3.4 Sample Size, Large Aggregate, and Wet Sieving

ACI Concrete Field Testing Technician Grade I Study Guide Exam

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1 Orientation: Certification Requirements, Written Exam, Performance Exam, and Study Sources

1.1 Credential Purpose and Official Definition 1.2 Eligibility and the Two-Part Certification Path 1.3 Written Exam Format and Dual Passing Rule 1.4 Performance Exam Format and Grading 1.5 Current Study Sources and CP-1 41st Edition 1.6 Validity, Recertification, and Myth Control

2 JTA, Performance Checklists, Common Fail Points, and Field Mindset

2.1 JTA as the Exam Blueprint 2.2 Written Knowledge Versus Performance Skill 2.3 Performance Checklists and the Six Demonstrations 2.4 Timing, Sequence, and Verbal Description Discipline 2.5 Common Fail Points and Result Recording 2.6 Field Mindset, Exam Habits, and Second Trials

3 ASTM C172: Sampling Fresh Concrete and Field Sample Control

3.1 Representative Sampling Purpose and Exam Role 3.2 Sampling Locations and Middle-Discharge Control 3.3 Composite Sample Timing, Remixing, and Protection 3.4 Sample Size, Large Aggregate, and Wet Sieving 3.5 Sequence With Slump, Temperature, Air, Density, and Specimens 3.6 Performance Exam Verbal Description and Field Habits

4 ASTM C1064 Temperature and ASTM C143 Slump

4.1 ASTM C1064 Purpose, Equipment, and Timing 4.2 Sensor Placement, Stabilization, and Reporting 4.3 Temperature Field Errors and Performance Habits 4.4 ASTM C143 Scope, Equipment, and Setup 4.5 Filling, Rodding, Lifting, and Measuring Slump 4.6 Invalid Slump Results, Reporting, and Integrated Habits

5 ASTM C138: Density, Unit Weight, Yield, and Gravimetric Air

5.1 Purpose, Equipment, and the Calibrated Measure 5.2 Sampling, Filling, and Consolidation Choice 5.3 Strike-Off, Cleaning, Mass, and Density 5.4 Yield, Relative Yield, and Batch Comparison 5.5 Gravimetric Air and Theoretical Density 5.6 Reporting, Validity, and Calculation Traps

6 ASTM C231: Pressure Air Method, Type B Meter, and Aggregate Correction

6.1 Scope, Principle, and When Pressure Air Fits 6.2 Type B Meter Equipment, Calibration, and Setup 6.3 Sampling, Bowl Filling, Consolidation, and Strike-Off 6.4 Type B Sequence: Water, Petcocks, Pressure, and Reading 6.5 Aggregate Correction Factor and Final Air Content 6.6 Reporting, Validity, and Invalid-Result Traps

7 ASTM C173: Volumetric Air Method, Rollameter, Alcohol Correction, and Validity

7.1 Scope, Equipment, and When the Volumetric Method Fits 7.2 Sample, Bowl Filling, Consolidation, and Strike-Off 7.3 Water, Alcohol, Initial Liquid Level, and Sealing 7.4 Inversion, Shaking, Rolling, and Air Release 7.5 Reading Agreement, Out-of-Range Steps, and Invalid Results 7.6 Alcohol Correction, Calculation, Reporting, and Performance Habits

8 ASTM C31: Making and Curing Cylinders and Beams, Initial Curing, and Transport

8.1 Purpose, Sample, Equipment, and Specimen Plan 8.2 Cylinder Molding, Consolidation, Finishing, and Identification 8.3 Beam Molding, Flexural Specimens, and Finishing 8.4 Initial Curing, Protection, Temperature, and Moisture 8.5 Standard Curing, Field Curing, Final Curing, and Interpretation 8.6 Transport, Lab Handoff, Reporting, and Common Failures

9 Integrated Field Workflow: Test Order, Documentation, and Quality Control

9.1 Field Sample to Report Workflow 9.2 Test Order and Parallel Timing 9.3 Documentation and Report Accuracy 9.4 Invalid Results and Retest Decisions 9.5 QA/QC Communication and Acceptance Context 9.6 Contamination, Delays, and Handoff Control

10 Written Exam Strategy: Numerical Values, Calculations, and Category Scoring

10.1 One-Hour Written Exam Pacing 10.2 Category Scoring and the No-Compensation Rule 10.3 High-Yield Numerical Values and Units 10.4 Density, Yield, and Gravimetric Air Calculations 10.5 Air Content Corrections and Validity Checks 10.6 Method-by-Method Practice Plan

11 Performance Exam Strategy: Equipment Setup, Examiner Communication, and Remediation

11.1 Performance Exam Map and Mindset 11.2 Equipment Setup, Station Control, and Safety 11.3 Examiner Communication and Speaking the Work 11.4 One-Step Errors, Timing, and Method Control 11.5 C172 Verbal Description Under Pressure 11.6 Remediation, Retest Planning, and Field Confidence

12 Final Review: Recertification, Career Paths, and Next ACI Credentials

12.1 Two-to-Six Week Final Review Plan 12.2 Final Week and Test-Day Checklist 12.3 CP-1, JTA, and Source Control 12.4 Recertification, Five-Year Cycle, and Re-Exam Requirement 12.5 Career Paths After Field Testing Grade I 12.6 Next ACI Credentials and Growth Map

3.4 Sample Size, Large Aggregate, and Wet Sieving

Key Takeaways Explain This Topic AI

A sample used for strength specimens must be at least 1 ft³ (28 L); smaller samples are allowed for routine slump, temperature, and air only.

