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A Consolidation of Concrete Progressions
Looking At As Many Concrete Derivatives As Possible

by Greg Frank

A Consolidation of Concrete Progressions

This one million-square-foot business park in Irvine, Calif., designed by Spurlock Landscape Architects of San Diego and constructed by Park West, features a walkway that was made with Lithocrete®, a type of reinforced concrete produced with recycled materials and manufactured by T.B. Penick & Sons, Inc.


Each year, three tons of concrete is used for every man, woman and child on the planet, making it the most widely utilized building material on Earth and the second most consumed material ever, right behind water, according to sciencedirect.com.

With such a large emphasis placed on concrete, coupled with virtually all of the world's infrastructure depending on it, it is no wonder that there has been a wide range of advancements to the industry. From self-healing concrete to stronger mixes, this article aims to consolidate a large amount of research pertaining to the development of new forms of concrete around the world.

As a word of disclaimer, many of the concrete forms discussed in this article are still under development and are not yet available to the public.

Self-Healing
Self-healing concrete mixtures can be a huge step towards limiting the need for concrete maintenance and repair. During an interview with Concrete.tv, associate professor, Hans Beushausen, from the University of Cape Town, South Africa, states, "Worldwide, most countries spend much more money on repairing concrete infrastructure than building new ones."

In fact, a 2017 estimate by the American Society of Civil Engineers stipulates that the government would need to spend $4.6 trillion to repair America's entire infrastructure. Couple this with the fact that the White House's Infrastructure Report Card deemed our country's infrastructure to be a D+, and there is no wonder why focus has been placed on concrete that can repair itself.

One self-healing concrete form already available on the market was developed by microbiologist Hendrik Jonkers from Delft University of Technology in the Netherlands. The concrete is created by adding a special type of bacteria, mixed with calcium lactate, to water and concrete components. When the concrete begins to crack, water seeps in and activates the bacteria, which then produces limestone to fill up the cracks.

On this note, the same species of bacterium used by Dr. Jonkers, S. pasteurii, is being implored for its use in protecting concrete sidewalks and roads from the damages produced by road salt. Researchers from Drexel University, a private university in Philadelphia, have discovered that concrete laced with this strain of bacteria, resists the damaging effects of calcium chloride (salt) better than regular concrete.



A Consolidation of Concrete Progressions

This section of sidewalk at Louisiana State University in Baton Rouge was installed using bendable concrete as a test-site for larger applications in the future.
Photo Credit: LSU College of Engineering


A Consolidation of Concrete Progressions

Under the pressures exerted by this stress test, normal concrete would break in half while bendable concrete is able to keep its structure and flex under the force.
Photo Credit: Youtube


A Consolidation of Concrete Progressions

Using a "bio-inspired" route, German scientists from the University of Konstanz were able to strengthen concrete to withstand 29,000 pounds of pressure per square inch by developing a nanomaterial similar to the structure found in sea urchin spines.


Fun fact; the first building in the world to use self-healing concrete was a life guard tower constructed in 2015 in the Netherlands that used Jonkers' mix. As expected, the results are a success, and the building has been able to heal its own cracks.

Another method of applying autonomous-repairing capabilities to concrete is with the use of a distinct fungus called Trichoderma reesi. Working the same way as the self-healing concrete infused with bacteria, researchers from Binghamton University, in New York, and Rutgers University, in New Jersey, trialed over 20 types of fungus to find the right one. Although, the bacteria infused concrete produces limestone when in contact with water, the fungus produces calcium carbonate instead.

Among the many other methods of self-repairing concrete is the use of microcapsules containing: minerals, epoxy and polyurethane, developed by Dolomite Microfluidics, of the United Kingdom. Albeit, still in development, the idea is that cracks in the concrete will rupture the microcapsules subsequently releasing the "healing" components found within.

Also, a scientific team from the Pacific Northwest National Laboratory in Washington developed an automatically repairing concrete mixture that contains 5 to 20 percent of man-made polymers. Reportedly, the polymers have the potential to heal concrete cracks in just a matter of hours.

