- What Is ACI-AGGREGATE-BASE, Exactly?
- Where This Credential Came From
- Exam Format: Written and Performance Components
- The Seven ASTM Standard Sections
- How Passing Is Determined
- Registration, Materials, and Retest Mechanics
- Who Actually Needs This Certification
- Alternate Pathways: AASHTO Holders and Level 1 Exemptions
- Building a Study Plan Around the Standard Sections
- Frequently Asked Questions
- ACI-AGGREGATE-BASE certifies technicians in the ASTM Methods track, one of two successors to the retired combined Aggregate Base program.
- The written exam is open-book, two hours, roughly 75 multiple-choice questions covering seven ASTM standard sections.
- Passing requires 60% minimum in every required section plus 70% overall on the written test.
- A separate closed-book performance exam demands hands-on demonstration of procedures; both parts must pass within one year.
What Is ACI-AGGREGATE-BASE, Exactly?
ACI-AGGREGATE-BASE refers to the Aggregate Base Testing Technician-ASTM Methods credential administered under the American Concrete Institute's certification structure. It verifies that a technician can correctly sample aggregate base materials, reduce samples to testing size, and run the standard soil and moisture-density tests that determine whether a base course meets specification. Certification is handled through ACI-approved sponsoring groups, with ACI examiners and proctors administering both parts of the exam and ACI performing the grading.
This is not a general "know concrete" credential. It is a narrowly scoped, standards-based qualification built around seven specific ASTM test methods. If you're comparing terminology, our companion piece on the ACI-AGGREGATE-BASE meaning and the breakdown of what ACI-AGGREGATE-BASE stands for both dig into naming and scope in more detail. For a broader landing page on the credential itself, see ACI-AGGREGATE-BASE Certification.
Where This Credential Came From
The ASTM Methods track is a successor to a retired, combined-methods Aggregate Base Testing Technician program. Rather than blending ASTM and AASHTO procedures into one exam, ACI split the discipline into two parallel, method-specific credentials: this ASTM Methods track and a separate AASHTO Methods track. The two are administered under distinct governing documents and use different reference workbooks, so a technician who trained under the old combined program should not assume the content lines up one-to-one with either successor.
The ASTM job-task analysis underlying today's exam content was approved February 13, 2026, and the governing policy document, CPP 620.5-25, was approved February 14, 2025. Together these define which tasks a certified technician is expected to perform and how the program itself is administered. If you want a plain-language walkthrough of what "ACI-AGGREGATE-BASE" means as a term versus as a job function, check What Is A ACI-AGGREGATE-BASE? and What Does ACI-AGGREGATE-BASE Mean?.
Exam Format: Written and Performance Components
Certification requires passing two distinct components, and understanding their format is the difference between walking in prepared and walking in guessing.
Written Examination
The written exam is open-book, meaning candidates may consult ACI-approved references during the test. It runs on a two-hour time limit and contains approximately 75 multiple-choice questions pulled from the seven ASTM standard sections listed below. Because it's open-book, the exam isn't testing memorization of exact numeric tolerances so much as your ability to locate and correctly apply the right procedure under time pressure - which is a very different skill than pure recall.
Performance Examination
The performance exam is closed-book and requires successful, hands-on demonstration of every required procedure. Verbal description is only accepted in place of a physical action where the official checklist explicitly permits it - you cannot talk your way through a step that requires demonstration. Approved simple-function, nonprogrammable calculators are allowed for calculations; mobile phones cannot serve as a substitute calculator on either exam component.
Key Takeaway
Both the written and performance components must be passed within a one-year window of each other. Passing one and letting the clock run out on the other means starting the unfinished component over.
The Seven ASTM Standard Sections
Unlike credentials built around abstract "domains" with assigned percentage weights, ACI-AGGREGATE-BASE's content areas are the actual ASTM standard sections a technician must know. There is no published equal-weight split across these seven - some standards involve more procedural steps and more exam questions than others - but all seven are independently graded, and you must clear the minimum threshold in each one, not just overall.
