**Laboratory Instructor's Manual**

**Table of Contents**

Introduction to Lab Instructor 1

Week 1 - Aggregate Testing 5

Week 2 - Binder Testing, Mixing and Compacting Asphalt Concrete 12

Week 3 - Asphalt Concrete Testing 20

**INSTRUCTOR'S MANUAL**

**Materials Needed Prior to Start of Class**

55-gal drum of coarse aggregate stockpile

55-gal drum of fine aggregate stockpile

5-gal of asphalt split into quart cans

**Lab Sessions**

The lab sessions are organized so that they can be completed in three
3-hour laboratory periods (Table 1). If more time is available, a second
week of aggregate testing by the students is recommended rather than
just the demonstrations. The binder tests are limited to demonstrations
for undergraduate classes because of the complexity of the equipment and
the ease with which it can be damaged. All demonstrations should provide
the raw data and the students should complete the required calculations.
All of the mixture tests are hands on.

A maximum of 16 students, divided into 4 groups, per lab session works
best. Set up four work stations, one for each of the hands on tests.
Demonstrations can be given to the entire lab class at one time.

**Lab Reports**

The lab assignment for the students is presented in the form of client
letter requesting the services of a consulting laboratory. The student's
report should be prepared as a response to this letter. This is as much
an exercise in technical writing as a laboratory report. Instructions to
the students, a sample letter assignment and a sample laboratory report
are included in the student's manual.

**TABLE 1. Recommended Organization for Laboratories.**

+------------------+--------------------------+--------+--------------+
| Lab Session      | Tests Covered            | Demo   | Class or     |
| Topic            |                          | or     | Individual   |
|                  |                          | Hands  | Groups       |
|                  |                          | On     |              |
+------------------+--------------------------+--------+--------------+
| Aggregates       | Material Finer Than      | Demo   | Entire lab   |
|                  | 75-μm by Washing         |        | class        |
| (Week 1)         |                          |        |              |
+------------------+--------------------------+--------+--------------+
|                  | Flat and Elongated       | Demo   |              |
+------------------+--------------------------+--------+--------------+
|                  | Percent Crushed Faces    | Demo   |              |
+------------------+--------------------------+--------+--------------+
|                  | Fine Aggregate           | Demo   |              |
|                  | Angularity               |        |              |
+------------------+--------------------------+--------+--------------+
|                  | Sand Equivalent          | Demo   |              |
+------------------+--------------------------+--------+--------------+
|                  | Gradation Analysis for   | Hands  | Individual   |
|                  | Each Stockpile           | On     | Groups       |
+------------------+--------------------------+--------+--------------+
|                  | Specific Gravity of Fine | Hands  | Individual   |
|                  | Aggregates               | On     | Groups       |
|                  |                          |        |              |
|                  |                          |        | (2 groups at |
|                  |                          |        | a time)      |
+------------------+--------------------------+--------+--------------+
|                  | Specific Gravity of      | Hands  | Individual   |
|                  | Coarse Aggregates        | On     | Groups       |
+------------------+--------------------------+--------+--------------+
| Asphalt Cement   | Rotational Viscometer    | Demo   | Entire lab   |
|                  |                          |        | class        |
| Asphalt Concrete |                          |        |              |
| Mixing and       |                          |        |              |
| Compaction       |                          |        |              |
|                  |                          |        |              |
| (Week 2)         |                          |        |              |
+------------------+--------------------------+--------+--------------+
|                  | Dynamic Shear Rheometer  | Demo   |              |
+------------------+--------------------------+--------+--------------+
|                  | Bending Beam Rheometer   | Demo   |              |
+------------------+--------------------------+--------+--------------+
|                  | Rolling Thin Film Oven   | Demo   |              |
+------------------+--------------------------+--------+--------------+
|                  | Pressure Aging Vessel    | Demo   |              |
+------------------+--------------------------+--------+--------------+
|                  | Mixing                   | Hands  | Individual   |
|                  |                          | On     | Groups       |
+------------------+--------------------------+--------+--------------+
|                  | Compaction               | Hands  | Individual   |
|                  |                          | On     | Groups       |
+------------------+--------------------------+--------+--------------+
| Asphalt Concrete | Moisture Sensitivity     | Demo   | Entire lab   |
| Testing          |                          |        | class        |
|                  |                          |        |              |
| (Week 3)         |                          |        |              |
+------------------+--------------------------+--------+--------------+
|                  | Maximum Specific Gravity | Hands  | Individual   |
|                  |                          | On     | Groups       |
+------------------+--------------------------+--------+--------------+
|                  | Bulk Specific Gravity    | Hands  | Individual   |
|                  |                          | On     | Groups       |
+------------------+--------------------------+--------+--------------+
|                  | Calculations for Mix     | Cla    | Entire lab   |
|                  | Design                   | ssroom | class        |
+------------------+--------------------------+--------+--------------+

