PSI - Issue 64

Eric Williams et al. / Procedia Structural Integrity 64 (2024) 1573–1580 Williams, Annooz, and Myers / Structural Integrity Procedia 00 (2024) 000 – 000

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2.2 Test specimens A simple and straight forward test to examine the bond strength of concrete reinforcement is the pull-out test. For this study, 28 pull-out test specimens were produced in accordance with RILEM Recommendations for the Testing and Use of Construction Materials (1994). Specimens ’ cover was increased to a 152 mm radius to attempt to induce pull-out failure of the rebar and ensure proper confinement of the rebar according to ACI Committee 408 (2003). Two replicants per sample type were produced, and equivalent specimens were created for 13 mm diameter rebar and 19 mm diameter rebar with embedment lengths of 5 bar diameters (d b ). The total height of the concrete portion of the specimen is 10 bar diameters, but for half of this height, the rebar is unbonded to the concrete using a PVC sleeve. The average thickness of the MKPC coating varied between the 13 mm and 19 mm bar sizes. For the 13 mm rebars, the coating thickness was 0.84 mm between the lugs and 0.33 mm on the lugs. For the 19 mm rebars, the coating thickness was 0.64 mm between the lugs and 0.46 mm on the lugs. The thickness could not be uniform along the surface of the rebar due to the surface tension of the MKPC while it was being applied. This is also why the thickness between lugs and on the lugs varies much more for the 13 mm rebar compared to the 19 mm rebar; the surface tension will not let the fluid MKPC settle between the smaller nominal lug spacing of the 13 mm rebar. In current ongoing investigations, thinner mil thicknesses of the MKPC coating are being investigated to better understand how thinner MKPC coatings affect bond behavior as well as anti-corrosion behavior to optimize the effectiveness of both considerations. To simulate a repair scenario in which exposed reinforcement is coated with MKPC and surrounded by a concrete repair material, some specimens were created with a 51 mm cover of repair material that was then surrounded by an additional 101 mm of concrete. Two repair materials were tested: a corrosion inhibitor (CI) repair material and a self-consolidating (SC) repair material. In addition, epoxy-coated bars and uncoated bars were tested. A summary of specimens can be found in Table 4, and a specimen cross-section can be found in Figure 1 for the 5d b 19 mm bar specimen. For the 13 mm bar specimen, the 5d b bonded and unbonded lengths were 65 mm respectively.

Table 4. Types of test specimens. Specimen type ID

Embedment material

Bar diameter ( mm )

Coating

CC13E CC13M CC13S CC19E CC19M CC19S CI13M CI13S CI19M CI19S SC13M SC13S SC19M SC19S

concrete concrete concrete concrete concrete concrete

13 13 13 19 19 19 13 13 19 19 13 13 19 19

Epoxy MKPC None Epoxy MKPC

None

CI repair material CI repair material CI repair material CI repair material SC repair material SC repair material SC repair material SC repair material

MKPC

None

MKPC

None

MKPC

None

MKPC

None