This group of people used diapers to build houses because they didn’t have enough sand?

In May 2023, a paper was published in Scientific Reports published by Nature Research. Siswanti Zuraida and two other researchers from Kitakyushu University in Japan used a special material to build a house, which is diapers.

Screenshots of related papers

Researchers have found that crushed disposable diapers can be added to concrete and mortar used in single-story buildings. Crushed disposable diapers can replace up to 10% of the sand used in structural columns and beams without changing the original bearing capacity of the house. They even used these materials to build a small house in Indonesia.

Faced with such a "smelly" news, you may be lost in thought. Replacing sand with discarded diapers can reduce garbage, which sounds environmentally friendly. But how much is the saved sand worth? Looking at this paper more carefully, the author Siswanti Zuraida is from Indonesia. The purpose of this study is to alleviate the problem of lack of building materials in Indonesia due to urbanization and population growth.

However, Indonesia is a country consisting of more than 17,000 islands. Logically, the last thing a country like this should lack is sand. This makes people wonder, are these people really doing research?

The front facade of a prototype house built with diapers. Image source: Scientific Reports

Don't rush to mock. There is a reason why this paper was reported in the journal Scientific Reports.

Careful readers may have noticed that we used "sand" instead of "sand" in the previous article. These two are not the same thing. In the dictionary, sand refers to very small rock powder, while sand is a tiny rock powder. The difference of "very" is because the two are different in size. In the industrial field, "sand" is a type of soil with certain quality requirements and is an important material in modern society. For example, sand is used to make mortar in construction, silicon dioxide is extracted from sand to make glass, and silicon is also extracted from sand to make chips.

Therefore, although these island countries have vast beaches and are not short of "sand", they are really short of "sand". Therefore, the seemingly inexhaustible "sand" cannot actually replace "sand" as a building material or manufacturing material. And "sand" is really not enough.

Can't we use the sand on the beach or in the sea? Copyrighted images in the gallery, reprinting and using may cause copyright disputes

Where does the sand come from?

Similar to fine sand, sand is also formed by the weathering and erosion of rocks, except that the particle size of sand is larger than that of sand. The main component of sand is silicon dioxide, but it also contains various impurities, so it will appear in different colors.

Generally speaking, sand is divided into three categories:

One is the sand in the desert;

One is the sea sand at the seaside;

Another type is river sand.

The biggest difference between these three types of sand is their particle size and smoothness. After a long period of friction, the sand in the desert and the sea sand have particles only a few tenths of a millimeter and a very smooth surface. In contrast, the diameter of river sand is about 1 mm and the surface is rougher.

This difference is directly the difference between what can be used and what cannot be used in the field of construction. The most commonly used concrete in modern construction requires mixing raw materials such as cement and mortar. The mortar cannot be too fine, and river sand is generally used. The sand in the desert is too small and too slippery. If it is used to build a house, the strength of the concrete will not meet the standard. Dubai, the capital of the United Arab Emirates, is located in the desert, but it still imports a large amount of river sand for construction.

Earlier news from Xinhua News Agency about Dubai importing sand. Image taken from Xinhuanet article "The Ignored "Sand Crisis""

Sea sand contains a lot of salt and is also not suitable for construction. When sea sand is used to make concrete, after a period of time, the walls or ceilings of the building will peel off, revealing the steel bars inside. In Taiwan Province of my country, this kind of house built with sea sand is called a sea sand house, which is easy to become a dangerous building. Even if it is not dangerous, the quality of this kind of house is very poor. Some unscrupulous businessmen sell inferior sea sand houses as good ones, which often causes disputes.

Desert sand and sea sand are not acceptable, so the only option left is river sand. In the past few decades, if there was a river near your hometown, you might often see sand mining ships working back and forth. The river sand collected was used for construction.

River sand is an important building material that many countries have to import. In the past, when China's economy had just taken off, the sand needed for construction was limited, and river sand seemed inexhaustible. In order to earn foreign exchange, China could export some river sand every year. Later, as China's urbanization process continued to accelerate, it became a river sand importing country. The price of river sand has also doubled. If you search the news, you will find that in the past few years, some areas have even restricted river sand from leaving the local area. The reason behind this is that river sand is too precious.

River sand mining site. Copyright image. Reprinting and using may cause copyright disputes.

In addition, river sand mining actually causes serious ecological damage. Illegal sand mining ships dig holes in the riverbed, which not only affects local organisms, but also changes the topography of the riverbed, affects downstream bridges, embankments and pipelines, affects the water quality and water level of the area, and even endangers river flood control. Therefore, in 2022, the General Office of the CPC Central Committee and the General Office of the State Council issued the "Opinions on Comprehensively Implementing the River Chief System", which includes the content of cleaning up and rectifying illegal sand mining. The shortage of sand has caused huge profits from sand. If it is not strictly managed, sand mining may cause big problems.

Seeing this, you will understand the intentions of the three scientists.
In terms of the amount of sand, there is enough in many places. However, river sand used to build houses may not be enough. Replacing some of the sand with garbage such as diapers may not only reduce the amount of garbage, but also save the sand itself. The paper also mentioned that this method of garbage utilization can be used in poor areas to build solid buildings with cheap materials. It seems that this research is worth continuing to see what other cheap materials may replace sand.

What else is sand good for?

After talking about river sand for construction, some people have already thought of the next level. As mentioned earlier, the sand in our country is also in short supply and now we need to rely on imports. Will there be no sand available? Or is it possible that imports are blocked because this most common thing is stuck?

To answer this question, we need to look at some common uses of sand. At present, apart from the sand in concrete, there is no shortage of other construction materials. Concrete has special requirements for sand, and there are other solutions, such as crushing rocks with machines to make artificial sand. The sand produced by this method is naturally not as cheap as the river sand prepared by nature. However, if we do not take this approach and just take it from the river, the damage caused may be more expensive.

Sand has two other uses. One is to remove impurities and make glass from silicon dioxide. This process does not require river sand, and there is no risk of insufficient sand at present. The other key is to extract silicon from sand as a semiconductor material to make chips. This sand is high-purity quartz sand, which can be used in optical fibers, photovoltaic cells, optical equipment, semiconductors and other fields.

In addition to the construction industry, sand is also important in technical fields such as semiconductor manufacturing.

Before 2010, my country needed to import high-purity quartz sand from an American company, which had a huge mine and could produce high-purity quartz sand. After 2010, my country had its own high-purity quartz sand production capacity, with both domestic and imported materials, and no longer dependent on the same company. Seeing this, you can rest assured that high-purity quartz ore resources will not be controlled by a few foreign companies.
To sum up, there is not enough sand, which is a real crisis, mainly because there is less and less high-quality sand used in construction.

my country is cracking down on illegal sand mining while solving the problem of sand production. However, the problem of sand becoming increasingly precious will not disappear and needs to be used with care. Finally, high-purity quartz sand required by the semiconductor and photovoltaic industries is also an important resource. my country currently has production capacity and multiple import channels. Even small sand has resource problems. Research on "building houses with diapers" may become more and more common in the future.

Author: Chen Chao, Master of Cognitive Neuroscience, Beijing Normal University

Review丨Zhu Xuanxuan, Senior Engineer, Beijing Municipal Engineering Design and Research Institute Co., Ltd.