What Is A CSTT?

The Short Answer: What a CSTT Is

A CSTT is a Concrete Strength Testing Technician: a person who has demonstrated, through ACI examinations, that they can prepare concrete specimens for strength testing and then break them correctly. The work centers on one question that every concrete project eventually asks: did the concrete reach the strength the engineer specified?

The answer depends on far more than pressing a button on a testing machine. A cylinder that is capped badly, loaded at the wrong rate or measured carelessly gives a number that can mislead an entire project team. The certification exists to make sure the person producing that number follows the standardized procedures that make results comparable from one lab to the next.

This article explains what the credential covers, how the examinations work, what the standards require you to know, and where it fits in the construction materials testing world. If you are comparing it to other credentials that happen to share the acronym, jump to the section on what a CSTT is not. For other framings of the same question, see our pages on what CSTT is and what CSTT stands for.

Who Issues the Credential

The Concrete Strength Testing Technician certification is offered by the American Concrete Institute (ACI). ACI does not typically run every exam session itself. Examinations are administered through ACI-approved Sponsoring Groups and resource centers, which are often local ACI chapters or state concrete associations. That means the practical experience of registering, paying and sitting for the exam happens at the local level, with fees and dates set by whoever is hosting.

This structure explains why two candidates in different states can report quite different costs for the "same" certification. The credential is the same; the sponsor's bundle of workbook, review class and exam fees is not. Our CSTT certification cost breakdown goes deeper on how those bundles differ.

What a CSTT Does on the Job

The certification is built around the laboratory side of strength testing. In practice, a certified technician typically does some combination of the following:

• Prepares cylindrical specimens for compression testing, including capping the ends so load is applied evenly
• Uses unbonded cap systems where the standard allows them, and verifies that the system is within its permitted limits
• Breaks cylinders in a compression machine, controlling the loading rate and recording peak load and failure type
• Breaks beam specimens in flexure using third-point loading, then calculates the modulus of rupture
• Documents results so they can be reported to engineers, contractors and ready-mix producers

Notice what is missing from that list: sampling fresh concrete at the job site, slump tests, air content and field curing. Those belong to a different ACI credential, discussed below. A CSTT lives in the world of hardened specimens and the machines that break them.

The Four Standards Behind the Certification

The exam content is organized around four ASTM standards. The current program's technical basis is C617/C617M-15, C1231/C1231M-15, C39/C39M-18 and C78/C78M-18. ACI's job-task analysis for the program groups the examination objectives under these four headings. They are not four equally weighted domains, so do not assume each one counts for the same share of your effort or your score. For a fuller walkthrough, see our guide to all four CSTT content areas.

Two Exams, Two Different Skills

A CSTT candidate faces two separate examinations, and they test different things. Treating the certification as a single multiple-choice test is one of the most common planning errors.

On question count, the sources differ slightly. The current ACI program page describes approximately 40 questions with at least eight per standard, while Certification Program Policy CPP 620.2-19 describes approximately 35 to 40 questions with 8 to 10 per standard. The safe way to read this is "roughly 35 to 40 questions, with several drawn from each of the four standards" rather than expecting an exact fixed number.

The performance exam is where hands-on candidates tend to relax and classroom-only candidates tend to struggle. Checklists mean the examiner is watching for each required step, and skipping or reordering a required step can fail a procedure even when your final result would have been fine. To judge how demanding the whole package is, read how hard the CSTT exam is.

Scoring Rules That Catch Candidates Off Guard

The written exam has a two-part passing rule: you need at least 60% on each standard and at least 70% overall. Both conditions must be met. That detail has real strategic consequences.

Several other rules shape how you should plan:

• One-year window: Both the written and performance examinations must be passed within one year.
• If you fail a practical procedure, you are allowed a second trial on the same day.
• Subsequent re-examination covers the entire failed written or performance component, not just the part you missed.
• If the one-year window closes before you finish, both components must be retaken.

For the broader question of how many candidates succeed, our CSTT pass rate article explains what is and is not publicly known rather than guessing at a figure.

Getting Certified: Registration and Fee Mechanics

There is no specific education or work-experience prerequisite for this credential. That makes it an accessible entry point into materials testing, though it also means exam preparation, not paperwork, is the real gate. Our CSTT requirements guide covers eligibility in more detail.

The workbook

The current study workbook is CP-19, 25th Edition (2022). ACI also accepts the 23rd and 24th editions because their technical basis is identical. The 25th-edition workbook does not include the ASTM standards themselves and is listed at USD 71 for ACI members or USD 136 for non-members. Note that ACI identifies first-printing errata for the workbook, but the linked errata document requires a sign-in, so check it if you hold an early printing.

Real fee examples

Because sponsors set their own pricing, the following are verified 2026 local examples, not national tariffs:

One caution on the Ohio Concrete figures: "member" there means Ohio Concrete membership, not ACI membership, so the rates are not interchangeable with ACI member pricing. The Las Vegas Chapter listing included an October 24, 2026 session at the time of checking. Because sessions and prices change, treat these as illustrations of the range and confirm with your local sponsor. For scheduling patterns, see our CSTT exam dates guide.

ACI also sells a separate on-demand preparation course, but completing it does not award certification. It is a study aid, not a substitute for sitting both examinations.

What a CSTT Is Not

Within ACI's own lineup, the Concrete Strength Testing Technician certification is easy to confuse with neighbors that sound similar. This site is limited to Concrete Strength Testing Technician only. In particular, it is not:

• ACI Field Testing Technician, Grade I: a separate certification focused on testing fresh concrete in the field.
• The combined Laboratory Testing Technician Level 1 credential: a distinct certification with its own scope.

Employers frequently ask for more than one of these ACI credentials, which is why people sometimes blur them together. If a job posting lists "ACI certification" without specifying, read the fine print to see which one it means. Also note that the acronym CSTT is used by unrelated certifications in other industries. Everything on this site, including fees, exam structure and standards, refers only to the ACI Concrete Strength Testing Technician program. Our companion page on CSTT meaning addresses the naming question directly.

Who Hires and Where the Credential Fits

Demand for strength testing comes from anywhere concrete is placed and verified. Typical employers include:

• Independent testing and inspection firms: the largest group, running labs that break cylinders and beams for many clients
• Ready-mix concrete producers: who test their own mixes for quality control
• General and specialty contractors: particularly on large projects with in-house quality programs
• Engineering consultancies and materials labs: supporting design verification and forensic work
• Public agencies and departments of transportation: especially where pavement flexural strength is specified

The credential tends to appear as a requirement or a strong preference in postings for lab technician and materials testing roles. It is also a common stepping stone: technicians often add the field-testing credential next, since the two together cover both fresh and hardened concrete. For a view of the market, see our CSTT jobs overview, and for the compensation question, the CSTT salary guide. Whether the investment pays off for you specifically is the subject of our ROI analysis.

Staying certified

Certification lasts five years. Recertification is not a paperwork renewal; it requires passing both the written and performance examinations again. Technicians planning a long career in testing should treat the five-year mark as a scheduled event, much like a calibration due date.

Preparing in a CSTT-Specific Order

Generic study advice is easy to find. What is more useful is sequencing your preparation around how these four standards relate to each other. Capping standards feed into the compression test, and the beam standard stands somewhat apart, so a sensible order follows the physical workflow of a lab.

Your own timeline may be shorter or longer depending on lab experience, and our CSTT study guide offers a fuller plan. A one-page recap of the details most likely to be tested is available in the CSTT cheat sheet. When you are ready to test your recall under realistic conditions, try the CSTT practice tests, which let you check performance standard by standard.

Frequently Asked Questions