ACI Field Testing I Exam Flashcards

Q: What is the ACI Concrete Field Testing Technician Grade I certification?

It is ACI's most widely held certification. It validates that a technician can correctly perform seven ASTM tests on freshly mixed concrete: sampling (C172), slump (C143), temperature (C1064), density/unit weight/yield (C138), air content by the pressure method (C231), air content by the volumetric method (C173), and making and curing test specimens (C31). The IBC and ACI 318 require Grade I certified technicians for acceptance testing of structural concrete on most building projects.

Q: How many questions are on the ACI Grade I written exam and how long is it?

The written exam is closed book, lasts 1 hour, and has 55 multiple-choice questions. ACI states there are between five and ten questions on each required ASTM test method or practice, so the exam is heavily weighted toward exact procedures, apparatus, and numerical tolerances rather than theory.

Q: What is the passing score for the ACI Grade I exam?

The written exam has a dual rule: at least 60% correct on each individual ASTM test method or practice AND at least 70% overall. A strong overall score cannot offset failing one method category. Candidates must also pass the closed-book performance exam, which requires demonstrating six of the methods and verbally describing C172 sampling.

Q: Are there prerequisites for the ACI Grade I exam?

No. There are no formal education, experience, age, or ACI membership prerequisites for Grade I certification. However, ACI strongly recommends studying the CP-1 Technician Workbook and the current editions of the seven ASTM standards, and completing a preparation class offered by a local ACI sponsoring group or chapter before testing.

Q: What does the ACI Grade I performance exam involve?

The performance exam is closed book. The candidate must physically demonstrate six of the seven required test methods and practices and give a verbal description of Practice C172 (sampling). An ACI examiner scores each procedure on a checklist; omitting a critical step can cause failure even when other tests are performed correctly. Both the written and performance exams must be passed for certification.

Q: How long is the ACI Grade I certification valid?

Grade I certification is valid for 5 years from the date all requirements are completed. Recertification requires successfully completing both the written and performance examinations again, which keeps technicians current as ASTM standards are periodically revised. The current cited editions are C1064-23, C172-17, C143-20, C138-23, C231-24, C173-24, and C31-24.

Question 1

Seven ASTM standards on the ACI Grade I exam

Accepted Answer

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.

Question 2

ACI Grade I written exam: format and passing rule

Accepted Answer

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.

Question 3

ACI Grade I performance exam requirement

Accepted Answer

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.

Question 4

C172: how many portions and from where in the batch?

Accepted Answer

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.

Question 5

C172: maximum time between first and final sample portions

Accepted Answer

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.

Question 6

C172: time limit to START slump, temperature, and air tests

Accepted Answer

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.

Question 7

C172: time limit to START molding strength specimens

Accepted Answer

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.

Question 8

C172: minimum composite sample size for strength tests

Accepted Answer

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.

Question 9

C172: required treatment of the sample before testing

Accepted Answer

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.

Question 10

C143: slump mold dimensions

Accepted Answer

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.

Question 11

C143: tamping rod specification

Accepted Answer

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.

Question 12

C143: layers and rod strokes for the slump cone

Accepted Answer

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.

Question 13

C143: how deep should the rod penetrate each layer?

Accepted Answer

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.

Question 14

C143: how is the cone lifted, and how is slump measured?

Accepted Answer

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.

Question 15

C143: maximum elapsed time for the whole slump test

Accepted Answer

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.

Question 16

C143: what to do if the concrete shears or falls away

Accepted Answer

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.

Question 17

C143: when is the slump test NOT applicable by aggregate size?

Accepted Answer

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.

Question 18

C1064: minimum concrete coverage around the temperature sensor

Accepted Answer

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.

Question 19

C1064: how long must the sensor stay immersed before reading?

Accepted Answer

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.

Question 20

C1064: required device accuracy and verification interval

Accepted Answer

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.

Question 21

C1064: time limit to complete the temperature reading

Accepted Answer

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

Question 22

C1064: which ACI documents set the temperature limits being checked?

Accepted Answer

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

Question 23

C231 vs C173: when must you use the volumetric method?

Accepted Answer

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.

Question 24

C231: Type A vs Type B pressure meter

Accepted Answer

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.

Question 25

C231: filling and consolidating the measuring bowl

Accepted Answer

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.

Question 26

C231: the aggregate correction factor

Accepted Answer

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.

Question 27

C231: Type B step before pumping the air chamber

Accepted Answer

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.

Question 28

C231: reading the gauge and rodding the bottom layer

Accepted Answer

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.

Question 29

C231: calibration frequency for the pressure meter

Accepted Answer

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.

Question 30

C231: why keep flanges and gasket surfaces clean?

Accepted Answer

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.

Question 31

C173: what instrument is used and why it is universal

Accepted Answer

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.

Question 32

C173: filling the base (bowl)

Accepted Answer

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.

Question 33

C173: role of isopropyl alcohol

Accepted Answer

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.

Question 34

C173: agitation and the final-reading agreement criterion

Accepted Answer

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.

Question 35

C173: what to do if the reading exceeds the neck scale

Accepted Answer

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.

Question 36

C173 vs C231: trade-off

Accepted Answer

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.

Question 37

C138: what does the unit weight test let you calculate?

Accepted Answer

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

Question 38

C138: density formula

Accepted Answer

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.

Question 39

C138: consolidation by measure size

Accepted Answer

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.

Question 40

C138: consolidation method vs slump

Accepted Answer

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.

Question 41

C138: yield and relative yield

Accepted Answer

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).

Question 42

C138: gravimetric air content

Accepted Answer

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.

Question 43

C138: measure calibration and pre-weighing prep

Accepted Answer

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.

Question 44

C31: standard specimen sizes and aggregate limit

Accepted Answer

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.

Question 45

C31: rodding rules for 6x12 vs 4x8 cylinders

Accepted Answer

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.

Question 46

C31: low-slump consolidation rule

Accepted Answer

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.

Question 47

C31: initial curing temperature and duration

Accepted Answer

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.

Question 48

C31: final (standard) curing condition

Accepted Answer

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.

Question 49

C31: demolding and transport timing

Accepted Answer

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.

Question 50

C31: standard-cured vs field-cured cylinders

Accepted Answer

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.

Free ACI Field Testing I Exam Flashcards

Filter by Topic

Jump to Card

About These ACI Field Testing I Flashcards

Topics Covered

Frequently Asked Questions

ACI Concrete Field Testing Technician Grade I

Explore More ACI Concrete Certifications

ACI Concrete Strength Testing Technician

ACI Tilt-Up Supervisor

ACI Adhesive Anchor Inspector

ACI Adhesive Anchor Installer

ACI Aggregate Testing Technician Level 1

ACI Aggregate Testing Technician Level 2

More From This Family