Compacted Unit Weight of Tire Shreds

Based on laboratory tests, the compacted unit weight of tire shreds ranges from 38 to 43 pcf.  This is about 1/3 the unit weight of other soils.  Table 1 below gives laboratory compacted dry unit weights from several different sources.     The unit weight of tire shreds when they are in place in the field will be higher than the range of lab results due to the material's compressibility.  The weight of overlying fill will provide additional compression of the tire shreds, resulting in an increase in unit weight.  During compaction, compactive energy only has a small effect on the dry unit weight, and water content will not affect compaction properties either.

Table 1. Summary of laboratory dry unit weights of tire shreds

Compaction method	Particle size  (in.)	Tire shred type	Source of  tire shreds	Dry unit weight (pcf)	Reference
Loose	3	Mixed	Palmer Shredding	21.3	(2)
Loose	2	Mixed	Pine State Recycling	30.1	(2)
Loose	1	Glass	F & B Enterprises	30.9	(2)
Loose	2	Mixed	Sawyer Environmental	25.5	(1)
Loose	2	Mixed	------	29.1	(5)
Loose	1	Mixed	------	30.5	(5)
Vibration	1	Mixed	------	31.0	(5)
Vibration	0.5	Mixed	------	29.5	(5)
50% Standard	1	Mixed	------	38.3	(5)
50% Standard	0.5	Mixed	------	40.0	(5)
60% Standard	3	Mixed	Palmer Shredding	38.7	(2)
60% Standard	2	Mixed	Pine State Recycling	40.1	(2)
60% Standard	1	Glass	F & B Enterprises	38.6	(2)
60% Standard	2	Mixed	Sawyer Environmental	39.0	(1)
Standard	2	Mixed	Sawyer Environmental	39.9	(1)
Standard	2	Mixed	------	39.6	(5)
Standard	1.5	Mixed	------	40.2	(5)
Standard	1	Mixed	------	40.7	(5)
Standard	0.5	Mixed	------	39.5	(5)
Standard	3	------	Rodefeld	37.1b	(4)
Standard	3	------	Rodefeld	34.9c	(4)
Modified	2	Mixed	Sawyer Environmental	41.2	(1)
Modified	2	Mixed	------	41.7	(5)
Modified	1	Mixed	------	42.7	(5)
----	2	Mixed	------	26 to 36	(3)

Notes:  a.  Compaction methods:
         Loose = no compaction; tire shreds loosely dumped into compaction mold
         Vibration = Method D 4253
         50% Standard=Impact compaction with compaction energy of 6,188 ft-lb/ft3
         60% Standard=Impact compaction with compaction energy of 7,425 ft-lb/ft3
         Standard = Impact compaction with compaction energy of 12,375 ft-lb/ft3
         Modified = Impact compaction with compaction energy of 56,250 ft-lb/ft3
b.  6-in. diameter mold compacted by 10-lb rammer falling 12 in.
c.  12-in. diameter mold compacted by 60-lb rammer falling 18 in.

References:

(1) Manion and Humphrey (1992); Humphrey and Manion (1992)
(2) Humphrey, et al. (1992, 1993); Humphrey and Sandford (1993)
(3) Bressette (1984)
(4) Edil and Bosscher (1992, 1994)
(5) Ahmed (1993); Ahmed and Lovell (1993)

Procedures

Soil test procedures are not directly applicable because tire shred samples always have more than 30% retained in the 3/4-inch sieve, and the standard 6-inch diameter mold cannot be used.  A 10-inch or 12-inch mold can be used for type A tire shreds.  The procedures of ASTM D 698 are used to obtain 60% of standard Proctor energy.  Compactive energy only has a small effect on the resulting dry unit weight, so it isn't necessary to use a higher compactive energy value.

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