This test method covers the procedure for the determination of clay lumps and friable particles in aggregates. Clay lumps and friable particles are objectionable materials in the aggregate due to contamination at the time the deposit was formed, at the time of quarrying, or at the time of hauling and handling. Clay lumps and friable particles are considered any agglomerated or soft particles retained on the No. 4 sieve and greater for coarse aggregate or No. 20 sieve for fine aggregates will include such terms as mud and clay balls. For coarse aggregates, Method A or Method B may be used to evaluate either stream flow or stockpile samples. The Engineer shall determine the method most appropriate for individual sources. If a sample does not meet specification limits for either test method, the sample is considered non-compliant.
The Fine Aggregate Clay Lumps & Friable Particles test should be requested if problems such as agglomerates or clay lumps are observed in a stockpile.
PROCEDURE
A. Apparatus
1. Balance for coarse aggregate - A balance having a capacity of at least 5000 grams, accurate to 0.5 gram.
2. Balance for fine aggregate - A balance having a capacity of at least 1000 grams, accurate to at least 0.1 gram.
3. Oven capable of maintaining temperature of 110 ± 5°C (230 ± 9°F) or hot plate used at a reduced temperature, and capable of providing a uniform heat until sample has dried to a constant weight.
4. Containers - Containers of a size and shape that will permit the spreading of the sample on the bottom in a thin layer.
4. Sieves - Sieves conforming to AASHTO M92, wire cloth sieves for testing purposes.
COARSE AGGREGATE
A. Sample
1. Coarse - Select a representative sample of material retained on the 4.75-mm (No. 4) sieve that will weigh at least 3000 grams.
METHOD A (Field or Hand Pick Test Method)
B. Test Procedure
1. Separate clay lumps and friable particles from the test sample by hand picking. The sample may be wetted and decanted if this aids identification. Oven-dry the clay lumps and friable particles to a constant weight.
2. Allow the clay lumps and friable particles to cool and determine the dry weight (L).
3. Dry the test sample to a constant weight.
4. Allow to cool and determine the dry weight (W).
C. Calculation
Calculate the percent of clay lumps and friable particles of coarse aggregates as follows:
Where:
P = percent of clay lumps and friable particles
L = dry weight of clay lumps and friable particles
W = dry weight of test sample
METHOD B (Laboratory Test Method)
D. Test Procedure
1. Wash over No. 4 (75-mm) sieve.
2. Oven-dry for at least 16 hours at a temperature of 230° ± 9°F (110°± 5° C)
3. Allow sample to cool and determine the dry weight (W).
4. Spread sample in a thin layer on the bottom of the container, cover it with water and allow it to soak for a period of 24 ± 4 hours.
5. After the soaking period, any particles that can be broken with fingers into fines removable by wet sieving over the No. 8 (2.36-mm) sieve shall be classified as clay lumps or friable particles.
NOTE: The breaking of clay lumps and/or friable particles shall be accomplished by squeezing and rolling them between the thumb and forefinger. The fingernails or mechanical tools shall not be used to break up the particles nor shall they be pressed against a hard surface.
6. Wet sieving is to be accomplished by passing water over the sample through the sieve while manually agitating the sieve, until all undersize has been removed.
7. The retained particles shall then be carefully removed from the sieve and dried at a temperature of 230° ± 9°F (110° ± 5°C).
8. Allow sample to cool, and weigh (R).
E. Calculation
Calculate the percent of clay lumps and friable particles of coarse aggregates as follows:
Where:
P = Percent of clay lumps and friable particles.
M = Dry weight of test sample after washing on the #4 sieve.
R = Dry weight of particles retained on the No. 8 (2.36-mm)(wt. of test sample after removal of clay lumps).
FINE AGGREGATE
A. Sample
For a fine aggregate sample, the size of the test sample of aggregate shall be a minimum of 300 grams after drying. For the test procedure, only the material coarser than 1.18 mm (No. 16) sieve will be tested (See Test Procedure).
B. Test Procedure
1. Oven-dry material to a constant weight at a temperature of 230° ± 9°F (110°± 5° C)
2. Allow sample to cool and dry sieve (do not wash) over No. 16 (1.18 mm) sieve.
3. From the material retained on the No. 16 (1.18 mm) sieve, measure a test sample of a minimum of 300 grams (W) and record the weight. This will be M1 in the equation below.
- Wash this sample over a 200 mesh sieve (75 µm) in accordance to AASHTO T11, dry retained material to a constant mass and record the weight. This value will be R1 and M2 in the equations below.
- Spread dried sample in a thin layer on the bottom of a container, cover with water and allow it to soak for a period of 24 ± 4 hours.
6. After soaking, any particles that can be broken with fingers into fines that are removable by wet sieving over the No. 20 (0.841 mm) sieve shall be classified as clay lumps or friable particles.
NOTE: The breaking of clay lumps and/or friable particles shall be accomplished by squeezing and rolling them between the thumb and forefinger. The fingernails or mechanical tools shall not be used to break up the particles nor shall they be pressed against a hard surface.
7. Wet sieving is to be accomplished by passing water over the sample through the sieve while manually agitating the sieve, until all undersize has been removed.
- The retained particles shall then be carefully removed from the sieve and dried to a constant weight at a temperature of 230° ± 9°F (110° ± 5°C).
9. Allow sample to cool, and weigh (R2).
C. Calculations
Calculate the percent of adhering particles of fine aggregates as follows:
For the 200 wash (Not to be added to loss total):
Where:
P1 = Percent of minus 200 mesh particles.
M1 = Initial mass of test sample (Coarser than 1.18 mm (No 16) sieve).
R1 = Dry weight of particles retained on the No. 200 (75 µm) sieve (wt. of test sample after removal of adhering particles).
Calculate the percent clay lumps and friable particles post soaking, breaking of agglomerates, and sieving on the No. 20 sieve:
Where:
P2 = Percent of clay lumps and friable particles.
M2 = Mass of test sample after 200 wash (Coarser than 1.18 mm (No 16) sieve).
R2 = Dry weight of particles retained on the No. 20 (0.841 mm) sieve (wt. of test sample after removal of clay lumps).