Painting new wood work
Painting new wood work

Painting new wood work

Learn : Painting new wood work : Knotting or killing the knot, Application of priming coat, Stopping, Application of finishing coats. Painting new wood work   Following points should be attended to before painting new wood work:   (i)        Only well seasoned timber should be painted otherwise not only shall the paint be spoilt but also due to dry rot the timber is likely to decay early. Also the paint surface will otherwise crack due to uneven shrinkage   (ii)       It is advisable not to paint excessively dry wood.   (iii)     Paint should be applied to only dry surface. (iv)      The surface to be painted should be rendered smooth, clean and free from rust or dirt. (v)       All nails should be punched in 1/2 cm below the surface. (vi)      Large and loose knots should be cut out and filled tightly with correctly fitting wooden pieces. (vii)    The surface should be…

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Removal of old paint and painting
Removal of old paint and painting

Removal of old paint and painting

Learn : Removal of old paint and painting : Remove the paint, old paint and painting Removal of old paint and painting REMOVAL OF OLD PAINT One of the following two methods could be employed to remove old paint from a surface : (i)        Burning the paint by directing the flame of a blow lamp on the painted surface and scrapping it. The method is quite suitable, quick and economical in case of iron or steel work but only expert workmen could be depended upon for its use in case of wood work. A little carelessness could leave the wood charred. (ii)       Applying any one of the following paint removers : (a)       Hot solution of equal parts of soap, potash and quick lime is applied on the surface and kept on it for 24 hours, after which washing with hot water will remove the paint. (b)       Two parts of quicklime and…

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Preparation of oil paints
Preparation of oil paints

Preparation of oil paints

Learn :Preparation of oil paints Learn : Composition of oil paint PREPARATION OF OIL PAINTS. To get started making oil paint, you’ll need: 1) Cold-pressed, raw, or unrefined linseed oil – Linseed oil tends to do much of the heavy lifting in many oil based paint formulations. The reason is that unlike most plant based oils, linseed oil is known as a drying oil. For example, if you were to spill some olive oil on your counter top, chances are it would still be wet to the touch many weeks later. Linseed oil is different in that if you were to spill some on your counter, it would dry to form a tough film within a few days. While you’ll be able to find linseed oil at most artist supply shops, you can also find it at the grocery store as flax seed oil. Despite what the fancy artist paint brands…

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Characteristics of a good paint
charecteristics of a paint,

Characteristics of a good paint

Learn : Characteristics of a good paint,Paints, Paints Classification Characteristics of a good paint Paints Paints  are used to protect metals, timber or plastered surfaces from the corrosive effects of weather, heat, moisture or gases etc. and also to improve their appearance. Paints Classification Paints in common use are classified as oil paints, water paints, cement paints and bituminous paints. There are some "special paints" used for special purposes e.g. heat resisting or fireproof paints, chlorinated rubber paints (for protection against acid fumes etc.) luminous paints (for visibility of painted surfaces in the dark) etc., etc. Characteristics Following are the Characteristics of a good paint:   (i)        It should have a good body or spreading power. (ii)       It should work smoothly and freely and be capable of being laid in a thin coat with the brush. (iii)     It should form durable, tough and resistant to wear film on drying.   (iv)     …

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Composition of oil paints
Composition of oil paints : Base,Vehicle,Drier,Colouring pigment,Thinner

Composition of oil paints

Learn :Composition of oil paints: Base: White lead, Red lead, Zinc oxide (or zinc white), Iron Oxide, and metallic powders such as Aluminum, Copper and Bronze etc. are the commonly used bases,Vehicle: Oils most commonly used as vehicles are : Linseed oil, Poppy oil. Nut oil and Tung oil. Colouring pigments,Solvent or thinner,Drier,Inert filler Composition of oil paints Oil paints consist essentially of – (i) a base, (ii) a vehicle (always an oil, generally raw or boiled linseed oil), and (iii) one or more colouring pigments. It may also contain one or more of (iv) a solvent or thinner, (v) a drier, and (vi) an inert filler. By suitable variation of the type and proportion of the various constituents the paints can be made dry, glossy or flat as desired. Other properties such as permeability to water could also be varied accordingly. All the possible constituents of paints are described in…

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Surkhi,Powdered broken brick (burnt brick)
Surkhi,Powdered broken brick (burnt brick)

Surkhi,Powdered broken brick (burnt brick)

