The ACI Aggregate Testing Technician (ATT) certification is a vital credential for professionals working in the construction materials industry. This certification, provided by the American Concrete Institute (ACI), ensures that technicians have the necessary skills and knowledge to conduct aggregate testing in compliance with industry standards. Whether you are an experienced technician or entering the field, obtaining an ACI Aggregate Testing Technician certification can significantly enhance your career prospects. Aggregate testing plays a crucial role in the construction process, as aggregates form the foundation of concrete and asphalt materials. Proper testing ensures the quality, durability, and performance of construction materials, making it an essential aspect of infrastructure development. Practice with the free ACI Aggregate Testing Technician practice test on PracticeTestGeeks (7 questions with answer explanations).
Numbers in brackets link to the official sources listed under Sources & last verified. Dates that have passed are removed automatically.
| Item | Detail | Source · Verified |
|---|---|---|
| Number of questions (Level 1) | About 100 multiple-choice questions (open-book)[1] | American Concrete Institute · Oct 25, 2026 |
| Number of questions (Level 2) | About 100 multiple-choice questions (open-book)[2] | American Concrete Institute · Oct 25, 2026 |
| Time limit | 2 hours per written exam[3] | American Concrete Institute · Oct 25, 2026 |
| Retake policy | Retake within 1 year of the first exam, otherwise redo both exams[3] | American Concrete Institute · Oct 25, 2026 |
| Validity | 5 years[1] | American Concrete Institute · Oct 25, 2026 |
| Renewal | Pass both the written and performance exams again[1] | American Concrete Institute · Oct 25, 2026 |
| Delivery | Written plus hands-on performance exam, run by ACI-approved sponsoring groups[3] | American Concrete Institute · Oct 25, 2026 |
| Eligibility | No education or experience required; Level 2 requires current Level 1[3] | American Concrete Institute · Oct 25, 2026 |
| Score release | Performance trial results (pass/fail) given immediately after each trial[3] | American Concrete Institute · Oct 25, 2026 |
Interactive ACI Aggregate Testing Technician resources on PracticeTestGeeks, free to start:
According to American Concrete Institute, “The two-hour written examination is open-book and consists of approximately 100 multiple-choice questions.”[1]
The content areas below are copied from the official ATT content outline published by American Concrete Institute. The right-hand column shows which of our practice sets covers it.
| Official content area | Practice on this site |
|---|---|
| AASHTO R 76-16/ASTM C702/C702M-11 – Standard Method of Test for Reducing Samples of Aggregate to Testing Size[1] | ATT Aggregate Sampling & Reduction Practise when to use a splitter or quartering, and how to keep the reduced portion representative of the field sample. |
| AASHTO R 90-18/ASTM D75-03 – Standard Method of Test for Sampling of Aggregates[1] | ATT Sampling Aggregates Practise where and how samples are taken from stockpiles, belts and bins, and how to avoid segregation. |
| AASHTO T 21/T 21M-15/ASTM C40/C40M-11 – Standard Method of Test for Organic Impurities in Fine Aggregates for Concrete[1] | ATT Organic Impurities Assessment Practise the colour comparison procedure and what the result does and does not tell you about the sand. |
| AASHTO T 27-14/ASTM C136-06 – Standard Method of Test for Sieve Analysis of Fine and Coarse Aggregates[1] | ATT Sieve Analysis & Gradation Practise sample preparation, sieve order, shaking and the percent passing and retained calculations. |
| AASHTO T 84-13/ASTM C128-12 – Standard Method of Test for Specific Gravity and Absorption of Fine Aggregate[1] | ATT Specific Gravity & Absorption Practise reaching the saturated surface dry condition and choosing the right formula for each type of specific gravity. |
| AASHTO T 85-14/ASTM C127-12 – Standard Method of Test for Specific Gravity and Absorption of Coarse Aggregate[1] | ATT Specific Gravity & Absorption Practise soaking, surface drying and weighing in water, and the calculations that follow from those masses. |
Prepare for the ATT - ACI Aggregate Testing Technician exam with our free practice test modules. Each quiz covers key topics to help you pass on your first try.
These are practice questions written for this site, not questions from the real exam. Each explanation shows why the right answer is right and why the others are wrong.
Question: If the water temperature during a specific gravity test deviates from 23°C, what adjustment must the technician make?
