How Does TEC Perform Against Galvanized and Uncoated Rebar in Concrete Cracks?

Every reinforced concrete structure cracks. For bridge owners and designers, the real question is not whether concrete cracks will form, but how many there will be, how wide they get, and what reaches the steel through them. The type of reinforcing bar has more influence on that outcome than many specifications acknowledge.

Over the past several years, university and state DOT research programs have tested textured epoxy-coated (TEC) reinforcing bars, produced under ASTM A1124, side by side with galvanized bars, uncoated black bars, and conventional smooth epoxy-coated reinforcement (ECR). This article summarizes what those crack tests found and what the results mean for bridge decks, marine structures, and parking garages.

Key Takeaways

• In side-by-side flexural tests, TEC bars produced more numerous and finer cracks than smooth ECR, a sign of stronger bond between the bar and the concrete.
• University of Kansas lap splice tests found the splice strength of TEC bars averaged 1.05 times that of uncoated bars, compared with 0.83 for smooth ECR.
• In a Clemson University study that tested all four bar types, TEC and galvanized bars both outperformed uncoated and smooth epoxy-coated bars on crack control, and the researchers could not separate the two.
• Crack width and distribution control how quickly water and chlorides reach the steel, so crack control is a durability property, not only an appearance issue.
• TEC combines bond performance comparable to uncoated bar with the barrier protection of a fusion-bonded epoxy coating.

Why Does Concrete Crack and Why It Matters for Reinforcement Selection

Concrete is strong in compression but weak in tension, and it changes volume throughout its life. The most common causes of concrete cracks are drying and plastic shrinkage, temperature changes acting against restraint, applied loads that put members into bending, and environmental exposure such as freeze-thaw cycling. Bridge decks are especially vulnerable. They are long, thin, restrained by the girders below, and exposed to the weather, so early-age transverse cracking is common within weeks of placement.

It helps to separate two kinds of cracking. Microcracking is fine, often invisible cracking within the paste and around aggregate. Structural cracks in concrete are the visible cracks that form when tension in a member exceeds the strength of the concrete, and they are what reinforcement is designed to control. Once a crack opens, the reinforcing bar carries the tensile force across it, and bond transfers that force back into the concrete on either side. When bond is strong, stress is shed into the concrete over a short distance, so the member forms many closely spaced, narrow cracks. When bond is weak, the member forms fewer cracks that open wider.

Width matters because cracks are the fastest route for water, oxygen, and deicing salts to reach the steel. ACI Committee 224 guidance suggests that crack widths around 0.007 in. (0.18 mm) are reasonable where deicing chemicals are present and about 0.006 in. (0.15 mm) for seawater exposure. That makes reinforcement selection a durability decision for bridge decks, parking structures, and marine elements, not only a strength decision.

Reinforcement Types

Uncoated black bar (ASTM A615 or A706) bonds well to concrete through its deformations. It relies entirely on the alkalinity of the surrounding concrete for protection, so once chlorides at the bar reach the corrosion threshold, the steel begins to corrode and the expanding rust cracks the cover.

Galvanized bar carries a zinc coating applied by hot-dip galvanizing (ASTM A767) or continuous galvanizing (ASTM A1094). Zinc protects the steel as a barrier, raises the chloride level needed to start corrosion, and corrodes sacrificially in place of the steel. Research at the University of Kansas found that galvanized bars needed more than twice the corrosion loss of conventional bars to crack the concrete cover, and in tests without an applied current they took roughly four times as long to crack it.

Smooth epoxy-coated bar (ASTM A775) has been used in bridge decks since the 1970s. Its fusion-bonded epoxy coating is chemically stable during the concrete curing process, and it isolates the steel from moisture and chlorides. The trade-off is the smooth coating, which reduces friction and adhesion between bar and concrete. For that reason, design codes apply a development and splice length modification factor to epoxy-coated bars.