Molding of strength specimens must begin within 15 minutes after fabricating the composite sample.

When aggregate is larger than a method allows, the sample is wet-sieved over the correct sieve before that test.

Wet sieving is a defined procedure that removes oversize particles while preserving the mortar and smaller aggregate fraction.

Last updated: June 2026

Planning Sample Size Before Testing Starts

The technician must know which tests are required before collecting concrete, because the required volume depends on them. If strength specimens (cylinders under C31/C31M or beams) will be molded, C172 requires a composite sample of at least 1 ft³ (28 L) . That volume must support the strength specimens and the fresh-property tests drawn from the same sample. Smaller samples are not prohibited for routine slump, temperature, and air-content testing when those are the only tests being run.

Size is necessary but not sufficient: the sample must still be representative . A full wheelbarrow taken from the wrong location is worse than a smaller, correctly obtained composite. At the same time, an undersized sample forces the technician to scrape corners, reuse disturbed material, or choose between required tests, and each of those creates preventable error. Plan for at least 1 ft³ whenever cylinders or beams are involved.

The 15-Minute Molding Window

C172 also sets a start limit for strength specimens: molding must begin within 15 minutes after fabricating the composite sample. This is separate from the 5-minute window for slump, temperature, and air. The practical consequence is sequencing: the technician typically runs the fresh-property tests first (within their 5-minute window), keeps enough concrete protected and remixed, and then molds cylinders so that filling the first mold begins within 15 minutes of the composite being made.

Situation Correct control Why it matters
Strength specimens required Collect at least 1 ft³ (28 L) Supports cylinders/beams plus fresh tests
Only routine fresh tests Smaller sample is allowed Avoids unnecessary handling
Molding cylinders/beams Begin within 15 min of fabricating composite Specimens represent fresh concrete
Oversize aggregate present Wet-sieve only when the method requires Keeps the test within its scope
Aggregate lost in collection Resample if representation is lost Lost stone skews density and air results
Large Aggregate and Wet Sieving

Large aggregate creates a second control issue. Certain fresh-concrete tests and specimen molds have maximum aggregate-size limits. When the concrete contains aggregate larger than a method allows, the sample may need to be wet-sieved over the appropriate sieve before that test is performed. Wet sieving is not routine cleanup; it is a defined procedure that removes oversize particles while preserving the mortar and the smaller aggregate fraction the method needs.

Wet sieving belongs in the planned workflow. If the mix design has a large nominal maximum aggregate, the technician should know which tests are affected before the truck arrives, and the sieve, pan, and tools should be clean and damp. Avoid washing paste away, letting aggregate pile up so mortar drains off, or letting wet sieving push a timed test past its allowed start window.

For performance-exam purposes, the candidate usually need not recite every mechanical movement of wet sieving. The JTA-level answer is to recognize when large aggregate can make a method inapplicable, state that oversize aggregate is removed by wet sieving when the method requires it, and note that the test is then run on the processed sample.

Field planning list:

Know whether cylinders, beams, air, density, slump, and temperature are required.

Collect at least 1 ft³ (28 L) whenever strength specimens will be molded.

Keep the sample representative while moving it to the test area.

Identify large-aggregate issues before the clock becomes a problem.

Document unusual sample treatment such as wet sieving.

Sizing the Sample to the Test Plan

The 1 ft³ (28 L) minimum is a floor, not a target. The technician should size the sample to the whole test plan with a margin for the concrete consumed and discarded along the way. A typical acceptance set might call for slump, temperature, air, density, and a set of cylinders. Each draws from the composite, and some concrete is lost to remixing, rodding, striking off, and cleanup. Collecting only the bare minimum invites a shortfall partway through.

A practical way to estimate is to add up the volume each test needs, then collect comfortably more than that total while still keeping every portion representative. Remember that the minimum applies to samples used for strength specimens ; if only routine slump, temperature, and air are required, a smaller sample is acceptable. The judgment call is knowing the test plan before the truck arrives.

Test drawn from the composite Approximate demand on the sample
Slump (C143) A filled slump cone plus the base material
Air content (C231/C173) A filled measuring bowl
Density/yield (C138) A filled, calibrated measure
Temperature (C1064) Embedded in the sample, no extra volume
Cylinders (C31) Several molds, the largest single demand
Why Removing Aggregate Changes the Concrete

Wet sieving must be understood as changing what is being tested , not just tidying the sample. When oversize particles are removed, the remaining material is mortar plus the smaller aggregate fraction; its density, air content, and behavior differ from the full mix. That can be exactly what a method requires when its equipment cannot accommodate the largest aggregate, but it means the result describes the processed material, not the as-delivered concrete with full-size stone.

For that reason, the technician records when wet sieving was performed so downstream users know the test was run on a wet-sieved sample. The same caution applies any time material is lost: if coarse aggregate bounces out or paste washes away, the sample is no longer representative, and the right action is to resample rather than test biased material.