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.
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Answer
Chemical Reaction: This involves the combination of cement with water to form calcium silicate hydrate, which gives strength to the concrete.
Physical Reaction: This includes the binding of water and the physical hardening of the cement paste.
Step 2
Briefly motivate why cement must not be stored longer than three months.
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Answer
Cement can absorb moisture over time, leading to clumping and a decrease in its quality. Prolonged storage can also result in a loss of strength and stability, making the cement ineffective for construction purposes.
Step 3
Name ONE purpose of lime in a mortar mix.
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Lime improves the workability of the mortar, making it easier to apply and ensuring better adhesion to the bricks or stones.
Step 4
Which ingredient is first put into the concrete mixer when concrete must be mixed?
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The first ingredient is typically the aggregate, such as gravel or sand, as it provides the bulk of the mixture.
Step 5
Name THREE methods that can be used for curing concrete.
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Retaining Formwork: Keeping the forms in place for a longer period allows the concrete to cure properly.
Covers: Using wet burlap or plastic sheeting to retain moisture in the concrete surface.
Curing Compounds: Applying chemical curing agents that keep moisture in the concrete mix.
Step 6
Briefly motivate why the cube test must be performed on concrete.
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The cube test evaluates the compressive strength of concrete, which is essential to ensure that the concrete meets the required strength standards for safety and durability in construction.
Step 7
Name TWO uses of Copper.
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Electrical Wires: Copper's excellent conductivity makes it ideal for electrical wiring.
Electrical Equipment: Components such as transformers and connectors benefit from copper's conductive properties.
Step 8
Name TWO uses of Zinc.
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Alloy Material: Zinc is commonly used to create various alloys like brass, which enhances material properties.
Covering for Iron and Roof Sheets: Zinc is utilized for galvanizing iron and manufacturing roofing sheets due to its resistance to corrosion.
Step 9
Make a neat sketch to illustrate the profile of channel iron.
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A sketch should depict a ‘C’ shaped cross-section, showing the two vertical flanges and the horizontal web in between.
Step 10
Name THREE properties of a good preservative for wood.
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Easily Absorbed: A good preservative should penetrate the wood for effective protection.
Cheap: Cost-effectiveness is important for widespread use.
Readily Available: Availability ensures that the preservative can be easily sourced when needed.
Step 11
Briefly describe the composition of plywood.
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Plywood consists of several layers of wood veneer, glued together with adjacent layers having their grain directions perpendicular to each other. This arrangement enhances strength and minimizes warping.
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.
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Answer
To calculate the volume of concrete, use the formula:
extVolume=extLengthimesextWidthimesextThickness
Convert thickness to meters: 75 mm = 0.075 m.
Thus,
extVolume=6mimes3mimes0.075m=1.35m3.
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.
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Calculate the wall area:
extArea=extLengthimesextHeight=4mimes2.4m=9.6m2.
Assuming a standard brick size of 0.2 m x 0.1 m, the area of one brick is:
0.2mimes0.1m=0.02m2.
Therefore, the number of bricks required:
ext{Number of bricks} = rac{9.6 m^2}{0.02 m^2} = 480 bricks.
