Experiment 1
- Bulking of Sand.
When measuring sand by volume, allowance should be made for the
fact that it can occupy a greater volume when damp than when it is dry.
This effect is known as BULKING. The extent of the bulking varies with the
moisture content and the coarseness of the sand. To determine the amount
of bulking, use is made of the fact that sand saturated with water occupies
the same volume as dry sand.
Equipment required:
• Graduated cylinder
• Ruler
• Damp sand
• Water
Procedure:
1. Loosely fill the damp sand into the
container to a height of D
2. Pour the sand onto a tray and half
fill the container with water
3. Return the damp sand to the tray,
stirring it to ensure that it is fully
saturated
4. When the sand has settled, its
height D1 is again measured and
recorded.
Calculations:
The percentage of bulking can be found using the formula:
Percentage bulking = D-D1x100
D1
Results:
D = 200
D1 = 180
Percentage bulking = 200-180 = 20 x100
180 180
= 11%
Note:
When volume batching materials for making concrete an extra volume of
sand equal to the percentage of bulking must be added.
Experiment 2
-The silt test.
To discover the amount of clay, silt or fine dust in a quantity of
aggregate: sand.
Equipment required:
• 250mm graduated cylinder
• Teaspoon
• Sand
• Salt
Procedure:
1. Pour 50ml of a solution of common salt
(NaCL) in water (approximately 1
spoon per 50ml) into the cylinder
2. Sand is gradually added until the
liquid reaches the 100ml mark
3. Add more solution until it reaches the
150ml mark
4. Shake contents vigorously
5. Allow to settle for 3 hours
6. Measure a ) the volume of the silt
b) the volume of the sand.
7. Use the following formula to calculate
the percentage of the silt content:
Height of silt layer x100 = % silt content
Height of sand
Results:
Test 1
Height of silt layer = 13 x 100 = 17% silt content
Height of sand 76
Test 2
Height of silt layer = 7 x 100 = 8% silt content
Height of sand 87
Note: The amount of silt may be considered acceptable if it does not
exceed 8%.
Experiment 3
- Percolation Test.
Equipment required:
• Shovel
• Water
• Meter rule
Procedure:
1. Dig a trial hole 100x250x500mm
2. Fill the hole with water to a depth of 250mm
3. Check and note the time required for the water to soak away in minutes
4. Divide the total time required for water to soak away by 10. This will
give the time required for 1 inch of water to soak away in minutes
5. By referring this time “r” to the following table it is possible to get the
length of drain or area of soak-pit which will be required.
“T”- Time in minutes Length of Drain Area of soak-pit
in metres in metres2
1 1.370 12
2 3.040 12
3 9.760 15
4 30.400 17.3
5 34.960 19.5
10 48.040 25.8
15 56.240 32.3
30 78.995 44.2
60 104.880 59.4
Table to determine the size of soak-pit and drain.
NOTE: No drain should exceed 20m in length. When the required length
exceeds 20m, two or more drains should be used. There should be at least
3m of a space between drains.
Results:
It took 7minutes for all the water to soak away. Therefore a soak-pit
of 25.8m2 and a drain 48.040m long would be suitable for the piece of land
tested. Since the drains cannot be longer than 20m, 3 separate drains
should be used.
Experiment 4
- To measure the percentage of moisture in a piece of timber.
Equipment required:
• Sample of timber
• Weighing Scales
• Oven
Procedure:
1. Cut a sample piece of the timber 12mm thick and 200mm form the end
of the piece of timber
2. Record it’s weight, this being the Original Weight
3. Place in oven and dry until it stops loosing weight and weigh the piece
again, the Dry Weight.
4. The percentage of moisture in the wood can be calculated using the
following formula:
Percentage of Moisture = Original Weight-Dry Weight x100
Dry Weight
Results:
In the experiment the following results were obtained:
Original Weight = 46 grams
Dry Weight = 40 grams
Loss of weight = 6 grams
This 6grams is the weight of moisture eliminated from the piece and
calculate the moisture content by using the formula above.