Textured epoxy-coated bar (ASTM A1124) starts with the same fusion-bonded epoxy base coat, then receives a textured epoxy surface treatment applied while the bar is still hot. The two layers fuse into one continuous coating, and the textured surface restores the mechanical interlock that a smooth coating removes. The goal is the corrosion protection of epoxy with the bond of uncoated steel. For background on how chlorides drive corrosion in each of these systems, see Corrosion and Steel Reinforcement, a technical overview from the Epoxy Interest Group.

How Crack Tests Evaluate Reinforcement Performance

Researchers use several complementary tests to see how a bar’s surface affects bond and cracking:

• Beam-end bond tests (ASTM A944) cast a bar into a concrete block and pull it until bond fails. Results are compared with uncoated bar from the same heat of steel. ASTM A1124 uses this test to qualify textured coatings.
• Lap splice tests load full-size beams with spliced bars in bending. They mirror the conditions that design codes are calibrated against.
• Flexural cracking tests hold beams under sustained or repeated load and record the number of cracks, their spacing, their average and maximum widths, and the total crack area.
• Shrinkage and thermal tests restrain deck-like specimens and track how strain and cracking develop as the concrete dries and changes temperature.

No single metric tells the whole story. More cracks with tighter spacing and smaller widths point to good bond. Total crack area and maximum crack width relate most directly to how easily chlorides can reach the steel. Laboratory specimens are smaller and more controlled than a real deck, so DOT engineers generally look for consistent trends across test types and research teams rather than relying on a single result.

TEC vs Galvanized vs Uncoated Rebar in Crack Tests

The most direct comparison of all four bar types comes from research by Brandon Ross and Amir Poursaee at Clemson University for the Wisconsin Department of Transportation. In one series, beams reinforced with uncoated, smooth epoxy, continuously galvanized, and textured epoxy bars were placed under sustained four-point bending, and every crack was measured. To cancel out batch-to-batch differences in the concrete, each result was expressed as a comparison index relative to the average of all four bars, where values below 1.00 mean better than average.

Bar type	Overall index (6 crack and stiffness metrics)	Index for crack area and max width
Textured epoxy-coated (TEC)	0.93	0.92
Continuously galvanized	0.95	0.87
Uncoated black bar	1.02	0.97
Smooth epoxy-coated (ECR)	1.12	1.24

Lower values indicate better crack control. Source: Murphy, A., Comparison of Flexural Cracking in Reinforced Concrete Beams with Different Rebar Coatings, Clemson University (2021).

Across the six measures, TEC bars performed about 7 percent better than the average and galvanized bars about 5 percent better, while smooth ECR performed about 12 percent worse. On the two measures most closely tied to corrosion risk, total crack area and maximum crack width, galvanized and TEC bars came out 13 and 8 percent better than average. The researchers concluded that galvanized and TEC bars performed similarly and that neither was clearly superior, and they described the results as preliminary because of the limited number of specimens.

The full WisDOT program broadened the comparison to five coatings and added cyclic and shrinkage testing. Textured epoxy bars were the only type that finished better than average in both load and shrinkage cracking tests.

Figure: Crack control relative to the average of all bar types. Chart created by EIG from WisDOT Project 0092-19-01 data (Ross and Poursaee, 2021).

Research sponsored by the Illinois Department of Transportation points the same way. In flexural tests at the University of Illinois Urbana-Champaign, crack widths in specimens reinforced with TEC bars were as low as half those in matching specimens with smooth ECR, and digital image correlation showed about 25 percent lower strain in the surrounding concrete. Large-scale deck specimens with TEC bars were also stiffer and deflected less.

Crack Width and Distribution Performance

In every Clemson test series, beams reinforced with TEC bars formed the most cracks, and their crack spacing was the lowest or near the lowest. Beams with smooth ECR had the widest average cracks in every series and the largest maximum widths. This is the pattern engineers want: the load is shared across many fine cracks instead of being concentrated in a few wide ones. Comparisons between TEC and galvanized bars on crack width were mixed from one series to the next, and uncoated bars landed close to the overall average.

