4.1 Name TWO reactions which take place during the hydration process of cement - NSC Civil Technology Woodworking - Question 4 - 2017 - Paper 1

Cement can absorb moisture from the air over time, leading to premature hydration. This results in clumping, decreased effectiveness, and reduced compressive strength, which ultimately compromises the integrity of the concrete mix.

Lime enhances the workability of the mortar, making it easier to handle and apply.

The first ingredient put into the concrete mixer is usually coarse aggregate, such as gravel.

1. Retaining formwork: Keeping the molds in place helps retain moisture.
2. Covers: Using wet burlap or plastic sheeting to keep the surface damp.
3. Curing compounds: Applying special sprays that form a moisture-retaining film on the surface.

The cube test is essential to determine the compressive strength of concrete, ensuring that it meets structural requirements and standards before use in construction.

A neat sketch should depict the 'C' shape of channel iron, illustrating the flanges at the top and bottom with a vertical web connecting them.

1. Easily absorbed: The preservative should penetrate the wood effectively.
2. Cheap: Cost-effective options are preferable for wide usage.
3. Not harmful: Must be non-toxic to ensure safe handling and application.

Plywood is made from thin layers of wood veneer glued together with the grain direction of adjacent layers oriented perpendicular to each other. This cross-graining technique improves stability and strength.

To calculate the volume, use the formula:
$Volume = Length imes Width imes Thickness$
Convert thickness to meters: 75 mm = 0.075 m.
Thus,
$Volume = 6 m imes 3 m imes 0.075 m = 1.35 m^3$

Assuming standard brick dimensions, calculate the number of bricks using:
$Bricks = \frac{Length \times Height}{Area \ of\ one\ brick}$
Convert length and height into the same units as the brick size to find the total required.