From buildings that monitor their own structural health to concrete that rehabilitates itself, smart materials are changing the way we build. These innovations offer advanced functionality and efficiency, and promote sustainability and the circular economy.
Smart materials change their properties in response to external changes, like temperature, light, pressure or electricity. These changes are reversible and adaptive.
1. Self-healing concrete
Concrete is one of the most critical components of modern infrastructure, but it often deteriorates over time due to environmental factors like weather and traffic. This deterioration can lead to cracks and structural problems that compromise the safety of buildings and infrastructure.
Self-healing concrete offers a solution by allowing structures to autonomously repair themselves when they develop cracks. This cutting-edge material incorporates microcapsules of a healing agent or bacteria into its composition. When a crack occurs, the capsules rupture and release the healing agents, which then react with moisture and other compounds to seal the crack and restore the structure’s integrity. This innovative technology eliminates the need for manual repairs, saving money and reducing maintenance requirements.
In addition to cost savings, self-healing concrete also reduces the carbon footprint of construction projects by eliminating the need for additional materials and minimizing waste. This revolutionary material can also extend the lifespan of existing structures, reducing the need for costly replacements and improving the safety of occupants.
USC Viterbi School of Engineering researchers have developed a way to use bacteria to self-heal concrete, using a process known as biomineralization. The team replaced the natural aggregates in concrete with engineered ones that contained healing minerals, then mixed the concrete and added water to create a paste-like material. They then embedded a 2D network of microchannels in the concrete and struck the formwork, creating walls with a self-healing capacity.
2. Self-sensing concrete
Traditionally, electric-resistance strain gauges and piezoelectric strain sensors are used in concrete structures to evaluate its strength and durability. However, they often experience limitations such as limited sensing range and low sensitivity. In contrast, self-sensing concrete uses embedded sensor technology to convert external stimuli into structural health monitoring (SHM) data that can be monitored in real time.
This type of smart concrete consists of a mixture of traditional materials and conductive fillers such as carbon black, short and continuous carbon fibers, steel slag, nickel powder, magnetic fly ash, graphite powder and carbon nanomaterials functional fillers to create an electrical network. By varying the amount and concentration of these fillers, different sensing properties can be achieved. For example, adding CNT/CFs extends and stabilizes conductive paths, which can improve the performance of sensing concrete in mechanical deformation.
Another important aspect of sensing concrete is its ability to withstand environmental changes and maintain a stable conductive property. This is mainly due to the fact that the conductive properties of concrete are influenced by moisture content, thermal expansion and external force.
Sensing concrete has the potential to transform the construction industry, making it more environmentally friendly and efficient. Moreover, it will allow for more proactive measures against damage and enhanced occupant safety. With continued research, it is expected that this next-generation material will continue to grow in popularity and eventually disrupt the sector for good.
3. Self-tinting glass
From drugs that release at the first signs of infection to buildings and structures that react to weather conditions, materials science continues to make discoveries that could revolutionize the world. These ‘smart’ materials are used to enhance structural performance and energy efficiency, thereby reducing construction costs and increasing longevity of buildings and structures.
Smart glass is a prime example of such innovative construction technology. It is a transparent material that changes its transparency in response to external stimuli. It is based on electrochromic materials and operates with either transformers or controllers which can be controlled manually or automatically.
Kinestral, a California-based company, developed a smart window called Halio that uses electrochromic glass and is capable of changing its transparency with an electric voltage or current. This glass can be turned on and off using smartphones, tablets, wall mounted controls or voice activation, allowing tenants to manage light and privacy levels depending on the day of the week and the season.
Another interesting smart glass product is PDLC (polymer displacive liquid crystal) that can be changed from clear to opaque with the application of a varying amount of voltage or current. This technology can be integrated into buildings with IoT sensors and provides a range of benefits, including energy savings and improved comfort for building tenants. It is also easier to install than traditional dynamic glass.
4. Shape-memory alloys
Shape memory alloys are a unique class of metals that exhibit two-way shape memory. They are able to recover apparent permanent strains after being deformed mechanically, and then heated. The reason they do this is that they have two stable phases – the high-temperature phase, called austenite, and the low-temperature phase, called martensite (martensite can be in one of two forms: twinned or detwinned). These crystal structures are not as rigid as those found in ordinary metals, and their properties are controlled by thermal-mechanical effects such as shear lattice distortion and transformation-induced plasticity.
These characteristics make them perfect for construction applications, as they can withstand repeated stress cycles without any loss in functionality. They can also be easily deformed and then reheated, allowing for simple structural changes and reducing overall construction times.
Currently, shape-memory alloys are most popular as rotary actuators for use in applications like hermetic joints in metal tubing and replacement of sensor-actuator closed loop systems that control water temperature. They can also be used for a variety of other tasks, such as the positioning of sensors or relocating equipment within a building.
As the technology continues to advance, it is likely that shape-memory alloys will be used in a wider range of applications across construction. This will drive market growth, and prominent players in the industry are focusing on research and development to explore new uses for this revolutionary material.