ACI Aggregate Level 1 common mistakes
ACI Aggregate Level 1 · Understand the traps and how to avoid them.
Splitting a field sample with a riffle splitter or quartering without first drying or otherwise accounting for the moisture that makes fine particles cling and segregate, so the reduced test portion is not representative of the lot.
Candidates treat sample reduction as a purely mechanical step and forget that wet, sticky material does not split uniformly; fines stay with one pan and the reduced sample is biased coarse or fine.
What to do instead
Reduce the sample while it is in a condition that flows freely (surface-dry or oven-dry as the test method requires), use a splitter sized to the top size, and verify that the two halves are visually similar in grading before accepting either as the test portion.
Reporting moisture content on an as-received basis when the specification or the calculation in use requires oven-dry basis (or vice versa), mixing the two conventions within one report.
The mass lost divided by the original mass and the mass lost divided by the dry mass give different numbers, and candidates grab whichever denominator they used last.
What to do instead
Write the basis explicitly next to every moisture value, compute from the recorded oven-dry mass, and cross-check that the reported value plus the dry mass reconciles to the original wet mass.
Determining bulk density (unit weight) by filling the measure in one pour and striking off, rather than placing material in layers with the specified rodding or vibration.
Single-pour filling is faster and gives a plausible-looking number, so the compaction procedure gets skipped under time pressure.
What to do instead
Follow the layer count, rodding pattern, and tamping depth in the method, calibrate the measure's volume with water first, and record the measure mass and volume on the data sheet so the calculation is auditable.
Calculating percent passing but not checking that the cumulative masses retained reconcile to the original sample mass within the allowed tolerance, then reporting a gradation that silently lost material during sieving.
Candidates focus on the sieves and the arithmetic of percent passing, treating the mass balance as a formality rather than the control that catches lost or spilled material.
What to do instead
Sum all retained masses plus the pan, compare to the initial dry mass, and if the difference exceeds the method's tolerance, discard the result and re-run rather than adjusting numbers.
Using the wrong sieve series or reporting percent retained where the specification is written as percent passing (or reporting individual versus cumulative retained interchangeably).
The three quantities are easy to convert and candidates lose track of which column the specification table actually references.
What to do instead
Convert everything to percent passing before comparing to the specification, label each column with its definition, and verify the first and last sieves against the stated nominal maximum size.
Running a specific gravity and absorption test without properly bringing the sample to saturated surface-dry condition, judging SSD by feel instead of by the prescribed method.
SSD is a subjective-looking state and candidates either leave the surface too wet or over-dry it, which shifts both bulk specific gravity and absorption.
What to do instead
Use the method's defined SSD criterion (for example the cone test or a documented roll-and-towel procedure), perform the determination promptly after reaching SSD, and record the SSD mass and oven-dry mass so absorption can be recomputed and checked.
Performing a soundness or durability test without controlling the specified number of cycles, solution concentration, or temperature, and then reporting the loss as if the full conditioning had occurred.
These tests run over days and the intermediate handling steps (draining, rinsing, drying) are easy to abbreviate, especially when the schedule slips.
What to do instead
Log cycle count, solution strength or condition, and temperature at each stage on a run sheet, and treat any deviation as an invalid run rather than reporting a partial-cycle result.
Comparing a test result directly to a specification limit without first confirming the sample's designated size fraction, use category, or test method matches the one the limit was written for.
Specification tables are dense and candidates match on the property name alone, ignoring the size designation or application row that governs acceptance.
What to do instead
Before judging pass or fail, state the size fraction, application, and method the limit applies to, and confirm the lab's reported value was produced by that same method.
Using an out-of-tolerance balance, sieve, or measure and treating the calibration sticker as sufficient evidence that the equipment is fit for the test.
Candidates equate 'has a sticker' with 'verified', and skip the as-found check, the daily check, or the verification of the specific range being used.
What to do instead
Check the equipment against the tolerance the test method requires for the range in use, record the verification (mass check, sieve condition, measure volume) on the data sheet, and remove any item that fails from service.
Recording raw data on loose scraps or entering calculated values only, so the original masses, tare weights, and observations cannot be reconstructed, and reporting a result that cannot be traced back to the bench.
Candidates see paperwork as separate from the test and back-fill a clean number into the report, losing the intermediate values and any anomaly notes.
What to do instead
Record every raw mass and observation directly into a bound or controlled record at the time of measurement, retain tare and equipment IDs, and have the report generated from those raw entries so any result can be independently recomputed.