Week 1

Aggregate Testing

**Week 1**

**Demonstrations**

**AASHTO 11-91 Materials Finer than 75-μm (No. 200) Sieve in Mineral
Aggregates by Washing**

***Equipment needed:***

Plastic bucket with handle (about 1-gal size or slightly larger)

75-μm (No. 200) sieve

Either a 2.36 (No. 8) or 1.18 (No. 16) mm sieve

Bottle of liquid dish soap

Large metal pan

Access to at least one sink

***Prepare before class:***

> One ziplock bags (1-gal size) with 2,500 g of dry coarse aggregate
> (note dry mass on outside of each bag).

***Steps for Class:***

1.  Record dry mass of aggregate on sieve analysis data sheet.

2.  Stack sieves with No. 200 on bottom and place in sink

3.  Put aggregate in bucket and enough water to cover aggregate

4.  Agitate sample so that fine material is washed off of aggregate
    surface

5.  Immediately pour water with suspended fine material over sieves

6.  Repeat until water is reasonably clean after agitation

7.  Empty aggregate from bucket into pan

8.  Wash any material retained on each sieve into pan

9.  (This is described - not necessary for demo) Place pan in oven and
    dry overnight. Record dry mass in appropriate spot on sieve analysis
    data sheet.

**Week 1**

**Demonstrations**

**ASTM D4791-95 Flat Particles, Elongated particle, or Flat and
Elongated Particles in Coarse Aggregate**

***Equipment needed:***

Proportional Caliper Device

***Prepare before class:***

> Sieve a small amount of coarse aggregate until about 100 particles of
> aggregate retained on the 12.5 mm (½ in) sieve are obtained

***Steps for Class:***

1.  Select an aggregate and set end of calipers farthest away from pivot
    point to longest dimension.

2.  Without moving the calipers, remove aggregate and try to fit
    narrowest dimension in caliper opening at the other end

3.  If aggregate fits in second opening, put it in the flat and
    elongated pile.

4.  If aggregate does not fit in second opening, put it in another pile.

5.  At the end, record number of particles in each pile. Record.

6.  When finished, store in labeled ziplock bag for future use.

**Week 1**

**Demonstrations**

**ASTM D 5821 Determining the Percentage of Fractured Particles in
Coarse Aggregate**

***Equipment needed:***

None

***Prepare before class:***

> Sieve a small amount of the coarse aggregate stockpile over a 4.75 mm
> sieve. Prepare a sample of about 500 grams of the material retained on
> this sieve. Wash and dry this material. Store in ziplock bag.

***Steps for Class:***

1.  Spread aggregate on clean flat surface

2.  If an aggregate face has at least one fractured face at least the
    width of the maximum cross sectional area, put it in the "fractured
    face" pile.

3.  Create a second pile of aggregates which do not meet this criteria.

4.  Determine the number of particles in each pile. Record numbers.

5.  Recombine sample and repeat to determine percentage with two or more
    fractured faces.

6.  When finished, store in labeled ziplock bag for future use.

**Week 1**

**Demonstrations**

**AASHTO T 304 Uncompacted Void Content of Fine Aggregate (Method A)**

***Equipment needed:***

Fine aggregate angularity apparatus (funnel on stand, 100 cm^3^
cylinder)

Metal spatula (about 100 mm long by about 20 mm wide)

Scale that is readable to 0.1 grams

Large pan (cookie sheet works well).

***Prepare before class:***

Wash and dry about 1,5000 gram of fine aggregate

> Sieve dry aggregate over stack of sieves (4.75, 2.36, 1.18, 0.6, 0.3
> mm + pan)
>
> Combine fractions to meet mass per sieve size shown in test method and
> store in small labeled ziplock bag

***Steps for Class:***

1.  Determine the mass of the cylinder. Record on data sheet.

> 2\. Place cylinder under funnel.

