- [기술동향]Fracture-resistant con...
- EVANSTON, Ill. — The bipartisan infrastructure deal will invest $110 billion of new funds for roads, bridges, and major projects over the next five years. But one scientist says rather than patching crumbling roads, it’s time to build better ones.This time of year, construction crews around the country are busy repairing the damage left behind following months of fluctuating temperatures. 173,000 miles of our highways and major roads are in poor condition. As moisture seeps into the pavement and freezes, it expands, causing fractures that eventually lead to potholes.Inside her laboratory, far from the stress of crumbling roads, scientist Ange-Therese Akono is trying to find a solution to the problem.“How can we create a new type of cement that will be more resistant to water, so less porous - that will absorb less water?” asked Akono.Akono, an associate professor of civil and environmental engineering at Northwestern University says longer-lasting material could save taxpayers billions in repairs and help reduce the carbon footprint. She’s been using nano materials to develop what she calls ‘smart concrete.’The concrete, which doesn’t have a snazzy name just yet, is a secret recipe that is combined with a nano compound called "graphene." It’s made up of a single layer of atoms arranged in a honeycomb lattice structure.“We can think of a net that's going to be enmeshed with the grains of cement,” explained Akono. “And that mesh is really, really strong. So that's going to be preventing cracks from propagating. And it's going to hold the cement together.”The mixture tightens up the pores of the concrete at a molecular level. The result is a more water and fracture-resistant building material that she says is more durable and highly functional.“Right now, it's been 30% stronger than the average cement - or the classical cement that we've been using,” said Akono.Better concrete could save billions.According to AAA, 1 in 10 drivers sustains vehicle damage significant enough to need repairs after hitting a pothole. Those damages cost drivers $26.5 billion in 2021 alone. In Indiana - ranked second in the nation for its problems with potholes - they’ve dedicated 155,000-man hours, used 12,200 tons of material and spent $5.7 million on pothole repairs in one recent year.“When you have this cycle of freezing and thawing, then you're going to start propagating cracks. And then those micro-cracks then lead to larger macro cracks and potholes that we have,” said Akono.Aside from the additional headaches caused by traffic congestion due to road repairs, Akono says stronger concrete would also benefit the environment.Concrete is made with a cement mix. Fossil fuels are used to manufacture cement and the chemical process produces additional carbon dioxide which accounts for about 8% of all greenhouse gas emissions worldwide.“If you can increase the strength, if you're going to increase the durability, then we can cut down the volume of concrete or cement needed to be able to achieve a given project,” said Akono.Because in the end, sustainability is the smoothest road into the future, she says. Provided by Denver7 (https://www.thedenverchannel.com)Source : https://www.thedenverchannel.com/news/national/fracture-resistant-concrete-could-help-fight-climate-change
2022.04.05
- [행사정보]8th International Co...
- 8th International Conference on Self-Healing Materials ICSHM-MILANO 2022The conference is the eighth of a successful series encompassing all classes of self-healing materials, which gathered researchers from all around the world steering research in the emergent field of self-healing. A broad spectrum of industries is impacted and represented by the field including aerospace, automotive, transportation, microelectronics, architecture, civil engineering and construction, electronics, medicine. previous editions were held in Yokohama (Japan, 2019), Friedrichshafen (Germany, 2017), Durham, (USA, 2015), Gent (Belgium, 2013), Bath (UK, 2011), Chicago (USA, 2009), Noordwijk aan Zee (Netherlands, 2007) Conference TopicsThe conference aims to collect and to disseminate the latest results of the multidisciplinary international research on selfhealing materials. The conference topics will include (not an exhaustive list):self-healing materials: cementitious, polymers, ceramic and metals, composite materials;self-healing coatings and paints - self-healing materials for functional applications (including self-sensing);self-healing triggering mechanisms, including physical, chemical, other types;self-healing technologies: mineral admixtures, capsules, functionalized fibers/aggregates, shape-memory polymers /alloys, bacteria, vascular systems;bio-inspired materials - characterization methods for self-healing;numerical modelling of self-healing processes;durability and long-term performance of self-healing materials and artefacts;real scale application, scaling-up and commercialization issues;life cycle analysis/societal impact of self-healing materials;Mixed interdisciplinary keynote lectures providing a state of the art overview on horizontal topics delivered by international leaders in R&D on the conference topics will open each conference day. Poster presentations for PhD student projects will be organized with a prize for best paper and presentation. Source : http://www.icshm2022.org/?fbclid=IwAR1LhDokb8sl5QmbBB2SmpFKezNbylVX0tDvHRU4kYcnYsHEDbFc5HWRj3w
2022.03.24
- [기술동향]How DOD’s Old Con...
