Does
the Type of Glue and
Size of Fill Affect the Strength of a Brick?
1st
Place School Level - 5th Grade February 2002
1st Place Elementary Division Physics District Level - March 5-7, 2002
(RIMS County Competition is April 23, 2002)
 By Sarah Schoelles |
The purpose of this experiment was to see what effect different glues and different size fill has on the strength of a brick.
I compared the strength of bricks made with all-purpose white glue and plaster of Paris using fine, medium and coarse fill sizes. The bricks were made in a plastic soap mold and measured 2"x4"x1/2".
I measured the weight each brick could bear by hanging a board underneath the brick with a coathanger looped over the brick and centered between two sawhorses. I added red bricks to the board until the brick broke in half and noted the weight on a results table. I did three tests of each glue type and fill size then computed the average weight.
The results were that the all-purpose white glue bricks could bear more weight than the plaster of Paris bricks. Using all-purpose white glue, the coarse fill bricks were strongest, the medium fill were second, and the fine fill were last. Using plaster of Paris, the fine fill bricks were strongest, the coarse fill bricks were second, and the medium fill were last.
My hypothesis should be rejected. The all-purpose white glue bricks held more weight than the plaster of Paris bricks with all sizes of fill. The strongest fill size was different between glue types. I thought the fine fill would always be first, the medium fill second, and the coarse fill third.
The purpose of this experiment is to see what effect different glues and different size fill has on the strength of a brick. I became interested in this when I saw the World Trade Center towers collapse on September 11, 2001. Maybe buildings will not collapse in disasters like this or in earthquakes if I could make a stronger brick.
I think that the bricks made with plaster of Paris will be stronger than the bricks made with white glue because plaster is more like cement. The bricks made with fine fill will be the strongest because they will be more dense, then the medium fill brick, then the coarse fill brick with both glues.
The things that stayed the same in this experiment were:
· The mold used
· The amount of fill and glue to make each brick
· The weight set
· The way the bricks were weighed
The things that changed were:
· Two different glues were used
· Three different fill sizes were used
· The drying time
The things that were measured were:
· How much weight each brick could hold
|
BRICKS:
2 cups fine fill 2 cups medium fill 2 cups coarse fill 1 1/8 cups white glue 2 1/4 cups plaster of Paris 1 1/8 cups water 9 4 oz. bar soap molds Measuring cups - 1/8, 1/4, 1/3 Fork, spoon and bowl |
WEIGHING DEVICE:
2 sawhorses 4 ft. 1"x10" board 2 3 ft. 1"x10" boards 5 yds. heavy-duty ½" polyester rope Wire coathanger Weight set or red bricks (at least 300 lbs.) Weight scale (to 300 lbs.) |
ONE - MAKE THE BRICKS: I measured 1/3 cup of the fine fill and 1/8 cup of white glue into a bowl. I mixed these two together using the fork until the fill was covered with glue. I pressed the mix into a 4 oz. soap mold with the backside of the spoon to make sure there were no air pockets. I did the same thing with the medium fill and then the coarse fill. I let these dry in the molds for 3 days, then I took them out to let them dry completely for another 5 days. I made 3 bricks of each sized fill so I had 3 fine, 3 medium and 3 coarse bricks made with white glue.
Then, I measured 1/8 cup of water and ¼ cup of plaster in a bowl instead of glue and I mixed in the fill. I made 3 bricks with each sized fill using the plaster so I had 3 fine, 3 medium and 3 coarse bricks. The plaster bricks needed to dry for one week.
TWO - MAKE THE WEIGHING DEVICE: I drilled 4 holes in each corner of the 4-foot
board and cut the rope in half. I pushed the pieces through the holes and
tied the ends together with a square knot. I wrapped the coathanger through
the loops of the two ropes. I placed two sawhorses together side-by-side and
put two 3 ft. boards between the two about 3 inches apart. I placed red bricks
on top of the boards, then put the coathanger inbetween the bricks and around
the brick to hold the weight. The edges of the brick to hold the weight were
½" in on each side of the red bricks.
