The beads are used at the junction of wall to ceiling plaster and plaster to other materials. There are various types of galvanized steel beads and stops which are produced to employ with plaster and plasterboard as angle and stop reinforcement. In the latter, surfaces are treated by combination of silica sand and polymer and the bond is provided by silica sand grain after the polymer is dried. In the former method, polyvinyl acetate is brushed on the surface and plaster is spread over when the PVA is still sticky which creates bond. There are two different solutions for surfaces with low suction include PVA bonding agent and polymer bonding agent. Therefore, it is advised to decrease water absorption degree by either liquid primer or spraying water before plastering. The degree of water absorption by dense smooth surface bricks which assist in plaster adhesion is called suction.īlocks produced by light weight concrete have large suctions that prevent attaching plasters to surfaces properly. Machine pressed bricks with high density and smooth surfaces absorb suitable amount of water that will help adhering plasters to surfaces. Plaster keys limit or restrain shrinkage of the cement that is principal component of undercoat plaster. The mechanical keys which adhere hardened plaster to the surfaces is created after spread wet undercoat plaster is dried. Bricks or blocks with rough and solid surfaces possess means of mechanical adhesion when plaster is applied to the background walls or ceilings. ![]() Type of plaster and its application varies depending on the surface of the wall or ceiling which are set to be plastered. There are various types of gypsum plaster that are produced by heating gypsum to a specific degree for example anhydrous gypsum manufactured by heating gypsum up to 170 C o, hemihydrates gypsum produced by heating gypsum more than 170 C o.įurthermore, depending on applications for walls or ceilings gypsum plasters can be categorized such as casting, undercoat, finish, one coat and machine applied plaster. Moreover, small expansion of gypsum is considered significant propertied that prevent shrinkages and cracks. So, important gypsum plaster that is employed as under coat, finish coat, and replaced lime and cement broadly. Gypsum plaster is widely used plaster materials that could be mined naturally or produced as a by-product. Plasticizer is a liquid that added to the mixture to ease plaster spreading over the surface. Mixture of sand and cement might be plastic and require experienced and skill labor therefore plasticizer or lime is added to the mixture usually by volume ratio of 1cement:0.25 lime: 3 sand or 1 cement to 4 sand with plasticizer. Grey powder Portland cement is mixed with water by the ratio of 1cement to 3 or 4 clean washed sand by volume as an under coat for hard background for example brick block walls and partitions. Lime plaster could be used for ancient structure restoration and rehabilitation. Lime plaster might be shrink after drying so animal hair of about 5 Kg is used for 1 m 2 to avoid lime plaster cracking and shrinking. Not only this mixture is used for under coat but also used as finish coat. Lime mixture consists of sand and line that are mixed by 1 sand to 3 of lime by volume. Types of Plaster based on Material Used Lime Plaster Types of Plaster Finishes used in Building Construction are:.Plaster Finishes to Timber Joists and Studs.Types of Plaster based on Material Used.Finally, finish coat is applied for the surface.įigure-1: Advantages of Two Under Coat of Plaster That is why spreading thin layer and permitting to harden followed by employing second under coat is the best practice as shown in Figure 1. This is because thick under coat tend to sag due to weight of thick wet plaster. Moreover, walls constructed from irregular and different size stones might require three coating. In this case under coat which is low cost coarse grain material is used to render the surface followed by finish coat that is thin layer of fine grain materials. However, there are surfaces that irregularities are more than 3cm. Wet materials that spread over wall or roof surfaces should not be more than 0.3 cm. Recently, wall surfaces in modern houses are finished with bricks or blocks or aesthetically pleasing stones to show beautiful appearances. The prime purpose of plastering is to obtain hard and smooth surface that could be painted and provide nice aesthetic appearances. At the beginning, wet materials are spread over the block or brick works and then suitable equipment is used to make the surface smooth level. □ Reading time: 1 minute Plastering is a process by which coarse surfaces of wall or ceiling roofs are changed or turned or rendered to provide smoothness.
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