3.  Place finger over bottom of funnel.

4.  Pour aggregate into top of funnel.

5.  Remove finger and let aggregate flow into cylinder.

6.  Use spatula to strike off excess aggregate on top of cylinder. Take
    care not to bump or vibrate cylinder.

7.  Brush off excess aggregate on cylinder.

8.  Determine the mass of the aggregate and the cylinder. Record on data
    sheet.

9.  After test is complete, save material in ziplock bag. It can be used
    again for other labs to save preparation time.

**Week 1**

**Demonstrations**

**ASTM D 2419 Sand Equivalent Value of Soils and Fine Aggregate**

***Equipment needed:***

2 Graduated cylinder and stopper

3-oz penetration tins with lid

Straight edged spatula

Funnel

Working solution in bottle with hose, hose clamp, and irrigation tube

Rod and assembly (see test method)

***Prepare before class:***

Screen fines stockpile over a 4.75 mm sieve

> Dampen material, heap in pile, and fill tin until overly full. Strike
> off excess and pour sample into one of the graduated cylinders.

Repeat for second graduated cylinder

Irrigate one cylinder before class. Shake this one about 20 minutes
before needed.

***Steps for Class:***

1.  Demonstrate irrigation of sand in cylinder. Stopper and shake.

2.  Use second cylinder to take reading by inserting rod into cylinder
    and reading both the sand and clay values. Record.

**Week 1**

**Hands On**

**AASHTO T 84-95 Specific Gravity and Absorption of Fine Aggregates**

***Equipment needed (need 2 sets so that 2 groups can work at the same
time):***

Digital scale which can be read to the nearest 0.1 grams

500 ml glass volumetric flask

Metal cone mold and tamper

Hair drier (for warm, gently moving air)

> Large flat metal pan if non-absorptive surface not available (large
> cookie sheet works in a pinch)

Pan turner

4 large metal pans (for drying aggregate)

Wash bottle filled with water

Felt pens for labeling pans

***Prepare before class:***

> Screen fine aggregate over 4.75 mm screen and keep material that
> passes screen

Place 1,000 g of this material in each of four ziplock bags

> Add about 4 percent water by mass of aggregate (this assumes that the
> absorption of the aggregate is less than 4 percent) and seal bag.

***Steps for Class:***

1.  Empty damp aggregate onto cookie sheet and spread out.

2.  Use hair drier to help dry aggregate to saturated surface dry (SSD).

3.  Use pan turner to continually move aggregate around so that it dries
    uniformly.

4.  When aggregate approaches SSD, clear a space on cookie sheet, place
    metal cone in center and loosely fill with aggregate.

5.  Lightly tamp aggregate with 25 light drop starting about 0.5 mm (0.2
    inches) above the surface each time.

6.  Firmly hold cone and brush aggregate away from base.

7.  Lift mold vertically. At least a portion of the aggregate won't be
    able to hold its shape at SSD.

8.  Repeat steps 2 through 7 until SSD condition is reached.

9.  Partially fill flask (pycnometer) with water and add 500 ± 10 g of
    SSD aggregate. Record mass of SSD aggregate used.

10. Fill flask with additional water until about 90% full. Roll and
    gently agitate to eliminate all air bubbles. The tip of a paper
    towel can be used to disperse foam.

11. Bring the water level in the flask up to the volumetric mark.
    Determine and record mass of flask, water, and aggregate.

12. Tare pan, record mass, and empty aggregate and water into pan. Use
    wash bottle to rinse flask into pan.

13. Label pan and place in oven to dry overnight.

14. Next morning, remove pans from oven, cool to room temperature and
    determine the mass of the pan and aggregate. Post results for
    students.

**Week 1**

**Hands On**

**AASHTO T 85-91 Specific Gravity and Absorption of Coarse Aggregate**

***Equipment needed:***

Scale which reads to 0.1 grams with an attachment for weighing samples
under water

Wire basket with handle

Water tank

4 buckets or large pans for soaking aggregates

Large terry cloth towels

Spray bottle filled with water

***Prepare before class:***

Screen a large sample of the coarse aggregate over a 4.75 mm screen

Save the material retained and waste the material passing

Prepare 4 samples of:

2,500 g of coarse aggregate, washed and left in pan under water

***Steps for Class:***

1.  Determine mass of basket under water. Record.

> 2\. Pour excess water off of aggregate.

