Effect of resin injection on bond recovery for damaged reinforced concrete structure
Manabu Kanematsu (Tokyo University of Science) Mariko Sekine (Tokyo University of Science)
Hiroshi Suzuki（Japan Atomic Energy Agency）
1. Introduction
It is currently important to make best use of many existing reinforced concrete (RC) buildings foryears by effective maintenance. For instance, rebar corrosion in concrete causes bond degradation
between rebar and concrete, resulting in decreasing structural performance of the RC structures. In
our previous experiment in 2014A0087, it is found that cracks induced by swelling of corrosion
products around rebar degrade the bond stress between rebar and concrete. One of available
methods to protect against further corrosion is a resin injection technique, which is widely utilized
for RC buildings to repair cracks in concrete structures damaged by earthquakes and ageddegradation. This technique can inhibit the intrusion of degradation factors, such as water andoxygen, into concrete from outside by filling resin into cracks. In addition, it is expected to recoverfrom bond degradation between rebar and concrete by filling resin into the cracks, since the resin
reaching around rebar would play a role of adhesive between rebar and concrete using BL19(TAKUMI) in J-PARC MLF..
In this experiment, therefore, the effect of the resin injection technique on the bond condition ofRC was evaluated by carrying out the stress measurement using the neutron diffraction technique.
2. Experiment
The RC specimen used in this study is schematically illustrated in Fig. 1(a). A ferritic steel
deformed-bar with 9.53 mm in nominal diameter was embedded in a cylindrical concrete with 51
mm in diameter and 460 mm in length. The embedded depth of the rebar was 430 mm, andun-bonded region with 110 mm in length was artificially introduced for determining the reference
lattice parameter at this region. The specimen mounted on the tensile frame was set up on theTAKUMI diffractometer, and oriented 45 degrees to the incident beam.
The electrical corrosion method was utilized to provide corrosion on the rebar in concrete. The
current with 34.56 Ah in total was applied to the RC specimen for 24 days. Figure 1(b) shows thesurface and inside views of specimens subjected to the corrosion test. Large splitting cracks inducedby swelling of corrosion products can be observed. The stress distributions were measured underFig. 1 (a) A schematic illustration of the RC specimen used in this study and (b) thesurface view of the specimen and inside view of the another specimen with the same
1treatment.

pull-out loading before and after repairing cracks by the epoxy resin injection.
3. Results
Figure 2 shows the axial stress distributions along rebar in the RC specimen subjected to thecorrosion test before and after repairing cracks by the epoxy resin injection. The stress distribution
before repairing was measured about three years ago in 2014A0087. The stress distribution in theregion from X=50 mm to 250 mm exhibits small gradient due to bond degradation around thespitting cracks. After repairing by epoxy resin injection to cracks, the axial stresses decrease
rapidly along rebar toward X=150 mm, showing recovering of bond resistance between rebar andconcrete.

Fig. 2 Axial stress distributions before and after repairing measured by neutron diffraction.

4. Conclusion
In this experiment, the stress measurements of the RC specimen subjected to a corrosion test weremeasured by neutron diffraction before and after repairing cracks by the epoxy resin injection. As aresult, it was found that bond resistance between rebar and concrete can be recovered from bonddegradation due to rebar corrosion by repairing cracks. The resin injection repairing technique caninhibit the intrusion of degradation factors as well as this can play a role of making recovery frombond degradation between rebar and concrete by filling resin into the cracks.
In relevant experiment performed in 2017A0157, filling state of resin in cracks in the same RC
specimen was observed by use of neutron imaging technique. The recovering mechanism of bondresistance will be discussed by comparing the direct inside image of the RC specimen with thestress distribution measured in the current experiment.

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