A recent study published in Materials explored the potential of using agricultural waste film as a binder in construction composites, offering an alternative to traditional cement slurry.
Study: Recycling of Agricultural Film Wastes for Use as a Binder in Building Composites. Image Credit: XXLPhoto/Shutterstock.com
Background
If you’ve ever wondered what happens to all the plastic wrap used in farming, the answer often isn’t pretty. LDPE, the plastic commonly used in agricultural films, is lightweight, affordable, and durable, but it doesn’t hold up well under prolonged exposure to sun and moisture. Worse, recycling LDPE can be complicated, and improper disposal leads to soil, water, and air pollution.
Given these challenges, scientists have been exploring alternative ways to reuse LDPE waste. One promising idea is to incorporate it into construction materials. But it’s not without hurdles. Previous studies showed that while adding plastic waste to building composites is possible, too much can make the mix harder to work with and reduce the density of the final product. This study dove deeper into the topic to see if LDPE film could genuinely compete with cement slurry as a binder.
Study Overview
The researchers used LDPE waste collected from farms and combined it with sand and gravel from quarries in eastern Poland. To prepare the composites, they followed a four-step process:
- They first determined the melting point of the LDPE recyclate.
- Next, they tested how much of the molten plastic the sand and gravel could absorb (known as maximum aggregate saturation).
- Then, they developed a recipe for the composite with the maximum saturation level.
- Finally, they created additional mixtures by gradually decreasing the aggregate saturation.
The final lineup included 12 mixtures labeled F20 to F100, with the numbers representing the percentage of LDPE waste in the mix by weight. The preparation process involved mixing heated LDPE film waste with pre-heated sand and gravel, adjusting the proportions until the grains were coated with a thin layer of molten plastic.
Once prepared, the composites were put through rigorous testing. They were evaluated for consistency (using the cone drop method), volumetric density, water absorption, compressive strength, and flexural strength. Microscopic analysis using scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy provided additional insight into how well the materials bonded.
Results and Discussion
The study revealed how changing the ratio of LDPE film waste to aggregates affected the properties of the composites. For volumetric density, the F20 mixture (with the least plastic) stood out as the densest, while mixtures with higher plastic content, such as F90 and F100, had significantly lower densities—48.7 % and 50.7 % less than F20, respectively. This trend showed that as more plastic was added, the composites became lighter but less compact.
Water absorption followed a similar pattern. F20 absorbed the most water at 2.19 %, while F100, made entirely of LDPE waste, was completely water-resistant. This suggests that increasing the amount of plastic in the mixture improves water resistance but comes at the cost of other properties.
When it came to compressive strength, F40 performed best, showing the highest resistance to pressure. By comparison, F20 had the lowest compressive strength—71.8 % less than F40. Composites with very high plastic content, such as F90 and F100, also showed reduced compressive strength, at 30.6 % and 44.3 % lower than F40, respectively.
Flexural strength, which measures the material’s ability to resist bending, peaked with the F70 composite. F20, by contrast, had 53.9 % lower flexural strength than F70. The trend continued with mixtures like F80, F90, and F100, which showed decreases of 20.2 %, 25.9 %, and 27.1 %, respectively, compared to F70.
On a closer level, SEM analysis revealed that the recycled LDPE bonded well with the sand and gravel aggregates. The images showed no cracks, voids, or weak spots in the composites, suggesting that the materials maintained good structural integrity regardless of the plastic content.
Conclusion
This study shows that recycled agricultural film waste can be a practical alternative to cement slurry in construction materials. By tweaking the mix of LDPE waste, sand, and gravel, the researchers uncovered some interesting trade-offs—like how more plastic makes the material lighter and water-resistant but can affect strength. F40 stood out for its compressive strength, while F70 was the best at resisting bending. The best part is that these materials can be recycled again, making them a smart choice for eco-friendly construction and giving new life to what would otherwise be plastic waste.
Journal Reference
Zegardło, B., Maraveas, C., Rastawicki, K., Woliński, P., & Bombik, A. (2025). Recycling of Agricultural Film Wastes for Use as a Binder in Building Composites. Materials, 18(2), 251. DOI: 10.3390/ma18020251, https://www.mdpi.com/1996-1944/18/2/251
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