However, as promising as this form of concrete may seem, in a paper titled "Self-Healing Concrete in Commercial Construction" by James Frazier of California Polytechnic State University San Luis Obispo, he states that there are several problems with self-healing concrete, including: the price, the potential of released harmful products into the air and the lack of sufficient testing.

Stronger
One of the main ways to reduce the amount of concrete produced is to make it stronger, which, in turn, makes it last longer and reduces the need for frequent repairs. Of all the research compiled for this article, this category is by far the largest, and the substances used to strengthen concrete range from common household items to the somewhat obscure.



A Consolidation of Concrete Progressions

Professor Hendrik Jonkers, from Delft University of Technology in the Netherlands, holds up a core sample of his self-healing concrete.
Photo Credit: European Patent Office


A Consolidation of Concrete Progressions

This self-healing concrete contains a type of bacteria naturally found near volcanoes that can create limestone when it comes into contact with water. By doing this, internal cracks within concrete structures can be repaired. According to the European Patent Office, the bacteria can lay dormant for up to 200 years and fill cracks "up to any length provided they have a width of no more than 0.8 millimeters."
Photo Credit: European Patent Office


An interesting study regarding the improvement of concrete tensile and compressive strengths is being conducted by a German research team from the University of Konstanz, who are studying sea urchins in order to develop a nanomaterial that binds only to concrete and reportedly makes the concrete between 40 and 100 times more fracture resistant. In a test, the scientists demonstrated that the concrete could withstand 29,000 pounds per square inch of pressure, (normal concrete can typically withstand between 3,000 and 6,000 psi of pressure.)

Additionally, federal officials are working with researchers from Oregon State University and Purdue University to test a wood-infused concrete mixture that is reportedly 15 percent stronger than normal concrete. This experimental combination laces wood nanoparticles, measured at 15,000 times smaller than the head of a pin, into the concrete mixture in order to strengthen it and to explore new avenues of sustainably creating concrete.

What is more, the engineering department at the University of Michigan has formulated a mixture of ultra-high performance concrete that can reportedly withstand pressures of up to 22,000 psi. Their recipe removes gravel from the concrete formula and replaces it with different types of sand, resulting in a much more dense concrete. This specific derivative of concrete has already been utilized to reinforce a bridge in St. Clair County, Mich., which was completed in 2017. Furthermore, the Federal Highway Administration's website has an interactive map of all the highway bridges in the United States and Canada that use ultra-high performance concrete.

Scientists from the University of Exeter in England have mixed in graphene, stating the composite material is "more than twice as strong and four times more water-resistant than existing concretes."

In an effort to make concrete not only stronger, but also more sustainable, researchers at the University of Nebraska are using a heavily discarded bio-product that is widely available in the state: corn. Reportedly, Nebraska produces 1.6 billion bushels of corn each year. Previously, the corn stalks, leaves, and husks were discarded; however, now the college is looking into using that discarded bio-material to make concrete stronger and eco-friendlier.

"We take corn stover, burn it, turn it into ash and then the ash is used as a substitute in cement for fly ash, which is a by-product of coal," said Jim Vaux, University of Nebraska's department chair of industrial technology, in an interview with a local news station.



A Consolidation of Concrete Progressions

The colorful petri dishes are holding fungi spores in a screening process for the application of self-healing concrete. The inset shows how the fungi germinates into threadlike hyphal mycelium.
Photo Credits: Congrui Jin, Ph.D. | Binghamton University


A Consolidation of Concrete Progressions

This is a transmission taken from an electron microscope showing the microscopic cellulose nanoparticles. The nanoparticles are 15,000 times smaller than the head of a pin and are being laced into concrete to make it stronger. A parking lot in South Carolina is currently in the process of testing the experimental concrete.
Photo Credit: Purdue Life Sciences Microscopy Center


Our neighbors to the north are producing a greener, stronger concrete derivative using hemp. Canadian Greenfield Technologies, a company located in Calgary and formed by Mike Pildysh, is using bast fibers, derived from hemp stalk, to make concrete stronger. According to producer.com, this form of hemp-reinforced concrete has been used to "build skateboard parks across Canada" and was also used in Beijing to "construct the bobsled and luge tracks for the 2022 Winter Olympics."
Undergraduate students at the Massachusetts Institute of Technology have established that by adding bits of plastic that have been exposed to high levels of gamma radiation to cement paste, a concrete mixture as much as 20 percent stronger than traditional blends can be created.