3.  Empty aggregate onto predampened towel.

4.  Dry aggregate until surface is uniformly dull (no free water). Take
    care to keep aggregate not being dried covered with sides of towel.

5.  Empty aggregate into wire basket and determine mass of aggregate at
    SSD. Record mass.

6.  Hang basket under water and determine mass under water. Record.

7.  Remove basket from water. Tare pan, record mass, and empty aggregate
    into pan. Take care not to lose any material. Dry overnight.

8.  Next morning: Remove pans from oven, cool to room temperature,
    determine dry mass of pan and aggregate. Post for students.

**Week 1**

**Hands On**

**AASHTO T 27-93 Sieve Analysis of Fine and Coarse Aggregate**

***Equipment needed:***

Stack of sieves from 12.5 to 0.075 mm with pan and lid

Mechanical shaker

Soft brushes for cleaning fine mesh screens

Wire brushes for cleaning large wire screens

Misc. pans for transferring aggregates from sieves after weighing

***Prepare before class:***

> Obtain an aggregate sample from each stockpile (see test method for
> amount for a given size aggregate)
>
> Oven dry, record the oven dry mass, and wash each sample the day
> before class (or earlier). Store in ziplock bag with original mass
> information if done further ahead than one day.

***Steps:***

1.  Clean, tare (record), and stack sieves with the largest on top and
    the smallest on the bottom.

2.  Pour oven dry aggregate from T11-91 into top of sieve stack, place
    lid on stack, and position in the mechanical shaker.

3.  Start shaker and run for 10 minutes.

4.  After equipment stops shaking, take stack out, separate sieves and
    obtain the mass of both the sieve and the aggregate retained on each
    one. Record each measurement.

5.  Clean and re-stack sieves.

**Week 2**

**Binder Testing**

**Mixing and Compaction of Asphalt Concrete Mixtures**

**Week 2**

**Binder Demonstrations**

**AASHTO TP 5-93 Determining the Rheological Properties of Asphalt
Binder Using a Dynamic Shear Rheometer (DSR)**

***Equipment needed:***

> Dynamic Shear Rheometer.
>
> Test plates - base plate which screws into DSR unit and spindle;
> either 8 mm for intermediate or 25 mm for high temperature testing.

Specimen Mold - silicone rubber mold for forming asphalt binder
specimens.

Trimmer - specimen trimmer with straight edge at least 4 mm wide.

***Prepare before class:***

Heat asphalt to 135 C.

Turn control box on by switch on back right of box.

Screw base plate into unit hand tight.

Turn software on by clicking DSR icon.

> Turn temperature control on in software.

Set temperature to desired range.

Place spindle on base plate to heat to temperature.

Set gap after equilibrated. Refer to manual.

Pour asphalt into specimen mold.

***Steps for Class:***

1\. Place asphalt specimen on preheated spindle.

2\. Lower spindle on to base plate.

3\. Trim sample flush to edges of plates and remove excess material.

4\. Place cover into base plate to allow for thermal conditioning.

5\. Press start on software.

6\. Discuss G\* and phase angle.

7\. After sample has run, print results.

**Week 2**

**Binder Demonstrations**

**AASHTO TP 48-96 Viscosity Determination of Asphalt Binder Using
Rotational Viscometer** ***Equipment needed:***

Brookfield (or similar) viscometer with all attachments

Thermosel temperature control system

1 oven set at 135^o^C

1 three ounce container

1 scale that measures to the nearest 0.1 gram

Protective gloves for handling equipment subjected to heat

1 extraction tool to handle the hot sample chamber

1 stop watch for timing 3 one-minute intervals

***Prepare before class:***

Set Thermosel to the desired test temperature (135^o^C)

Preheat sample chamber, spindle, and the 3-oz. Container of asphalt

Level viscometer and thermo container

Set up viscometer to handle the desired spindle number (#27)

Weigh sample chamber

Prepare asphalt sample and set equipment for testing (10.5 ± 0.1 g
asphalt)

Equilibrate the sample temperature

***Steps for Class:***

1.  Set the motor speed by pressing the "speed" key on the keypad.

2.  Use the arrow keys to set the desired testing speed at 20 rpm. (For
    soft binder samples, the speed may need to be increased in order to
    increase the torque value so that it falls within the acceptable
    range of 2-98% torque).

3.  Set the display to read viscosity by pressing the "Set Display" key
    until the viscosity in centipoise (cP) is shown in the upper left
    corner of the display.