Domain 1: ASTM D75/D75M - Standard Practice for Sampling Aggregates
Covers correct field sampling technique, sample size requirements, and how sampling location and method affect result validity.
- Know minimum sample sizes by aggregate nominal size
- Understand acceptable sampling equipment and locations
Domain 2: ASTM C702/C702M - Reducing Samples of Aggregate to Testing Size
Covers splitting and quartering techniques used to reduce a field sample down to a representative test portion without introducing bias.
- Mechanical splitter vs. quartering method procedures
- Avoiding segregation errors during reduction
Domain 3: ASTM D4318 - Liquid Limit, Plastic Limit, and Plasticity Index of Soils
Covers Atterberg limits testing used to classify the fine fraction of base material.
- Multipoint vs. one-point liquid limit procedure
- Correct plastic limit rolling technique and PI calculation
Domain 4: ASTM D7928 - Particle-Size Distribution by Sedimentation (Hydrometer) Analysis
Covers determining gradation of the fine-grained fraction that sieve analysis alone cannot resolve.
- Hydrometer calibration and correction factors
- Sedimentation timing and reading intervals
Domain 5: ASTM D2216 - Laboratory Determination of Water (Moisture) Content by Mass
Covers the oven-drying method for determining moisture content, a foundational calculation used throughout compaction testing.
- Drying temperature and duration requirements
- Mass measurement precision and rounding rules
Domain 6: ASTM D1557 - Compaction Characteristics Using Modified Effort
Covers the modified Proctor compaction test (56,000 ft-lbf/ft³) used for higher-effort compaction specifications.
- Mold size selection by material gradation
- Moisture-density curve construction and optimum moisture determination
Domain 7: ASTM D698 - Compaction Characteristics Using Standard Effort
Covers the standard Proctor compaction test (12,400 ft-lbf/ft³), the companion method to D1557 at lower compactive effort.
- Distinguishing standard vs. modified effort setups
- Layer count and blow count requirements by method
For a deeper section-by-section breakdown with the reasoning behind why each standard matters on the job, see the full ACI-AGGREGATE-BASE Exam Domains Guide.
How Passing Is Determined
ACI-AGGREGATE-BASE uses a dual-threshold scoring rule on the written exam that catches candidates who are strong in some areas but weak in others:
- At least 60% correct within every required standard section individually
- At least 70% correct overall across the full exam
This means you cannot compensate for a weak Domain 4 (hydrometer analysis) by acing Domain 5 (moisture content) - you need a passing floor in each section on its own. The performance exam has no percentage score; it is graded as successful or unsuccessful demonstration of each required procedure against the official checklist. A closer look at exactly how these thresholds are applied is available in our ACI-AGGREGATE-BASE Passing Score guide.
Registration, Materials, and Retest Mechanics
Candidates use CP-46, first edition, as the official ASTM workbook, and should apply any applicable errata issued for that edition. Note that CP-47 belongs to the separate AASHTO Methods track and is not the correct reference for ASTM Methods candidates - mixing up the two workbooks is a common and avoidable early mistake. As of a September 10, 2026 check, ACI listed CP-46 at $133 for non-members and $69 for members; these are workbook purchase prices, not examination registration fees, so budget for them separately from testing costs.
Because sponsoring groups (not ACI directly, in most cases) schedule the actual written and performance sessions, testing windows vary by region and administrator. For a realistic sense of how to plan around scheduling and the one-year window between components, see ACI-AGGREGATE-BASE Exam Dates. And if you're mapping out the full cost picture beyond the workbook, our Certification Cost breakdown walks through the pieces.
Who Actually Needs This Certification
Aggregate base testing sits at the intersection of geotechnical and paving work - the layer between subgrade and pavement that has to be sampled, classified, and compacted correctly before anything gets paved on top of it. Employers who typically require or prefer this certification include:
- Geotechnical and materials testing laboratories serving highway and site-development projects
- DOT-adjacent inspection firms verifying base course compliance on public infrastructure work
- Earthwork and paving contractors running in-house QC on base placement and compaction
- Construction materials engineering (CoMET) firms performing third-party acceptance testing
If you're evaluating whether this is a career-relevant credential to pursue or how it might affect hiring prospects, the ACI-AGGREGATE-BASE Jobs overview and the ROI analysis both look at that question from different angles. For general compensation context, see the Salary Guide.
