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Last day for Registration: Nov.1, 2017

Please conduct these experiments under teacher's or parent’s supervision.

Project 1:Building Bomb Shelters
Project 2: Designing Buildings for a healthy, safe living

Write down the details of your experiments, your observations, results and conclusion. Bring it to Brainquest and tell us what you learned from these experiments.

Experimental Design – 10 points
Answering Questions – 20 points
Results – 10 points

Each School can send TWO teams PER project, with a maximum of 5 members per team.

Research Quest Project 1: Building Bomb Shelters

Cement exists naturally in some areas of the world. Israel has natural deposits of cement were formed 12 million years ago, by spontaneous combustion of limestone and oil shale. However, the rest of us need to manufacture cement.

syrian-concrete-structureCement is an ingredient of concrete. Cement alone cannot stand against the forces of nature like gravity, soil heaving, floods and winds. But it can withstand most natural disasters with the help of gravel and sand. The first concrete structures were built by the Nabataea traders or Bedouins in the regions of southern Syria and northern Jordan around 6500 BC. They built their homes with pounded clay and coated the exterior with a damp layer of burned limestone. This coating reacted chemically with gases in the air to form a hard, protective surface. Nabataea improved this coating by adding silica sand to limestone, then heated it in the kilns, to make concrete.

Around 3000 BC, the ancient Egyptians made bricks from mud mixed with straw. They used gypsum and lime mix to join these bricks while building the pyramids. By 200 BC, Romans mixed limestone with the volcanic soil from the foot of Vesuvius to make concrete. The soil, pozzolan, had alumina and silica and therefore made the concrete stronger. This concrete was used to build the public baths panteon_cupulaof Rome and the Pantheon with its 142 feet wide giant dome, which still exists today.

After the fall of the Roman Empire in 476 AD, the techniques for making Pozzolan cement were lost until the documents were discovered in 1414 AD.After several improvements by people from various countries, Portland cement, the most popular type of cement we use today, was patented on October 21, 1824 by Joseph Aspdin of UK. He named his cement Portland because its color resembled the high quality building stones quarried on the British Isle of Portland. Portland cement is a fine powder made by blending crushed limestone with clay or shale, sand and iron ore. The powder is heated in kilns and then mixed with a small amount of gypsum.

About 50% of cement is Tricalcium silicate. This is responsible for the early strength of concrete. The rest 50% contain Dicalcium silicate (25%), Tricalcium aluminate (10%) Tetracalcium aluminoferrite (10%) and Gypsum (5%). All of these hydrate slowly over 28 days.

When you add water to a mix of sand/gravel and cement, this is what happens:

Tricalcium silicate + water --- Calcium silicate hydrate + Calcium hydroxide + heat
or
2Ca3SiO5 + 7H2O  3CaO.2SiO2.4H2O + 3 Ca(OH)2 + 173.6kJ

Due to the release of hydroxide (OH-) ions, the pH rises rapidly to 12 or higher, making the concrete highly caustic/corrosive.

concretetimezerosmconcreteparthydratedconcreteincompletehydrationconcreteperfect

The newly formed calcium hydroxide and calcium silicate hydrate begins to crystallize. These crystals provide "seeds" for more calcium silicate hydrate to crystallize and grow over them. As the crystals grow thicker and bigger, it becomes more difficult for water molecules to reach the unhydrated Tricalcium Silicate lying under them. Perfectly hydrated concrete (picture 4) can be achieved by using
 I) same size gravel that is free of dirt/particles
ii) Using just enough water
iii) compacting the concrete while pouring it.

The speed of the reaction is dependent on the rate of diffusion of water through the calcium silicate hydrate coating. The hydration will continue as long as both water and unhydrated compounds are present. This is why it is important to water the newly poured concrete so that it is hydrated properly. Hydration is what gives strength to concrete. It can take years for hydration to be complete.

When concrete dries, it stops getting stronger. Too little water to make concrete means dry, crumbly concrete. Too wet means soft and brittle concrete. Just enough water will hydrate the concrete fully. But excess water will remain between crystals. Over time, this water will evaporate, leaving empty air spaces. These pores make concrete weaker and leaky. Also, if water reaches the unhydrated areas at a later date, Calcium hydroxide will leach forming white patches.

In conclusion, the strength of concrete is inversely proportional to water: cement ratio. The more water you use to mix concrete, the weaker the concrete mix. The less water you use to mix concrete, the stronger the concrete mix.