4.  During the calibration period, observe the viscosity. The viscosity
    will decrease as the temperature of the sample rises. When the
    viscosity reading remains constant, the temperature is considered
    equilibrated.

5.  Read and record a viscosity value at one-minute intervals for a
    total of three readings. The viscosity measurements are in units of
    centipoise (cP). Convert cP to Pascal\*seconds (Pa\*s) by dividing
    by 1,000.

6.  Record the test temperature, spindle number, spindle speed (rpm),
    and viscosity (Pa\*s) to the nearest 0.1 Pa\*s.

**Week 2**

**Binder Demonstrations**

**AASHTO TP 1-93 Determining the Flexural Creep Stiffness of Asphalt
Binder Using the Bending Beam Rheometer (BBR)**

***Equipment needed:***

Bending Beam Rheometer.

Aluminum Molds - at least 2 beams

> Calibration Equipment - Step Block, 4 weights at 100 g. each,
> stainless steel beams (one thick, one thin).

***Prepare before class:***

Heat PAV aged asphalt to 135 C.

Turn Nitrogen on at bottle and at 2 way valve.

Calibrate machine by following steps in software.

Make beam mold. Refer to manual.

Pour asphalt into mold and let cool for 45 minutes.

Trim beam and remove beam from mold.

Place beam in bath for 60 [+]{.underline} 5 minutes.

***Steps for Class:***

1\. Test beam according to software.

2\. Discuss thermal cracking and low temp cracking.

3\. Print Report.

**Week 2**

**Binder Demonstrations**

**AASHTO PP 1-93 Accelerated Aging of Asphalt Binder Using a Pressurized
Aging Vessel (PAV)**

***Equipment needed:***

PAV Unit

Stainless Steel Pans

Balance - readable to 0.1 gram.

Bottled Air

***Prepare before class:***

Day before class: RTFO 8 bottles of material.

Scrape material from bottles into single container.

Pour 50 g. into pan each pan

Place pans in rack and place rack into PAV.

Tighten bolts on lid to 50 psi with torque wrench.

When PAV reaches temperature, push start button.

PAV test takes 20 hours plus handling time.

Plan test so completion is at appropriate time.

***Steps for Class:***

1\. Make sure pressure is released when test is completed.

2\. Remove bolts from lid.

3\. Take rack from PAV and transfer material into container.

4\. Discuss long term aging.

**Week 2**

**Binder Demonstrations**

**AASHTO T Rolling Thin Film Oven Aging**

***Equipment needed:***

RTFO Oven

Bottles - at least 3 - 1 empty, 1 before test, 1 after test

***Prepare before class:***

Place 35 g of asphalt in two of the three jars. Keep one for "show and
tell"

> Place the other in the RTF oven and heat until the jar is completely
> coated. Take the jar out, cool down and use as an example of how the
> jar will look after test is complete.

***Steps for Class:***

1\. Show class bottles.

2\. Open door to oven

3\. Turn sample rack on.

4\. Demonstrate air flow set to 4000 ml/min.

**Week 2**

**Binder Demonstrations**

**AASHTO T?? (new test method) Direct Tension Testing**

***Equipment needed:***

Direct Tension Tester

Aluminum Molds - at least 4 specimens

Plastic End Pieces

***Prepare before class:***

Heat PAV aged asphalt to 135 C.

Make DTT mold. Refer to manual.

Pour asphalt into mold and let cool for 45 minutes.

Trim mold and remove specimen from mold.

Place specimen in bath for 60 [+]{.underline} 5 minutes.

***Steps for Class:***

1\. Place specimen into position.

2\. Test specimen. Refer to manual.

3\. Discuss fracture properties.

**Week 2**

**Hands On**

**AASHTO TP 4-93 Preparing and Determining the Density of Hot Mix
Asphalt Specimens by Means of the SHRP Gyratory Compactor**

***Equipment needed:***

Large mixer with wire whip

Scale with at least 20,000 gram capacity

2 Ovens - one for heating aggregates, one for heating asphalt (hot pot
works also)

Gyratory compactor

Spatulas or large spoons for stirring mix

Pans for heating aggregates

***Prepare before class:***

> Prepare twelve 4,500 gram pans of aggregates blended to meet target
> gradation and place in oven at least 6 hours prior to class
>
> Preheat asphalt (in quart cans in oven, at least 2 hours prior to
> class - MAKE SURE TO VENT CANS.