Alternate Pathways: AASHTO Holders and Level 1 Exemptions
Two shortcuts exist for candidates who already hold related ACI credentials, and both are worth knowing before you assume you have to start from zero.
Current AASHTO Methods Holders
A technician who currently holds the Aggregate Base Testing Technician-AASHTO Methods certification can earn the ASTM Methods credential by passing only the ASTM written examination, provided it's done within one year of obtaining the AASHTO certification. This avoids retaking a full performance exam if the underlying skills largely overlap.
Aggregate Testing Technician-Level 1 Holders
Current holders of the Aggregate Testing Technician-Level 1 credential may receive specified performance-procedure exemptions on the ASTM Methods performance exam. The exact procedures exempted are defined by ACI's program documentation, so confirm current specifics with your sponsoring group before assuming full exemption.
Full eligibility details, including any prerequisite documentation sponsoring groups may request, are covered in ACI-AGGREGATE-BASE Requirements.
Building a Study Plan Around the Standard Sections
Because the written exam is open-book, preparation time is better spent building familiarity with where information lives in CP-46 and practicing calculations than trying to memorize the workbook cover to cover. A staged approach that treats each ASTM standard as its own mini-unit works well against this exam's structure:
Sampling and Reduction (Domains 1-2)
- Drill D75/D75M sample-size tables until they're second nature
- Practice C702/C702M splitting and quartering steps in sequence
Soil Classification Testing (Domains 3-4)
- Run through D4318 liquid/plastic limit calculations by hand
- Review D7928 hydrometer correction factors and timing tables
Moisture Content (Domain 5)
- Memorize D2216 drying temperature and mass-precision requirements
- Practice moisture-content calculation shortcuts for speed under the time limit
Compaction Methods (Domains 6-7)
- Contrast D1557 modified effort vs. D698 standard effort setups side by side
- Practice plotting and reading moisture-density curves for optimum moisture
Performance Drills and Full Review
- Rehearse each procedure physically against the official checklists
- Take timed open-book practice sets to simulate the two-hour written exam
A comparison of the two exam components side by side can clarify how differently you need to prepare for each:
| Aspect | Written Exam | Performance Exam |
|---|---|---|
| Format | Open-book, multiple-choice | Closed-book, hands-on demonstration |
| Length/Volume | Two-hour limit, ~75 questions | All required procedures per checklist |
| Passing Standard | 60% per section, 70% overall | Successful demonstration of each procedure |
| Retest Scope | Entire written exam | Entire performance exam |
For a structured walkthrough of first-attempt preparation, see our ACI-AGGREGATE-BASE Study Guide, and if you want a candid assessment of where candidates tend to struggle, How Hard Is the ACI-AGGREGATE-BASE Exam? covers that directly. Once you're ready to test your recall against realistic questions, practicing on our practice test platform is a faster feedback loop than re-reading the workbook. A quick-reference companion is also available in the ACI-AGGREGATE-BASE Cheat Sheet.
Frequently Asked Questions
No. The combined-methods program is retired. ACI-AGGREGATE-BASE (ASTM Methods) is one of two active successor tracks, alongside a separate AASHTO Methods credential, each with its own workbook and procedures.
The written exam contains approximately 75 multiple-choice questions and must be completed within a two-hour time limit. It is open-book using ACI-approved references.
No. Approved simple-function, nonprogrammable calculators are permitted, but mobile devices cannot be used as calculators on either the written or performance exam.
You retake only the failed component in full - the entire performance exam, not selected procedures - but you must complete it within one year of your first passed component, since both parts must be passed within that window.
Certification is valid for five years. Renewal requires passing both the written and performance examinations again, not simply submitting continuing education credit.