- The military’s old concrete will repair its own cracks if researchers can pull off what the Defense Advanced Research Project Agency hopes under its new BRACE program. DARPA’s Biological Technologies Office announced the four-and-a-half-year BRACE research program—short for Bio-inspired Restoration of Aged Concrete Edifices—March 17. Companies and research institutions have until April 8 to register for a Proposers Day informational event scheduled for April 13. A Broad Agency Announcement for BRACE should be published “in the coming weeks,” the agency said in a statement. Citing the Defense Department’s concrete airfields and missile silos, the agency acknowledged in the statement that “maintaining and repairing concrete is of increasing strategic importance to both defense and civilian infrastructure.” Surface treatments for repairing cracks are “short-lived and do not address the underlying causes of decay,” so DARPA wants to figure out how concrete can repair itself from within by adding a vascular system, inspired by the arteries and veins in biological organisms, to transport “healing substances” through the concrete, according to the release. DOD also needs new approaches to quickly repair airfields after attacks, DARPA said in a pdf describing the Proposers Day event: “Rapid patching of craters is the current repair strategy to repair runway surfaces after an attack,” according to the pdf. “New approaches are needed that will work with DOD’s Expedient and Expeditionary Airfield Damage Repair (E-ADR) capability to restore airfield operations with a minimal logistical footprint.” New research already suggests that “cross-disciplinary technologies” can impart “self-healing capabilities” to old concrete, according to the statement. The Proposers Day will include cross-disciplinary teaming opportunities. If successful, BRACE will “prevent new damage, shorten repair time, and reduce maintenance costs, allowing for extended infrastructure service life,” said BRACE program manager Matthew J. Pava in the statement. “Today’s DOD has inherited, and relies upon, a significant amount of concrete infrastructure from the 1940s and 1950s that cannot be easily replaced,” Pava said. Research will take place in two technical areas. The first will involve figuring out how to impart existing concrete with vascular systems—which in addition to transporting the healing substances should involve some self-monitoring so people will be able to know the systems are working down deep in the concrete. The second technical area will involve practical ways to put the systems into the concrete and how to maintain and repair them. “While BRACE is focused on DOD applications, our hope is that the technologies generated will have potential civilian benefits as well,” Pava said in the statement. Provided by AIR FORCE (https://www.airforcemag.com)Source : https://www.airforcemag.com/how-dods-old-concrete-infrastructure-could-start-to-fix-itself/
2022.03.24
- [기술동향]Can Concrete Heal I...