Portland cement, sand, aggregate (gravel or pebbles or stone), and water make up the four main ingredients of concrete. The ratio of aggregate: sand: cement determines the compressive strength of the concrete mixture. A concrete mixture ratio of 1 part cement, 2 parts sand, and 3 parts aggregate will produce a concrete mix with compression strength of approximately 3000 psi. This is the most generic version of concrete used. But construction of multistory commercial complexes or roads need a compressive strength of 8000 psi or higher. This mixture may be quite dry and have 8 parts of aggregates and sprayed with the help of a motorized gun.

If a mixture has no aggregates (only sand, cement and water) then it is called mortar. Mortar is used in coating brick, stone walls and in joining stones, bricks and tiles. We will use mortar for our experiments.

Note: Wear gloves or plastic bags on your hands; wear a plastic bag or hood over your face when doing these experiments. DO NOT touch cement with bare hands or without covering your nose and eyes. Conduct these experiments under an adult supervisor. Wear plastic over your clothes. Your clothes and shoes may become unusable after doing these experiments.

Experiment 1: How much water?

If the concrete or mortar mixture has too much liquid, it runs and drips while pouring or coating. If it is too dry, there may be gaps while pouring or coating. In this experiment, named Slump test, we discover the recipe that gives us the best workable mortar.

Cut off the bottom of 4 styrofoam/plastic cups or any other containers that are cone shaped. Place them inverted on leveled ground.  Make the following four mixes. Stir and mix well with a wooden scale or a ladle. After pouring them into the cups/containers, remove air bubbles by stabbing the mortar with the ladle to compact.
 

slumptestcopy

i) Mix 150gms of cement with 225gms of sand. Add 25ml water

ii) Mix 150gms of cement with 225gms of sand. Add 50ml water

iii) Mix 150gms of cement with 225gms of sand. Add 75ml water

iv) Mix 150gms of cement with 225gms of sand. Add 100ml water

Carefully remove the cups by lifting them straight up. Measure the height of concrete cones. The mixture that retained 50% - 75% height of the original cup is the best workable mortar. Higher the height, too little water. Lower the height, too much water. The picture above is only an example. Fifty- percent slump may not be given by 75ml water.

Note down your recipe for the best workable mortar and use this composition for rest of the experiments.
In New York, we have only 150 days with above-freezing temperatures. And it rains or snows once or twice every week throughout the year. This means we can do outdoor construction only 43.5% of the year. Sometimes the temperature on sunny days in Autum/Spring may be +10*C but after sunset around 3.30pm, it can drop to –10*C. If we poured concrete during day in above-freezing temperatures, it won’t be cured or hydrated by night. In summer, if we pour concrete and it rains the next day, our concrete may not cure because our soil temperature is only 20*C even in the height of summer. If we pour concrete 3 feet below the ground level, temperatures there hover around 12*C to 15*C.

In southern USA where temperatures soar above 35*C in summer, concrete cures or hydrates too fast where it is exposed to sun and cures slower in the shade. This uneven curing is not good because

i) Water would have evaporated from the mixture before concrete in sunny areas cures

ii) Water cannot reach the deep pores where unhydrated Tricalcium silicate exists if concrete cures too fast.
Luckily, Material Scientists and Chemical Engineers have developed additives to speed up or slow down the curing.

In the following experiment, we add simple additives to speed and retard concrete curing and learn its advantages.

Experiment 2: Can we change the speed of Hydration or curing of Concrete?

Insulate a large container or cardboard box by wrapping/filling it with Styrofoam or sawdust/coir. Bend one end of 3 drinking straws and tape the end to prevent water from getting in. Make 3 sets of regular mortar mix from the recipe in Experiment 1, in 3 small plastic containers.

additives

Leave the first container unmodified.

Add 2% Calcium Chloride, (of weight of the cement) to the second container and mix thoroughly. For example, if you used 150gms of cement, you must add 3 gms of CaCl2.

Add 2% sugar (of weight of the cement) to the third container and mix thoroughly.

Place the modified straw in the center of each container. Insert one thermometer into each straw. Close the lid of the bigger plastic container. Record the temperature every 5 minutes for 30 minutes. And then every 15 minutes until the temperature stabilizes in all 3 containers. Draw a graph.

Answer these questions:
i) What was the highest temperature and where and when was it seen?
ii) Which mixture had the earliest temperature stabilization?
iii) Why do these 3 mixtures display peaks at different times?

Now, take out insulation and fill the big container with ice. Repeat this experiment and note the difference in peak temperatures and stabilization time.

