Processing fly ash and waste into paving bricks.

Utilizing fly ash from the municipal solid waste incineration plant in Can Tho, Associate Professor Dr. Huynh Trong Phuoc and his colleagues at Can Tho University have successfully researched and produced concrete paving bricks (commonly used for sidewalks and courtyards) with high load-bearing capacity and durability, meeting current technical standards. This research has high practical application as it both solves local environmental problems and creates a scientific and technological foundation for the development of sustainable and circular building materials.

The project team, along with representatives from the Can Tho Center for Application of Advanced Science and Technology, stood on a section of sidewalk paved with bricks made from fly ash aggregate, discussing the effectiveness of the paving bricks after a period of use.

This is the achievement of the scientific research project "Research and reuse of fly ash from municipal solid waste incinerators as raw materials for the production of construction materials" led by Can Tho University, with Assoc. Prof. Dr. Huynh Trong Phuoc as the project leader. The project was carried out from October 2023 to March 2026 and has just been approved by the city's scientific council.

According to statistics, the waste-to-energy plant in Can Tho City discharges an average of about 70 tons of fly ash per day from its municipal solid waste incinerator, equivalent to 25,000 tons per year. If not effectively reused, this fly ash will quickly exceed the temporary storage capacity of the collection area, increasing operating costs, environmental management costs, and long-term safety monitoring costs. Within the scope of this research project, scientists have utilized this fly ash as aggregate for the production of concrete paving bricks (self-interlocking concrete bricks/terrazzo), thus solving the environmental problem while meeting local material needs.

Through numerous complex processes, the research team developed a technological process for manufacturing concrete paving bricks using fly ash from municipal solid waste incineration plants, utilizing at least 50% fly ash as a substitute aggregate. From this, they produced 4,500 concrete paving bricks measuring 300×300×50 mm, meeting current technical standards for flexural strength, water absorption, and surface abrasion resistance. These bricks were then tested on a 400m² section of sidewalk at the Can Tho Center for Advanced Science and Technology Application (An Binh Ward).

Monitoring over a rainy-dry season cycle, the paving layer met the technical requirements. Comparison of soil and water samples before and after a rainy-dry season cycle showed no signs of heavy metal or hazardous component release from the fly ash-based concrete blocks into the surrounding soil and water environment.

In particular, bricks made with fly ash are 10-20% lighter than bricks made from traditional natural aggregates (with crushed stone as the main aggregate and cement as the common binder). This makes transportation and construction more convenient. Currently, brick pressing is done using hydraulic pressing technology, which helps the material mixture to be easily shaped, resulting in high quality and productivity.

The project's results achieved: the bricks meet technical requirements, are manufactured using a production line and methods similar to traditional paving bricks, do not present significant technological barriers, and are competitively priced compared to traditional materials. Environmental analysis showed no adverse impacts during the initial monitoring period.

Associate Professor Dr. Huynh Trong Phuoc, the project leader, stated: “We hope that the management agency and the unit receiving the research results will consider and support the implementation of expanded pilot models in several locations with different ground conditions and exploitation intensity (urban sidewalks, public parks, light yards), in order to assess stability in typical scenarios. Expanding the pilot under various usage conditions will increase representativeness and reliability, providing a basis for issuing guidelines for expanding the research on the application of fly ash from municipal solid waste incineration to other materials with the potential to use recycled aggregates, based on a full assessment of mechanics, durability, and environmental safety. In addition, we hope to consider integrating the research results into pilot programs for the development of environmentally friendly building materials at the local level, linked to the goals of sustainable development, circular economy, and emission reduction in the construction industry.”

Text and photos: LE THU

Source: https://baocantho.com.vn/che-bien-tro-xi-rac-thanh-gach-lat-via-he-a203475.html