Answer: B. Apply a temperature correction factor from the standard table
Explanation:
The correct answer is to apply a temperature correction factor from the standard table. The specific gravity methods expect the water to be near 23°C, and they supply a correction for when it is not, so the result can still be used.
Rejecting the test and rerunning it at exactly 23°C is wrong because the method does not demand a rerun for a small deviation. Adding 0.001 for every degree above 23°C is wrong because the correction is not a flat amount you invent; it comes from the published factors. Saying no adjustment is needed within 5°C of 23°C is wrong because the method has no such tolerance band.
Rule to remember: when a test condition drifts from the reference value, look for the correction in the standard rather than guessing or ignoring it.
Question: What is the minimum sample size for a washing test on a fine aggregate (maximum size 3/8 in.) per ASTM C117?
Answer: C. 300 g
Explanation:
The correct answer is 300 g. ASTM C117 sets minimum sample masses by the maximum particle size of the material, and fine aggregate with a maximum size of 3/8 in. falls at that value.
The answers of 100 g and 200 g are too small. A sample that light would not be representative, and the amount of material washed through the sieve could be skewed by a few particles. The answer of 500 g is more than the minimum for this size. It is not wrong to use more in general, but it is not the minimum the question asks for.
Rule to remember: minimum sample size depends on maximum particle size, so find the size first and then look up the mass in the table of the standard.
Question: Which ASTM standard covers the determination of bulk density of aggregates?
Answer: B. ASTM C29
Explanation:
The correct answer is ASTM C29, the method for bulk density, also called unit weight, and voids in aggregate.
ASTM C40 is wrong because it covers organic impurities in fine aggregate, not density. ASTM C117 is wrong because it covers materials finer than the No. 200 sieve, determined by washing. ASTM C128 is wrong because it covers specific gravity and absorption of fine aggregate, which is a different property from bulk density, since bulk density includes the spaces between particles.
Rule to remember: match the property to the standard. Density with voids points to C29, while specific gravity and absorption point to the C127 and C128 pair.
Start with the official outline and the list of standards above. Because the written exam is open-book, practise looking things up, not memorising them. Know where the sample-size tables, correction factors and calculation steps sit in each standard so you can find them quickly.
Work through the practice sets in the order the tests are done in a lab: sampling and reduction first, then sieve analysis, then specific gravity and absorption, then the quality tests such as organic impurities, materials finer than the No. 200 sieve, unit weight and voids. After each set, read the explanation for every question you missed and open the matching standard to find the exact passage.
Keep a short list of mistakes. Group them by cause: wrong standard, wrong sample size, wrong formula, or a calculation slip. Redo the sets that cover your most common cause until the errors stop repeating.
The performance exam is hands-on, so reading is not enough. Ask your sponsoring group what the procedure checklist looks like, and rehearse each step in order with the real equipment if you can. Use the practice questions for the written part and treat them as a study aid only, since they are not real exam questions.
The ACI Aggregate Testing Technician certification is essential for professionals in construction materials testing.
Level 1 and Level 2 certifications validate skills in performing standardized aggregate tests.
Certified technicians play a critical role in ensuring quality control and compliance with ASTM and AASHTO standards.
Study guides, training courses, and hands-on experience are key to passing the ACI certification exam.
ACI certifications are valid for five years and require recertification to stay up-to-date.
The ACI Aggregate Testing Technician certification is designed for professionals who perform tests on fine and coarse aggregates in accordance with ASTM and AASHTO standards. The certification is divided into two primary levels: Level 1 and Level 2, each with distinct requirements and competencies.
Enhances technical skills and industry knowledge.
Provides career advancement opportunities in the construction and materials testing industry.
Ensures compliance with ASTM and AASHTO standards for aggregate testing.
Demonstrates professional credibility and competency.
Contributes to quality control in construction projects.
An ACI Aggregate Testing Technician (ATT) is a certified professional responsible for performing standardized tests on aggregates used in concrete and asphalt production. These tests help determine aggregate properties such as gradation, specific gravity, absorption, and resistance to degradation.
Sampling and testing aggregates according to industry standards.
Measuring physical and mechanical properties of fine and coarse aggregates.
Ensuring quality control in material production and construction projects.
