Historically, several materials have been used in construction for thousands of years. Most of these materials are inherently sustainable, durable and do not require much skilled labour to manufacture and construct. One such material is an adobe brick. Read on to learn about what adobe bricks are, how they are made and the advantages and limitations of adobe clay houses.
What are Adobe Bricks?
Derived from the old Arabic word ‘al-tuba’, ‘adobe’ is a Spanish word referring to mud bricks. As the meaning suggests, adobe bricks are made from mud/ clay, mixed with other natural elements like sand and straw. Due to its simple manufacturing and building process, adobe brick construction has been popular across the world since the 8th century BC. Many adobe buildings dating back to more than 900 years ago can still be found in use in different regions of Asia, Europe, Africa and America. This intrinsic durability, along with the sustainable nature of adobe bricks, makes them a popular building material choice even in modern construction.
How are Adobe Clay Bricks Made?
Components of Adobe Bricks
Although there are regional variations across the world, adobe in construction typically has the following components:
- Clay (20-40%): Formed by the interaction of water with rocks containing silicate materials, adobe clay is the main ingredient of adobe blocks. Finely grained clay (with diameter of around 0.002mm) is ideal and acts as a binder for all the other components.
- Silt, Gravel and Sand (60-80%): Gravel of size 0.2-2mm and sand of size 0.06-2mm are used to reduce the amount of cracking in adobe bricks. However, increasing the amount of sand and gravel can reduce the brick strength and the use of sand with high salt content can reduce durability.
- Straw/ Cow Dung: Although these are not mandatory components, straw and/or cowdung can be used to stabilise the mixture and make it more workable during the manufacturing process. Other materials like bamboo, rice husk, weeds and grass can also be used as alternatives.
Additional materials like Portland cement and lime are often used to stabilise and strengthen adobe blocks in modern construction.
Manufacture of Adobe Construction Material
- Soil Analysis and Sieving: The selected soil is tested in a lab or at the site itself (through simple tests like compression tests, bottle tests and visual tests). It is then passed through a sieve to filter out larger rocks and waste particles.
- Mixing: All the tested materials are mixed together with water in specified proportions to form a uniform mixture with optimal strength and workability. Often, a process called ‘pugging’—which involves mixing manually with the feet—is adopted for mixing the ingredients.
- Molding: The mixture is placed into open wooden moulds (generally of sizes around 36cm x 25cm x 7cm) and compacted. In case of very dry weather conditions, the moulds are wetted or oiled before placing the mixture inside.
- Drying: The mixture is left undisturbed to dry in the sun for a few days, after which the moulds are removed and the mixture is left to dry for a couple of weeks more. The dried mix is then ready to be used as adobe bricks (after the necessary visual or mechanical strength tests are completed).
Although adobe bricks can easily be manufactured locally on-site, proper testing for strength by qualified professionals is required to ensure their durability and safety for use in construction.
Why Opt for Adobe Clay Houses?
The use of adobe in construction offers several benefits over conventional materials. Some of the important advantages are:
- Durability: Under normal or very dry weather conditions, an adobe building can last for hundreds of years.
- Eco-Friendly: Made with all natural materials that are generally sourced locally or from the construction site itself, adobe bricks are extremely eco-friendly. The lack of need for transportation of materials and the low-energy manufacturing process significantly reduce carbon emissions.
- Biodegradable: These bricks are completely biodegradable and can undergo natural decomposition after being broken down. In case non-biodegradable additives like cement are used for stabilisation during manufacture, the blocks can be disintegrated and the same mixture can be reused for making new blocks.
- Thermal Insulation: Adobe blocks have excellent thermal insulation properties. They can absorb and store heat during the day time, helping keep spaces cool. This heat is slowly released at night to provide warmth when the temperatures drop.
- Reduced Cracking: Every adobe brick is allowed to shrink before being used in construction. This process reduces the possibility of shrinkage later on, helping prevent the formation of cracks (which are common issues in burnt clay brick walls).
- Cost-Effective: Manufactured without any high-end machinery and not requiring very skilled labour, adobe construction is much more cost-effective than construction with conventional materials.
Limitations of Adobe Brick Construction
- Low Earthquake Resistance: Adobe walls are heavy, making them brittle and lowering their strength during seismic activity. Tectonic movements during earthquakes can lead to high levels of cracking, disintegration and separation at the corners, which can eventually lead to structural failure and building collapse.
- Maintenance and Finishing Requirements: When left exposed, adobe blocks can undergo extreme weathering and corrosion under harsh weather conditions, especially in coastal areas where the salt content in air is high.
- Low Moisture Resistance: When exposed to high levels of moisture and humidity, adobe blocks can crack, soften and collapse. Protective coatings like lime plaster or slurry washes are required to prevent this, which can significantly increase the construction cost.
- Wall thickness: Since adobe bricks are typically used to build load bearing walls, the wall thicknesses can range between 0.25m and 0.80m. This is much higher than walls built with conventional materials like clay bricks and concrete and leads to reduced usable area in buildings.
Using Adobe for Construction
Many of the limitations of adobe building construction, such as low earthquake and moisture resistance, can be overcome by adding stabilisers or using eco-friendly finishing materials like lime plaster. Although these methods can increase the construction cost, the numerous other benefits of adobe construction far outweigh the cons. Sustainable materials like adobe bricks can significantly help reduce the negative impacts of the construction industry on the environment, making them important building solutions. To explore the use of more eco-friendly materials in the construction of your home, contact Brick & Bolt—a leading end-to-end construction services provider in India—today!