Percentage of Moisture = 46-40 x100 = 15%
40
NOTE: Timber cannot be used for woodwork immediately after a tree is
felled and converted into logs as it contains moisture. It must be seasoned
first to eliminate some of this moisture.
Experiment 5.
- To determine the Refractive Index of a Glass Block.
Equipment required:
• Block of glass
• Pins
• Drawing board
• Paper
• Ruler
• Protractor.
Procedure:
1. Fix the sheet of paper to the
drawing board
2. Lay the glass block flat on the
centre of the paper and mark
it’s outline in pencil
3. Stand two pins, P1 and P2
obliquely in line with one side
of the block
4. Place pins P3 and P4 on the
other side of the block, so as
to be lined with P1 and P2,
viewed through the block.
5. Mark the position of the four pins, and then remove them together with
the block
6. Join P1 with P2 and P3 with P4, extending them to intersect the outline
of the block
7. Connect the points of intersection and also draw lines through them at a
normal to the block, i.e. at right angles
8. Measure angles:
i, incidence,
r, refraction,
e, emergence.
9. Repeat stages 3 to 7, but for a different angle of incidence.
Results:
These may be tabulated as follows
Angle Trigonometric Refractive
-Degrees Ratio Index
i = 30 sin i = sin 30 = 0.5
r = 18 sin r sin 18 0.309 1.62
i = 45 sin i = sin 45 = 0.707
r = 60 sin r sin 60 0.866 0.8164
You will see that the angles i and e are equal, i.e. the incident and
emergent rays are parallel (this applies only if the sides of the block are
parallel).
The ratio (sin i/sin r) is a constant for all possible values of i and r.
this constant is known as the refractive index of the material.
Experiment 6
- To determine the reflection at a Plane Surface.
Equipment required:
• Plane mirror (approx
25x100mm)
• Pins
• Drawing board
• Paper
• Ruler
• Protractor.
Procedure:
1. Fix the sheet of paper to the drawing board
2. Draw a straight line across the width of the page at the centre
3. Place the mirror upright on the paper, so that the mirrored surface
coincides with the line
4. Stand a pin directly in front of the mirror and approx 150mm away from
it. This will act as an object and call it Object Pin, O
5. Place two further pins (P1, P2) in front of the mirror obliquely in line
with the image, I, of the object pin – which itself appears to be
somewhere behind the mirror. To do this, the eye must be level to the
board, so that a sighting line can be made
6. Set up another two pins, (P3, P4), as in stage 5, on a different sighting
line
7. Mark the position of all pins, then remove then from the sheet
8. Draw lines P1-P2 and P3-P4 and extend them to meet behind the mirror
9. Join to point O, the points of intersection of both lines with the mirror
surface (A and B). Also draw perpendicular lines from the mirror
surface to points A and B
10. Draw a line connecting point O and I intersecting the mirror surface at
M.
Results:
Light from the object pin enters the eye after being reflected in the
mirror, and the two rays, OA and OB are reflected along (P2P1) and P4P3)
respectively. The image appears to be a point in line with both reflected
rays, and is therefore seen at I, the point where they intersect.
I. Measure OM and MI. They will be found to be equal.
II. Measure angles i and r and i1 and r1 with a protractor.
These are known as the angles of incidence, i and i1, and reflection, r
and r1. The corresponding values for incidence and reflection should be
equal.
Conclusions:
1. The image appears as far behind the mirrored surface as the object is
in front.
2. The angle of incidence of any ray is equal to that of reflection.
Experiment 7
- To determine if a bent copper pipe straightens when frozen.
Equipment required:
Copper Pipe
•
Two stoppers
•
Water
•
Freezing facility.
•
Procedure:
1. Bend the copper pipe
2. Place stopper on one end
3. Fill pipe with water
4. Seal the other end with
second stopper
5. Place in freezer for 24
hours.
Results:
Open freezer and remove the copper pipe after the 24-hour period.
Examine the pipe, which has straightened.
Note:
If this was to occur in buildings the pipe would pull away from the
walls and burst easily so all pipes should be insulated to prevent the freezing
of the pipes.
