実験報告書様式（一般利用課題・成果公開利用）（ ※本報告書は英語で記述してください。ただし、産業利用課題として採択されている方は日本語で記述していただいても結構です。 ）MLF Experimental Report

提出日 Date of Report
Sept 22nd, 2014

課題番号 Project No.

装置責任者 Name of responsible person

2014A0087

Kazuya Aizawa, Stefanus Harjo

実験課題名 Title of experiment

装置名 Name of Instrument/（BL No.）

Measurement of stress distribution along rebar in reinforced concrete using
pulsed neutron diffraction

TAKUMI/ BL19

実験責任者名 Name of principal investigator

実施日 Date of Experiment

Hiroshi Suzuki

June 22nd – June 26th, 2014

所属 Affiliation
Japan Atomic Energy Agency
試料、実験方法、利用の結果得られた主なデータ、考察、結論等を、記述して下さい。（適宜、図表添付のこと）
Please report your samples, experimental method and results, discussion and conclusions. Please add figures andtables for better explanation.
1. 試料 Name of sample(s) and chemical formula, or compositions including physical form.
A ferritic steel deformed-bar (bamboo rebar) with 9.53 mm nominal diameter was embedded in a cylindricalconcrete with 51 mm in diameter and 460 mm in length. The embedded depth of the rebar was 430 mm, andun-bonding region with 110 mm in length was artificially introduced. Three different corrosion rates including
no corrosion were provided using the electrical corrosion method. The current with 20.16 Ah in total was applied
to the specimen for 12 days (lower corrosion rate), providing corrosion products of 219 mg/cm2 in calculation,and that with 34.56 Ah in total was applied to the specimen for 24 days (higher corrosion rate), providing 375
mg/cm2. Very large cracks were observed for the specimen with higher corrosion rate because of swelling ofcorrosion products while the specimen with lower corrosion rate has only small cracks.

2. 実験方法及び結果 （実験がうまくいかなかった場合、その理由を記述してください。）
Experimental method and results.

If you failed to conduct experiment as planned, please describe reasons.

The engineering diffractometer, TAKUMI, installed at BL19 in MLF (Materials and life Science
Experimental Facility) of J-PARC (Japan Proton Accelerator Research Complex) was utilized. The reinforced
concrete specimen mounted in the loading device was set up on the XYZθ positioner, oriented 45° to theincident beam. The gauge volume defined by the incident gauge definition slit and radial collimators was5×5×10 mm3. The high intensity mode with low instrument resolution designed to be Δd/d=0.4 was selected,
and diffraction patterns from the deformed rebar over the range of d-spacing from 0.5 to 2.7 Å weremeasured in the axial and lateral directions simultaneously using both detector banks installed at ±90o. The
average lattice constants in these directions were determined by multi-fitting procedure. The strain
distributions were measured at 10 mm intervals along the deformed rebar under different tensile loadings, i.e.
approximately 30 MPa, 125 MPa and 250 MPa.

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2. 実験方法及び結果（つづき） Experimental method and results (continued)
Figure 1 shows comparison of the axial stress distributions along the embedded rebar with three different
corrosion rates at 250 MPa applied loading. The stress distribution for no corrosion specimen shows similar
result to the previous work published in [1] (2012B0058), i.e. the tensile stress increases towards the end of
the bonding region (x=0) in the anchorage region. The stress distribution for the specimen with lower
corrosion rate is similar to the no corrosion specimen, but the compressive stresses in the bonding region
decreases probably due to stress release that may be caused by the corrosion products. The bond resistancefor the lower corrosion specimen, determined by the slope of the stress distribution in the anchorage region,
is higher than that for no corrosion specimen. Corrosion products may improve mechanical bonding
performance between concrete and rebar. Since it was insufficient to eliminate bonding in the un-bonding
region for the specimen with higher corrosion rate, the applied stress at x=0 mm is 150 MPa, lower thanapplied loading, 250 MPa. The stress distribution for the specimen with higher corrosion rate is quite
different from others. An increase in the tensile stress is observed around large cracks (approximately fromx=20 mm to 200 mm), showing bond deterioration. However, the rebar could not be slipped out fromconcrete because the anchorage region was left from x=200 mm. As described above, the change in the stress
distribution with corrosion rate can be assessed by measuring the stress distribution using neutron diffraction.
The neutron diffraction is expected to bring new knowledge on the bond deterioration mechanism due tocorrosion.
Reference[1] H. Suzuki, K. Kusunoki, Y. Hatanaka, T. Mukai, A. Tasai, M. Kanematsu, K. Kabayama and S. Harjo,
Meas. Sci. Technol. 25 (2014) 025602 (8pp).

300
Higher corrosion
Lower corrosion
No corrosion

250
Axial stress, MPa

200

150
100
500-50-100-100

0100
200
Position along rebar x, mm300Fig. 1 Comparison of axial stress distributions along the embedded rebar withdifferent corrosion rates under 250 MPa loading.

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