Image Credit: Yurchanka Siarhei/Shutterstock.com
Nanotechnology is a division of scientific research and engineering focused on both comprehending and managing matter at the molecular level. It is becoming more common to leverage nanotechnology to improve performance, durability, sustainability, and other qualities of concrete.
The growing interest in nanotechnology includes a variety of applications, including in sustainable civil and environmental engineering. A few of the nanotechnology breakthroughs in these areas range from the improvement of the rheology, durability, and strength attributes of concrete, all of which have been proven to depend on the nanoscopic qualities of various constituents.
Key changes at the nanoscopic level can significantly affect behavior and major characteristics. According to experts, the function of concrete and sustainable construction can be greatly improved using nanotechnology.
A lot of the study on the usage of nanotechnology in concrete has centered on nanostructures, the alteration of these atomic-scale structures, and the fracture mechanism of cement-based products. The purpose of these efforts has been enhancing the bulk qualities of concrete to make thinner structures, achieving quicker setting times and lower levels of environmental impact. Some of the latest developments in this area have focused on using novel and recycled materials as additives.
Nanotechnology has so far been shown to be useful for preventing cracks and decrease shrinkage. The application of nanotechnology tools and nanomaterials to observe and customize the permeability of a concrete system is also being investigated to yield longer-lasting structures.
Nano-engineering is predicted to generate a new generation of customized, multi-purpose, composites with exceptional performance and durability, most likely having an array of novel attributes, including low electrical resistance, self-cleaning, self-healing, and self-sensing capabilities.
To achieve these results, nanomaterials have been of significant interest, as the attributes of concrete are dictated by the various traits of its ingredients. Some of these revolutionary nanomaterials being used in concrete are:
The addition of nanoscale aluminum oxide (nano alumina) to concrete, especially ultra-high-performance concretes (UHPC) significantly reduces setting times.
Micro silica is already a popular concrete additive, and nano-silica has been identified for having significant potential to improve UHPC, with regards to durability and strength. Nano silica has also been found to improve workability at the lowest quantity of superplasticizers. A major drawback is its cost and scarcity in certain parts of the world.
Kaolin is a layered silicate mineral that has many different uses, including medicinal uses. Research has shown that fine-milled nano metakaolin promote the hydration of cement, significantly improve the compressive strength of cement, and reduce water absorption.
Nano clay is nanoparticles of layered mineral silicates, and it is one of the most affordable materials that have shown promising results in polymers.
Typically measuring around 1 nm thick and 70 to 150 nm wide, nano clay particles have a distinct ‘‘platelet” structure that makes them an excellent candidate for nanotechnology. Valuable structural attributes of nano clay include chemical stability, an interlayer space, high hydration capacity, swelling capability, and a high reactivity.
Focusing on C-S-H Gel
One major focus of concrete nanotechnology research is calcium–silicate–hydrate (C–S–H) gel, which is the dominant product produced by the chemical reactions between cement and water.
C–S–H gel has nanoscale characteristics that are challenging to model and investigate. Responsible for structural integrity and other attributes, C-S-H gel is a crucial component with important nanometer features.
The framework of C-S-H is similar to that of clay, with thin strata of solids divided by a spongy gel layer filled with adsorbed water. C-S-H gel is classified into two different categories: low density and high density. While both forms have been researched thoroughly, scientists still do not know how the structures of each kind of C-S-H gel affect the mechanical qualities of concrete material. Broadly speaking, low-density gel appears to be more promising than high-density gel because it readily expands into the porosity, which is the most significant quality of C-S-H gel in concrete.
Researching Carbon Nanotubes in Steel-Reinforced Concrete
The bond strength of steel reinforcements is among the most critical factors in the design of concrete structures. A recent study revealed that incorporating carbon nanotubes (CNTs) can lead to a boost in the bond, compressive and tensile strengths of steel-reinforced concrete compared to control specimens.
In the study, a scanning electron microscope study of both control and CNT specimens revealed that nanotubes were well structured. This indicated that CNTs behave as bridges spanning micro-cracks, and this explains the boost in mechanical qualities of these concrete products.
The study team said the width of steel bars had a major role in failure during pull-out and corrosion testing. Adding CNTs raised the corrosion rate of steel bars, albeit within the recognized risk limits. While positive results were achieved, some great benefits of using CNTs were limited and called “moderate” by the study team.
Resources and Further Reading
Olafusi, O. et al. Application of nanotechnology in concrete and supplementary cementitious materials: a review for sustainable construction. SN Applied Sciences. [Online] Available at: https://link.springer.com/article/10.1007/s42452-019-0600-7
Hassan, A. Effect of Adding Carbon Nanotubes on Corrosion Rates and Steel-Concrete Bond. Scientific Reports. [Online[ Available at: https://www.nature.com/articles/s41598-019-42761-2
Zhan, P. Utilization of nano-metakaolin in concrete: A review. Journal of Building Engineering. [Online] Available at: https://www.sciencedirect.com/science/article/abs/pii/S235271021932128X