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4.1 Name TWO reactions which take place during the hydration process of cement - NSC Civil Technology Woodworking - Question 4 - 2017 - Paper 1
Question 4
4.1 Name TWO reactions which take place during the hydration process of cement. 4.2 Briefly motivate why cement must not be stored longer than three months. 4.3 Na... show full transcript
Worked Solution & Example Answer:4.1 Name TWO reactions which take place during the hydration process of cement - NSC Civil Technology Woodworking - Question 4 - 2017 - Paper 1
Step 1
Name TWO reactions which take place during the hydration process of cement.
Answer
The two primary reactions during cement hydration are:
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Chemical Reaction: This occurs when water is added to cement, leading to the formation of calcium silicate hydrate (C-S-H) and calcium hydroxide.
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Physical Reaction: The added water integrates with cement particles to harden and bond them together, providing strength to the concrete.
Step 2
Briefly motivate why cement must not be stored longer than three months.
Answer
Cement should not be stored longer than three months because it tends to absorb moisture from the air, which can lead to clumping and deterioration of its chemical properties. This moisture absorption can reduce its effectiveness in the hydration process, compromising the strength and durability of hardened concrete.
Step 3
Step 4
Step 5
Name THREE methods that can be used for curing concrete.
Answer
Three methods of curing concrete include:
- Retaining Formwork: Keeping the formwork in place to maintain moisture.
- Ponding: Creating water pools on the concrete surface to keep it wet.
- Spraying: Regularly spraying water onto the concrete to prevent it from drying out.
Step 6
Briefly motivate why the cube test must be performed on concrete.
Answer
The cube test is essential to assess the compressive strength of concrete. By testing the samples, engineers can ensure that the concrete meets the required strength specifications for structural safety and durability.
Step 7
Name TWO uses of each of the following materials in the construction trade: 4.7.1 Copper
Answer
Two uses of copper in construction are:
- Electrical Wires: Used extensively for electrical wiring due to its excellent conductivity.
- Water Pipes: Employed in plumbing systems for its non-corrosive properties and durability.
Step 8
Name TWO uses of each of the following materials in the construction trade: 4.7.2 Zink
Answer
Two uses of zinc in construction are:
- Alloy Material: Used to create alloys such as brass to improve strength and durability.
- Covering for Iron and Roof Sheets: Acts as a protective coating to prevent rusting and corrosion.
Step 9
Step 10
Name THREE properties of a good preservative for wood.
Answer
Three key properties of a good wood preservative include:
- Easily Absorbed: Ensures that the preservative penetrates deeply into the wood grain.
- Cheap: Cost-efficient for widespread application without sacrificing quality.
- Not Poisonous to Humans and Animals: Safety in usage and handling, ensuring it poses minimal risk.
Step 11
Step 12
Use the quantity list on ANSWER SHEET A and determine the volume of concrete which will be needed for a floor with a length of 6 m, width of 3 m and thickness of 75 mm.
Answer
To calculate the volume of concrete needed for the floor:
- Convert thickness from mm to meters: 75 mm = 0.075 m.
- Volume = Length × Width × Thickness = 6 m × 3 m × 0.075 m = 1.35 m³.
Thus, a total of 1.35 m³ of concrete will be required.
Step 13
Use the quantity list on ANSWER SHEET A and determine the number of bricks which will be needed for a cavity wall with a length of 4 m and a height of 2,4 m.
Answer
To determine the number of bricks needed:
- Calculate the area of the wall: Length × Height = 4 m × 2.4 m = 9.6 m².
- Assuming the average size of a brick is 0.2 m², the number of bricks required will be:
- Number of Bricks = Total Area / Area of One Brick = 9.6 m² / 0.2 m² = 48 bricks.
Thus, 48 bricks will be needed.