The mortar for the final coat is usually made by mixing cement and coarse sand in the mix proportion of 1:3 and is placed in about 1 mm thickness.
The pebbles used for dashing should be well washed and thrown wet onto the final coat. The pebbles may be tightly tapped into the mortar with a wooden float or with the flat of the trowel.
This finish of plaster possesses all the advantages of the roughcast finish and is recommended in similar conditions. Pebbledash plaster finish is mostly used for covering exterior walls and provide an aesthetic appearance to the structure.
Plaster of Paris
Plaster of paris or simply plaster is a type of building material based on calcium sulphate hemihydrates. This is a smooth finish achieved by plaster of paris generally applied on internal walls.
According to ‘M.G. Goyal’ (Author of Construction Handbook for Civil Engineer & Architect, Vol 2) Gypsum, a rocklike mineral (IS: 1290) known chemically as hydrous calcium sulphate (CaSO42H2O) is found in many parts of the world, usually combined with impurities such as clay, limestone, and iron oxides. In its pure form gypsum is white, a chalk like material but in combination with impurities, it may be gray, brown or pinkish. Relatively pure calcined gypsum is known as Plaster of Paris, after the huge beds of it that underlie the city of Paris where it was mined in abundance in the late nineteenth and early twentieth centuries.
The origins of plaster of Paris can be traced to Montmartre in North Paris where it was extensively mined from. It is also known as POP.
As described by ‘S.C. Rangwala’ (Author of Engineering Materials book), Plaster of Paris is prepared by heating gypsum crystals at the temperature of 160–170 °C (248–356 °F). It loses about 14.7% of its water content in the form of steam. The resulting product is the hemihydrate of calcium sulphate and it is known as first settle plaster or the “Plaster of Paris”.
The pebbles used for dashing should be well washed and thrown wet onto the final coat. The pebbles may be tightly tapped into the mortar with a wooden float or with the flat of the trowel.
This finish of plaster possesses all the advantages of the roughcast finish and is recommended in similar conditions. Pebbledash plaster finish is mostly used for covering exterior walls and provide an aesthetic appearance to the structure.
Plaster of Paris
Plaster of paris or simply plaster is a type of building material based on calcium sulphate hemihydrates. This is a smooth finish achieved by plaster of paris generally applied on internal walls.
According to ‘M.G. Goyal’ (Author of Construction Handbook for Civil Engineer & Architect, Vol 2) Gypsum, a rocklike mineral (IS: 1290) known chemically as hydrous calcium sulphate (CaSO42H2O) is found in many parts of the world, usually combined with impurities such as clay, limestone, and iron oxides. In its pure form gypsum is white, a chalk like material but in combination with impurities, it may be gray, brown or pinkish. Relatively pure calcined gypsum is known as Plaster of Paris, after the huge beds of it that underlie the city of Paris where it was mined in abundance in the late nineteenth and early twentieth centuries.
The origins of plaster of Paris can be traced to Montmartre in North Paris where it was extensively mined from. It is also known as POP.
As described by ‘S.C. Rangwala’ (Author of Engineering Materials book), Plaster of Paris is prepared by heating gypsum crystals at the temperature of 160–170 °C (248–356 °F). It loses about 14.7% of its water content in the form of steam. The resulting product is the hemihydrate of calcium sulphate and it is known as first settle plaster or the “Plaster of Paris”.
