In a groundbreaking study published in the journal *Developments in the Built Environment* (translated from Thai as “Advancements in the Built Environment”), researchers have discovered a novel way to enhance recycled aggregate concrete using graphene quantum dots (GQDs). This innovation could revolutionize the construction industry by transforming waste materials from building demolitions and out-of-service railway sleepers into high-performance concrete.
The lead author, Anand Raj from the Advanced Railway Infrastructure, Innovation and Systems Engineering (ARIISE) Research Unit at Chulalongkorn University in Bangkok, Thailand, explains the significance of this research: “The disposal of construction and demolition waste (CDW) is a pressing environmental challenge. By recycling CDW as coarse aggregate in concrete, we can conserve natural resources. However, this often reduces strength and durability due to residues, increased porosity, and the potential formation of ettringite.”
Raj’s team investigated the use of recycled coarse aggregates from CDW and dismantled railway sleepers, combined with GQDs, to enhance concrete performance. They tested eighteen concrete mixes with varying percentages of recycled aggregates, both with and without the addition of 0.3% GQDs by weight of cement.
The results were promising. Concrete made with recycled aggregates from random sources showed a reduction in both compressive and flexural strengths by 21.7% and 18.2%, respectively, primarily due to increased porosity and ettringite formation. However, the addition of GQDs improved both compressive and flexural strengths by about 15% by promoting the formation of calcium silicate hydrate (C-S-H) gel.
Concrete incorporating recycled aggregates from used railway sleepers exhibited a smaller reduction in compressive strength, up to 11%, and a lower reduction in flexural strength, reaching up to 7%. Microstructural analysis revealed that GQDs facilitated the formation of crystalline precipitates, enhancing both the strength and durability of the concrete.
This research has significant commercial implications for the construction and energy sectors. By enhancing the performance of recycled aggregate concrete, this innovation could lead to more sustainable and cost-effective building materials. It also opens up new possibilities for the energy sector, where high-performance concrete is crucial for infrastructure projects.
As Raj notes, “Our new insights suggest that incorporating GQDs into concrete with recycled aggregates not only helps conserve environmental resources but also enhances overall material performance.” This breakthrough could shape future developments in the field, paving the way for more sustainable and efficient construction practices.
The study, published in *Developments in the Built Environment*, offers a glimpse into the future of construction materials, where waste is transformed into high-performance resources, and sustainability is at the forefront of innovation.