30 June 2001
DETERMINATION OF FLEXURAL STRENGTH AND MODULUS
E-1. SCOPE. These procedures describe preparation and testing of bituminous concrete to
determine flexural strength and modulus of elasticity. The procedures are an adaptation from tests
conducted on portland cement concrete (PCC) specimens.
E-2. APPLICABLE STANDARDS. The standard applicable to this procedure is ASTM C 78.
E-3. APPARATUS. The following apparatus are required:
a. A testing machine capable of applying repetitive loadings for compaction of beam
specimens 152 by 152 by 533 millimeters (6 by 6 by 21 inches) to the design density (an Instron
electromechanical testing machine meets this requirement).
b. A steel mold, suitably reinforced to withstand compaction of specimens without distortion.
d. A 22,240-Newton (5,000-pound) load cell.
e. An X-Y recorder.
f. A testing machine for load applications conforming to ASTM C 78 (a Baldwin or Tinius
Olsen hydraulic testing machine is suitable for this purpose).
E-4. MATERIALS. Sufficient aggregate and bitumen meeting applicable specifications to produce
six 152- by 152- by 533-millimeter (6- by 6- by 21-inch) test specimens are required. In the event
the proportioning of aggregate and bitumen, bitumen content, and density of compacted specimens
are not known, additional materials will be required to conduct conventional Marshall tests to
develop the needed mix design data.
E-5. SAMPLE PREPARATION.
a. Prepare in a laboratory mixer four portions of paving mixture for one 152- by 152- by
533-millimeter (6- by 6- by 21-inch) beam test specimen consisting of aggregate and bitumen in
the proportions indicated for optimum bitumen content. The total quantity of paving mixture
should be such that when compacted to a uniform 152- by 152-millimeter (6- by 6-inch) cross
section, the density of the beam will be as specified from previous laboratory mix design tests or
other sources. The temperature of the paving mixture at the time of mixing should be such that
subsequent compaction can be accomplished at 1212.8 degrees Celsius (2505 degrees
Fahrenheit). Place two of the four portions in the 152- by 152- by 533-millimeter (6- by 6- by
21-inch) reinforced steel mold and compact to a 76-millimeter (3-inch) thickness with a 152- by
152-millimeter (6- by 6-inch) foot attached to the repetitive loading machine. Shift the mold
between load applications to distribute the compaction effort uniformly. Add the remaining two
portions and continue compaction until the paving mixture is compacted to exactly a 152- by