THREE - BREAK THE BRICKS: I slowly added weight by the pound then I added a red brick when I reached 5 pounds to the board under the sawhorses until my brick broke in half. I took the board, rope, hanger and red bricks and put them on a scale to weigh it. I did this with all 9 bricks of white glue bricks and wrote each result down. Then I did the same with the plaster of Paris bricks.
Break the Brick Results
(Weight in lbs.)
| White Glue |
1st
|
2nd
|
3rd
|
Average
|
|
Fine Fill
|
132
|
138
|
134
|
134.7
|
|
Medium Fill
|
238
|
185
|
226
|
216.3
|
|
Coarse Fill
|
245
|
231
|
263
|
246.3
|
| Plaster of Paris | ||||
|
Fine Fill
|
89
|
46
|
51
|
62.0
|
|
Medium Fill
|
41
|
42
|
54
|
45.7
|
|
Coarse Fill
|
68
|
40
|
49
|
52.3
|
I used a metal muffin pan to make the bricks, but the bricks would not come out of the pans. I went to a craft store to find a different kind of mold, and I found a plastic 4-ounce soap mold. The bricks came out of the soap molds easier.
I used a casting resin with a hardener as my second glue, but the resin bricks melted the plastic soap molds and two of the resin bricks were soft. I had to choose another glue and modify my hypothesis. I decided to use plaster of Paris since it is more like cement and mixes with water. The plaster bricks came out of the mold wetter than the white glue bricks and dried slower.
When I mixed up the fill with the glues, the fine fill soaked up the glue faster than the medium and coarse fill. The fine fill bricks came out of the mold easier.
I started the experiment with a plastic bucket, a ribbon tied around the brick, and fishing weights. I put the weights in the bucket. The brick held all of that weight, so I switched to a coffee can and some 20-gauge wire twisted to the bucket and looped around the brick. I used some 5 lb. and 3 lb. weights from my dads weight set. The brick held all of this weight too. Then I switched to a car wash bucket and used a couple of red bricks. The bricks held all of this weight too. Then I switched to a 5 gallon plastic bucket with a coathanger and looped it around the brick. I used some red bricks from the side of our house, which weigh about 5 lbs. each. The brick held all of this weight too. I went to the woodpile at the side of the house and drilled a hole in each corner of the board to put a rope through, then I attached the coathanger to the ropes. This worked the best and could hold up to 300 lbs. I was very surprised that the bricks could hold so much weight. I thought they would break at about 15 lbs. at the most.
When the bricks were about to break, you could hear them cracking. You could also see them bend in the middle and little cracks form under the wire.
This experiment would have different results if I had used a different amount of fill or glue, if I used another kind of fill or glue, or if I had put the bricks in the oven to bake like regular bricks because the bricks would have dried faster and the heat could have changed the strength of the glue.
My hypothesis should be rejected. The white glue bricks were stronger than the plaster bricks. The coarse fill bricks were the strongest, the medium bricks were second, and the fine bricks were third using the white glue. The fine fill bricks were the strongest, the coarse bricks were second, and the medium bricks were third using plaster of Paris.
MASONRY - Masonry is the working of stone, brick and blocks. The Egyptians, Greeks, and Japanese used big blocks of stone without cement to build temples. The Romans figured out how to use cement with clay bricks to build walls, arches, and roads.
BRICKS - Bricks are made out of clay fired in a kiln. Some bricks are dryed in the sun and air. Bricks are used for houses, walls, fireplaces, patios and roads. The kind of clay makes a difference in a bricks strength.
GLUE - Glue is from expired animals, usually horses and fish. It is used for working with wood and paper. Plaster of Paris is gypsum heated to 250 to 360ºF. It is used to make molds, casts for broken bones, and for carving.
STRENGTH - I found a place that tests bricks called The National Brick Research Center. They do many different tests to see how strong bricks are. There was also a study in Egypt to make bricks stronger by using shale (a rough clay).
PRIMARY SOURCES
DOCUMENTS AND TELEPHONE CALLS
The National Brick Research Center, Anderson, South Carolina. E-mail and telephone call from January 16, 2002 to Dr. Denis Brosnan from Diane Schoelles. http://virtual.clemson.edu/groups/NBRC/