Bond Strength and Mechanical Interaction with Concrete

Crack behavior follows bond, and bond is where TEC differs most from smooth ECR. In beam-end tests at the University of Kansas, the bond strength of TEC bars ranged from 0.97 to 1.00 times that of uncoated bars. In lap splice tests, TEC splice strength averaged 1.05 times that of uncoated bars, while smooth ECR averaged 0.83. Follow-up beam-end testing on No. 6 TEC bars measured bond strength at 100.3 percent of uncoated bar from the same heat. Based on that work, the researchers recommended raising the ASTM A1124 bond requirement from 96 to 99.5 percent of uncoated bar and treating the textured coating as providing bond equivalent to uncoated reinforcement.

Galvanized bars also bond well, and some researchers attribute this to the interaction between the zinc surface and fresh cement paste. In the WisDOT program, galvanized results varied by process and test type: hot-dip galvanized bars finished 5 percent better than average in shrinkage tests, while continuously galvanized bars finished slightly below average in both load and shrinkage tests. Early textured coatings evaluated in Illinois in 2018 showed slip resistance that dropped off quickly after peak load, and that research fed into the optimization of the texture profile now standardized in ASTM A1124.

Corrosion Protection Implications of Crack Behavior

Tighter, better distributed cracks slow the movement of chlorides to the bar, but each system protects the steel differently once chlorides arrive. Uncoated bar has no protection beyond the concrete itself. Galvanized bar delays corrosion with its zinc layer, which is consumed over time as it protects the steel. Epoxy and textured epoxy coatings isolate the steel as a barrier.

A 2025 University of Illinois study put TEC and ECR specimens through 11 months of cyclic chloride ponding, including specimens that had been cracked under service-level loads and specimens with intentional coating defects. None of the TEC specimens, loaded or unloaded, with or without defects, showed signs of corrosion on half-cell potential or macrocell current measurements. Only the uncoated bar specimens crossed the corrosion thresholds, after about six months. The same study again observed wider cracks and a larger load drop after first cracking in the ECR specimens than in the TEC specimens. Longer-term corrosion and fatigue testing sponsored by IDOT is ongoing.

Infrastructure Applications Where Crack Control Matters Most

Crack control pays off wherever chlorides and moisture are present and repairs are disruptive.

• Bridge decks take deicing salts, heavy truck traffic, and freeze-thaw cycles, and they commonly crack at an early age. IDOT pursued textured bars specifically to reduce deck cracking and hold cracks tighter, and has placed TEC bars in multiple bridge decks. In September 2026, the deck was poured on the first U.S. bridge built entirely with ASTM A1124 reinforcement.
• Marine and coastal structures see constant chloride exposure from seawater and spray, where tolerable crack widths are tighter still.
• Parking structures and exposed slabs collect salt carried in on vehicles and rarely get the maintenance attention that bridges do, so slowing chloride ingress at cracks extends the time to the first repair.

See how coated reinforcement has performed in real structures in our Project Examples.

Performance Benefits of TEC in Crack Control

Taken together, the research points to three benefits of TEC:

1. Crack control. TEC bars produce more numerous, narrower cracks than smooth ECR and perform at or above uncoated bar in flexural and shrinkage tests.
2. Bond. TEC matches uncoated bar in beam-end and lap splice tests, which supports eliminating the coated-bar development length penalty as specifications catch up with the research.
3. Corrosion protection. The fusion-bonded epoxy barrier remains in place beneath the texture, and early chloride exposure testing has shown no corrosion activity on TEC specimens.

There are practical considerations. TEC is a coated product, so it should be shipped, stored, placed, and touched up using the same practices as epoxy-coated bar. EIG’s guidance on Handling Epoxy-Coated Rebar covers bundling, padded supports, storage, and field repair of coating damage.

On cost, a 2023 life-cycle framework from the Illinois Center for Transportation estimated a modestly higher initial material cost for TEC than for ECR, along with a longer interval before the first deck repair, about 57 years compared with about 49. The authors found overall life-cycle costs for the two to be similar and noted that long-term data are still limited. Initial cost also does not capture the savings that come from shorter splice lengths and less congested reinforcing cages when bond equivalence is recognized in design.

