime and following the correct procedures, builders and contractors can ensure that their lime concrete is structurally sound and durable.
Proportioning of Lime Concrete
The method for determining the proportions of aggregate to lime mortar involves measuring by volume. Specifically, the lime mortar mix should consist of 40 parts, while the aggregate should consist of 100 parts of 40 mm nominal size graded stone aggregate, gravel, or brick aggregate as specified. These proportions are important to ensure the proper composition of the mortar and aggregate mixture.
Mixing of Lime Concrete
The mixing of lime concrete should be done using a mechanical mixer. However, in certain situations, hand mixing may be permitted. Prior to mixing, the brick aggregate must be thoroughly soaked in water for at least 24 hours. On the other hand, the stone aggregate or gravel must be washed with water to eliminate any foreign materials, dirt, or dust.
1. Machine Mixing
Mixing of coarse aggregate and wet ground mortar in a mixer’s drum should be done while the drum is revolving. The quantity of materials loaded should not exceed the rated capacity of the mixer. Gradual addition of water up to the required quantity is necessary. The wet mixing process of a batch should continue for at least two minutes in the drum until the concrete achieves a uniform color with materials uniformly distributed, and consistency is obtained.
The lime concrete’s consistency should be such that the mortar does not tend to separate from the coarse aggregate. If segregation occurs after unloading from the mixer, the concrete must be removed. It is important to discharge the entire batch of concrete before pouring materials for the new batch into the drum.
Before suspending the work, the mixer must be cleaned by revolving the drum with plenty of water each time.
2. Hand Mixing
Hand mixing of wet lime mortar is allowed, but only if it is performed on a clean and watertight masonry platform that is large enough to provide ample space for mixing. The platform must be free of any contaminants and impurities that could potentially affect the quality of the mortar.
To prepare the lime mortar, it must be placed on top of the aggregate. Turning of the mixture must be done repeatedly, with the addition of water as needed, until the desired consistency is achieved. The aim is to create a uniform mix of the required consistency that will produce the desired results.
It is crucial to ensure that the consistency of the lime concrete is appropriate so that the mortar does not separate from the coarse aggregate. This ensures that the mortar is of high quality and will provide the desired level of strength and durability. Therefore, the mixing process must be carried out with care and attention to detail to achieve the desired results.
Placing and Compaction
The process of laying lime concrete involves placing it in layers while it is still fresh. Each layer must be firmly compacted before the subsequent layer is added. To ensure proper consolidation, the thickness of each layer should not exceed 15 cm. Joints, if needed, should be staggered in different layers, unless otherwise specified.
The ramming process is crucial to the success of the concrete laying. Heavy iron rammers, weighing between 4.5 kg and 5.5 kg, are required for this purpose, and their area should not exceed 300 sq. cm. The ramming process should continue until a layer of mortar completely covers the surface of the laid lime concrete.
It is important to note that once concrete has been laid on a particular day, it must be thoroughly consolidated on the same day before work is stopped. Additionally, fresh concrete must be protected from rain using suitable coverings to prevent damage.
In summary, the process of laying lime concrete involves placing it in layers, consolidating each layer thoroughly, and using heavy iron rammers for compaction. Joints should be staggered, and the thickness of each layer should not exceed 15 cm. Freshly laid concrete must be consolidated on the same day and protected from rain with appropriate coverings.
Curing of Lime Concrete
Concrete is a commonly used building material that must be cured properly to achieve its full strength and durability. The curing process involves maintaining the appropriate moisture levels in the concrete to allow it to fully hydrate and harden over time. Once the concrete has been placed and compacted, the initial curing process begins.
After approximately 24 hours, when the concrete has begun to harden, it is crucial to start the curing process. This involves keeping the concrete damp with the use of moist gunny bags, sand, or other suitable methods. The goal is to maintain the appropriate level of moisture in the concrete for a minimum of 7 days.
Proper curing is essential for achieving the desired properties of the concrete, including strength and durability. The use of moist gunny bags, sand, or other methods helps to keep the concrete hydrated and prevents it from drying out too quickly, which can result in cracks and reduced strength. Therefore, it is important to follow the recommended curing practices to ensure the best possible outcome for the concrete.
FAQs on Lime Concrete
What is lime concrete?
Lime concrete is a type of composite mixture that is made up of three key components: lime, sand, and gravel. Lime serves as the binding material, while sand is used as the fine aggregate, and gravel is the coarse aggregate. The appropriate proportions of each ingredient are carefully measured and mixed to create a durable and versatile building material.
The use of lime in concrete has been prevalent for centuries and continues to be a popular choice today due to its unique properties. Lime has the ability to self-heal small cracks that may form in the concrete over time, which helps to prolong the life of the material. Additionally, lime concrete has a high resistance to water and can withstand harsh weather conditions, making it an ideal choice for outdoor structures and buildings.
Sand and gravel are also important components of lime concrete, providing texture and strength to the material. The fine particles of sand fill the gaps between the larger gravel pieces, creating a smooth surface that is easy to work with. Meanwhile, the coarse gravel provides structural support and enhances the durability of the concrete.
Overall, lime concrete is a reliable and versatile building material that has been used for centuries. Its unique properties make it an ideal choice for a wide range of construction projects, from historic restorations to modern buildings.
What is the mix proportion of lime concrete?
The mix ratio for lime concrete can vary depending on the type of construction project. However, a commonly used mix ratio for lime concrete is 1:2:3, which refers to the proportions of lime, sand, and coarse aggregate used in the mix. This ratio is a general guideline that can be adjusted as needed for specific construction applications. Overall, the mix ratio for lime concrete plays a critical role in determining the strength and durability of the final product.
What are the properties of lime concrete?
Lime concrete is a construction material with various desirable properties. It offers good workability and plasticity, allowing it to be easily molded into the desired shape. Another benefit is that it has a certain level of waterproofing ability, which can help prevent subsoil dampness. Additionally, lime concrete is resistant to weathering effects, making it a durable choice for outdoor structures.
Bases constructed with lime concrete can bear sufficient loads, making it a suitable choice for buildings and infrastructure. However, it’s worth noting that lime concrete requires more time for setting compared to other construction materials. Moreover, it attains significantly less compressive strength at the initial stage of setting.
Finally, one of the most significant benefits of lime concrete is its environmental friendliness. The production of lime requires less energy than Portland cement, and the carbonation process of lime concrete emits less carbon dioxide, making it a sustainable choice for eco-conscious construction projects.