Author Name : Avantika Chamoli
Predominantly over the last hundred years, infrastructure has been dependent on the traditional materials like steel, concrete, timber etc. Their functions have been static and singular. Let us take structural steel as an example; Steel resists tension but it is blind to rest of the things the material is a part of. We find the faults only when the structure is inspected or either the damage is visible to the naked eyes. But what if the materials responded to the stimuli by themselves? The solution to several of such problems is SMART MATERIALS.
What are smart materials?
Smart materials are engineered materials which respond to environmental factors like temperature fluctuations, freezing thawing cycles, humidity, wind load etc, and act accordingly. These materials behave dynamically unlike prosaic materials who are passive in nature. Smart materials are not restricted to do a single task but also fulfill the end objective that is protecting the structure from sudden failure. They detect and respond accordingly.
Examples of smart materials used in infrastructures are:
1. Self- Healing Concrete:
2. Shape memory alloys:
3. Piezoelectric materials
4. Electroactive materials
5. Embedded optic fiber sensors
From passive to responsive infrastructures
We all know infrastructure has been passive since the very start. Introduction of smart materials breaks the loop. For example: the bridges were designed to withstand the known forces like predicted live loads, wind loads and seismic loads. The intensity of these loads was calculated beforehand according to the terrain, utility and previous data of the place along with the factor of safety. The bridge is checked by regular inspection and many a times the failure might not visible beforehand. Introduction of smart materials like embedded optical fibers and self-healing concrete exhibits a prominent upgrade in material science. These materials detect, resist and even perform the needful changes required making the structure responsive. In civil engineering the ultimate goal has always been safety, comfort and cost and smart materials checks all these three parameters. This shifts the major goal from just trying to resist inevitable damages to using materials which actually detect, respond and correct the damage.
Smart materials and their application in infrastructures:
Usage of smart materials is a sensible choice because by detecting or healing before the actual loss not only reduces economic cost but also enhances sustainability and safety. Some of the applications of these materials are:
1. Self- healing concrete:
We all know the most critical issue faced due to concrete is its cracking. Once a crack appears water and other elements get to the core, causing corrosion which leads to deterioration of the life span of the respective structure by years. A crack is detected only after it is visible. Self-healing concrete is a mixture of specialized agents like dormant bacteria sources (for e.g. bacillus), chemical capsules and superabsorbent polymers. Whenever a crack occurs, the water seeps in, which wakes up the bacteria, it feeds and precipitates calcium carbonate which fills the cracks. There is one more microencapsulation approach. The self-healing ability enhances durability and life span of the structure. This material can be used in various places in future:
and temperature fluctuations. Self-healing concrete are very beneficial in these situations
Tunnels and groundwater structures: These structures are continuously exposed to groundwater pressure. High pressure can easily lead to cracks and if water seeps into these cracks the whole structure fails. Hence self-healing concrete is the best choice in c.
2. Light emitting cement:
Light emitting cement is also known as luminescent or photoluminescent cement. These cement particles absorb and store light during the daytime and reflect it in the night time. This material is extremely useful in pathways, road demarcations and in the mitigation of accidents caused by poor lighting. In India, poor road lighting is a critical infrastructural hazard that contributes significantly to severe nighttime collisions and fatalities, According to The Times of India, suggests that according to experts about 15% of all road accidents and deaths on Indian Highways occur due to poor illumination.
3. Shape-memory alloys:
Shape-memory alloys are those which return to their initial shape when the temperature rises. Such materials are being analyzed for application in high seismic zones as they can retain their original shape even after high deformation. This would increase the safety of the structure and also reduce the cost which could have been increased in repairing the damage done by the earthquake.
4. Embedded fiber optic sensors:
These fibers are embedded into the materials. They record various significant structural parameters like stress, strain, temperature etc. They provide real time monitoring facility. These sensors are one of the greatest inventions of civil engineering. These preserve the structural integrity and boost the safety. These sensors can be used in dams and other critical structures to detect and mitigate the hazard beforehand.
5. World-wide structures which used smart materials
The Millennium Bridge (London) – embedded structural sensors are used
TU Delft Underpass (Delft, Netherlands) – self-healing concrete is used
One Central Park (Sydney, Australia)- photo-reflective smart coatings used
Akashi Kaykio Bridge (Japan)- shape-memory alloys are used
There are various Indian projects which have utilised smart materials like:
Mumbai Metro Line 3 (Aqua Line)
State Highway-141 (Rakskoppa–Sutagatti, Karnataka)
ABCD Building (Administrative and Business Centre of Dholera)
Conclusion:
I believe that smart materials can transform the future of infrastructure. Though the change will be not be smooth because these materials have their own drawbacks. Some of them include high initial cost, materials utilization span, maintenance etc. These materials are still to be researched in depth for their swift and dominant use. On the other side of the coin, these materials address the most critical problems of infrastructure including prevention from catastrophic failure, reduction in maintenance cost and major decrease in inspection work.
The main emphasis would be on cost reduction, validation and standardization of smart materials rather than inventions in the coming decades. For nor smart materials cannot completely substitute but can surely add a layer of safety and convenience onto the conventional materials.
