Bulking of Sand

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

1 2 3 4 5 10 15 30 60

Length of Drain in metres 1.370 3.040 9.760 30.400 34.960 48.040 56.240 78.995 104.880

Area of soak-pit in metres2 12 12 15 17.3 19.5 25.8 32.3 44.2 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 -Degrees

Trigonometric Ratio

i = 30

sin i = sin 30 =

r = 18

sin r

sin 18

0.5 0.309

i = 45

sin i = sin 45 = 0.707

r = 60

sin r

sin 60

Refractive Index

0.866

1.62

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.