ACI Field Testing I flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

ASTM C172

Standard practice for sampling freshly mixed concrete; requires a representative sample from the middle portion of the batch, protected from contamination and evaporation.

Representative sample

A sample that contains the same proportions of ingredients as the batch; obtained from the middle discharge and not from segregated or contaminated material.

Composite sample

A sample made by combining increments from several portions of a batch; it is remixed before testing so the result represents the whole batch.

Sampling receptacle

A clean, dampened container used to catch fresh concrete; it must not contain set concrete, dirt, or chemicals that could alter the sample.

ASTM C1064

Standard test method for temperature of freshly mixed concrete; uses a calibrated immersion thermometer and requires reading after stabilization.

Thermometer immersion depth

At least 3 in. (75 mm) of the thermometer sensing portion must be immersed in concrete, away from the container walls.

Temperature report precision

Report fresh concrete temperature to the nearest 0.5°C (1°F), matching the precision of the calibrated thermometer and specification.

Infrared thermometer limitation

An infrared device measures surface temperature and is not an acceptable substitute for the ASTM C1064 immersion measurement of fresh concrete.

ASTM C143

Standard slump test for hydraulic cement concrete; uses a 12-in. mold, three layers, and 25 rod strokes per layer.

Slump mold dimensions

The standard slump cone is 12 in. (300 mm) high, with an 8 in. (200 mm) bottom diameter and a 4 in. (100 mm) top diameter.

Slump measurement

The vertical drop from the original top of the mold to the displaced center of the concrete, reported to the nearest 1/4 in. (5 mm).

Slump test timing

The entire slump test must be completed within 2.5 min after sampling; a sample that has stood is not retested.

ASTM C138

Standard test method for density, yield, and gravimetric air content of concrete using a calibrated measure of known volume.

Unit weight formula

Density equals the mass of concrete in the measure divided by the measure volume; report as lb/ft³ or kg/m³.

Yield formula

Yield equals total batch mass divided by measured unit weight; relative yield compares actual yield with design volume.

Gravimetric air formula

Air content equals 100 times one minus measured unit weight divided by theoretical air-free unit weight.

ASTM C231

Standard pressure-method test for air content of fresh concrete; based on Boyle's law and requires an aggregate correction factor.

Aggregate correction factor

A value subtracted from the pressure meter gauge reading to account for air trapped in porous aggregate; determined for the specific aggregate combination.

Pressure meter leakage

Leakage at the lid or valve causes the gauge to read incorrectly; clean the flange and seal the meter before pressurizing.

Pressure method limitation

The pressure method may be unreliable for highly porous or lightweight aggregate unless the aggregate correction is verified.

ASTM C173

Standard volumetric method for air content; removes air from a concrete sample by agitation and reads the water-level drop.

Volumetric air reading

Air content is read directly from the graduated neck of the meter after repeated agitation until the reading stabilizes.

Volumetric meter agitation

Invert and roll the meter repeatedly to release entrapped air; continue until the air volume reading no longer changes.

Volumetric method suitability

Best suited to dense-aggregate concrete that can be agitated; stiff mixtures or gas-releasing aggregate can give inaccurate results.

ASTM C31

Standard practice for making and curing concrete test specimens in the field; covers molds, consolidation, initial curing, and transport.

6 x 12 in. cylinder layers

Fill a 6 x 12 in. cylinder in three equal layers, rodding each layer 25 times with the standard rod.

4 x 8 in. cylinder layers

Fill a 4 x 8 in. cylinder in two equal layers, rodding each layer 25 times with the standard rod.

Initial curing temperature

Keep freshly made field specimens at 60 to 80°F (16 to 27°C) and prevent moisture loss for 24 ± 8 h before demolding.

ASTM C617

Standard practice for capping cylindrical concrete specimens; caps must be flat, perpendicular to the axis, and sound.

Compressive strength formula

Compressive strength equals the maximum test load divided by the cylinder cross-sectional area, reported in psi or MPa.

ASTM C39

Standard test method for compressive strength of cylindrical specimens; specifies centering, loading rate, and reporting.

Capping defect effect

An uneven, thick, or voided cap can create eccentric loading and lower the measured compressive strength.