March 4, 2024

Finding low-cost, sustainable building materials is important to the environment and to providing affordable housing. Researchers have created a composite building material by replacing sand in concrete and mortar with a common, non-degradable waste product: used disposable diapers.

Access to affordable and adequate housing is a fundamental human right. This is a growing problem, especially in many low-income countries where supply and demand are mismatched.

Building materials are often the most expensive component of home construction, accounting for 80% of the cost. While the use of materials such as natural fibres, earthen materials and industrial construction waste has been explored, concrete remains the mainstay of home construction – indeed, any building – for its strength and durability. But concrete leaves a large carbon footprint.

Researchers at Kitakyushu University in Japan were looking for a way to preserve the benefits of concrete while making it more environmentally friendly and cheaper to produce. They turned to a common non-biodegradable waste: disposable diapers.

In conducting the study, the researchers wanted to address Indonesia’s significant population growth and demand for low-cost housing. Along with population growth comes an increase in waste. Indonesia’s total waste in 2019 was 29.21 million tons; this figure rose to 32.76 million tons in 2020.

according to Maritime Fair Trade, Indonesia ranks sixth globally in terms of disposable diaper usage. Many used diapers are dumped in the country’s rivers and waterways, causing pollution through leached chemicals and microplastics. This research could address two important issues: cleaning up the environment and providing low-cost building alternatives.

The researchers prepared concrete and mortar samples by mixing washed, dried and shredded used disposable diapers with cement, sand, gravel and water. The samples were cured for 28 days. Curing is the process of maintaining sufficient moisture in concrete within a temperature range conducive to cement hydration, the chemical reaction between cement and water that contributes to its strength and durability.

Mixtures containing different proportions of disposable diaper waste were tested to see how much pressure they could withstand before they burst. The researchers then calculated the maximum amount of sand that could be replaced with diaper waste to safely build a house with a floor plan of 43 square meters (36 square metres).

They found they could replace 10 percent of the sand in the concrete needed for the columns and beams in a three-story building with disposable diaper waste. In single-storey homes, this increases to 27 per cent. In terms of the mortar used to make the partition walls, the researchers could replace up to 40 percent of the sand with diaper waste. For the leveling of floors and garden paving, it can replace 9% of sand. They found that exceeding these ratios made the concrete unsuitable for construction.

Overall, the researchers found that up to 8 percent of all the concrete and mortar structures needed to build a single-story house with a floor plan of 36 square meters could be replaced with single-use diaper waste. This equates to 60 cubic feet (1.7 cubic meters) of trash.

“The study concluded that adding used diapers to concrete did not significantly reduce its strength,” the team said. “This shows that using diapers to make composites is feasible, especially in terms of developing environmentally friendly and cost-effective materials.”

The researchers believe their disposable diaper concrete has a wide range of applications beyond building houses in Indonesia. This is important because disposable diapers are the third largest contributor to landfills worldwide. Globally, more than 18 billion disposable diapers end up in landfills each year.

“Regarding the social and economic advantages of this paper, the development of materials can range from low-tech to high-tech,” they said. “These procedures are relatively easy and inexpensive to perform.”

The researchers are aware of the current limitations of using waste diapers as a construction material. On the one hand, there is a need to work with waste disposal facilities to collect used diapers from households and sterilize them. Second, machines that shred used diapers on a large scale will be needed.

Nonetheless, the study highlights the potential of using non-degradable waste as a construction material, addressing sustainability issues and providing low-cost housing.

The study was published in the journal scientific report.

source: Kitakyushu University pass Urik Alert!