ASTM C78 – Flexural Strength of Concrete (Using
Simple Beam) Exam
ASTM C78 – Flexural Strength of Concrete (Using
Simple Beam) Exam
ASTM C78 – Flexural Strength of Concrete (Using
Simple Beam) Exam
EXAM COVERAGE
1. Test Method Scope and Apparatus Requirements – equipment specifications,
bearing blocks, loading rates, and machine verification.
2. Specimen Preparation and Geometry – beam dimensions, span-to-depth
ratios, molding and curing requirements.
, 3. Third-Point Loading Configuration – load application points, simply supported
conditions, and flexure zone mechanics.
4. Gap Elimination and Contact Requirements – leather shims, grinding, capping,
and gap tolerances.
5. Loading Rate Calculations and Control – stress rate equations, initial load
application, and continuous loading without shock.
6. Fracture Location Determination and Measurement – middle third criteria,
outside middle third within 5%, and discard criteria.
7. Modulus of Rupture Calculation Formulas – PL/bd² for middle third, 3Pa/bd²
for outside, and variable definitions.
8. Specimen Measurement Procedures – three measurements across
dimensions, fracture location measurement, and reporting precision.
9. Reporting Requirements and Precision – nearest 0.05 MPa, identification,
curing history, and moisture condition.
10. Common Errors and Result Validity – drying effects, mishandling, sawing
beams, and correlation limitations.
,ASTM C78 – Flexural Strength of Concrete (Using
Simple Beam) Exam
1. What is the primary purpose of ASTM C78 testing as it relates to concrete
pavement and structural design applications?
A. To determine the compressive strength of cylindrical concrete specimens
B. To measure the flexural strength or modulus of rupture of concrete beams
C. To evaluate the density and unit weight of hardened concrete
D. To assess the slump and workability of fresh concrete mixtures
Correct Answer: B
Explained Point Form Notes:
Choice A: Compressive strength is determined by ASTM C39 using cylindrical
specimens, not ASTM C78.
, Choice B: ASTM C78 specifically determines flexural strength, commonly
called modulus of rupture, using a simple beam with third-point loading 1 7 .
Choice C: Density and unit weight are determined by ASTM C138 for fresh
concrete or ASTM C642 for hardened concrete.
Choice D: Slump testing is governed by ASTM C143 and measures fresh
concrete consistency.
2. In the ASTM C78 third-point loading configuration, where exactly are the two
load application points positioned relative to the beam span?
A. At the quarter points of the span length from each support
B. At the third points of the span length from each support
C. At the center and quarter points of the span length
D. At a distance equal to the beam depth from each support
Correct Answer: B
Simple Beam) Exam
ASTM C78 – Flexural Strength of Concrete (Using
Simple Beam) Exam
ASTM C78 – Flexural Strength of Concrete (Using
Simple Beam) Exam
EXAM COVERAGE
1. Test Method Scope and Apparatus Requirements – equipment specifications,
bearing blocks, loading rates, and machine verification.
2. Specimen Preparation and Geometry – beam dimensions, span-to-depth
ratios, molding and curing requirements.
, 3. Third-Point Loading Configuration – load application points, simply supported
conditions, and flexure zone mechanics.
4. Gap Elimination and Contact Requirements – leather shims, grinding, capping,
and gap tolerances.
5. Loading Rate Calculations and Control – stress rate equations, initial load
application, and continuous loading without shock.
6. Fracture Location Determination and Measurement – middle third criteria,
outside middle third within 5%, and discard criteria.
7. Modulus of Rupture Calculation Formulas – PL/bd² for middle third, 3Pa/bd²
for outside, and variable definitions.
8. Specimen Measurement Procedures – three measurements across
dimensions, fracture location measurement, and reporting precision.
9. Reporting Requirements and Precision – nearest 0.05 MPa, identification,
curing history, and moisture condition.
10. Common Errors and Result Validity – drying effects, mishandling, sawing
beams, and correlation limitations.
,ASTM C78 – Flexural Strength of Concrete (Using
Simple Beam) Exam
1. What is the primary purpose of ASTM C78 testing as it relates to concrete
pavement and structural design applications?
A. To determine the compressive strength of cylindrical concrete specimens
B. To measure the flexural strength or modulus of rupture of concrete beams
C. To evaluate the density and unit weight of hardened concrete
D. To assess the slump and workability of fresh concrete mixtures
Correct Answer: B
Explained Point Form Notes:
Choice A: Compressive strength is determined by ASTM C39 using cylindrical
specimens, not ASTM C78.
, Choice B: ASTM C78 specifically determines flexural strength, commonly
called modulus of rupture, using a simple beam with third-point loading 1 7 .
Choice C: Density and unit weight are determined by ASTM C138 for fresh
concrete or ASTM C642 for hardened concrete.
Choice D: Slump testing is governed by ASTM C143 and measures fresh
concrete consistency.
2. In the ASTM C78 third-point loading configuration, where exactly are the two
load application points positioned relative to the beam span?
A. At the quarter points of the span length from each support
B. At the third points of the span length from each support
C. At the center and quarter points of the span length
D. At a distance equal to the beam depth from each support
Correct Answer: B
