Advancements in nano-enabled cement and concrete: Innovative properties and environmental implications

Abstract

As concrete is one of the most used construction materials, lowering its environmental impacts is crucial for a more sustainable built environment. The incorporation of nanomaterials in concrete is a fast-growing field of research because a small amount of nano-compounds can significantly improve some of its properties. Few works have assessed the trade-offs between concrete properties improvement and environmental impacts. This paper reviews the main nanomaterial applications in concrete over the last decade with a focus on their environmental implications. Attention is given to nanotechnology applications boosting innovative properties (i.e., self-compacting, self-cleaning, self-healing, and self-sensing) and green concrete blends incorporating residues, identifying the underlined potential environmental impacts of these applications. Finally, some research gaps and future research directions are identified.The literature analysis showed that some nanomaterials can improve the mechanical properties of concrete, increase durability, and effectively promote the reduction of cement content, which results in a decrease of CO2 emissions. To allow the comparability of studies and relate carbon emissions with mechanical properties, a carbon intensity index is suggested. Despite different environmental impacts may be reduced in nano-enabled blends, cradle-to-gate life cycle assessment studies showed an increase in other impact categories. Nanomaterial production is often highly energy-intensive, not fully optimized, and still performed at the lab scale. Despite nanomaterial incorporation in concrete is increasing, studies regarding its environmental impacts or its potential ecotoxicity and toxicity (e.g., from a safe and sustainable-by-design perspective) are still scarce and require further investigation.