Sustainable
Much of the effort surrounding new concrete derivatives focuses on reducing the harmful environmental effects that result from concrete production. According to the International Energy Agency, concrete production results in about 7% of the total carbon emissions worldwide. That being said, many research groups have sought to develop different methods and discover different ingredients that aim to make the production of concrete more environmentally friendly.

Among the pioneers of greener concrete is an assembly of civil engineers at Kansas State University, who have taken agricultural residue ash, (derived from agricultural waste products like corn stover, wheat straw and rice straw) and used it to replace Portland cement, the most common cement used for the creation of concrete. One source postulates that by removing Portland cement from the mixture, the carbon emissions are 80 to 90 percent lower. Additionally, the college states the concrete is 32 percent stronger than average.

An odder method of reducing concrete's carbon emissions was learnt by academics at Britain's Lancaster University, who used a regular house blender to cut up carrots and beets and then combined this with a concrete mixture. Lead researcher Mohamed Saafi told Reuters, "Adding about half a kilogram of carrot nanomaterial will reduce about 10 kilograms of cement per one cubic meter of concrete;" reducing the amount of cement needed and, ultimately, reducing the amount of carbon released into the atmosphere. What this ultimately tells us is that even concrete should eat its veggies!

Research at the University of Bath in the United Kingdom has led to a breakthrough in the use of plastic as an added material to replace sand in concrete mixtures. The team was able to show that by replacing ten percent of sand with plastic particles of the same size and shape (made from crushed plastic bottles,) the structural integrity of the concrete was not compromised. One source calculates that this method could save 820 tons of sand a year while simultaneously reducing the level of plastic waste.

Innovative
Besides stronger concrete forms, there is the innovative and unique side that doesn't always aim to improve the usability, but rather seeks to advance concrete in an alternative direction.



A Consolidation of Concrete Progressions

Director of the Pacific Northwest National Laboratory, Carlos Fernandez, displays a model of the polymer-infused concrete he and his colleagues are developing.
Photo Credit: Andrea Starr | Pacific Northwest National Laboratory


A Consolidation of Concrete Progressions

This is transparent concrete developed by a Hungarian company named Litracon®. The concrete was invented in 2001 by Áron Losonczi and it works by running optical fibers from one end of a poured concrete piece to another.
Photo Credit: Litracon® - Light-transmitting concrete www.litracon.hu


See-through concrete is one such invention. A Hungarian company developed it in 2001 by running optical fibers through the concrete. Reportedly, the concrete walls inlayed with these fibers can transmit light to over 50 feet and the over-all strength is not affected by the inclusion of the fibers.

Another novel idea is bendable concrete. A Louisiana State University team, led by senior research associate Gabriel Arce, received funding from the Transportation Consortium of South-Central States to produce and test a form of bendable concrete. Just recently, in December of 2018, LSU began testing the material on a section of campus sidewalk.

In an article on engineering.com, Arce states, "Compared to typical concrete, our cost-effective ECC material has about 300 times more deformation capacity, more than two times the flexural strength, and a higher compressive strength."

Cement-less concrete is also a newfangled idea, and is being advanced by scholars at Kaunas University of Technology in Lithuania. Instead of using Portland cement, they use "alkali-activated industrial waste products," like fly ash, biofuel bottom ash, and silicagel. Allegedly, the final product has the same strength as traditional concrete, yet is more resilient to acid, heat and cold.