Gravel or aggregates, though chemically inert, give strength to concrete and reduce the cost of concrete. Types and sizes of aggregates determine the density of concrete. Large aggregates mean less shrinkage and curling. The most common concrete mix uses -inch or -inch gravel. But we can also use large size gravel or tiny pebbles.

Concrete has great compressive strength i.e., when we walk on concrete, it does not get compressed. But concrete has poor tensile strength i.e., if concrete is pulled, it doesn’t return to its original shape. Rather it develops cracks. This is why you see cracks on walls. When the soil under a building settles, the wall and the mortar coating get pulled unevenly. Since neither the wall nor the mortal coating can stretch, they develop cracks. But if we place steel bars or mesh in between stones as a skeleton, then the whole wall acts as one piece and sinks at the same rate, leaving no cracks.

In the following experiment, we will learn how properties of concrete change with different types of aggregates.

Experiment 3: Can you build a concrete boat?

You can use Toothpaste boxes or Incense boxes or any cardboard cylinders as moulds for this experiment. But moulds for all types of concrete must be of same size. Below are some sample concrete recipes but you can use any aggregates you like (row 3).

    water

    Amount required to get workable consistency

    cement

    50g

    50g

    50g

    50g

    50g

    sand

    100g

    100g

    100g

    100g

    100g

    aggregate

    pieces of granite
    (jalli kallu)

    pieces of broken clay pot

    styrofoam bits

    5g sawdust

    35g tiny pebbles

 

 

 

Pour each mixture into a mould and let it cure. Make sure all pieces measure the same (example: 3cm x 2cm block). Remove the moulds and water the pieces after they are cured and wait for 48 hours.

stresstestWeigh each sample and record its weight. Half-fill a measuring cylinder with water. Note down the initial reading. Then slide one sample of concrete (without splashing). Record the reading. Subtract the initial reading to get the amount of water displaced by the sample concrete piece. Repeat this with the remaining pieces. Calculate the density of each sample by dividing the mass by its volume.

Did any piece of concrete float? Why?
Can you build a boat with any of the compositions you developed?

Perform a stress test to see which sample is the strongest. Place each piece on the gap between 2 tables as shown in the picture. Hang a plastic mug from it using strong rope. Fill the mug with weights/stones until the concrete piece

breaks. Wait for one minute after adding each stone. Weigh the stones to get the weight that broke the concrete piece. Repeat this experiment with all of your samples and determine which composition gave you the strongest concrete.

Now that you know how to make the strongest concrete, you are probably ready to build bomb shelter!

Please remember that there no right or wrong answers since the results depend on the type of materials used and the location where the experiments are conducted. Write down the details of your experiments, your observations, results and conclusion. Bring them to Brainquest and tell us what you learned from these experiments.

ResearchQuest Project 2: Designing Buildings for a healthy, safe living

Buildings in our country are not built with residents’ health and safety in mind. Building collapse is quite common. Building multistory structures with mere one-foot deep foundation on sandy soil is common practice. Our walls are built with heavy Laterite stones. Do we know if the soil underneath can take the building's weight?

In USA and most developed countries, government regulates the building process. In New York, before building a home, a structural engineer makes 8ft deep hole and tests different layers of soil. The results determine the dimensions (depth and width) of the foundation and the maximum weight of the building. The town places markers on 4 corners and builders must build within the markers. At every stage, a Town inspector inspects the process to see if the builder is following the town regulations (The book of building regulations has 2000 pages; electrical, plumbing and heating/ventilation have their own 2000 page books). Bribing the inspector does not work because if the building collapses or gets burned in fire, then the town has to pay replacement cost to the owner as a penalty for approving the faulty building.

Note: Wear gloves or plastic bags on your hands; wear a plastic bag or hood over your face when doing these experiments. DO NOT touch cement with bare hands or without covering your nose and eyes. Conduct these experiments under an adult supervisor. Wear plastic over your clothes. Your clothes and shoes may become unusable after doing these experiments.

In the following experiment, we measure the weight-bearing capacity of different soils

Experiment 1: Which one of these soils can bear the most weight?

You will need to collect various types of soil such as sand, crushed Laterite, clay and soil from your home.

soiltestcopy

Take wooden rod or any solid cylinder with 3 to 5 cm diameter. Hold a tape against the rod and mark the entire rod every millimeter to make it look like a graduated cylinder. Attach a piece of plywood to one end using glue or nails. Leave it for 24 hours until the rod is bonded to plywood firmly. Place a container on a stool. Fill the container to 3/4th level with one type of soil.