Preheat mixing bowl and molds

> Predetermine for the students: asphalt contents, appropriate mixing
> and compaction temperatures, and numbers of gyrations

Note: The test method calls for three samples at each of three asphalt
contents. It is suggested that two samples/group be compacted using 4
asphalt contents so that as many students as possible have a change to
get "hands on" experience. The test method also calls for short term
aging, but this would make labs too long. Explain that this would occur,
but in order to fit work into lab period, this step has been eliminated.
That is, compact the samples immediately after mixing.

***Steps for Class:***

1.  Take bowl out of oven and place on scale. Gently add aggregate to
    bowl and use spoon to make a depression in center of aggregate.

2.  Add a predetermined amount of asphalt (1 group = 1 asphalt content)

3.  Place on mixer and mix thoroughly.

4.  (Would normally place in shallow pan here but because of time
    constraints, place mix directly into hot mold).

5.  Place mold in compactor per manufacturer's directions and compact to
    desired number of gyrations.

6.  Repeat steps 1 through 5 for second sample.

7.  For third sample, repeat steps 1 through 3 only. Do not compact the
    third sample. This will be used for determining the maximum specific
    gravity in the next lab session. Empty mix from bowl into pan,
    cover, label, and store.

**Week 3**

**Testing of Asphalt Concrete Samples**

**Week 3**

**Hands On**

**AASHTO T 166-93 Bulk Specific Gravity of Compacted Bituminous Mixtures
Using Saturated Surface-Dry Specimens**

***Equipment needed:***

Scale which reads to 0.1 grams with apparatus for weighing under water

Water bath

Large terry cloth towels

Spray bottle filled with water

***Prepare before class:***

Use samples compacted by students the previous week

***Steps for Class:***

1.  Dampen towel.

2.  Determine the mass of the dry specimens. Record.

3.  Place specimen in water for 3 to 5 minutes. Determine mass under
    water at the end of this time. Record.

4.  Remove specimen from water and quickly blot dry on damp towel (dull
    finish is SSD condition).

5.  Place SSD specimen on scale and determine mass. Record.

**Week 3**

**Hands On**

**AASHTO T 209-94 Theoretical Maximum Specific Gravity and Density of
Bituminous Paving Mixtures**

***Equipment needed:***

Scale which reads to 0.1 grams with apparatus for weighing under water

Water bath

Large flat tray or cookie sheet

Dual stage vacuum pump with fittings per test method

Residual vacuum manometer

Shaker table

Metal bowl with vacuum lid

***Prepare before class:***

Use loose mix sample prepared by students the previous week

***Steps for Class:***

1.  Warm sample and break up clumps.

2.  Determine mass of bowl (without lid) under water. Record.

3.  Determine the oven dry mass and place sample in metal bowl.

4.  Cover with water, place vacuum lid on bowl, then place entire set up
    on shaker table. Clamp down.

5.  Start vacuum pump and gradually increase pressure until residual
    vacuum manometer reads 3.7 ± 0.3 kPa. Start shaker table and
    maintain both pressure and agitation for 15 ± 2 minutes.

6.  Stop shaker table and pump. Gradually release pressure and remove
    top.

7.  Suspend bowl and sample under water for 10 minutes then determine
    the mass under water. Record.

**Week 3**

**Demonstration**

**ASTM D4867 Effect of Moisture on Asphalt Concrete Paving Mixtures.**

***Equipment needed:***

25^o^C water bath

60^o^C water bath

Load frame which moves at 50 mm/minute

Indirect tensile breaking head

***Prepare before class:***

> Mix and compact a set of six samples at an optimum asphalt content and
> between 6 to 8 percent air voids

Determine the bulk specific gravity of the sample. Record.

Determine the heights of the samples. Record.

Record appropriate maximum specific gravity for the mix used.

Calculate the air voids. Record.

Saturate samples 3 of the 6 and determine the SSD mass. Record.

Soak overnight in the 60^o^C water bath

2 hours before class, put samples in 25^o^C water bath

***Steps:***

1.  Give all recorded data to the students.

2.  Take samples out of water bath and put in breaking head.

3.  Place breaking head and sample in load frame.

4.  Determine the maximum load the sample can take before the load
    begins to drop off.

5.  Repeat until all samples (dry included) have been tested.