Colombian engineer uses coconut shells to extend concrete lifespan

In Colombia, a new approach to construction materials is emerging through the innovative use of coconut shells. Physical engineer Miguel Angel Gomez Aristizabal, a master's student at the National University of Colombia, is transforming these shells into carbon nanotubes to enhance cement's durability. These nanotubes, derived from agro-industrial waste, reinforce cement by reducing its permeability, thereby delaying steel corrosion and extending the lifespan of structures.

Gomez Aristizabal's research involves a process where coconut shells are subjected to pyrolysis to produce biochar. This material is then combined with metal salts and exposed to microwave irradiation to synthesize carbon nanotubes. The nanotubes' surfaces are modified to ensure even dispersion in water, preventing clumping during testing.

The study compared cement samples with and without nanotubes, including commercial variants, under saline conditions simulating coastal environments. Results indicated that coconut shell-derived nanotubes reduced steel corrosion rates by 50% to 70% in early stages. Although commercial nanotubes initially performed better, the research highlights the potential of using waste materials for nanotube production.

While concrete is typically perceived as impermeable, water and salts can penetrate over time, leading to steel corrosion and structural damage. The nanotubes act as a barrier, delaying the onset of corrosion by hindering the passage of corrosive agents through the cement.

The most significant protective effect of the nanotubes was observed during the initial hardening phase of cement. As the material densifies naturally, the protective differences between samples diminish. The research focused on the nanotubes' ability to delay steel corrosion, with future studies aimed at incorporating them into concrete mixtures used in construction.

The ultimate goal is to apply this technology in structures exposed to harsh conditions, such as those in coastal areas, to extend their service life and reduce maintenance costs. This research underscores the potential of carbon nanotubes derived from coconut shells as a sustainable alternative in the construction industry.