Cut a round hole slightly wider than the diameter of your rod on a piece of plywood or cardboard or styrofoam sheet. Place 2 tables of identical height overhanging your soil container. Place plywood/styrofoam with hole on the table. This plywood/styrofoam will hold the wooden rod straight but should NOT support it (not tightly holding it). Now insert the wooden rod until it touches the surface of soil. Place a plastic container/mug on top of the plywood attached to the rod. Note the reading where the rod touches the soil. Add little water to the mug. Note down the reading on the rod where it touches the soil to see how much it sank. Keep adding water to the mug until the rod shows the same reading twice (or it cannot sink any deeper).

Repeat this experiment with other soils. Note down how much each soil sank until it stabilized and note how much water it took to sink the rod to the maximum extent.

Answer these questions:

1. Which soil is the best for building home?

2. Why do soils differ in their capacity to hold weight?

Repeat this experiment with wet soil. Saturate your soils with water and place them in the container. And check how much weight they can take before sinking.

In monsoon season, you may have noticed that your floors seem wet. Sometimes walls and ceiling (if made of concrete) may feel damp. Have you wondered why?

Concrete and stone are porous. They allow moisture to seep through their pores. In monsoon season, air is very moist. Humidity may be 80 to 90%. Water vapors in the air seep through these holes into the house. When warm air saturated with water comes in contact with cool stone or floor, water starts precipitating because air cools and cooler air cannot hold as much moisture as warm air. This is similar to a glass holding cold water sweats on the outside. Damp walls and floors promote growth of mould and bacteria. People living in such homes get infections and allergy during monsoon season. But we can resolve this problem easily.

i) Either we need to stop the water entering the wall/floor from outside or coat a waterproof material from inside or both.
ii) Install a dehumidifier to remove moisture from air.

Second option is expensive because a dehumidifier consumes lot of power. So, let us try the first option.

Experiment 2: How to Prevent condensation on walls and floors during monsoon season?

Make a moisture meter using this circuit or any other circuit.

moisturemeter2copy

Make 4 concrete bricks using a plastic container as mould. The recipe for concrete is 1: 2 ratio of cement: sand. Add water and mix well with a piece of wood. The mixture should be same consistency as gadbad ice cream.

moisturetestcopy

Get 4 large containers. Fill half of the container with soil. Place one concrete brick in the first container.
Place a plastic sheet in the second container and place a concrete brick over it.

Place a sheet of styrofoam in the third container and place a concrete brick over it.
Coat the last brick with oil paint or waterproof paint. When dry, place it in the fourth container.

Wet the soil thoroughly. Re-wet the soil as it dries. Check the moisture in the bricks after 7 days, using the moisture meter

Answer the following questions:

1. Which brick had the most moisture? Why?
2. Which brick had the least moisture? Why?
3. Which combination is good for a roof?

Homes with concrete roof and walls are much warmer than the homes with terracotta tile roof and mud walls. Concrete roof and walls provide safety against insects, snakes, thieves and fire. Terrace also acts as a patio in the sky and allows us to enjoy cool evenings. Only disadvantage is the warmth. There are ways to bring temperatures down using science.

i) Install vents close to the ceiling. So, the hot air can escape through the vents, especially when a ceiling fan is on.

ii) Coat the roof with mortar to make it smooth. Then paint it glossy white. Smooth white surfaces reflect heat. So the roof does not absorb heat as much.

iii)  Place a tarpaulin and put planting soil up to 12 inches. Plant drought tolerant grass or weeds that grow only 10 to 12cm tall. Plants absorb sunlight and provide a barrier for sunlight. Yet people are able to put chairs and sit on the roof. This technique is called ‘green roof” and is very popular in New York City where people don't have gardens.

Experiment 3: How to cool your home without an Air conditioner?

Find 4 identical cardboard boxes. Paint two of them white. Paint the other two grey or cement color. Place them outside where they get the same amount of sun.

roofcolorcopy

Add soil about 6cm high in 2 containers. Plant some sun-loving plants. Water the soil well.  Place one container on white box and the other on grey box. Note the temperatures inside all 4 boxes. Record temperatures once every hour, even after sunset, for 7 days.

Answer these questions.

1. Which box had the highest temperature?

2. Which box showed the first rise in temperature?

3. Which box showed the first drop in temperature?

4. Which box showed the least temperature?

Your results are dependent on the materials used and the location of your experiments. So, there are no right or wrong answers. Write down the details of your experiments, your observations, results and conclusion. Bring them to BrainQuest

 

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