CHAPTER 5 clay and clay producte.ppt CHAPTER 5 clay and clay producte.ppt
- 1. CHAPTER 5 CLAY AND CLAY PRODUCTS Clays: - are finely grained soils resulted from decay of rocks * Chemical constituents of clay - hydrate of alumina silicate (Al203. 2Sio2.2H20) - Silica (Si O2) - Ferric Oxide (Fe2O3) - Lime (Cao) - Magnesia (Mgo) - Carbon dioxide (Co2) - Alkalies, water, etc.
- 2. BRICKS • Are building materials manufactured from clays (raw material) • Are most extensively used materials of construction because of their strength, durability, insulating property against heat and sound.
- 3. Raw material •Clay 20 - 40% •Sand 30 - 50% •Others (lime, silt, cement, etc.) - 20 - 35%
- 4. Functions Of Constituent Materials a) Alumina: - is a fine-grained mineral, which makes the major part. -Becomes plastic when mixed with water and is capable of being molded to the desired shape. -On drying it loses its plasticity and becomes hard
- 5. Constituent Materials cont …… b) Silica: - is useful in reducing shrinkage & wrapping in burning - its presence in bricks produce hardness and durability; however, a large percentage of uncombined silica is undesirable because it leads to brittleness of the product. - silica fuses only at very high temperature (which is lowered in the presence of alumina and iron oxide)
- 6. Constituent Materials cont …… c)Lime: - When present in small quantities, lime acts as a flux and lower the fusion point of silica. Excess of lime may cause the bricks to melt & loose their shape It also acts as a binder to the clay & silica particles leading to greater strength.
- 7. Constituent Materials cont …… d)Iron Oxide:- Lowers fusion point of silica & the clay and hence helps the fusion of brick particles. - Imparts the color of the clay and the burnt product. (Light yellow to red depending on its percentage) . Higher % make bricks dark blue. The appropriate iron type should be used - e.g. if iron present in the form of pyrites (sulphides of iron), it can get oxidized, crystallize and split the bricks to pieces.
- 8. Constituent Materials cont …… •e) Magnesia:- Usually present in small quantity (1%) in clay and together with the iron oxide, it gives the brick darker or even black colour. - It also lessens wrapping of bricks in burning.
- 9. MANUFACTURE OF BRICKS Raw material (clay) should be - excavated and crushed mixed with water to the desired consistency (mix until the whole mass becomes homogenous and plastic(=tempering)) the tempered clay is then fed in to molds made of timber or metal & pressed (hand molding) or extruded through a rectangular hole( mechanical molding) and cut to desired length. The brick at this stages called green brick
- 10. MANUFACTURE OF BRICKS CONT…. Drying green brick Burning: - (900 - 12000c) in a kiln Cooling: two to three days for kiln burnt bricks Then we have the brick
- 11. Quality Of Bricks Depend On Constituent materials efficiency of the kiln mix proportioning burning temperature
- 12. TYPES OF BRICKS Two types of clay bricks that are manufactured in Ethiopia at present. 1) Solid clay bricks i. Brick without holes/depression ii.Brick with holes up to 20mm& are of holes less than 25% lb. iii.brick with depression not exceeding 25% of the base area and having a max. depth of depression 10 mm. 2) Hollow clay bricks and beam tiles.
- 13. TYPES OF BRICKS CONT…… Solid clay bricks: a) brick without holes or depression. b) brick with holes up to 20mm each and Area of holes 25% bl L b h
- 14. TYPES OF BRICKS CONT…..
- 15. TYPES OF BRICKS CONT….. Hollow clay bricks and beam tiles a) with two faces keyed ( combed, or scared) for plastering or rendering. b) with two faces smooth and suitable for use with out plastering or rendering on either side. c) with one face smooth and other face keyed for plastering. Fig. Hollow clay bricks Fig Hollow Clay beam tile L = 25 cm L = 30 cm h = 16 cm b = 40 cm b = 25 cm 12 cm = h
- 16. CLASSES OF BRICKS Adobe brick - brick that is not burnt in a kiln at all. - traditional - adding lime increases bonding Sand-lime brick - not burnt at high temperature. - cement can sometimes be used. Kiln burned brick - brick burnt at high T0. Concrete bricks - is like a concrete block- relatively coarser agg. (6mm Diameter ) is used. - are lighter in wt than concrete blocks - less density. - are fire resistant. - less sound transmission.
- 17. TYPES OF BRICKS (DEPENDING ON FUNCTION) Common bricks - for general building purpose. Facing bricks - with a better quality control - for better appearance. Glazed face bricks - have shiny characteristic due to spraying of some salts which results a shiny luster after burning. Firebricks - bricks for fire resistance. - dark in color. Paving bricks - used in walkways, pavements. Engineering bricks - for use where high strength and / or low water absorption are required
- 18. Testing And Classification Of Bricks •Tests - visual inspection - as shape, color, blister, cracks. •Checking of dimension and plainness. •Compressive strength. •Water absorption •Saturation coefficient •Efflorescence - assed by repeated wetting and drying of test bricks.