Free ACI Field Testing I Exam Flashcards

C172 sampling, C143 slump, C1064 temperature, C138 density/unit weight/yield, C231 pressure air, C173 volumetric air, and C31 making & curing specimens. All test FRESH concrete. C39 (compressive strength) is NOT included.

55 multiple-choice questions, closed book, 1 hour. Must score at least 60% on EACH ASTM method AND at least 70% overall. A high overall score cannot rescue one failed method category.

Closed book. Physically demonstrate six of the seven methods and verbally describe C172 sampling. Scored on a checklist by an ACI examiner; missing a critical step can fail a test. Certification valid 5 years.

At least two regularly spaced portions taken from the MIDDLE of the discharge — never the very first or very last of the batch. Portions are combined and remixed to form a representative composite sample.

15 minutes maximum between obtaining the first and last portions of a composite sample. Transport and remixing must be done as quickly as possible to keep the sample representative.

Begin within 5 minutes after obtaining the final portion of the composite sample. These quick tests must start fast before hydration and evaporation change the concrete.

Within 15 minutes after fabricating the composite sample. This ensures cast cylinders/beams represent the concrete at placement and are not affected by delay before consolidation.

At least 1 ft^3 (28 L). Smaller samples are allowed for routine slump, temperature, or air tests, but strength specimens require a full cubic foot to be representative.

Remix the combined portions with a shovel the minimum amount needed for uniformity. Protect from sun, wind, evaporation, and contamination. Never add water or sieve out mortar.

Frustum of a cone: 8 in. (200 mm) bottom inside diameter, 4 in. (100 mm) top inside diameter, 12 in. (300 mm) height. The large opening sits on the base plate.

Round, straight steel rod, 5/8 in. (16 mm) diameter, 16 in. or 24 in. long, with a hemispherical (rounded) tip of the same 5/8 in. diameter for consistent consolidation.

Fill in 3 layers, each about one-third of the mold's VOLUME (not height), and rod each layer 25 times. Layer heights are roughly 2-5/8 in., 6-1/8 in., then full 12 in.

Rod throughout the depth of each layer. The bottom layer is rodded without striking the base plate; the middle and top layers penetrate about 1 in. (25 mm) into the layer below.

Raise the mold vertically 12 in. in 5 +/- 2 seconds with no lateral or torsional motion. Slump = vertical distance from the original top of the mold down to the displaced original center of the specimen.

2-1/2 minutes from the start of filling until the mold is removed, performed without interruption. Exceeding this allows the concrete to begin setting and skews results.

Disregard the test and run a new test on another portion of the sample. Shearing indicates the mix lacks cohesiveness and the standard slump test is not applicable to it.

Not applicable when more than 10% of the aggregate is retained on the 1-1/2 in. (37.5 mm) sieve. Such mixes may be wet-sieved over a 1-1/2 in. sieve before testing.

At least 3 in. (75 mm) of concrete must surround the sensor in all directions so ambient air does not influence the reading. The method applies to aggregate up to 3 in. nominal max size.

Leave embedded until the reading stabilizes — a minimum of 2 minutes and a maximum of 5 minutes after insertion. Reading too early or too late introduces error.

Accurate to +/- 1 degF (0.5 degC) over 30-120 degF. Verified at least once every 12 months against a reference thermometer traceable to a national standard, and any time accuracy is in doubt.

Complete within 5 minutes after obtaining the sample. The reading is recorded only once the embedded sensor has stabilized (2-5 minutes).

ACI 305 (Hot Weather Concreting) and ACI 306 (Cold Weather Concreting). C1064 readings verify compliance with their placement-temperature limits.

C231 (pressure) is NOT valid for lightweight, highly porous, or air-cooled slag aggregate. Use C173 (volumetric / roll-a-meter) for those concretes — no aggregate correction factor is needed.

Type A applies a known pressure by lowering a water column and reads air on a standpipe. Type B equalizes a known volume of air at a known pressure with the concrete's air and reads a dial directly. Type B is most common in the field.

3 approximately equal layers, each rodded 25 times with the 5/8 in. rod. After rodding each layer, tap the bowl sides 10-15 times with the mallet to close rod holes and release trapped air.

Accounts for air trapped in the pores of dense aggregate that the meter reads but is not paste air. It is determined on the project aggregate and SUBTRACTED from the indicated air to get true air content.

