The nation’s concrete roadways receive a whole lot of wear and tear, particularly in regions that experience extreme changes in temperature during the summer and winter. These temperature fluctuations can cause paved concrete surfaces to expand and contract, resulting in cracks that require seasonal repairs and replacement.
Thanks to the efforts of a mechanical engineering professor at Louisiana State University, however, transportation officials could soon be able to treat concrete roadways with a polymer-based sealant that mitigates the effects of seasonal expansion and contraction to prevent cracking. This, in turn, could save states a great deal of money in repairs each year.
Engineering professor Guogiang Li first began experimenting with polymer-based sealants in 2009, after receiving funding from the National Cooperative Highway Research Program and the Louisiana Research Transportation Center. His first prototype was a one-way memory shape polymer that could stretch and compress in response to seasonal temperature fluctuations. Then, in 2012, he created an improved two-way shape memory polymer sealant and combined it with asphalt to improve its ability to bond with concrete and resist environmental wear.
Following a successful round of laboratory testing, transportation departments in Louisiana, Texas and Minnesota will begin testing the concrete sealant’s performance on real roadways this year. This testing and certification process is expected to be complete by the end of 2019. If it performs as advertised, the polymer-based sealant could become a common feature of concrete roadways throughout the country.
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Although cold temperatures are typically a greater obstacle when working with concrete, hot summer days can present some unique challenges as well. To understand how extreme heat affects freshly-poured concrete, it’s important to first have a clear understanding of how the concrete-setting process works.
Concrete sets via an exothermic reaction called hydration.
When concrete hydrates, it absorbs moisture and forms solid crystals around the aggregate particles in the mix. The process of hydration is slowed by cold temperatures and accelerated by heat. On especially hot days when crystallization happens more quickly, the crystals have less time to strengthen before the hydration process is complete. Evaporation can also compromise the strength of the concrete’s surface layer. This, in turn, can make the concrete more susceptible to cracking.
The good news is, there are a few strategies you can employ to help concrete retain moisture on hot days and ensure that the finished product is as strong as possible.
- When pouring concrete in temperatures above 85°F, it’s a good idea to use a concrete mix with a higher volume of coarse aggregate particles. This can prevent the concrete from shrinking as it hydrates.
- If possible, pour concrete early in the morning before the temperature peaks.
- Spray cool water on the side forms and subgrade prior to pouring concrete slabs.
- Use tarps or other sunshades to keep paved surfaces cool and prevent evaporation while the concrete sets.
- Make sure you have enough help to mix, pour and finish the concrete without interruptions in between each step.
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Additive manufacturing processes—also known as 3D printing—are being used to make everything from medical devices to engine components, and now the U.S. Army is even using employing a similar technique to build concrete structures.
The U.S. Army Corps of Engineers has devised a system that allows them to create lightweight concrete structures quickly with a massive 3D printer. Once the technique is perfected, Army officials expect that they will be able to build temporary structures in a fraction of the time it currently takes to build using conventional methods.
It’s probably no surprise that 3D printing concrete structures is no easy feat.
Normal concrete–which contains a mix of aggregates like crushed stone, sand, gravel, and more–tends to clog printing machinery and cause equipment failures. To overcome this issue, the Army created its own concrete mix with sand, fly ash, silica fume, clay, a liquid admixture and water. This concrete mix is then paired with mesh layers to build strong, durable structures.
Army officials are optimistic that they will find a variety of practical applications for its new concrete and 3D printing process. These include building concrete barriers, barracks, training facilities and more in areas with limited resources. In the future, businesses in the civilian sector may even adopt similar additive manufacturing techniques to build concrete structures in record time as well.
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Has a vehicle with a leaky oil pan left a dark oil stain on your concrete driveway? It’s a good idea to remove these stains sooner rather than later so that they don’t have an opportunity to soak into the concrete. Oil and grease stains will also need to be cleaned before the driveway is resealed.
Start With Cat Litter
If the stain is relatively small, you can start by applying a generous amount of cat litter to the affected area. Cat litter is an absorbent poultice that effectively sucks oil and grease out of concrete. Let the cat litter sit on the oil stain for about 30 minutes, and then use a heavy tool like a tamper to scrub the litter into the stain. Once you’re done, you can sweep up the remaining cat litter and discard it.
