Striving for Better Construction: “KAIZEN PROJECT” Activity Diary Vol. 4

Hello, I’m Nakanishi, a JICA Volunteer currently working at the Provincial Works Supervision Unit in Alotau, Milne Bay Province.

In this series, I share updates on my activities and the local environment. In the previous report, I explained preventive maintenance for road facilities to the staff of the office. This time, I would like to report on a bridge inspection we conducted together, following Japan’s standard bridge inspection guidelines.

Next, we performed a close visual inspection of the joints between the concrete deck and the parapet (Photo 3). If there are steps or irregularities, it may indicate problems with the bearings or abutments that support the deck. Water infiltration from these joints can cause various issues under the bridge. As expected, when we checked underneath, we found white deposits leaking from the concrete deck (Photo 4).

These deposits are called “free lime,” which occurs when calcium in the concrete dissolves in water and crystallizes on the surface. While this mainly affects appearance, if water enters through cracks and causes free lime, it can lead to corrosion of the reinforcing steel inside the concrete. Unfortunately, we could not observe the cracks this time because of formwork left during construction, so we plan to remove it and check the internal condition next time.

Finally, we inspected the abutments. Both sides showed significant scouring around the foundations (Photos 1 and 5). On the starting side, we found a vertical crack about 1.5 mm wide. This likely occurred due to shear stress when the downstream side settled after scouring, while the upstream side remained intact. To monitor this, we marked the crack location and date for future observation (Photo 6).

The project manager who supervised the design and construction of this bridge also joined the inspection. This was a great opportunity to reinforce the importance of regular bridge inspections among the staff. Based on these findings, we will assess the bridge’s condition and discuss appropriate measures together.