Close the main air valve, open both petcocks, and inject water through one petcock until it flows out the opposite petcock free of air. Close both petcocks before pumping up the chamber.

Lightly tap the gauge to stabilize the needle, then read to the nearest 0.1% air. Rod the bottom layer through its depth without forcibly striking the bottom of the bowl.

Calibrate whenever accuracy is in doubt, at least annually, and after rough handling or a significant elevation change. Calibration checks operating pressure and verifies the reading with a known-volume vessel.

Concrete residue or grit on the bowl/cover sealing surfaces prevents an airtight seal, causing leakage during pressurization and a falsely HIGH air reading. Clean thoroughly after every test.

A volumetric air meter ('roll-a-meter'). It works on ALL concretes including lightweight and porous aggregate because it relies on displacement and agitation, not pressure, so no aggregate correction is needed.

2 approximately equal layers, each rodded 25 times with the 5/8 in. rod. After rodding each layer, tap the bowl sides 10-15 times with the mallet to close rod holes and release trapped air.

A measured amount of 70%+ isopropyl alcohol is added to suppress foam from entrained air during rolling. The amount used determines a defined alcohol correction applied to the apparent reading.

Invert and roll/tilt until aggregate is free, then re-agitate at about 1-minute intervals. The reading is final when two consecutive readings agree within 0.25% air content.

Re-run the test with a new portion of the sample. A reading above the graduated scale signals abnormally high air or a procedural error and must not be estimated or reported.

C173 advantage: works with any aggregate, no aggregate correction. C173 drawback: slower — repeated rolling and successive-agreement readings take several minutes versus under a minute for a pressure test.

Density (unit weight), plus calculated yield, relative yield, cement content, and gravimetric air content. Yield verifies that batch quantities match the mix design.

Density = net mass of concrete (filled measure minus empty measure) divided by the calibrated volume of the measure. Reported in lb/ft^3 (normal-weight concrete ~140-150) or kg/m^3.

Small measures (0.2-0.4 ft^3): 2 layers, 25 rod strokes each. Large measures (0.5-1.0 ft^3): 3 layers, 50 rod strokes each. Aim for ~1 stroke per 2 in^2 of surface; tap sides 10-15 times per layer.

Slump < 1 in.: must use internal vibration. Slump 1-3 in.: rodding or vibration. Slump > 3 in.: rodding. Match the method to workability to avoid segregation or trapped air.

Yield = total mass of all batched materials divided by measured density (volume produced per batch). Relative yield = actual yield / design yield; < 1.00 means under-yielding (less concrete than designed).

Compare measured density to the theoretical air-free density computed from mix proportions; the percentage difference is gravimetric air. It is an independent check on C231 or C173 air results.

Calibrate by filling with water at a known temperature and dividing the water mass by water density to get volume (at least annually). Strike off flush with a sawing motion and clean all concrete/water off the exterior before weighing.

Cylinders are 6x12 in. or 4x8 in.; beams are 6x6 in. (or 4x4 in. when aggregate <= 1 in.). Nominal max aggregate must not exceed 1/3 of the cylinder diameter.

6x12 in.: 3 layers, 25 strokes each, 5/8 in. rod. 4x8 in.: 2 layers, 25 strokes each, 3/8 in. rod. Subsequent layers penetrate ~1 in. into the layer below; tap mold 10-15 times per layer.

Concrete with slump < 1 in. must be consolidated by internal vibration (rodding not allowed). 1-3 in. allows either method; > 3 in. uses rodding. The vibrator must not touch the mold sides or bottom.

Initial curing up to 48 hours, on a level rigid surface free from vibration and protected from moisture loss. Temperature: 60-80 degF for f'c < 6,000 psi; 68-78 degF for f'c >= 6,000 psi.

After initial curing, standard-cured cylinders are kept at 73.5 +/- 3.5 degF in a moist room (>95% RH) or immersed in lime-saturated water, so strength reflects mix proportions, not variable curing.

Demold standard-cured cylinders 24 +/- 8 hours after casting. Transport to the lab within 4 hours after the end of initial curing, protected from damage, drying, and freezing.

Standard-cured cylinders are used for ACCEPTANCE (per ACI 318 / IBC, tested per C39). Field-cured cylinders estimate IN-PLACE strength for form removal, shoring release, or post-tensioning — not for acceptance.