Concrete is one of the most widely used construction materials globally, but its production is responsible for significant carbon dioxide emissions. Recent research has aimed to combat this issue by exploring sustainably sourced alternatives, such as rice husk ash (RHA) and advanced additives like carbon nanotubes (CNTs). A recent study delved deep, investigating how the inclusion of RHA and various proportions of multi-walled carbon nanotubes can improve the mechanical properties and durability of concrete.
This research distinguishes itself by evaluating concrete mixtures where 15% of the traditional Portland cement content is replaced by rice husk ash and varying concentrations of multi-walled carbon nanotubes are incorporated. Researchers found substantial enhancements to the concrete's performance, particularly when 0.1% of MWCNTs were added, leading to significant improvements without compromising workability.
The mechanical testing showed promising results. With the addition of just 0.1% MWCNTs, the concrete demonstrated improved density and elastic modulus, alongside reduced sorptivity and drying shrinkage. Specifically, the 28-day sorptivity dropped as much as 28.76%, showcasing superior resistance to water absorption compared to traditional mixtures.
Further testing revealed remarkable findings concerning durability, particularly with resistance to aggressive environmental conditions. When subjected to sulphate and acid attacks, concrete with the right proportion of MWCNTs exhibited reduced mass loss and less decline in compressive strength. For example, losses were reduced between 50.93% and 61.71% after exposure to sulphate for 111 days, compared to the control mixture.
This enhancement is attributed to the unique properties of carbon nanotubes, which not only bridge microcracks but also densify the internal structure of the concrete, creating barriers to harmful agents. Authors of the article highlighted, "Adding 0.1% multi-walled carbon nanotubes and 15% rice husk ash yielded satisfactory results, significantly improving durability compared to concrete without multi-walled carbon nanotubes." This suggests employing CNTs could fundamentally change how concrete materials respond to environmental challenges.
Investigators conducted thorough evaluations of environmental impact, calculating the embodied carbon index for their concrete mixtures. They determined the sustainability of RHA concrete with embedded CNTs is confirmed as it presents lower carbon emissions compared to standard concrete production methods. The CI value of the RHA concrete improved markedly upon the addition of MWCNTs, with reported reductions up to 16.51% for the tensile strength strengths.
While this study showcases significant advancement, it also paves the way for larger implementation and future inquiries. The notable performance of RHA concrete fortified with carbon nanotubes places these materials at the forefront of sustainable construction materials. These findings are promising for future infrastructure projects seeking to lessen their carbon footprint and embrace greener practices.
Researchers advocate for more extensive trials and industrial application of such sustainable materials, which not only utilize agricultural waste but also contribute significantly to reducing the environmental impact of concrete production. The road to sustainable construction is complex, but integrating rice husk ash with cutting-edge technology like CNTs holds great potential for revolutionizing the concrete industry.