Use a Degreaser
If there’s still evidence of a stain after using the cat litter method, you can use a concrete degreaser to loosen the oil and make it easier to remove. Just dilute the degreaser according to the directions on the bottle, and use a scrub brush and some elbow grease to scour the stain away.
Try a Microbial Cleaner
For particularly stubborn stains, consider using a microbial cleaner instead. These products contain enzymes that digest the oil and convert it into harmless byproducts. The enzymes will continue to consume the oil until it’s gone, at which point they will die off leaving your driveway clean and spot-free. This is the same method that’s used to clean beaches and waterways following oil spills.
Recent advances in nanoengineering have allowed scientists at the University of Exeter to develop an innovative new technique that incorporates graphene into conventional concrete production. The graphene-infused concrete is reportedly twice as strong and four times more water resistant than traditional concrete mixes. It also reduces the amount of materials needed to make concrete by about 50 percent, which could significantly reduce the carbon footprint of large-scale construction projects.
So what makes this experimental concrete so strong and durable?
Graphene is an emerging “supermaterial” with a wide array of industrial applications, many of which are only just beginning to be realized. It consists of a single layer of carbon atoms bonded together in a pattern of hexagons resembling a honeycomb. This unique atomic structure makes graphene the strongest material in the world. It’s also so thin that it’s technically classified as a two-dimensional material.
The researchers at the University of Exeter were able to incorporate this remarkable material into concrete mix by suspending it in water. The end result was a graphene-infused concrete that is low cost and compatible with current manufacturing requirements.
“This ground-breaking research is important as it can be applied to large-scale manufacturing and construction. The industry has to be modernized by incorporating not only off-site manufacturing, but innovative new materials as well,” said lead study author Dimitar Dimov in his comments.
Thanks to the efforts of Dimov and his team, graphene could make the concrete of the future even stronger, more sustainable and more water resistant than modern concrete mixes.
Thanks to their exceptional durability, concrete driveways typically last years longer than driveways paved with asphalt. Concrete is also stronger than asphalt, which can be beneficial if you regularly park heavy vehicles or equipment in your driveway.
That said, no paving material is completely impervious to the elements. Over time, excessive wear can cause concrete to crack and spall, spoiling its appearance and reducing the expected longevity of a driveway. The good news is, there are a few simple steps every homeowner can take to make sure their concrete driveways remain in good condition for many years to come.
Apply a Sealcoat
This is perhaps the single most effective thing you can do to protect your driveway from the elements. A sealcoat prevents cracking by protecting the surface of the concrete from moisture penetration. Ideally, concrete driveways should first be sealed a few months after they’re paved, and then resealed at least once every two years.
Make Repairs Early
Sooner or later, you’ll start to notice small cracks forming on the surface of your driveway. By filling these minor cracks with an epoxy injection, you can prevent them from becoming much larger cracks in the future. It’s much easier and more cost-effective to make these minor repairs rather than wait for them to become more serious issues.
Avoid Chemical Treatments
De-icing chemicals make it easier to shovel your driveway in the winter, but they can also accelerate wear on concrete. Instead of using rock salt or other harsh chemicals on your driveway, opt for gentler alternatives like sand, alfalfa meal or cat litter to give you some extra traction in snow and ice.
Invest in Professional Paving
A concrete driveway’s lifespan will depend largely on whether or not it’s properly installed. Concrete paving might look pretty straightforward, but getting the job done right is easier said than done. If you haven’t had much experience working with concrete in the past, it’s typically best to leave driveway paving to the professionals. This way, you can be completely confident in the structural integrity of your new driveway.
Do you have an old concrete driveway that’s starting to crack from years and wear and tear? At this point, you might be thinking about tearing it up and repaving it with fresh concrete.
But what if we told you a group of scientists is developing a new “self-healing” concrete that could stop small cracks from becoming huge fissures?
Recently, researchers from New York’s Binghamton University teamed up with Ning Zhang of Rutgers University to create a new kind of concrete that uses fungus to repair itself. By incorporating the fungus Trichoderma reesei into their concrete mix, the researchers were able to create paved surfaces that automatically re-seal themselves as small cracks develop.
The fungal spores lay dormant at first, but as soon as micro-cracks start to form in the concrete, the spores spring into action by mixing with water and oxygen to create calcium carbonate, a hard chemical compound that seals these tiny cracks before they become any larger.