SURKHI Surkhi,Powdered broken brick (burnt brick) locally called surkhi is used as fine aggregate in lime mortar. Surkhi,Powdered broken brick shall be prepared by finely grinding well burnt good quality bricks free from under burnt particles of soluble salts, pyrites and adherent coatings of soil or silt. The maximum quantity of clay, fine silt and fine dust present shall not exceed five per cent by weight. Requirements for Broken Brick (surkhi) fine Aggregate for use in Lime Mortar FUNCTIONS OF SURKHI IN MORTAR Surkhi,Powdered broken brick is used as an adulterant but it imparts strength and hydraulic properties to the mortar. To develop more strength is should be ground very finely with lime in the mortar grinding mill. Surkhi mortar is a mixture of lime,surkhi and water. It is lime morta in which sand has been substituted by surkhi for economy and strength. Note:- surkhi is finely powdered burnt clay…

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Analysis of T beam working stress method
Analysis of T beam working stress method

Analysis of T beam working stress method

Learn : Analysis of T beam working stress method : Neutral Axis is Within the Flange (n < Df), Neutral Axis Lies in the Web of the Beam (n >Df) ANALYSIS OF T BEAM Consider the section of a T-beam shown in Fig. 2.14 (a). The analysis of a T-beam comprises of following two cases : (i)        Neutral axis is within the flange. (ii)       Neutral axis is in the web. Case 1 : Neutral Axis is Within the Flange (n < Df)  Equivalent or Transformed Section The equivalent section of the T-beam in terms of concrete is shown in Fig. 2.13 (b). The concrete below the neutral axis is assumed to be cracked and the area of steel is replaced by an equivalent concrete area which is equal to m.Ast. The compression area is rectangular in shape as n < Df. Thus, this flanged beam can be analyzed exactly as…

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T beams and terms used in T beams in Reinforced cement concrete

T beams and terms used in T beams : Breadth of Web (bw),Thickness of the Flange (Df),Overall Depth of the Beam (D),Effective Width of the Flange (bf),Effective width of the compression flange of the flanged beam in Reinforced cement concrete T beams and terms used in T beams in Reinforced cement concrete T BEAMS In RCC construction, slabs and beams are cast monolithic-ally. In such construction, a portion of the slab act integrally with the beam and bends along with the beam under the loads. This phenomenon is seen in the beams supported slab system as shown in Fig. 2.11. The portion of the slab which acts integrally with the beam to resist loads is called as Flange of the T-beam or L-beam. The portion of the beam below the flange is called as Web or Rib of the beam. The intermediate beams supporting the slab are called as T-beams and the…

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Steel beam theory is used to find the MR of doubly reinforced beam

Steel beam theory is used to find the approximate value of the moment of resistance of a doubly reinforced beam specially when the area of compression steel is equal to or more than the area of the tensile steel. Steel beam theory moment of resistance of a doubly reinforced beam The moment of resistance of a doubly reinforced beam consists of : (i)        Moment of resistance of compression concrete and the corresponding tensile steel (Ast1) i.e., moment of resistance of balanced section (M1). (ii)       Moment of Resistance M' of the compression steel (Asc) and the additional tensile steel (Ast2). In the steel beam theory : (i)        Concrete is completely neglected. (ii)       The moment of resistance is taken equal to the amount of the couple of compressive and tensile steel. (iii)     The permissible stress in compressive steel is taken as equal to the permissible stress in tensile steel. \[\therefore M _{r}=\sigma…

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Types of problem in doubly reinforced beams working stress method

Types of problem in doubly reinforced beams working stress method: Determination of moment of resistance of the given section,Determination of actual stresses in concrete and steel,Design of the section. Types of problem in doubly reinforced beams working stress method Determination of moment of resistance of the given section. Determination of actual stresses in concrete and steel. Design of the section.  Determination of Moment of Resistance             Given : (i)        Dimension of the beam section (b and d) (ii)       Area of tensile steel Ast and area of compressive steel Asc (iii)     Permissible stress in concrete {σcbc) and permissible stress in steel (σst)             Procedure : Calculate \[m=\frac{280}{3\sigma_{cbc}}\] Calculate critical neutral axis (nc) \[\frac{n_{c}}{d-n_{c}}=\frac{m.\sigma_{cbc}}{\sigma_{st}}\] Calculate actual neutral axis depth (nc) \[\frac{b.n^{2}}{2}+(1.5m-1)A_{sc}(n-d_{c})=m.A_{st}(d-n)\] Compare n and nc (a)       If n>nc the section is under reinforced      (fully stressed) Maximum tensile stress developed in steel = σst Maximum compressive stress developed in concrete \[\sigma_{cbc}(where  \sigma'_{cbc})is  less …

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