Why do sun-dried bricks break in water and kiln-fired bricks do not?

Sun-dried bricks, made from a mixture of clay, sand, and water, are not fired at high temperatures, leaving them porous and weak. When exposed to water, their structure absorbs moisture, causing them to weaken and disintegrate. In contrast, kiln-fired bricks undergo a high-temperature firing process that vitrifies the clay, resulting in a dense, hard product that is less porous and highly resistant to water damage. This thermal transformation gives kiln-fired bricks their durability and strength.