Building Material and Construction 312338 Practical 16 Answers
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| Building Material and Construction 312338 Practical 16 Answer |
Practical Significance
Building finishes include plastering, pointing, painting, etc. The main objective is to protect the surface from atmospheric agents and to improve its appearance. Plastering is the process of covering rough surfaces such as walls, columns, ceilings, etc. Plastering is done by mortar (binding material) which is a combination of fine aggregate and water in suitable proportion. The binding material may be lime, cement, or mud. Pointing is the art of finishing mortar joints so make them watertight. For plastering and pointing various tools are used.
Observations &Precautions to be followed
1. Type of plasterwork and how to apply.
2. Material used for plaster and its preparation.
3. Method and type of pointing.
4. Equipment used for plastering and pointing work Use safety measures on site.
5. Listen and follow the instructions given by the site in charge.
6. Maintain discipline during the Visit.
1. Answer: Cement Plaster:
Properties: Strong, durable, water-resistant, commonly used modern choice.
Process:
- Base coat with a coarser mix for better bonding.
- Finishing coat with a finer mix for a smooth surface.
2. Answer :
Lime: This has been a dominant plaster material for centuries. It comes in two types:
- Fat lime: Creates a smooth and workable plaster, good for interior walls. Requires slaking (soaking in water) for proper setting.
- Hydraulic lime: Sets harder and faster than fat lime, suitable for exterior use or areas with moisture.
Plaster Preparation:
The specific preparation method depends on the chosen materials. Here's a general outline:
- Slaking lime (if using): Fat lime is soaked in water for several days to allow it to slake (hydrate) properly.
- Mixing binder and aggregate: The chosen binder (lime, cement, or a combination) is mixed with sand and any additional dry ingredients in the desired proportions.
- Adding water: Water is gradually added while mixing to achieve a workable paste. The ideal consistency depends on the application (base coat, finish coat).
- Application: The prepared plaster is applied to the wall in multiple layers, with each layer allowed to dry before applying the next.
3. Answer :
Methods:
- Hand Pointing: The traditional way involves using a trowel to apply and shape the mortar manually.
- Tuck Pointing: A specialized technique that involves filling raked-out joints with mortar and creating a recessed groove in the center, typically enhanced with a contrasting material for decorative purposes.
- Tooling Pointing: Utilizes specific pointing tools to produce various shapes and finishes on the mortar joints.
Types of Pointing :
- Flush Pointing: The most common type is when mortar is applied to fill the joint and leveled to be flush with the brick or stone surface, providing a clean and modern appearance.
- Recessed Pointing: Mortar is pushed into the joint but remains a few millimeters beneath the surface of the brick or stone, forming a shadow line and providing potential drainage benefits in certain situations.
- Beaded Pointing: Creating a raised bead along the joint by tooling the mortar achieves a convex finish, which adds a decorative touch.
- Struck Pointing: The mortar surface is tilted inward slightly to assist with water drainage, similar to flush pointing.
- V-Pointing: A deep groove is raked into the finished flush joint to create a V-shaped channel. Offers a rustic look.
4. Answer:
Plastering:
- Hawk: A flat board, which is square in shape and has a handle underneath, is used as a portable platform to hold and transport plaster from the mixing area to the work surface.
- Trowels: There are various trowel types for different plastering applications:
- Bucket Trowel: I was accustomed to scooping plaster from the mixing bucket and transferring it to the hawk.
- Finishing Trowel: A blade that is wider and flatter is used for smoothing and achieving a plaster surface that is level.
- Corner Trowel: A smaller trowel with a pointed end that is perfect for applying and smoothing plaster in tight corners.
- Darby: A long and straight leveling tool is utilized for larger areas to establish a smooth surface before applying the finishing trowel.
- Mixing A durable bucket is needed for mixing plaster, and a power mixer can be used to efficiently mix large amounts, particularly when using cement-based plaster.
- Floats: Tools that are flat and used for smoothing wet plaster surfaces are available in various materials such as wood or plastic, each with different textures for achieving unique finishes.
- Spray gun (Optional): Large-scale projects might utilize specialized plaster spraying equipment.
- Level and Straightedge: For checking the flatness and plumb (vertical alignment) of the plasterwork.
- Safety Gear: Safety glasses, dust mask, and gloves for protection.