Understanding Unburnt or Sun Dried Bricks

Unburnt or sun dried bricks are types of bricks that are not fired in a kiln. Instead, they are shaped from clay and then left to dry naturally, typically under the sun. This process is simpler and less energy-intensive than firing, making the bricks cheaper and quicker to produce. However, this lack of firing significantly impacts their physical properties and suitability for different construction purposes.

Analysis of Statement a: Usage in Temporary and Cheap Structures

Statement a says: "Unburnt or sun dried bricks can be used only in the construction of temporary and cheap structures."

• Sun dried bricks are much less durable and strong compared to burnt bricks.
• They have low resistance to moisture and erosion.
• Due to their fragility and susceptibility to weather, they are generally not suitable for permanent, load-bearing structures that need to withstand significant stress and environmental exposure over time.
• They are often used in areas with dry climates or for non-critical constructions like partition walls, temporary shelters, or structures where cost is a primary concern and longevity is not the main requirement.

Therefore, the statement that unburnt or sun dried bricks are used only in temporary and cheap structures is largely accurate, reflecting their limitations in standard permanent construction.

Analysis of Statement b: Exposure to Heavy Rains

Statement b says: "Unburnt or sun dried bricks should NOT be used at the places exposed to heavy rains."

• The binding properties of unfired clay are highly dependent on maintaining a low moisture content.
• When sun dried bricks get wet, especially from heavy rains, the clay material absorbs water, causing it to soften and lose strength.
• Repeated exposure to rain leads to erosion and disintegration of the brick material.
• Structures built with unburnt bricks in areas with heavy rainfall would quickly deteriorate or even collapse.

Hence, it is crucial that unburnt or sun dried bricks are protected from water, particularly heavy rain. They are unsuitable for use in climates or locations where they will be directly exposed to significant precipitation.

Conclusion on Statements about Sun Dried Bricks

Based on the properties and common uses of unburnt or sun dried bricks, both statements are true:

1. Statement a is true because their lack of strength and durability limits their use mainly to temporary or low-cost constructions.
2. Statement b is true because they are highly vulnerable to water damage and disintegration when exposed to heavy rains.

Revision Table: Unburnt vs. Burnt Bricks

Additional Information on Sun Dried Brick Construction

While unburnt or sun dried bricks have limitations, they are part of traditional building techniques in many parts of the world, especially in dry regions. Structures made from sun dried bricks often require protective plasters or renders to shield them from rain and moisture. Examples include adobe construction, where clay-based bricks are sun-dried and used to build walls, often then plastered with mud or lime-based mixes for weather resistance.

The choice between unburnt and burnt bricks depends heavily on the climate, the intended lifespan and purpose of the structure, and the available resources.