Brick-making clays encompass diverse materials with varying silica and alumina percentages, categorized into three classes:

(a) Surface Clay: Predominantly utilized in Pakistan, surface clays, typically 3 to 4 feet deep, form the majority of bricks.

(b) Shales: Derived from decomposed rock, shale clays are sourced, often found in proximity to mountainous regions.

(c) Fire-Clays: Situated deeper beneath the surface, fire clays exhibit a more consistent chemical composition compared to surface or shale clays.

To achieve uniform consistency, raw clays are frequently blended and subsequently processed through grinders and screens to attain the optimal particle size for water mixing.

The mixing and forming phase employs three primary processes:

a) Extruded Bricks: In the stiff mud process, clay is mixed with water to achieve a plastic consistency. The mixture is then forced through a die, extruding a clay column similar to toothpaste. The column provides two dimensions, and the third is obtained by cutting it with a wire.

b) Molded Bricks: In the soft mud process, an older method, a higher water content is utilized. The mix is placed in wooden or steel molds to shape the required unit size. Molds are lubricated with sand or water, resulting in sand struck or water-struck bricks.

c) bClays: with low plasticity are employed in the dry press process.

Following the formation of bricks, the next step involves drying them to eliminate excess free water. Apart from sun drying, this process is accomplished in direct dryers, where temperatures, drafts, and humidity are carefully controlled.

Bricks undergo firing and cooling in a kiln, an oven-type chamber capable of reaching temperatures between 870°C and 1100°C (1600-2000°F), depending on the raw material type.

Two main types of kilns are employed:

1. Periodic
2. Continuous.

Material testing is a crucial quality control aspect in civil work. Standard tests for bricks include:

1. Crushing Strength Test
2. Water Absorption Test
3. Efflorescence Test
4. Efflorescence After Construction
5. Dimensional Test