Advancing Crack Control and Durability with TEC

The research is consistent across Clemson, Wisconsin, Illinois, and Kansas. Smooth epoxy coatings reduce bond and allow wider concrete cracks. TEC restores bond to the level of uncoated bar and produces finer, better distributed cracking, while keeping the epoxy barrier that protects the steel. Galvanized bar also controls cracking well and relies on sacrificial zinc for protection. Uncoated bar bonds well but offers no protection once chlorides reach it.

The right choice depends on exposure, service life targets, and how difficult future repairs will be. For structures where deicing salts, seawater, or long design lives are in play, TEC gives designers a way to address crack control and corrosion protection with a single bar.

Explore technical papers, specification guidance, and research summaries from the Epoxy Interest Group. Learn More.

Frequently Asked Questions

Why does concrete crack?

Concrete cracks when tensile stress exceeds its tensile strength. Common causes are drying and plastic shrinkage, temperature changes against restraint, bending under load, freeze-thaw damage, and the expansion of corroding steel.

Are small cracks in reinforced concrete a problem?

Fine cracks are expected in reinforced concrete and are accounted for in design. They become a durability concern when they are wide enough to let water and chlorides reach the reinforcement quickly, which is why crack width and distribution matter.

Does epoxy-coated rebar cause wider cracks?

Smooth epoxy-coated bars have lower bond than uncoated bars, and studies show they tend to form fewer, wider cracks. Textured epoxy-coated bars under ASTM A1124 restore bond to the level of uncoated bar and produce finer cracking.

Is TEC better than galvanized rebar for crack control?

In the Clemson comparison, TEC and galvanized bars both outperformed uncoated and smooth epoxy-coated bars, and the researchers found neither clearly superior. The two systems protect steel differently: TEC with an epoxy barrier and galvanized bar with sacrificial zinc.

References

1. Murphy, A. J. (2021). Comparison of Flexural Cracking in Reinforced Concrete Beams with Different Rebar Coatings. M.S. thesis, Clemson University. open.clemson.edu/all_theses/3535
2. Ross, B., and Poursaee, A. (2021). Textured Epoxy Coated and Galvanized Reinforcement to Reduce Cracking in Concrete Bridge Decks and Components. WisDOT Project 0092-19-01. rosap.ntl.bts.gov/view/dot/62705
3. Andrawes, B., Perez Claros, E., and Zhang, Z. (2022). Bond Characteristics and Experimental Behavior of Textured Epoxy-Coated Rebars Used in Concrete Bridge Decks. FHWA-ICT-22-001. doi.org/10.36501/0197-9191/22-001
4. Aryal, A. M., Truman, K., Darwin, D., and O’Reilly, M. (2023). Bond Strength of Textured Epoxy-Coated Bars. SL Report 151, University of Kansas Center for Research.
5. Thapa, S., Darwin, D., O’Reilly, M., and Lepage, A. (2025). Beam-End Bond Tests of Textured-Epoxy-Coated No. 6 Reinforcing Bars. SL Report 24-1, University of Kansas Center for Research. hdl.handle.net/1808/35930
6. Danner, K. M. (2025). Corrosion Performance of Coated Steel Bars in Cracked and Uncracked Reinforced Concrete Beams. M.S. thesis, University of Illinois Urbana-Champaign. hdl.handle.net/2142/132695
7. O’Reilly, M., Farshadfar, O., Darwin, D., Browning, J., and Locke, C. E. (2018). Corrosion-Induced Concrete Cracking for Uncoated and Galvanized Reinforcing Bars. ACI Materials Journal, 115(6).
8. Gombeda, M. J., Lallas, Z. N., and Rivera, E. (2023). Optimal Approach for Addressing Reinforcement Corrosion for Concrete Bridge Decks in Illinois, Phase II. FHWA-ICT-23-004. doi.org/10.36501/0197-9191/23-005
9. Tobias, D. H. (2025). Textured Rebar Update. Illinois DOT presentation, NC2 Spring 2025 meeting.