Alpha breathing

EVOCATION

Ceramic tiles ceramic tile is tile made of clay

Characteristics of Ceramic tiles Water absorption Durability Not affected by oxygen Abrasion resistance Impact resistance Breaking strength Chemical resistance - resistant to almost all acids, alkalies,

Uses of Ceramic tiles used almost everywhere- on walls, floors, ceilings, fireplaces, in murals, and as an exterior cladding on buildings.

Timbers Wood suitable for building or engineering purposes Applied to trees measuring not less than 0.6m in girth.

Characteristics of Soft timber Light in weight Light in colour It is resinous It has straight fibres It has distinct annual rings Comparatively weak It can be split easily

Characteristics of hard timber Heavy in weight Dark in colour Non-resinous Close grained Does not show clear annual ring Strong Durable Eg. Sal Teak Etc.,

Uses of timber Used for doors & windows, roofing materials, etc., For formwork of cement concrete, scaffolding, etc., For making railway coach wagons. For making furniture, agricultural, musical instruments and sports goods. For making railway sleepers, packing cases, etc., Used for temporary bridges & boat construction.

Formwork

scaffolding

railway coachwagons, packing case

Cement mixture of burned (at high temp.) calcareous & argillaceous material. Calcined product is called clinker Clinker + gypsum- pulverised to fine powder – cement.

Properties of cement 1.It should be uniform in colour 2.Feel uniform, cool when touched and should sink in water 3.Free from lumps 4.Cement mortar should have a compressive strength of 11.5 N/mm 2 & 5.Tensile strength of 2N/mm 2 at the age of 3 days. 6.At the age of 7 days compressive strength should be 17.5 N/mm 2 & tensile strength not should be <2.5 N/mm 2 7.% of alumina and iron oxide should not be less than When ignited should not loose 4% of its weight. 9.Sulphur content should not be > 1.5% 10.Weight of magnesia should not exceed 5% 11.Specific surface should not be less than 2250 mm 2 /mg 12.Initial setting time should be 45 minutes & final setting time shall be around 10 Hours 13.Expansion should not be > 10 mm

Uses of cement Cement mortar used for masonry work, plastering, pointing & joints of pipes, etc., Binding material in concrete Construction of bridges, culverts, dams, tunnels, etc., needs cement. Manufacture of precast piles, pipes, garden sheets, etc., Underwater construction – quick setting cement. Floor finishing – White & coloured cements Repair works of cracks – Expansive cements

quick setting cement

Types of cement Quick setting cement Low heat cement High alumina cement Expanding cement Rapid hardening cement Acid resistant cement Sulphate resisting cement White cement Coloured cement Portland puzzolana cement

Aggregates Occupy 70-75% of the total volume of concrete Inert material

Aggregates Coarse aggregate e.g. Gravel – > 4.75mm Fine aggregate e.g. sand – Between 4.75 & 0.075mm Silt – varies from 0.02mm – 0.075mm Clay – <0.02mm

Characteristics of aggregates cheap fillers hard material provide for volume stability reduce volume changes provide abrasion resistance

Uses of aggregates Aggregates are used in construction to provide drainage, fill voids, protect pipes, and to provide hard surfaces. They are also used in water filtration and sewage treatment processes. In concrete it provides a rigid skeletal structure and to reduce the space occupied by the cement paste. Railway ballast generally consists of a tough igneous rock, such as granite, with large (40-50 mm size) angular pieces that lock together. Because of the way igneous rock is formed it is highly resistant to pressure and does not break easily.

Concrete Mixture of (cement + sand + crushed rock + water) Types: –Light weight –High density –Polymer

Characteristics of concrete It has high compressive strength. Free from corrosion Hardens with age Steel reinforcement is placed to take up tensile stress (RCC) Shrinkage occurs when it hardens It is porous due to the presence of voids Has hard surface to resist abrasion.

Uses of concrete Used for construction of RCC flat-roof slabs, bridges, dams, chimneys etc., Coloured concrete – Ornamental finishes in buildings, park lanes, separating lines of road surfaces, etc., Light weight concrete – multi-storeyed constructions No-fines concrete – cast-in-situ external load bearing walls of single & multi-storey houses, retaining walls, etc., Sleepers in railways Prestressed concrete in bridges. Nuclear reactors – High shielding capacity for radioactivity.

PUZZELS Which letter is midway between the letter two letters below the letter immediately to the left of the letter G, and the letter three letters above the letter immediately to the right of the letter V?

Ans: L

What number should replace the question mark?

Ans: 8. Sol. Each number in the segment at the bottom is the sum of the four numbers in the sections either side. Thus = 18

Mind map

Assessment The initial setting time of cement should not be less than _____ minutes. (a)10 (b) 20 (c) 30 (d) 40 The expansion of cement should not be greater than ____ when soundness test is conducted (a) 4 mm (b) 6 mm (c) 8 mm (d) 10 mm Cement mortar at the age of three days should have a compressive strength of (a) 11.5 N/mm 2 (b) 12.5 N/mm 2 (c) 13.5 N/mm 2 (d) 15 N/mm 2