Adobe Bricks-What is the Composition for Optimum Strength? (Jennifer Kim)

Materials needed

Each group needs:

• 1 adobe mold and extruder (see below)

• 10 paper Dixie cups (5 oz or ~150 ml) of clayey soil (potting soil will not work)

• 10 paper Dixie cups (5 oz or ~150 ml) of playground sand

• 1/2 gallon (2.2 l) container of fibrous material, loosely packed (dead grass, straw, pine needles, etc.)

• 3 one-gallon (4.4 l) plastic bags, to separately hold the soil, sand, and fibrous material

• 1 large (24 oz or ~700 ml) container (bowl, re-usable plastic, or gallon jug with the top cut off)

• 1 piece of cardboard, 16-in x 16-in (~ 40 cm x 40 cm)

• 1 container of water, ~16 oz (500 ml)

• 1 paper Dixie cup (5 oz or ~150 ml) for measuring

• 1 permanent marker

• Design Worksheet, one per student

• (optional) Pre/Post Quiz, two per student

For teacher to make adobe molds and extruders (one set per group):

• wooden board, 16-in x 1-in x 2-in (41 cm x 2.5 cm x 5 cm), to make an adobe mold (cut into 4 boards that are 4-in [10 cm] long)

• foam core board, 4-in x 6-in (10 cm x 16 cm), for the extruder

• foam core board scrap, to make a handle for the extruder

• eight 2-in nails per mold

• hammer

• hand saw

• hot glue gun and glue sticks

For the entire class to share:

• meter or yard stick

• projector to show two Microsoft PowerPoint presentations to the class

• (optional) disposable gloves

• (optional) newspaper or butcher paper to cover work surfaces

• (optional) box or desk fan, to aid in brick drying

• (optional) small step ladder, for standing on when drop testing bricks

Procedure

With the Students: Day 1

1. (optional) Administer the Pre/Post Quiz. See the Assessment section for details.

2. After the Introduction/Motivation section, introduce the activity using the Day 1 Presentation.

3. Divide the class into groups of three students each.

4. Hand out to each student a copy of worksheet page 1.

5. Assign each group a different variable to test (water content, straw content, sand content). Have the students circle on their worksheet the variable they are testing.

6. Make an example brick in front of the class to show students how adobes are made. (Steps: Carefully mix the ingredients in a bowl with your hands, wet the mold, place the mixed ingredients inside the mold, gently pack the ingredients into the mold, scrape the top flat, use the extruder to push the completed brick onto a piece of cardboard.)

7. Distribute the materials and molds to each group, along with a piece of cardboard.

8. Have students begin mixing and forming their own bricks. When a brick is complete, have them label it on the piece of cardboard with the marker (A, B or C).

9. When all three bricks are complete, have each group write their names at the top of the pieces of cardboard with the marker and store the bricks in a sunny place to dry. The bricks need at least 3–4 days to dry completely. Drying them in front of a blowing fan takes about two days.

With the Students: Day 2

1. Hand out to each student a copy of worksheet pages 2-5.

2. Have students carry their labeled bricks to a designated test area, such as a level concrete surface outside.

3. Test the bricks by dropping them from progressively higher heights until they show substantial failure. You may need a small step ladder to get high enough so they break when dropped. Do this either as a class activity in which each group tests their own bricks, or as an observation time in which the entire class watches you test each brick. Make sure students record their test information on their worksheets.

4. If the testing is done as an observation time, have each student record the data of at least three other groups (two of which tested separate independent variables) on their worksheets. If each group tests their own bricks, have students gather information from several other groups after testing is complete.

5. Return to the classroom and show the Day 2 Presentation.

6. Have each student graph test results for each of the three variables on pages 3-4 of the worksheet.

7. Spend a few minutes leading a class discussion to analyze experimental results so far (as described in the Assessment section). Why might team results be different from each other? What other variables might be affecting brick strength? How can make our manufacturing process more uniform to reduce some of these differences among teams?

8. Challenge each group to develop an ideal adobe brick design based on analysis of the test results and graphs.

9. Give teams time to each make one brick following their own "recipe," using a procedure similar to Day 1. Make sure each group labels its brick. Have them fill in the "model brick recipe" information on worksheet page 5. Store the bricks in a sunny place to dry.

With the Students: Day 3

1. Make sure students still have worksheet page 5 (which was handed out on Day 2).

2. Test each group's brick in a manner similar to that on Day 2.

3. Have each student keep track on their worksheets of the "recipes" and drop heights for all groups.

4. Lead a class discussion to explore what was discovered during these testing experiments. (See a list of suggested post-activity questions and topics in the Assessment section.)

5. (optional) Administer the Pre/Post Quiz. See the Assessment section for details. Click here for answer key

Questions

• Pre/Post Quiz

• Pre/Post Quiz Answers

Photos