The corrosion of steel reinforcement inside a concrete structure is undesirable in the following ways: (i) The presence of rust impairs the bond strength of deformed reinforcement because corrosion occurs at the raised ribs and fills the gap between ribs, thus evening out the original deformed shape. In essence, the bond between concrete and deformed…
Varnish is the solution of resins or resinous substances like amber, copal, shellac, gum resin etc. in solvents like oil, turpentile, alcohol etc. Depending upon the solvents used varnishes are classified as, oil varnishes, turpentilevarnishes, spirit varnishes and water varnishes. The desirable characteristics of an ideal varnish are 1. It should give glossy surface. 2. Should be…
Distempers are the cheaper variety of paints in which chalk is used as base and water is used as a carrier.The emulsifying agent which is commonly used is glue or casein. Distempers are available in powder form or in the form of paste. They are to be mixed with hot water before use.The surface to be distempered should be…
1. It should be possible to apply easily and freely. 2. It should dry in reasonable time. 3. It should form hard and durable surface. 4. It should not be harmful to the health of workers. 5. It should not be easily affected by atmosphere. 6. It should possess attractive and pleasing appearance. 7. It…
Paints are applied on the surfaces of timber, metals and plastered surfaces as a protective layer and at the same time to get pleasant appearance. Paints are applied in liquid form and after sometime the volatile constituent evaporates and hardened coating acts as a protective layer. Constituents of Paint The essential constituents of paints are:…
Cement is used widely for the construction of various structures. Some of them are listed below: (i) Cement slurry is used for filling cracks in concrete structures. (ii) Cement mortar is used for masonry work, plastering and pointing. (iii) Cement concrete is used for the construction of various structures like buildings, bridges.water tanks, tunnels, docks, harbours etc….
(a) Soundness Test: It is conducted by sieve analysis. 100 gms of cement is taken and sieved through IS sieve No. 9 for fifteen minutes. Residue on the sieve is weighed. This should not exceed 10 per cent by weight of sample taken. (b) Setting Time: Initial setting time and final setting time are the two important…
(i) Chemical properties: Portland cement consists of the following chemical compounds: (a) Tricalcium silicate 3 CaO.SiO2 (C3S) 40% (b) Dicalcium silicate 2CaO.SiO2 (C2S) 30% (c) Tricalcium aluminate 3CaO.Al2O3 (C3A) 11% (d) Tetracalcium aluminate 4CaO.Al2O3.Fe2O3 (C3AF) 11% There may be small quantities of impurities present such as calcium oxide (CaO) and magnesium oxide (MgO). When water is added to cement, C3A is the first…