Name: Curt Blimline / Contact Info: / Date:15-Jul-13
Lesson Title: Concrete Basics / Unit #:
5 / Lesson #:
1 / Activity #:
1 / Worksheet: b
Activity Title: It’s Set in Concrete Activity
Worksheet Title: It’s Set in Concrete Worksheet

It’s Set in Concrete

Background

Concrete is composed of (cement + water) + aggregates. Aggregates are materials that add volume to concrete. They are usually classified as course (large) or fine (small). Examples are rocks, gravel, or sand. The cement and water reacts and forms a paste which bonds the aggregate substances to the paste as it hardens. The proportions of cement, water, and aggregates determine the properties of the resulting concrete. In this laboratory investigation, several tests used to determine the usefulness of a particular aggregate in making concrete will be explored.

Objectives

  1. After completing this laboratory investigation, the student will be able to
  2. determine if an aggregate substance is appropriate for use in concrete.
  3. accurately predict the effect of aggregate sizeon void space in concrete.

Materials/Equipment (per team)

For Silt Test

  • Aggregate samples
  • clay (kitty litter)
  • sand
  • vermiculite
  • Clear wide-mouth plastic bottle with lid (approx. 200 mL) - 3
  • Ruler
  • Water

For Organic Matter Test

  • Aggregate samples
  • clay (kitty litter)
  • sand
  • vermiculite
  • Clear wide-mouth plastic bottle with lid (approx. 200 mL) - 3
  • Sodium hydroxide solution (1 M) – 300 mL
  • Water

For Void Test

  • Aggregate samples (assorted)
  • Brick nuggets
  • Clay (kitty litter)
  • Sand
  • Marble rock
  • Pea Gravel
  • River rock
  • Rubber mulch
  • Vermiculite
  • Clear wide-mouth plastic bottle with lid (approx. 200 mL) - 3
  • Graduated cylinder (100 mL)
  • Water

Procedure

Silt Test

This test will demonstrate whether an aggregate is acceptable for use in concrete.

  1. Add 3 cm (50 mL line) of a different aggregate to each of 3 plastic bottles.
  2. Add 3 cm (100 mL line) of water to each bottle.
  3. Shake vigorously for a minute or two and then allow to stand for approximately 30 minutes or until the liquid portion becomes clear.
  4. Measure the height of the layer above the aggregate with the ruler.
  5. Record your observations and data.

Organic Matter Test

This test will demonstrate the relative quantity of organic matter in an aggregate.

  1. Half fill (60 mL line)3 plastic bottles each with a different aggregate.
  2. Add 1M sodium hydroxide (NaOH) to fill each bottle.
  3. Cap the bottles and shake each vigorously for a minute or two.
  4. Let stand undisturbed overnight.
  5. Observe and record any changes in color to the liquid over the aggregate.

Void Test

This test will demonstrate the effect of aggregate size on the total volume of space between aggregate particles.

  1. Fill (120 mL line) a plastic bottle with an aggregate.
  2. Fill a 100 mL graduated cylinder with water to the 100 mL mark.
  3. Add water to the bottle until it is filled. If more than 100 mL of water is needed, refill the graduated cylinder to the 100 mL mark.
  4. Record the aggregate type and the amount of water added.
  5. Complete this process for 2 more aggregates.
  6. Repeat steps 1-5 with two aggregates at a time and filling the bottle with one-half of each aggregate. Use the aggregates that you used previously. You should have 3 combinations.
  7. Record the aggregate combination and the total water added.
  8. Drain each aggregate sample and return to appropriate aggregate containers.

Data

Silt Test

Aggregate Name / Height of Silt Layer (mm) / Observations

Organic Matter Test

Aggregate Name / Color of Liquid Layer / Observations

Void Test

Aggregate Name / Water Added (mL) / Observations

Conclusions

  1. Based on the results of the silt test, which of the aggregates tested would be suitable for concrete? Explain and support your reasoning with data.
  1. Based on the results of the organic matter test, which of the aggregates tested would be suitable for concrete? Explain and support your reasoning with data.
  1. Based on the results of the void test:
  2. What effect does the size of the aggregate have on the total space between aggregate particles? Explain and support your reasoning with data.

3

  1. What effect does the mixing of aggregate sizes have on the total space between aggregate particles? Explain and support your reasoning with data.

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