Modified Marshall Hammer Compaction Method



Modified Marshall Hammer Compaction Method

1. Scope

1.1 This method of test is intended for determining the maximum density of aggregate surfacing material that is compacted in a 101.6mm mold with a Marshall hammer.

2. Apparatus

2.1 Molds - The 101.6mm diameter mold shall meet the AASHTO T99 apparatus requirements.

2.2 Compaction Hammer - The 4.536kg hammer shall meet the requirements shown in AASHTO T245.

2.3 Compaction Base - A block of concrete weighing not less than 91kg supported by a relatively stable foundation, or a sound concrete floor.

2.4 Balances, Scales, Drying Oven, Sieves, Mixing Tools, Containers must meet AASHTO T99 requirements.

2.5 Straight edge ruler capable of reading 1 mm or smaller.

3. Sample - A representative field sample weighing at least 23 kg.

4. Procedure

4.1 Dry the field sample in air or by use of a drying apparatus such that the temperature does not exceed 60oC. Separate the sample over a 19-mm sieve and record weights of the plus and minus 19-mm materials. Calculate the percent plus 19 mm and discard the plus 19-mm material afterwards.

4.2 Dampen all the 19-mm minus material to approximately 4 percent below optimum moisture.

4.3 With the collar attached to the mold and base, measure the inside height from the base inside the mold to the top of the attached collar, to the nearest 1 mm (height will be used in the volume calculations in Section 5).

4.4 Weigh mold with attached collar and base. Compact material in the mold in three layers, with forty blows per layer. Total thickness of the three layers should be close to 125 mm. Do not remove collar!!

4.5 Weigh mold, collar, and base with compacted sample and calculate the wet weight of the sample.

4.6 To the nearest 1 mm, measure the vertical distance from the top of collar down to the surface of the compacted sample in four places approximately 90o from each other. Average the four measurements and record (the average measurement will be used in the volume calculations in Section 5).

4.7 Extrude all material from mold and dry it all to constant weight at 110 + 5oC to determine percent moisture content; do not re-use material.

4.8 Add and mix the following amount of water to remainder of the dampened sample:

Amount of Water Added = (Remaining Wet Sample Weight) x 1.5%

4.9 Repeat steps 4.4 thru 4.8 until one of the following conditions exist:

a. A decrease or no change in the compacted wet density (kg per cubic meter). Wet density will have to be calculated after each trial using the height of sample (see Section 5).

b. Excess free moisture exudes from the base of the mold during compaction.

5. Calculations

Volume (V) of Individual trial or sample:

V(m3) = (Mold Cross Sectional Area) x (material height) / (1E09)

V(m3) = (3.1416) x (50.8 mm)2 x (material height) / (1E09)

V in cubic meters (m3) = 8.107E-06 x material height in mm

Material = (height from Sec 4.3) - (avg measurement from Sec 4.6)

height

Wet Density in kilograms = Wet Weight (kg) from Sec 4.5

per cubic meter V(m3)

Dry Density in kilograms = Wet Density (kg/m3)

per cubic meter 1 + % Moisture

100

6. Moisture Density Relationship - See this section in AASHTO T99. Add the following:

(a) Optimum moisture content may also be the point at which moisture exudes from the mold during compaction.

(b) Maximum density shall be adjusted for the plus 19-mm material contained in the field sample, but not used in the test. The adjustment shall be made by the following formula:

Adjusted Max

Density = (Maximum Density) + (0.125) x (Percent Plus 19mm)

7. Report - The report shall include the following:

(a) The optimum moisture content as a percentage, to the nearest whole number.

(b) The maximum dry density in kg per cubic meter to the nearest whole number.

(c) The percent plus 19-mm sieve size material in the original field sample.

(d) The adjusted maximum density in kg per cubic meter using the formula from Section 6(b).

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