- USC researchers create an alternate approach to self-healing concrete that is low cost and upholds the innate strength of the original material.Concrete is the second-most used material in the world after water, favored for its high compressive strength, which allows it to support heavy loads. But concrete also has low tensile strength, meaning it’s easily pulled apart—or cracked–under stress. Changes in temperature or humidity can also make concrete crack. Since it’s difficult to create concrete that doesn’t crack, some are trying instead to create concrete that is self-healing.USC Viterbi School of Engineering researchers created a new method for developing self-healing concrete that replaces the natural aggregates (pieces of rock) in concrete with engineered aggregates that contain healing agents within them. Unlike other methods pursued over the past two decades, their method prioritizes keeping costs low and maintaining other properties of concrete, particularly strength and production method.The researchers, which include Associate Professor of Civil and Environmental Engineering Bora Gencturk and Ph.D. candidate Xiaoying Pan, identified the prevailing methods of self-healing concrete such as adding bacteria, which is activated by chemical reactions resulting from a crack to heal the space. This could also include placing microcapsules containing healing agents inside the concrete, which are activated once the concrete is stressed. These methods, Pan said, are prohibitively expensive, making them impractical in real-world applications.“Normally the price of concrete is around $150 per cubic meter,” she said, “But using bacteria-infused self-healing concrete, that price can increase to $6,000 per cubic meter.”It is not just the cost that is off-putting, she said, but there were other drawbacks, such as the higher-level expertise and technical knowledge required to mix the concrete appropriately that might slow and complicate the construction processes. There were also structural issues, where adding such materials to the concrete results in weakening the concrete’s original compressive strength.To combat these drawbacks and offer a realistic option for self-healing concrete that can be easily adopted by the industry, the researchers proposed creating support inside the concrete that is reminiscent of existing aggregate structures that already help make concrete. These engineered aggregates contain healing agents within them that are activated when they encounter cracks that break them open. The first step in this process, outlined in the team’s recently published research, is figuring out what the best designs are for these engineered aggregates, with regard to providing the best healing result of various types of cracks. Optimal Healing, Without Sacrificing Concrete’s StrengthCracks in concrete, much like degradation of other structures, for example bridges, do not become readily noticeable until they are already quite large or widespread. At this point, repair is costly, requiring workers to identify and measure the crack(s), assess the concrete damage, design the best healing method and prepare the concrete for repair—injection of a glue polymer that needs to completely cure.While self-healing concrete is nothing new, Pan said, previous approaches were not practical or sustainable on a large scale. “Basic reactions could cure cracks a few micrometers in size, but not larger.” About 20 years ago, she said, materials scientists began developing new methods that would allow for bacteria or microcapsules containing self-healing materials to be mixed into the concrete and activated upon stress/ impact. However, these approaches were not only expensive, she said, but “anytime you put holes in concrete, it will naturally create weaknesses.”Understanding that the rocklike aggregate structures within concrete help to create its strength, the USC Viterbi researchers realized that recreating those structures could help achieve a self-healing concrete, while creating a shell within which the self-healing material could be infused. In their most recent paper for Construction and Building Materials, the researchers created a computational model that helps identify which shape and size of engineered aggregate is optimal for varying sizes of cracks. “When we have different configurations of concrete structures,” Pan said, “those structures tend to have different crack sizes. In that case, we want to know how to select the best size and shape for the engineered aggregate to create an optimal healing effect.”The research, Pan said, applies to other self-healing concrete approaches, not just the engineered aggregate approach they favor. “It’s a mathematical model, so it can apply to other self-healing concrete materials that put healing materials within a shell structure.”The model can offer suggestions for optimal engineered aggregate formation for different cases like one big crack versus multiple small cracks or more likely, a bunch of cracks that are connected to one another. The next step in their research, Pan said, is to find out how the overall strength of concrete is impacted by different sizes and shapes of engineered aggregates. The two models will hopefully then result in recommendations that provide optimal healing effects, while maintaining the structural integrity and strength originally found in concrete.Following this, Pan said they will conduct additional research on types of materials to work with. Materials such as polyurethane and sodium silicate are good candidates that work well as healing agents. Meanwhile, Pan said, a good candidate for the engineered aggregate material is cement. “Cement is cheap and won’t increase the price of concrete dramatically,” she said.In the lab thus far, the team has tested some smaller samples that have only one or two engineered aggregates inside. A key test is to see what happens with water flow through a large crack—whether it exhibits healing or whether the water flows easily through the space, indicating the absence of healing. This is also a key component of why it is important to fix cracks sooner rather than later. “When concrete is cracked, water can flow through it very fast and bring with it aggressive, corrosive agents,” Pan said. “That can lead to more damage.”Self-healing concrete could help increase the longevity of structures close to water sources, or in wet climates, Pan said, helping them to maintain their functionality. Provided by USC Viterbi (https://viterbischool.usc.edu)Source : https://www.airforcemag.com/how-dods-old-concrete-infrastructure-could-start-to-fix-itself/
2022.03.07