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CP 23 Page 1
Colorado Procedure 23-08 Standard Method of Test for
Determining Maximum Dry Density and Optimum Moisture of the Total Sample of Soil-Rock Mixture 3.5
1. SCOPE 1.1 This method of test is intended for determining the maximum dry density and optimum moisture content of the total sample of soil-rock mixture on which the maximum dry density and optimum moisture content of the minus No. 4 material has been determined, and correcting this density and moisture for the percentage of rock rock in the soil-rock mixture. mixture. The percentage of rock is determined using material obtained from the immediate vicinity of the density test. 2. REFERENCED DOCUMENTS 2.1
Colorado Procedures: CP 22 Determining Density Density of Soil and Soil-Aggregate Mixtures InPlace by the Sand Replacement Method CP 26 Determining the Durability of Shales for Use as Embankments
2.2
AASHTO Procedures: T 85 Specific Gravity and Absorption of Coarse Aggregate T 99 Moisture-Density Moisture-Density Relations of Soils Using a 2.5-kg Rammer and a 305-mm Drop T 180 Moisture-Density Moisture-Density Relations of Soils Using a 4.54-kg Rammer and a 457-mm Drop
3. APPARATUS 3.1
Wire basket – basket – (as in Figure 1).
3.2 Balance - Capacity of 2500 g or more and sensitive to 0.1 g. 3.3 Container displaced water.
Beaker
to
catch
the
3.4 Volumetric Displacement Apparatus (as in Figure 2).
Drying Equipment Equipment - Stove or oven.
4. PROCEDURE 4.1 Determine the maximum dry density and the optimum moisture content of the minus No. 4 material in accordance with AASHTO T 99 or T 180, Method A. 4.2 Determine the bulk specific gravity of the rock fraction of the sample as follows: 4.2.1 Obtain a representative representative sample sample of material from the immediate vicinity of the density test. test. The depth of the sample hole should be between 5 to 10 inches (125 to 250 mm). Process the sample over the No. 4 sieve to obtain a 1.5 to 2.0 kg specimen of minus 3 in. (75 mm) plus No. 4 rock. rock. Thoroughly wash wash the specimen to remove all dust or other coating from the surface of the particles and dry to a o o o constant weight (mass) at 230 F ± 9 (110 C ± o 5 ). Record this weight (mass) (mass) as the weight (mass) in grams of oven dry specimen. 4.2.2 Immerse the specimen specimen in water for a period of 24 hours. hours. Remove the specimen specimen from water and roll it in a large absorbent cloth until all visible films of water are removed, although the surfaces of the particles still appear to be damp. The larger larger fragments fragments may be wiped individually. Take care to avoid evaporation during the operation operation of surface drying. drying. Obtain the weight (mass) and record in grams of the saturated surface dry specimen. 4.2.3 Place wire wire basket in the volumetric displacement apparatus and fill with water to a point about 3/8 inch (10 mm) above the spout. Allow excess water to run out. After excess water ceases to drip, place the tared beaker under the spout. Partially remove remove the basket, basket, place the specimen in the basket and then immediately into into the container. Take care to avoid splashing or spilling water over the rim. Weigh the displaced water and record in grams of water displaced by the specimen.
CP 23 Page 2 NOTE 1: The bulk specific gravity may also be determined by the method described in AASHTO T 85. 4.2.4 Calculate the bulk specific gravity from the following formula or use the nomograph in Chapter 200. A1 Bulk specific gravity = W Where: A1 =
weight (mass) in grams of oven dry specimens, weight (mass) in grams of water displaced by the specimen.
W =
NOTE 2: This procedure may be used to determine specific gravities other than bulk using the following formulas: Bulk specific gravity
B = 1 (saturated surface dry) W
weight (mass) in grams of saturated surface dry specimen, weight (mass) in grams of water displaced by the specimen.
W =
4.5 Weigh the entire soil rock mixture from the density test hole as described in CP 22 or from a hole directly below the nuclear moisture/density gauge test site. Dry the entire o specimen to a constant weight (mass) at 230 F o o o _ + 9 (110 C ± 5 ) and determine the moisture content and dry weight (mass) of the entire specimen. Separate the material by using a No. 4 sieve and weigh the fraction retained. Calculate the percentage retained as follows: Percent Plus No. 4 (rock)
4.3 Calculate the total percent absorption of the plus No. 4 fraction as follows:
Total percent absorption
=
B1 - A1 X 100 A1
4.4 For aggregates that have a total absorption of more than 2% as calculated in 4.2.4, the following formula shall be used to calculate the percent "Field Absorption" and the results used in the moisture correction calculations: Percent Field Absorption
=
C1 - A 1 X 100 A1
Where:
C1 =
Dry wt. of + No. 4 Dry wt. of total specimen
X 100
5.1 The maximum dry density and optimum moisture content of the minus No. 4 material determined in accordance with AASHTO T 99 or T 180, Method A, shall be corrected for the percentage of plus No. 4 rock in the density test by the following formulas or by use of the nomographs provided in Chapter 200.
Corrected Maximum Dry Density
MoistureContent
=
M f x Pf + M c x Pc 100
Where: Pf = Pc =
Dc = weight (mass) in grams of oven dry specimens, weight (mass) in grams of specimen from test area prior to drying.
Pf x D f + Pc x 0.9D c 100
=
Corrected Optimum
Df =
A1 =
=
5. CALCULATIONS
Where: B1 =
NOTE 3: The specimen for C1 is obtained from the embankment after it has been subjected to the wetting and compacting procedures normal for the area. The intent is to determine as nearly as possible the actual moisture content of the rock particles in place. The surface of the rock particles shall be cleaned of all surface coating with a wire brush prior to weighing.
Pc =
Percent fine particles by weight (minus No. 4); Percent coarse particles by weight (plus No. 4); Maximum dry density of fine particles 3 (minus No. 4), kg/m (pcf); 1000 * bulk specific gravity (G m) (oven dry basis) of coarse particles, kg/m 3, or 62.4 x bulk specific gravity (G m) (oven dry basis) of coarse particles, pcf.; Percent coarse particles by weight (plus No. 4);
CP 23 Page 3 Mf = Mc =
Moisture content of the fine particles (minus No. 4); Moisture content of the coarse particles (plus No. 4).
6. LIMITATION FOR USE OF CP 23 6.1 CP 23 shall not be used when the plus No. 4 fraction of the sample consists of cinders or other light porous rock since an accurate specific gravity determination is difficult to make on this type of material. For these materials AASHTO T 99 or T 180 Method C or D shall be used. 6.2 The plus No. 4 fraction of the sample shall be determined to be Rock-like (Durable) or Soil-like (Non-durable) either visually, by experienced field personnel or in the Central Laboratory., according to CP 26.
If the plus No. 4 fraction is classified as Nondurable then CP 23 will not apply and the total sample shall be treated as minus No. 4 material for moisture/density determination. NOTE 3: Non-durable plus No. 4 material will usually be found in soils with a classification of A-6 or A-7. 7. RECORD 7.1 CDOT Form # 24, Moisture - Density Relation. 7.2 CDOT Form # 584, Moisture - Density Relation Graph.
Figure 23-1 - Bulk Specific Gravity A No. 8 mesh brass cloth basket approximately 5 1/2” (140 mm) in diameter by 5 1/2" (140 mm) height in a frame of 3/4" (19 mm) X 1/32" (0.8 mm) soft brass or stainless steel.
CP 23 Page 4
Figure 23-2 - Bulk Specific Gravity Volumetric displacement apparatus with overflow device
