Study guide
4.6 Invalid Slump Results, Reporting, and Integrated Habits
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
4.6 Invalid Slump Results, Reporting, and Integrated Habits
Key Takeaways Explain This Topic AI
If part of the concrete shears off or collapses, the slump is invalid; disregard it and retest on another portion of the sample.
If two consecutive tests shear or collapse, the concrete likely lacks the plasticity or cohesiveness C143 requires.
Slump is reported to the nearest 1/4 in. (5 mm) at the displaced original center, never averaged from a sheared pile.
Slump must be started within 5 minutes of obtaining the C172 sample and completed within 2.5 minutes once filling begins.
Last updated: June 2026
Recognizing a Valid Slump
The slump test does not end when the cone is lifted — the technician must read the shape and decide whether the result is valid. A true slump settles evenly and stays generally cohesive. A shear slump occurs when one side slides down and off, leaving an asymmetric mass. A collapse slump occurs when the concrete falls apart completely, typical of a very wet or harsh mix.
If a portion of the concrete shears or falls away , the test is disregarded and a new test is made on another portion of the sample . Measuring the remaining pile and reporting it as a normal slump is a frequent exam error. If a second consecutive test also shears or collapses, the concrete probably lacks the plasticity and cohesiveness the method requires, and that condition is noted rather than forced into a number. Highly flowable concrete may need slump flow; very stiff concrete may be outside C143's useful range.
Distinguishing the three shapes is a frequent performance-exam checkpoint. In a true slump the mass settles fairly symmetrically and you measure to the displaced original center. In a shear slump roughly half the cone slips down and to one side, leaving a slanted top; the result is invalid even though a ruler could still reach the concrete. In a collapse slump the concrete subsides completely and spreads, typical of a high-water or low-cohesion mix. The exam wants the candidate to name the shape, not just a number, and to act on shear or collapse by retesting rather than reporting.
Reporting Without Overprecision
Reporting requires accuracy without false precision. Slump is measured immediately as the vertical difference to the displaced original center of the specimen and reported to the nearest 1/4 in. (5 mm) . Do not average a shear slump, estimate from the side of the pile, or add decimals beyond the 1/4 in. increment. The field report includes units and ties the result to the sampled load along with the C1064 temperature, air content, and density from the same sample.
- Condition after lift Technician action Reason
- Even, cohesive settlement (true slump) Measure and report Valid shape
- One side shears away (shear slump) Disregard, retest another portion Shape invalid
- Mass falls apart (collapse slump) Disregard, retest another portion Shape invalid
- Two consecutive shear/collapse Note lack of plasticity/cohesiveness C143 may not apply
- Twisted or bumped cone Repeat; technician caused error Procedure disturbed specimen
Timing, Coordination, and Performance Habits
Timing links C143 back to C172. Slump must be started within 5 minutes after obtaining the final portion of the composite sample , and the C143 test itself must be completed within 2.5 minutes without interruption once filling begins. In a full field set, the slump cone cannot be an afterthought; the base, mold, rod, scoop, and ruler are staged before sampling so temperature, slump, and air all happen inside their respective windows.
It helps to memorize the two clocks separately. The 5-minute clock starts when the final portion of the composite sample is obtained and governs when slump (and temperature) must begin. The 2.5-minute clock starts when filling the cone begins and governs how long the slump procedure itself may take. Mixing these up is a common written-exam error: candidates wrongly say the whole test must finish 5 minutes after sampling, or that there is no internal limit once filling starts.
Performance-exam habits are concrete and observable: keep both feet on the foot pieces until the mold is ready to lift, count rod strokes to 25 consistently, keep surplus concrete above the top layer before strike-off, lift 12 in. in 5 plus or minus 2 seconds straight up, measure at the displaced original center, and speak the result clearly without arguing a bad shape into a valid one.
Slump also coordinates with the other fresh tests sharing the same composite sample. After remixing the C172 sample, many technicians run slump and temperature first because both have short windows, then proceed to air content (C231 or C173) and density (C138), and finally mold strength specimens (C31). Because slump must start within 5 minutes of sampling and finish within 2.5 minutes, it is rarely the last test performed. Planning the order before concrete arrives keeps every method inside its own time limit and prevents a rushed, invalid slump caused by doing it after slower tests.
A last reporting reminder: never adjust a reported slump to make a load look acceptable, and never combine a discarded shear test with a later valid test by averaging. Report only the valid, single measurement to the nearest 1/4 in., note any retest, and let the data stand.
Final field checklist:
Start slump within 5 minutes of the final C172 sample portion.
Complete the C143 procedure without interruption within 2.5 minutes.
Read the shape: true, shear, or collapse.
Retest a fresh portion when shearing or collapse invalidates the result.
Report the measured slump to the nearest 1/4 in. at the displaced original center.