30 Questions
What is the primary purpose of mortar?
To glue masonry units together or attach them to a receiving structure
What is the recommended cement to sand ratio for first-class mortars?
1 part cement to 3 parts sand
What is the purpose of adding hydrated lime to cement mortar?
To increase the workability and strength of the mortar
What is the recommended cement to sand ratio for the top surface of floors and walks?
1 part cement to 1 part sand
What is the primary difference between mortar made with fine sand and mortar made with coarse sand?
Mortar made with fine sand requires a much larger quantity of cement to obtain a given strength
What is the preferred method for mixing large quantities of mortar?
Mixing in a mechanical mixer
What are the types of bricks most frequently used in architecture?
Common brick only
What special characteristics do glazed bricks have?
Smooth outer surface with a dull finish or gloss
Which type of brick is used for lining furnaces, fireplaces, and chimneys?
Fire (refractory) brick
In what pattern are bricks laid for a herringbone bond?
Diagonal pattern
Which type of bond consists of five stretcher courses and then a header course?
Common Bond
What is the purpose of facing bricks in masonry work?
To provide specific surface characteristics for exposed surfaces
What is the purpose of bonding plaster?
Develops more adhesive strength for interior finish on smooth concrete walls or ceilings
When is lightweight gypsum plaster typically used?
When weight is important and for fireproofing other materials like steel
What is the composition of a sand float finish?
1 Keene’s cement, ¼ lime putty, 1/10 fine white sand by weight
What is the purpose of Keene’s cement?
Mixed as a hard finish for two and three-coat gypsum plaster for interior use
What is the key function of molding plaster?
Specially designed for ornamental plaster work and castings
When should a 1/3 gypsum plaster, 1 lime putty mixture be used?
As a hard finish in combination with fine white sand
What are the usual mortar joint sizes between brick courses?
3/16” and ½”
Which ingredient is NOT typically used in the production of Concrete Hollow Blocks?
Lime
What type of aggregates can be used in the production of lightweight concrete hollow blocks?
Cinders, Expanded slag, Expanded shale or clay
Which type of concrete hollow block has the highest fire resistance?
Expanded slag block
For what purpose should CHB of 100mm (4”) thickness be used?
Interior partition walls where weather-tightness is not needed
Which type of concrete hollow block is NOT mentioned in the text?
Pillars
What does the term 'plaster' typically refer to?
Gypsum plaster
What is the purpose of adding fiber or hair to the plaster mixture?
To increase the strength of the first coat
In a three-coat plastering job, what is the purpose of the brown coat?
The straightening coat applied after the scratch coat
What is the purpose of the scratch coat in a three-coat plastering job?
To act as a binding coat for the subsequent coats
In a two-coat plastering job, how are the scratch coat and brown coat applied?
The scratch coat and brown coat are combined into one coat
What is the recommended practice for retempered mortar?
Discard the mortar once it has begun to set and retemper a new batch
Study Notes
Mortars and Plasters
- Mortar: a proportioned mixture of siliceous materials (sand, crushed stone) and cement (lime, Portland) that hardens into a stonelike mass
- Mortar is used to glue masonry units to each other or to a receiving structure like a wall or floor
- Plaster: mortar applied to wall surfaces as a preparation or a hard finish coat
Cement Mortar
- A proportioned mixture of cement, fine aggregate, and water
- For first-class mortars, 1 part of cement should be mixed with not more than 3 parts of sand
- Replacing 10-15% of cement with hydrated lime gives greater workability and increases strength
- Mixing can be done by hand or mechanical mixers, with the latter preferred for large quantities
Unit Masonry
- Bricks: types include common, facing, glazed, and fire (refractory) bricks
- Standard brick size: 3-3/4” x 2-1/4” x 8”
- Brick work: common bond, English bond, Flemish bond, and herringbone patterns
Types of Plaster and Their Uses
- Gypsum plaster: bonding plaster, lightweight gypsum plaster, and fire-resistant plaster
- Gypsum plaster uses: interior finish, smooth concrete walls or ceilings, and fire-proofing other materials
- Keene's cement: used for hard finish, mixed with alum or borax, and burned at 932°F
- Plaster of Paris: used for ornamental plaster work and castings
Concrete Hollow Block
- A hollow masonry unit made of water, Portland cement, and aggregates like sand, gravel, and crushed stone
- Lightweight concrete hollow blocks can be made with aggregates like cinders, expanded slag, and expanded shale or clay
- Standard CHB sizes: 100mm (4”), 150mm (6”), and 200mm (8”) x 200mm (8”) x 400mm (16”)
- Types of concrete hollow block include stretchers, corner blocks, headers, jamb blocks, and beam or lintel blocks
This quiz covers the topic of mortars and plasters, which are proportioned mixtures of siliceous materials and cement that harden into stonelike masses. Mortar is used to glue masonry units or surface finishing materials, while plaster is applied to wall surfaces as preparation or finishing.
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