The researchers are still perfecting their product, so you won’t be able to take advantage of it just yet. But at some point in the not-so-distant future, you might be able to repave your driveway or sidewalk with a new type of concrete that is extremely resistant to cracking. Who would’ve thought that a fungus could make concrete even more durable than it already is?
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Concrete driveways are known for being extremely durable and long-lasting, but they can still be damaged in extreme weather conditions. In the winter, when temperatures fall below freezing and snow accumulates on surfaces, concrete driveways can be more likely to experience environmental damage.
One fairly common type of damage that can occur during the winter is called spalling.
Also known as scaling, spalling occurs when the thin top layer of concrete chips or flakes away from the rest of the paved surface. When scaling becomes widespread, it can eventually expose the aggregate and leave the driveway vulnerable to further damage. In the past, you may have noticed this spalling phenomenon on worn concrete sidewalks that haven’t been repaved in a while.
The good news is, there are steps you can take to prevent spalling on your driveway this winter.
You can start by sealing your driveway to add an extra layer of protection in harsh weather. Sealing products are a great investment that can extend the lifespan of your driveway and prevent environmental damage such as spalling and cracking.
You should also try to limit your use of rock salt and other de-icing chemicals on the driveway. These products do a great job of melting ice on surfaces, but their harsh chemical compositions can accelerate wear on concrete driveways. Instead, use gentler alternatives such as sand, cat litter or alfalfa meal to increase traction on your driveway without causing damage.
All it takes to prevent spalling is a little preparation! Need a hand with your next concrete paving project? Give us a call today to get started!
Concrete is a famously durable building and paving material, but even the most robust concrete mix can be damaged by prolonged exposure to heavy wind and rain. Harsh environmental conditions can accelerate concrete deterioration, reducing the effective service life of concrete structures and paved surfaces.
Engineers have been experimenting with ways to weatherproof concrete for decades.
Most of these weatherproofing techniques have involved applying protective materials to the finished concrete, but these treatments tend to be highly toxic and bad for the local environment. Recently, however, a group of researchers at Brunel University London developed a creative new way to protect concrete from wind and rain without utilizing toxic chemicals.
This technique utilizes a crystallizing admixture in conjunction with a wax-based curing agent. First, the crystallizing admixture is applied to fresh, uncured concrete. Then, after about an hour, the curing agent is applied to the concrete as well.
“The material works by absorbing water that exists within the concrete to form crystals,” said head researcher Mazen Al-Kheteen in an interview. “Whenever the crystals are formed they line the pores of the concrete, allowing it to breath. It also works on repelling water that tries to penetrate through.”
Al-Kheteen and his team hope that their environmentally-friendly weatherproofing treatment will save companies valuable time and money by reducing the amount of maintenance that is required to maximize the lifespan of concrete structures. The treatment could be particularly cost-effective because it can be applied on both wet and dry concrete surfaces “without affecting its performance.”
The research team’s weatherproofing treatment is still in development, but preliminary results have been very promising. Before too long, it could become a readily available option for concrete projects in areas prone to harsh weather conditions.
Concrete mixtures have evolved quite a bit over the course of the last several thousand years. Whereas the ancient Romans added volcanic ash their concrete to allow it to set underwater, modern concrete often features chemical admixtures to control its hardening rate and tensile strength. Engineers are always looking for ways to make stronger, more durable concrete mixtures, and a team of MIT undergrads may have just made a surprising new breakthrough.
The students set out to make industrial concrete stronger and more-environmentally friendly by experimenting with different additives. In their preliminary research, the students found that some types of plastic become stronger when exposed to gamma radiation. This gave them an idea: Why not use plastic bottles from the local recycling center to create a strengthening agent for their concrete mixture?
After developing their hypothesis, the students went to work gathering recycled plastic bottles and crushing them into fine particles with a ball mill and hand tools. Then, they used a cobalt-60 irradiator (which is often used to decontaminate food in commercial settings) to bombard the crushed plastic with gamma rays. After adding the irradiated plastic to a standard concrete mixture, the students ran a series of tests and found that the concrete was 15 percent stronger than their control samples.
“We know that the plastic makes it denser and forms particular crystalline structures in the material that make the final concrete stronger,” said assistant professor Michael Short in an interview.
Now, the team of students hopes to refine their technique and explore ways to make the plastic-infused concrete marketable to construction companies. They’re currently working on a proposal to the National Science Foundation for additional funding. With continued research and development, the students may be able to create an innovative new type of exceptionally strong, eco-friendly cement.