In the construction of power plants, designers and constructors will give priority to the use of high-quality concrete and other building materials in the core.However, a study by Nagoya University found that, thanks to the unique concrete formula, the walls of the old power plant, which has ceased to operate, have actually become stronger over time.It is reported that concrete structures based on ordinary cement will need to be repaired after being immersed in seawater for decades.
Data chart: hamaoka nuclear power station, Japan (from:wiki / CC BY-SA 3.0）
By contrast, the Italian maritime barrier, which has been tested for more than 2000 years, is still standing. A recent study has uncovered the mystery of this phenomenon.
The researchers pointed out that the original composition of ancient Roman concrete contained volcanic ash that could be dissolved when salt water penetrated, and then formed some kind of bauxite. This unique formula could make the concrete more solid with more use.
Unfortunately, although this ingredient sounds like the perfect additive to enhance the strength of cement, the actual operation is quite difficult.
To make such crystals, it is necessary to reach a temperature above 70 ℃ (158 ℃) in the laboratory, which will weaken the strength of the concrete itself.
In the wild, it seems that some other type of chemical process can produce minerals at lower temperatures and strengthen the structure of concrete.
Previously, we have found this fact on the ancient Roman seawall. Now, researchers from Nagoya University have witnessed the process on the walls of the nuclear power plant.
Research Map (from ScienceDirect)
It is reported that the researchers took samples from a thick concrete wall and a flat plate of unit 1 of Japan's hamaoka nuclear power plant. The device has been operating at full power for 16.5 years from 1976 to 2009, exposing the walls to 40 ~ 55 ℃ (104 ~ 131 ℃).
Surprisingly, aluminum tobermorite was also detected in the samples. Through calculation, the research team believes that the strength of the concrete wall has increased more than three times compared with the early stage.
Research correspondent ippei Maruyama said: "we found that this kind of reaction is similar to the concrete in ancient Rome, which can greatly enhance the strength of the power plant walls.".
(photo from:Nagoya University)
After careful inspection, the research team detected retained water in the wall, which reacted with silicate and other minerals in the concrete, increased the alkali content of the wall, and at the same time, more silicon and aluminum ions could be used for reaction, finally forming a unique structure.
Looking forward to the future, the researchers hope that this discovery can improve the concrete formula, so that we can use stronger, environmentally friendly and durable concrete buildings as soon as possible.
The original title is "long term use of modern Portland cement concrete: the impact of Al tobermorite formation".