Following ASTM and AASHTO testing procedures to maintain consistency.
Documenting and reporting test results to engineers and project managers.
With the growing emphasis on infrastructure quality and sustainability, ACI-certified technicians are in high demand across various sectors.
ACI Aggregate Testing Technician - Level 1
The Level 1 certification focuses on fundamental aggregate testing procedures. To obtain this certification, candidates must demonstrate proficiency in the following tests:
Sampling Aggregates (ASTM C702/AASHTO T2)
Sieve Analysis of Fine and Coarse Aggregates (ASTM C136/AASHTO T27)
Specific Gravity and Absorption of Coarse Aggregates (ASTM C127/AASHTO T85)
Specific Gravity and Absorption of Fine Aggregates (ASTM C128/AASHTO T84)
Moisture Content of Aggregates (ASTM C566/AASHTO T255)
Materials Finer than No. 200 Sieve (ASTM C117/AASHTO T11)
The Level 2 certification builds upon Level 1 and includes additional testing methods such as:
Resistance to Degradation by Los Angeles Abrasion (ASTM C131 & C535/AASHTO T96)
Unit Weight and Voids in Aggregate (ASTM C29/AASHTO T19)
Sand Equivalent Test (ASTM D2419/AASHTO T176)
Each certification level requires passing a written and performance-based examination administered by ACI-approved testing centers.
To successfully obtain ACI Aggregate Testing Technician Level 1 certification, candidates should prepare thoroughly using study guides and training resources. Here are some essential study tips:
ACI Certification Study Guides (available through the ACI website)
ASTM and AASHTO Testing Standards
Practice Exams and Sample Questions
Hands-on Laboratory Training and Workshops
ACI Technical Documents and Field Testing Manuals
Understand Testing Procedures – Familiarize yourself with ASTM and AASHTO standard testing methods.
Practice Hands-on Testing – Gain experience by working in a materials testing lab.
Take Practice Tests – Review sample questions to assess your knowledge.
Attend ACI Training Sessions – Participate in training courses offered by ACI-accredited institutions.
Review Common Testing Errors – Learn from mistakes commonly made during aggregate testing.
By using these study resources and techniques, candidates can increase their chances of passing the ACI certification exam.
ACI certifications, including the ACI Aggregate Testing Technician certification, are valid for a period of five years. After this period, technicians must renew their certification by retaking the written and performance examinations.
Schedule Recertification Exams – Contact an ACI-approved testing center to register for renewal exams.
Update Knowledge on Testing Standards – Review any changes in ASTM and AASHTO testing procedures.
Participate in Refresher Training – Attend workshops to reinforce technical skills.
Complete Performance Evaluations – Demonstrate competency in practical testing methods.
Maintaining certification ensures that technicians stay current with industry standards and continue delivering accurate test results.
| Pros | Cons |
|---|---|
| ATT certification validates expertise recognized by employers nationwide | Must complete continuing education to maintain active certification |
| Opens doors to advanced positions and leadership roles | Pass rates vary — thorough preparation is essential for success |
| Demonstrates commitment to professional standards and ethics | Some certifications require prerequisite experience or education |
Try these questions from our free ACI Aggregate Testing Technician practice tests. The correct answer and an explanation follow each question.
What condition must fine aggregate be in to determine surface moisture?
Answer: C. Saturated surface-dry
The saturated surface-dry (SSD) condition eliminates the influence of surface moisture for accurate calculations.
What is the diameter of the tamping rod specified in ASTM C29?
Answer: B. 16 mm (5/8 in)
ASTM C29 specifies a smooth, straight steel tamping rod 16 mm (5/8 in) in diameter and approximately 600 mm (24 in) in length.
In the unit weight test, why is it important to avoid vibrating the measure during filling?
Answer: B. Vibration increases packing beyond the standard procedure, giving artificially high results
External vibration compacts aggregate beyond what the standard procedure intends, producing a unit weight higher than the standardized result.
In Moisture Content Testing, what is the FIRST step a ATT professional should take when encountering a new case or situation?
Answer: A. Conduct a comprehensive assessment and gather all relevant information
In Moisture Content Testing, a thorough initial assessment ensures all relevant factors are identified before deciding on an appropriate course of action. This systematic approach is fundamental to ACI Aggregate Testing Technician practice.
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