- What Is A ACI-AGGREGATE-BASE, Exactly?
- Who Issues This Credential
- How the Exam Is Actually Structured
- The Seven ASTM Standard Sections
- Pathways: AASHTO Holders and Level 1 Technicians
- CP-46 and Approved References
- Who Hires Someone With This Title
- Mapping a Study Plan to the Two Components
- Staying Certified: The Five-Year Cycle
- Frequently Asked Questions
- An Aggregate Base Testing Technician-ASTM Methods holder passes both a written and a performance exam within one year.
- The written exam is open-book, two hours, roughly 75 multiple-choice questions, using ACI-approved references only.
- Passing requires 60% minimum in every required standard section plus 70% overall on the written exam.
- The seven Domains correspond directly to seven named ASTM standards, not equal-weight topic buckets.
What Is A ACI-AGGREGATE-BASE, Exactly?
"ACI-AGGREGATE-BASE" on this site refers specifically to the Aggregate Base Testing Technician-ASTM Methods credential. It is not a generic industry nickname - it is one of two active successor titles to a retired, combined-methods Aggregate Base program, with this ASTM track running parallel to a separate AASHTO Methods track. If you've landed here wondering what the letters actually mean in practice, the short answer is: a person who has demonstrated, through a written test and a hands-on performance test, that they can correctly sample, reduce, classify, and compact aggregate base and soil materials according to seven specific ASTM standards.
For a plain-language breakdown of the acronym itself, see ACI-AGGREGATE-BASE Meaning and What Does ACI-AGGREGATE-BASE Stand For?. This article focuses on what the credential actually requires you to know and do.
Who Issues This Credential
Certification testing is administered by approved sponsoring groups and by ACI examiners and proctors, with grading performed by the American Concrete Institute (ACI). Candidates don't test directly against some abstract national board - a local sponsoring group runs the session, and ACI stands behind the scoring. The governing policy document for this program, CPP 620.5-25, was approved February 14, 2025, and the job-task analysis underlying the ASTM version of the exam was approved February 13, 2026. That job-task analysis is the actual source of what appears on the written and performance exams, which is why the seven Domain names map directly onto ASTM standard designations rather than loosely-defined skill categories.
If you want the full origin story of the acronym and how it differs from similarly-named programs elsewhere in the industry, What Is ACI-AGGREGATE-BASE? covers that in more depth.
How the Exam Is Actually Structured
There are two components, and both must be passed within a one-year window of each other. Confusing the two - or assuming one substitutes for the other - is one of the most common early mistakes candidates make.
Written Examination
- Format: Open-book, using ACI-approved references only.
- Length: Two-hour time limit.
- Question count: Approximately 75 multiple-choice questions.
- Passing standard: At least 60% in every required standard section AND at least 70% overall.
- Calculators: Approved simple-function, nonprogrammable calculators only. Mobile phones cannot be used as calculators, even in calculator mode.
Performance Examination
- Format: Closed-book, hands-on demonstration.
- Requirement: Successful demonstration of all required procedures.
- Verbal substitution: Allowed only where the specific checklist for that procedure permits a verbal description in place of a physical step.
Key Takeaway
The dual 60%/70% written scoring rule means you cannot "average out" a weak Domain by acing an easy one - every required standard section has its own floor. Study every one of the seven Domains, not just the ones that feel intuitive.
A retest, if needed, covers the entire failed component - not just the sections you missed. Failing the written exam means retaking the full written exam; failing the performance exam means redoing every required procedure again, not just the one you fumbled. For a section-by-section breakdown of exactly what "passing" requires, see ACI-AGGREGATE-BASE Passing Score 2026: Exactly What You Need to Pass.
The Seven ASTM Standard Sections
Unlike many certification exams that group content into loosely-labeled "domains," this credential's seven Domain entries are literally the ASTM standards themselves. Each one carries its own passing threshold on the written exam, and several also have a corresponding hands-on procedure on the performance exam.
Domain 1: ASTM D75/D75M - Standard Practice for Sampling Aggregates
Covers correct field sampling technique - where, how, and how much material to pull so that the sample is actually representative of the source.
