Test Methods and Specifications for Civil Materials

NCEES FE Civil spec: Materials, B. Test methods and specifications of metals, concrete, aggregates, asphalt, and wood. FE Reference Handbook: Materials Science/Structure of Matter and Mechanics of Materials chapters.

Construction materials are accepted or rejected based on standard tests, mostly ASTM and AASHTO methods. The FE Civil exam does not expect you to know test numbers, but it does expect you to know what each common test measures, what specimen it uses, and how to reduce the raw data to a result.

What the NCEES spec covers

Section B, "Test methods and specifications", covers tests for metals, concrete, aggregates, asphalt and wood. Questions are usually one of two kinds: identify the purpose of a test, or compute a result (strength, fineness modulus, specific gravity, moisture content) from test data.

Key concepts

Fresh concrete. The slump test measures consistency (workability). Air content, unit weight and temperature are checked at the same time.
Hardened concrete. Compressive strength comes from cylinders (6 × 12 in or 4 × 8 in in U.S. practice), usually at 28 days. Tensile strength is estimated with the split cylinder test, and flexural strength (modulus of rupture) with beam tests.
Steel. The tension test gives the stress-strain curve: modulus, yield strength (0.2% offset if there is no clear yield point), ultimate strength and elongation (ductility). Hardness and Charpy impact tests measure resistance to indentation and fracture toughness.
Aggregates. Sieve analysis gives gradation and the fineness modulus. Specific gravity and absorption tests support mix design. The Los Angeles abrasion test measures resistance to degradation.
Asphalt binder and mixes. Penetration and viscosity classify binder stiffness; Superpave grading uses performance tests. Marshall stability and flow, or gyratory compaction with volumetrics, are used for mixes.
Wood. Moisture content and specific gravity tests, plus strength tests parallel and perpendicular to the grain.

Core formulas

f_{c}^{'} = \frac{P}{π d ^{2} /4} f_{c t} = \frac{2 P}{π L d} (split cylinder) f_{r} = \frac{P L}{b d ^{2}} (third-point loading)

F M = \frac{\sum cumulative % retained on standard sieves}{100}

The standard sieves for fineness modulus are 3/8 in, No. 4, 8, 16, 30, 50 and 100. Fine aggregate for concrete typically has an FM between about 2.3 and 3.1; a higher FM means a coarser sand.

Where it is in the FE Reference Handbook

The Materials Science/Structure of Matter and Mechanics of Materials chapters cover the tension test and stress-strain behavior, hardness and impact testing, and concrete strength charts. Test procedures themselves are not reproduced in the handbook, so the purpose of each test is something to learn ahead of time.

Worked example

(a) A 6 × 12 in concrete cylinder fails at 113,000 lb. Find its compressive strength. (b) A sand sample has cumulative percent retained of 0, 2, 15, 35, 60, 82 and 96 on the 3/8 in, No. 4, 8, 16, 30, 50 and 100 sieves. Find the fineness modulus.

(a) Compressive strength.

A = \frac{π ( 6 ) ^{2}}{4} = 28.27 in^{2} f_{c}^{'} = \frac{113 , 000}{28.27} = 3, 997 psi \approx 4, 000 psi

(b) Fineness modulus.

F M = \frac{0 + 2 + 15 + 35 + 60 + 82 + 96}{100} = 2.90

An FM of 2.90 is a medium-coarse sand, within the usual range for concrete. Note that the No. 200 sieve and the pan are not part of the sum.

Common mistakes

Thinking slump measures strength. It measures consistency of fresh concrete only.
Including the No. 200 sieve or the pan in the fineness modulus.
Using percent passing instead of cumulative percent retained.
Using the cylinder length instead of its diameter for the loaded area in compression.
Reading yield strength at the proportional limit instead of with the 0.2% offset line.

Related concepts appear in the stresses and strains lesson.

Practice Problems

Try these from the free PolyCalc FE Civil problem bank. Each one has a full worked solution.

In common U.S. practice, concrete compressive strength is measured by loading which type of specimen? See the worked solution or practice the Construction Materials deck
Concrete slump primarily indicates which property of fresh concrete? See the worked solution or practice the Construction Materials deck
What does sieve analysis determine about an aggregate sample? See the worked solution or practice the Construction Materials deck
Maximum stability occurs at 5.2% binder, maximum bulk density at 5.0%, and 4% air voids at 4.8%. Averaging these, the optimum binder content is: See the worked solution or practice the Construction Materials deck

Related Calculators and Examples

Frequently Asked Questions

What does the slump test measure?

It measures the consistency or workability of fresh concrete. It does not measure strength, although a higher water content that increases slump also lowers strength.

How is concrete compressive strength measured?

By loading cylinders, usually 6 by 12 inches or 4 by 8 inches in U.S. practice, to failure at a standard age such as 28 days. Strength is the failure load divided by the cross-sectional area.

How do you calculate fineness modulus?

Add the cumulative percentages retained on the standard sieves (3/8 inch, No. 4, 8, 16, 30, 50 and 100) and divide by 100.

Back to all Materials topics