Along the same vein as Tesla's solar roofing tiles, Swedish cement firm LafargeHolcim debuted photovoltaic concrete panels at a French construction tradeshow back in November 2017. The company teamed up with German solar panel manufacturer, Heliatek, to overlay a flexible solar film that is just one millimeter thick, on top of concrete panels. Reports state that a 10-story building covered in 60% of these panels would be able to generate roughly 30% of its annual energy requirement.

This article only scratches the surface regarding all the new ways concrete is being enhanced around the globe. In order to read more on the advances of concrete, including additional information on the updates discussed in this article, visit landscapearchitect.com.






Concrete or Clay Pavers?


Clay Units
In "Specifications for and Classification of Brick," put out by The Brick Industry Association, the minimum compressive strength for a C 1272 heavy vehicular paving brick placed under severe exposure is 10,000 psi (any single brick of a random sample of 5 bricks), which is the highest minimum listed on the spec sheet. That classification of brick also has a minimum breaking load of 475 lb/in. and a maximum cold water absorption of 6%.

The high temperatures that they are fired at in a kiln protect them from rupturing in cold climates because there is no moisture inside to expand.

Unlike earlier mass-produced bricks, modern ones come in dozens of different shapes, sizes, colors and strengths. For example, the Belden Brick Company has specialty shapes that can accommodate curves, angles, corners, slopes or other dramatic effects. There are permeable paver options with units that have larger spacer bars that allow water to filter through open aggregate between the joints.

According to "TodayaEUR(TM)s Homeowner with Danny Lipford," maintenance requirements for clay pavers are low because they resist staining. Additionally, they are made with environmentally sustainable materials: clay and water.

And while they may chip or crack, they "last for generations." In fact, bricks are often salvaged, cleaned and reused. Another advantage cited is their timeless nature - "an aged, worn brick walkway retains its charm."

On the downside, surface textures are somewhat limited. Bricks are more challenging to cut and because they can vary slightly in dimension, can be trickier to install.

The BIA cautions that bricks from different production runs of a specific manufacturer "will have slightly different properties." And bricks from different manufacturers, even though they have the same appearance, may have different properties.



A Consolidation of Concrete Progressions

Concrete paver manufacturers are able to produce custom runs of their products. The red and yellow units in this backyard patio in Council Bluffs, Iowa, which was crafted by Paver Designs, were left over from a run that a Belgard producer turned out in the team colors of the NFL's Kansas City Chiefs.


A Consolidation of Concrete Progressions

Clay brick tiles and thin pavers are designed to be placed on top of an existing hardscape. While the height of these pavers are less than that of a normal brick paver - 3/8" for tiles and 1-3/8" for thins in this case - they are still very durable according to their manufacturer. For this outdoor room, thin pavers were installed on top of a concrete slab.


Concrete Units
According to the Interlocking Concrete Pavement Institute, concrete pavers are produced in tightly fitted, uniform entities making them easy to install. Their lifespan can last decades and "stained or broken pavers can be easily replaced without patches."

There is no shortage of shapes, sizes, colors (including multicolored), textures and finishes, and more are being introduced all the time, as are advances to concrete that improves many properties of the material.

ASTM's C 936, "Standard Specification for Solid Concrete Interlocking Paving Units," requires a minimum average compressive strength of 8000 psi, but according to Billy J. Wauhop Jr., a mechanical engineer and president of International Concrete Services, many producers routinely manufacture pavers with compressive strengths in excess of 9000 psi.

The standard also calls for an average absorption of no more than 5% and to be able to withstand at least 50 freeze-thaw cycles with no greater than 1% loss in dry weight.

ICPI cautions that added maintenance, such as using sealants, may be necessary. Cement.org, the Portland Cement Association's website, says that all concrete products can be damaged by acids but there are appropriate sealers that help prevent it.

"Today's Homeowner with Danny Lipford," a website that gives home improvement advice, points out that because they are dyed, their colors can fade over time, especially in areas with much ultraviolet ray exposure. And concrete pavers can wear gradually; eroding the finish away, which then exposes the aggregate underneath. Additionally, they vary in durability and strength depending on the manufacturer.



As seen in LASN magazine, February 2019.



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October 19, 2019, 8:29 am PDT

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