Does it seem like road crews are resurfacing the highways in your area with fresh asphalt practically every year? This is due to the fact that asphalt roads, for all their virtues, have fairly limited lifespans, particularly in regions that experience harsh winter weather.
Thanks to recent innovations in the paving industry, however, some contractors are now using thin layers of concrete to extend the lifespan of roadways by as much as two decades.
In recent years, unbonded concrete overlays—which are typically less than six inches thick and separated from existing roadways by an even thinner layer of nonwoven polypropylene fabric—have been used to rehabilitate damaged roads in a number of states including Iowa, Minnesota, North Carolina and California. According to the American Concrete Pavement Association (ACPA), concrete overlays currently account for about 12.5 percent of the total volume of concrete pavement that’s poured in the U.S. each year.
By using existing roadways as a base layer for support, unbonded concrete overlays offer a cost-effective, long-term alternative to full-depth paving work and asphalt resurfacing.
“you add more structure with a concrete overlay than an asphalt overlay just by nature of the materials being stronger,” said ACPA President and CEO Gerald Voigt in a recent interview with Equipment World. “They last longer; they’re stronger inch by inch … From a user impact standpoint, you’re getting 20-plus years out of a concrete overlay versus an asphalt overlay getting eight, nine, maybe 10 years.”
Keep an eye out—before too long you may see these concrete overlays being used to rehabilitate a damaged roadway near you.
Concrete might form the bedrock of modern urban construction, but its impact on the environment is raising concerns among climate researchers. Recent estimates suggest that Portland cement, the essential binding ingredient in concrete, accounts for roughly seven percent of global carbon emissions.
That could change soon, however, thanks to a multinational effort to drastically reduce the carbon output of the cement manufacturing process.
In Switzerland, for example, a group of scientists recently published a study that found it would be possible to reduce carbon emissions from the concrete sector by 80 percent without using carbon capture technology. These scientists argue that by optimizing concrete mixes, increasing the use of alternative fuels and recycling raw materials to produce the active ingredient clinker in cement, the concrete industry could effectively slash its carbon emissions by 2050.
Meanwhile, in Lithuania, another group of scientists is replacing Portland cement with alkali-activated industrial waste products such as fly ash to make concrete production more environmentally friendly as well. Although their carbon-cutting concrete is still in development, it is reportedly just as strong as conventional concrete and better able to resist damage from temperature fluctuations and exposure to acids.
Here in the United States, researchers at UCLA are also exploring innovative new ways to capture and repurpose carbon emissions from the cement manufacturing process. By creating a closed system wherein carbon dioxide is captured and recombined with calcium hydroxide to create limestone, they hope to make cement production a completely carbon-neutral process.
Thanks to the efforts of researchers all of the world, the concrete of the future may not only be stronger and more durable, but better for the environment as well.
India’s urban populations are growing at an unprecedented rate, and construction crews are having trouble keeping up with the demand for structural concrete due to a nationwide sand shortage. Meanwhile, the country’s lack of recycling infrastructure is allowing thousands of tons of waste plastic to pile up in city streets as well. But thanks to a joint effort between researchers at the University of Bath in the UK and Goa Engineering College in India, a new type of sustainable concrete could soon help to alleviate both these issues.
These researchers found that by replacing 10 percent of the sand in a conventional concrete mixture with waste plastic particles from ground up bottles, they could create a viable, eco-friendly construction material. If their plastic-infused concrete is widely adopted by India’s construction industry, the researchers estimate it could save 820 million metric tons of sand each year.
“The key challenge her was to have a limit between a small reduction in strengths, which we achieved, and using an appropriate amount of plastic to make it worthwhile,” said Principle Investigator Dr. John Orr in a statement. “It is really a viable material for use in some areas of construction that might help us to tackle issues of not being able to recycle the plastic and meeting a demand for sand.”
Although this concrete was specifically designed to help meet the unique needs of India’s construction industry, it could be useful in other regions with limited recycling capabilities as well.
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.
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.
At Bergen Mobile Concrete, our metered mobile mixers are designed to provide a consistent, quality product that can be mixed to your exact specifications. Best of all, you’ll never have to pay for more than what you use! Just give us a call to schedule your concrete delivery today.
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.
Need a hand with your next concrete paving or construction project? Our concrete buggies and metered mobile mixers are designed to make concrete work easy and efficient. Give us a call or contact us online today to learn more.
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.
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?
Ready to revitalize that crumbling old driveway? Our mobile mixers and buggy trucks make it easy and affordable to repave concrete surfaces such as patios, driveways and more. Give us a call to schedule your appointment today!
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.