Bricks, Tiles and Clay Products MCQs – Part 3
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Answer: C. 200 × 100 × 100
The nominal size of a brick is its standard size plus the thickness of the mortar joint. This is used for calculating masonry dimensions.
- Standard (Modular) Size: 190 mm x 90 mm x 90 mm
- Mortar Thickness (Standard): 10 mm
- Nominal Size: (190+10) mm x (90+10) mm x (90+10) mm = 200 mm x 100 mm x 100 mm.
Answer: C. 50%
For good brick earth, the combined proportion of clay and silt is critical for plasticity. The ideal composition includes about 20-30% clay and 20-35% silt. Together, their total content should be at least 50% to ensure the clay can be moulded effectively without cracking.
Answer: C. high temperature
Refractory bricks, also known as fire bricks, are specially manufactured to withstand extremely high temperatures without melting, spalling, or deforming. They are used to line furnaces, kilns, fireplaces, and other high-heat industrial applications.
Answer: C. 20
According to IS 1077, for the dimensional tolerance test, a sample of 20 bricks is selected at random. These bricks are then laid end-to-end, and the total length is measured to check if it falls within the permissible limits specified in the standard. This ensures consistency in the brick size.
Answer: B. ornamental work
Terra cotta, which means "baked earth" in Italian, is a type of earthenware clay ceramic. Due to its versatility and ability to be moulded into intricate shapes, it is widely used for decorative and ornamental work on building facades, such as cornices, mouldings, and decorative panels.
Answer: D. 24 hours
The Indian Standard IS 3495 (Part 2) specifies the procedure for the water absorption test. It requires the dry brick sample to be completely submerged in clean, cold water for a period of 24 hours to ensure maximum absorption for an accurate measurement.
Answer: B. 900ºC-1100ºC
Vitrification is the process during firing where clay particles begin to fuse together, making the brick hard, dense, and strong. For common low-melting clay bricks, this process occurs in the temperature range of 900°C to 1100°C. Firing below this range results in under-burnt, weak bricks, while firing above it can cause over-burning and distortion.
Answer: C. slight
IS 3495 (Part 3) provides a visual classification for efflorescence. When the area covered by the white, powdery salt deposits is more than nil but does not exceed 10% of the brick's surface area, the efflorescence is rated as slight.
Answer: A. reduced drying shrinkage
Adding fly ash to the brick mix helps to control the plasticity of the clay. Because fly ash is a non-plastic material, it reduces the overall shrinkage that occurs as the bricks dry, leading to fewer cracks and less warping.
Answer: D. four
Based on general quality, appearance, and strength, burnt clay bricks are commonly classified into four categories: First Class, Second Class, Third Class, and Fourth Class (or Jhama bricks), with each class having progressively lower quality and strength.
Answer: D. ((W2 - W1) / W1) × 100
The percentage of water absorption is calculated as the ratio of the weight of water absorbed to the original dry weight of the brick, multiplied by 100.
- Weight of water absorbed = (Wet weight) - (Dry weight) = W2 - W1
- Original dry weight = W1
- Percentage absorption = ((W2 - W1) / W1) × 100
| Id | Water absorption (%) | Average compressive strength (kN/m²) |
|---|---|---|
| S1 | 18 | 17500 |
| S2 | 20 | 21000 |
| S3 | 12 | 20000 |
| S4 | 10 | 14000 |
| S5 | 15 | 27000 |
Answer: B. S3 and S5 only
As per IS 1077, for bricks of class higher than 12.5 (including Class 20), the following criteria must be met:
- Average Compressive Strength: Should be ≥ 20 N/mm² (or 20,000 kN/m²).
- Water Absorption: Should be ≤ 15% after a 24-hour immersion test.
Let's evaluate each sample:
- S1: Water absorption (18%) is > 15%. FAIL.
- S2: Water absorption (20%) is > 15%. FAIL.
- S3: Water absorption (12%) is ≤ 15% and Compressive strength (20,000 kN/m²) is ≥ 20,000 kN/m². PASS.
- S4: Compressive strength (14,000 kN/m²) is < 20,000 kN/m². FAIL.
- S5: Water absorption (15%) is ≤ 15% and Compressive strength (27,000 kN/m²) is ≥ 20,000 kN/m². PASS.
Only samples S3 and S5 meet both criteria for Class 20 bricks.
Answer: A. 2.5 g/cm³
IS 2180: 1988 specifies the requirements for heavy-duty burnt clay bricks, which are used for structures carrying heavy loads like bridges and industrial foundations. The standard states that the minimum average bulk density for these bricks shall be 2.5 g/cm³.
Answer: C. 18%
IS: 654-1962 classifies Mangalore pattern roofing tiles into two classes based on quality. Class AA is the superior quality. The standard specifies that for Class AA tiles, the average water absorption shall not exceed 18 percent. For Class A tiles, the limit is 24 percent.
Answer: C. mosaic tiles
Mosaic tiles are precast concrete tiles where the top layer consists of a mixture of cement and small chips of marble, granite, or other colored stones. After setting, the surface is ground and polished to expose the decorative aggregate, creating the characteristic mosaic pattern.