- Sampling location and method selection by material type
Domain 2: ASTM C702/C702M - Standard Practice for Reducing Samples of Aggregate to Testing Size
Covers mechanical splitting and quartering methods used to shrink a field sample down to a laboratory-testable size without introducing bias.
- Splitter and quartering technique selection
Domain 3: ASTM D4318 - Liquid Limit, Plastic Limit, and Plasticity Index of Soils
Covers the Atterberg limits procedures used to classify fine-grained soil behavior.
- Liquid limit device setup and groove-closure counting
Domain 4: ASTM D7928 - Particle-Size Distribution of Fine-Grained Soils via Hydrometer Analysis
Covers sedimentation-based gradation testing for the fine fraction of a soil sample.
- Hydrometer reading correction and timing intervals
Domain 5: ASTM D2216 - Laboratory Determination of Water (Moisture) Content by Mass
Covers oven-drying moisture content determination - a foundational calculation that feeds into several other Domains.
- Mass measurement precision and drying-to-constant-mass criteria
Domain 6: ASTM D1557 - Compaction Characteristics Using Modified Effort
Covers modified Proctor compaction testing (56,000 ft-lbf/ft³).
- Mold selection, layer count, and blow-count procedure
Domain 7: ASTM D698 - Compaction Characteristics Using Standard Effort
Covers standard Proctor compaction testing (12,400 ft-lbf/ft³) - the companion method to Domain 6, with different energy input and often confused with it on the written exam.
- Distinguishing standard vs. modified effort setups
For a much deeper dive into each of these seven standards, including how they typically show up as multiple-choice questions versus performance checklist items, read the full ACI-AGGREGATE-BASE Exam Domains 2026: Complete Guide to All 7 Content Areas.
| Component | Format | Time Limit | Passing Standard |
|---|---|---|---|
| Written Exam | Open-book, ~75 multiple-choice questions | 2 hours | 60% per required section, 70% overall |
| Performance Exam | Closed-book, hands-on demonstration | N/A - task-based checklist | Successful demonstration of all required procedures |
Pathways: AASHTO Holders and Level 1 Technicians
Two existing credentials give candidates a shortcut into this ASTM track:
- Current AASHTO Methods holders can earn the ASTM credential by passing the ASTM written examination within one year of obtaining their AASHTO Methods certification - the performance component isn't automatically waived, so check the current requirements carefully.
- Current Aggregate Testing Technician-Level 1 holders may receive specified performance-procedure exemptions, reducing the hands-on demonstration burden for procedures already validated under that credential.
Neither pathway eliminates the written exam's Domain-by-Domain passing thresholds. For the full eligibility picture, including prerequisites for candidates with no prior credential at all, see ACI-AGGREGATE-BASE Requirements 2026: Eligibility, Prerequisites & How to Qualify.
CP-46 and Approved References
The official ASTM workbook for this program is CP-46, first edition - use it alongside its applicable errata, since standard-referencing workbooks are periodically corrected after initial publication. Note that CP-47 is a different workbook entirely, belonging to the separate AASHTO Methods track; using CP-47 to prepare for the ASTM written exam is a mismatch that will leave gaps in your standard-specific knowledge.
As of a September 10, 2026 check, CP-46 was listed at $133 for non-members and $69 for members. These are workbook purchase prices only - not examination fees, registration costs, or membership dues - so don't mistake the workbook price for the total cost of certification. A full cost breakdown, covering everything from workbook purchase to retest considerations, is available in ACI-AGGREGATE-BASE Certification Cost 2026: Complete Pricing Breakdown.
Who Hires Someone With This Title
The Domains covered by this credential - sampling, sample reduction, Atterberg limits, hydrometer gradation, moisture content, and both standard and modified compaction - are core testing tasks for materials testing laboratories, geotechnical and earthwork contractors, aggregate producers, and public agencies overseeing road base and subgrade construction. Because the exam is standard-by-standard rather than generalized, employers reviewing a resume with this credential can reasonably assume the holder has been individually checked out on each of the seven listed ASTM methods, not just tested on general soil mechanics familiarity. If you're evaluating whether this credential fits your career trajectory, ACI-AGGREGATE-BASE Jobs and ACI-AGGREGATE-BASE Salary Guide 2026: Complete Earnings Analysis go into more detail on typical employers and roles.
