Difference between clay bricks and concrete bricks

Concrete bricks	Clay bricks
Concrete bricks are far simpler to manufacture: Suitable sands, stone and cement are proportionately mixed together with water, vibrated in a press, allowed to cure for about 14 – 28 days and are then ready for use. Total process time 15 to 30 days. Energy costs are quite low and there is minimal pollution.          Concrete brick are formed in a mold and then allowed to cure (preferably for about 28 days).	Clay bricks are made in a process that starts with a suitable blend of clays that have to be mined, aged, then milled/mixed to even consistency. The clay is then extruded through a special press and sliced to size. These unburnt bricks are dried out before being placed in a kiln that is heated to between 700c and 1100c. Thereafter, when the firing is complete, the bricks need to be cooled and classified as to color and strength. The process is very energy intensive, generates large amounts of carbon dioxide, is quite difficult to control and takes up to 3 months to complete. If that was not all, the set-up cost of a reasonable factory is about 10 times that of concrete for the same output.
Concrete brick are mainly used for walkways, patios and fill-ins on concrete walls. Clay brick are used for building veneers, patios, walkways, retaining walls and more.	Clay brick have lower water absorption rates, higher strength (up to 5,000psi vs 1,200-1,800psi), have higher heat resistance, weather better, and hold their color better
Concrete bricks on the other hand tend to shrink about the same amount (partly curing and partly drying out) usually in the first 6 months after construction. So concrete masonry walls need contraction joints.	Clay bricks tend to expand after manufacture in the first few years of their life – about 3mm to 5mm over 10 meters of wall length. So expansion joints need to be provided.
Concrete bricks accept paint relatively well.	Clay bricks often exude metallic salts in their early years which cause paint to peel off.