Smart Paint to Detect Micro Cracks in Infrastructure Buildings

Civil infrastructure systems are large in nature and their deterioration process is quite complex as they are subjected to a coupled mechanical-environmental damage. Reliable health monitoring, including nondestructive evaluation, is an essential part of the feedback and monitoring system for infrastructures. Engineers are often caught by surprise when major structures collapse, because they’re so big and so hard to inspect. But a new innovation could make monitoring as simple as a new paint job!

Monitoring of civil structures using integrated wireless sensor technologies has been growing at a rapid pace in recent years. This is driven by industrial demand for sensor-based asset management to control maintenance cost, improve safety and mitigate unforeseen catastrophic failures. Developments in micro-fabrication and smart materials have led to the development of smart wireless sensors to monitor the structural performance of civil structures such as bridges, roads, tunnels and wind turbines. This research presents a new nanocomposite smart paint to detect structural damage and monitor key parameters affecting the durability of concrete structures. A low-cost green nanotechnology approach is used to fabricate the smart paint, consisting of recycled by-product fly-ash geopolymer matrix with carbon nanotube networks.

The microscopic structural problems that cause mines to collapse, wind turbines to crash, and bridges to fail are often impossible to detect before it’s too late. Even when they aren’t, traditional structural sensors can cost millions of dollars each year to maintain.

An innovative low-cost smart paint that can detect microscopic faults in wind turbines, mines and bridges before structural damage occurs is developed by researchers at the University of Strathclyde in Glasgow, Scotland and a team consists of Dr. Mohamed Saafi and David McGahon The environmentally-friendly paint uses nanotechnology to detect movement in large structures, and could shape the future of safety monitoring. Traditional methods of assessing large structures are complex, time consuming and use expensive instrumentation, with costs spiralling large amount of money each year.

However, the smart paint costs just a fraction of the cost and can be simply sprayed onto any surface, with electrodes attached to detect structural damage long before failure occurs. The engineers argue that the paint can do the work of the currently used "expensive instrumentation" or human inspectors at a fraction of the cost.There are no limitations as to where it could be used and the low-cost nature gives it a significant advantage over the current options available in the industry. The process of producing and applying the paint also gives it an advantage as no expertise is required and monitoring itself is straightforward.

The paint, which is made out of carbon nanotubes and fly ash, is sprayed onto surfaces much like any other kind of paint. It is aligned in precise manner which are capable of carrying an electrical current.   But this paint is special—it communicates wirelessly with battery-powered electrodes that are attached to the structure to detect structural micro-cracks. When a structural deficiency occurs in the structure, the nanotubes will start to bend.  This will cause a change in the conductivity of the current and engineers will be able to pinpoint the location of the structural deficiency.  Due to the contents of the paint, this is also an environmentally friendly product.

Typically, the process of monitoring the structural integrity of these types of structures can be quite costly.  It involves heavy equipment such as lifts and highly trained personnel.  The inspections are also visual, so most cracks and faults are not detected until they can be seen with the naked eye.  At this point, the structure will mostly likely need more money to fix, and the safety of the structure may already be in question.  The new smart paint will help detect areas of concern possibly even before they become a threat to the structural integrity of the structure, and hopefully this will help prevent failures and costly repairs.

Dr. Saafi said, "The paint is interfaced with wireless communication nodes with power harvesting and warning capability to remotely detect any unseen damage, such as micro-cracks in a wind turbine concrete foundation."  Energy harvesting methods might include using the vibrations of cars or trains going through a tunnel. The idea is to make it more sustainable so you're not running out to your bridge or structure to change the battery all the time. The research team is also examining the possibility of incorporating electrical impedance tomography technology into a structure to help locate cracks. This technology creates a conductivity map. If a change in conductivity indicates a crack, a finite element model will show the exact location within the structure. The researchers have been trying to discover the exact percentage of carbon nanotubes needed to make the product cost-effective. They have also conducted bending tests using strain sensors. Further tests will be carried out in the next couple of months. The smart paint technology could have far-reaching implications for the way we monitor the safety of large structures all over the world.

There are no limitations as to where it could be used and the low-cost nature gives it a significant advantage over the current options available in the industry. The process of producing and applying the paint also gives it an advantage as no expertise is required and monitoring itself is straight forward. There are no limitations as to where it could be used and the low-cost nature gives it a significant advantage over the current options available in the industry. The process of producing and applying the paint also gives it an advantage as no expertise is required and monitoring itself is straightforward.

 The smart paint offers several advantages compared with current sensor technologies including high compatibility with concrete hosting material, excellent durability and high conductivity. The smart paint is designed to be interfaced with wireless nodes to form a wireless sensor network for remote monitoring of civil infrastructure. The smart paint represents a significant development and is one that has possibly been overlooked as a viable solution because research tends to focus on high-tech options that look to eliminate human control. Our research shows that by maintaining the human element the costs can be vastly reduced without an impact on effectiveness.

References:

http://www.strath.ac.uk/media/departments/dmem/rpd2013/rpd_eBooklet.pdf

http://www.strath.ac.uk/civeng/news/smartpaintcouldrevolutionisestructuralsafety/

http://www.wired.co.uk/news/archive/2012-01/31/smart-paint-detects-faults