ACI Field Testing I cheat sheet

ASTM C172 governs sampling; the sample must represent the entire batch and be taken from the middle portion of the discharge, not the first or last material.

Use a clean, dampened receptacle; never sample from concrete contaminated by soil, set concrete, or excessive wash water.

Collect enough concrete to complete all required field tests and cast specimens; a common minimum is about 1 ft³ (28 L).

For a composite sample, combine increments from several portions of the batch and remix before testing; do not test a grab sample as if it were representative.

Begin temperature, slump, and air tests promptly after sampling; protect the concrete from sun, wind, and evaporation before testing.

Remix each test portion with a shovel before placing it in the test apparatus, but do not add water to make the sample easier to handle.

Record batch or truck identity, location, time, and any deviations; field test results are traceable only if sampling is documented.

Do not sample from a stationary pile or from a chute after segregation; obtain concrete while it is flowing and homogeneous.

ASTM C1064 covers temperature of freshly mixed concrete; use a calibrated thermometer with sufficient immersion depth.

Immerse the sensing portion at least 3 in. (75 mm) into the concrete, avoiding contact with the container, and read after at least 2 min or when stable.

Report temperature to the nearest 0.5°C (1°F), and compare it with the project specification limits for placing and curing.

Measure temperature on a representative sample immediately after sampling; do not let the sample sit in sun or wind.

An infrared thermometer measures surface temperature only and is not an acceptable substitute for ASTM C1064 immersion measurement.

For large batches or placements, take readings at multiple representative locations if the specification requires it.

Thermometer calibration should be verified against a reference thermometer; a damaged or drifting thermometer invalidates results.

Temperature affects setting time, strength gain, and air content; record it even when no limit is specified.

ASTM C143 slump mold: 12 in. (300 mm) high, 8 in. (200 mm) bottom diameter, and 4 in. (100 mm) top diameter.

Place the mold on a firm, level, nonabsorbent base, moisten the mold, and hold it firmly during filling.

Fill in three equal layers; rod each layer 25 times with a 5/8 in. (16 mm) bullet-nosed rod, distributing strokes uniformly.

Strike off the top, then remove the mold vertically in 5 ± 2 s without twisting or lateral movement.

Measure slump immediately as the vertical difference between the original top of the mold and the displaced center of the concrete.

Report slump to the nearest 1/4 in. (5 mm); if the concrete shears or collapses, record that condition because the value may not represent true slump.

Complete the slump test within 2.5 min after sampling; do not retest a sample that has been standing.

Slump is not a measure of workability for all mixtures; very dry or very wet concrete may require a different consistency test.

ASTM C138 determines density, yield, and gravimetric air content using a calibrated measure of known volume.

Density (unit weight) = mass of concrete in the measure ÷ volume of the measure; report in lb/ft³ or kg/m³.

Yield = total mass of the batch ÷ measured unit weight; relative yield = actual yield ÷ design volume.

Gravimetric air content = 100 × (1 − measured unit weight ÷ theoretical air-free unit weight).

Consolidate the concrete in the measure according to slump: rodding for normal concrete or vibration for low-slump concrete, following C138.

Strike off the surface, clean the measure, and determine mass to the required precision; the measure volume must be calibrated.

For yield calculations, use the actual total mass of all materials batched, including water and admixtures.

Gravimetric air content is less direct than pressure or volumetric methods and depends on an accurate theoretical unit weight.

ASTM C231 pressure method uses Boyle's law: pressurized air compresses the air voids and the gauge indicates air content.

Select a meter and calibration range appropriate for the expected air content and aggregate size.

Fill and consolidate the measure per C231, strike off, clean the flange, and clamp the lid to prevent leakage.

Apply the specified pressure, tap the meter to stabilize the reading, and read the gauge at the required pressure.

Air content = gauge reading − aggregate correction factor; determine the correction factor for the aggregate combination by calibration.

The pressure method is not suitable for highly porous or lightweight aggregates without a verified correction.

Check the meter for leakage and proper water level; a leaking or dirty meter produces false low or high readings.

Record the gauge pressure, reading, correction factor, and final air content.

ASTM C173 volumetric method measures air by removing it from a known concrete volume and reading the water-level drop.

Fill the measuring bowl, add water, and seal the meter; invert and roll the meter to displace air from the concrete.

Repeat agitation and settling until the air volume reading stabilizes; trapped air must be fully released.

Read air content directly from the graduated neck, usually to the nearest 0.1%.

The volumetric method is useful for concrete made with dense aggregate and for field checks where pressure equipment is unavailable.

Do not use the volumetric method for concrete that is too stiff to agitate or for aggregate that releases gas.

Keep the meter clean and check the seal; leakage or residual air causes inaccurate readings.

Record the final reading and any aggregate correction required by the procedure.

ASTM C31 covers making and curing field specimens; use molds and rodding equipment that meet the standard.

Cylinder size: 6 x 12 in. (150 x 300 mm) for nominal maximum aggregate up to 2 in.; 4 x 8 in. (100 x 200 mm) for smaller aggregate as permitted.

For 6 x 12 in. cylinders, fill in three layers and rod each layer 25 times; for 4 x 8 in. cylinders, use two layers and 25 strokes per layer.

Tap the outside of the mold 10 to 15 times after each layer to release entrapped air, then strike off the top.

Initial cure specimens at 60 to 80°F (16 to 27°C) and protect from moisture loss for 24 ± 8 h before demolding.

After demolding, cure specimens at 73.5 ± 3.5°F (23 ± 2°C) in limewater or a moist room until the test age.

Mark specimens clearly and transport them only after they are strong enough; protect them from vibration, freezing, and drying.

Do not use specimens with honeycombing, voids, or damaged ends for acceptance strength testing.

ASTM C617 covers capping cylindrical specimens; caps must be perpendicular to the cylinder axis and provide a smooth, flat bearing surface.

Sulfur mortar or cement paste caps should be thin and sound; excessive thickness or voids can reduce measured strength.

ASTM C39 compression test: measure specimen dimensions, center it in the testing machine, and apply load without shock.

Compressive strength = maximum load ÷ cross-sectional area; report to the required precision.

Use the specified loading rate for the cylinder size; do not adjust the rate to chase an expected result.

Reject or qualify specimens with damaged ends, improper caps, or visible defects before testing.

Record fracture pattern, age, dimensions, maximum load, and calculated strength.

Testing machine calibration and proper bearing block alignment are essential for valid strength results.