Analysis of Dangerously Rushed Apartment Construction (1): Expert Warns '90 Years Behind Japan, Durability at Most 10-15 Years' - Severely Lacking Materials, Zero Power Sources...

◆ Forced Labor Construction Projects

North Korea is notorious for its rushed construction projects. Under the propaganda slogan of "speed battles," large numbers of workers are mobilized day and night at construction and civil engineering sites. The goal is to push people to achieve unreasonable completion deadlines. These reckless large-scale construction projects have been repeated for over 60 years, with many lives lost in the past due to accidents during construction and building collapses. Near the lower reaches of the Yalu River, which was damaged by heavy rains in late July, construction of dozens of apartment buildings exclusively for disaster victims has been forced since early August. The Kim Jong-un regime ordered completion by December. But can people really live safely in these "speed battle" apartments? We asked an expert to analyze photos and videos taken at the site. (HONG Mari)

◆ Expert Analysis of Ruins-like Shoddy Construction Site

In mid-October, ASIAPRESS reported on the construction sites of apartments for disaster victims in Sinuiju City and Uiju County, North Pyongan Province, from the Chinese side of the border.

"Are these just ruins?" was our reporters’ honest first impression seeing the site from afar. Shaky formwork, stained outer walls, carelessly protruding reinforcement bars. Many workers crowded unusually densely on scaffolding made of thin, uneven lumber that looked hastily gathered together - even to a non-expert, this all appeared likely to cause serious problems after the apartments were completed.

How would it look to an expert? We showed photos and videos taken with a super-telephoto lens at the site to Professor Keiichi Imamoto of the Tokyo University of Science, who specializes in concrete strength and durability, and asked about the characteristics and problems of apartment construction.

◆ Removing Forms Before Concrete Sets... "Appears Extremely Rushed"

-- What can you tell from looking at photos of North Korean construction sites?

Imamoto: First, you can see they're rushing the construction a great deal. Looking at the concrete color in this photo (①), it appears they're removing the forms (stripping) and reusing them for upper floors before the concrete has sufficiently hardened after pouring.

-- Generally, how long should forms be left in place?

Imamoto: With temperatures around 20 degrees, Japanese specifications require leaving forms for 4-6 days for concrete to gain sufficient strength. At minimum 2-3 days. But from the photos, they appear to be removing them after at most one day, possibly even just half a day.

◆ Risk of Cracks and Spalling

-- What can happen if forms are removed too early?

Imamoto: It causes serious problems with building durability. Technically speaking, concrete is alkaline. While steel reinforcement rusts in air, it doesn't rust in an alkaline environment. However, concrete's alkalinity becomes neutralized by reacting with carbon dioxide (slightly acidic) in the air, and when this reaches the reinforcement, it starts to rust. Therefore, reinforced concrete structures are more durable when the concrete is stronger and denser, as this reaction is harder to progress.

However, when forms are removed too early, the concrete structure naturally can't become sufficiently dense, allowing air's carbon dioxide and moisture to reach the reinforcement faster. In other words, the concrete's lifespan...cracks and spalling (falling off) occur sooner.

◆ Zero Mechanical Power, Everything Done by Manual Labor

-- There seem to be many people at the site.

Imamoto: There appears to be no power source (for operating machinery). Normally, construction sites use concrete mixers, pump trucks, vibrators for compacting, etc. Power sources like electricity and fuel are needed to operate these machines.

However, in the photos, no such power sources are visible, and areas that could be finished with minimal workers if machines were available are being covered by manual labor. That's why there are so many people. They might not have the resources to run important power sources at the construction site.