Mapping a Study Plan to the Two Components
Because the written and performance exams are graded and structured differently, it helps to prepare for them somewhat separately rather than treating "studying" as one undifferentiated activity.
Sampling and Reduction Foundations
- Read D75/D75M and C702/C702M closely - these two Domains govern how every later test's sample is obtained and prepared
- Practice explaining, out loud, why an improperly reduced sample invalidates downstream results
Soil Classification Domains
- Work through D4318 (Atterberg limits) and D7928 (hydrometer gradation) calculations by hand until the arithmetic is automatic
- Cross-check answers against CP-46's applicable errata, since minor corrections can change worked examples
Moisture and Compaction Domains
- Drill D2216 moisture content calculations, since they underpin compaction curve interpretation in D1557 and D698
- Build a comparison chart distinguishing standard effort (D698) from modified effort (D1557) mold, layer, and blow-count specifics
Performance Rehearsal and Timed Written Practice
- Run full procedure walkthroughs under checklist conditions, noting which steps allow a verbal description instead of a physical demonstration
- Take timed, open-book practice sets simulating the two-hour, ~75-question format
This kind of structured week-by-week approach only works if it's anchored to the actual seven standards rather than generic test-taking habits. For a more exhaustive walkthrough of scheduling, reference tabbing, and open-book strategy specific to this exam, see ACI-AGGREGATE-BASE Study Guide 2026: How to Pass on Your First Attempt. And if you're still trying to gauge how demanding this exam is relative to your current experience level, How Hard Is the ACI-AGGREGATE-BASE Exam? Complete Difficulty Guide 2026 breaks that down further.
Running timed, scenario-style questions ahead of exam day - through resources like our practice test platform - is one practical way to get comfortable with the open-book, two-hour format before you're sitting in the actual testing session.
Staying Certified: The Five-Year Cycle
Certification is valid for five years. Renewal is not a paperwork-only process - it requires passing both the written and performance examinations again, the same as initial certification. That means the seven ASTM standards you studied the first time around are worth revisiting periodically rather than only cramming once and setting the material aside for half a decade. If you're deciding whether investing in this recurring credential is worthwhile for your specific role, Is the ACI-AGGREGATE-BASE Certification Worth It? Complete ROI Analysis 2026 weighs the considerations in more depth.
Key Takeaway
Because renewal requires both exams again, keep your CP-46 workbook and procedure notes rather than discarding them after your first pass - you'll want them again well before the five-year mark.
Before you register for either component, it's worth confirming current testing windows and any scheduling deadlines through your sponsoring group; general timing guidance is covered in ACI-AGGREGATE-BASE Exam Dates 2026: Testing Windows, Deadlines & Scheduling. And once you're comfortable with the seven Domains, a condensed reference like the ACI-AGGREGATE-BASE Cheat Sheet 2026: One-Page Review of Must-Know Facts can help with last-minute review. You can also run a broader self-assessment using practice questions modeled on the real exam format to see which of the seven standards need another pass before test day.
Frequently Asked Questions
No. Several credentials share similar acronyms across the industry. On this site, ACI-AGGREGATE-BASE refers specifically to the Aggregate Base Testing Technician-ASTM Methods credential administered with ACI grading, distinct from the parallel AASHTO Methods track and from the retired combined-methods program it succeeded.
The written exam is open-book, using ACI-approved references, contains approximately 75 multiple-choice questions, and has a two-hour time limit.
You need at least 60% in every required standard section and at least 70% overall. Missing the threshold on even one required section means you don't pass, regardless of your overall score.
No. Only approved simple-function, nonprogrammable calculators are permitted. Mobile devices cannot be used as calculators during the written examination.
A retest covers the entire failed component. If you fail the written exam, you retake the full written exam; if you fail the performance exam, you redemonstrate all required procedures again - not just the specific sections or tasks you missed.
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