Why is Ancient Roman Concrete So Durable?
(Excerpted from an article in Science Magazine)
Modern concrete—used in everything from roads to buildings to bridges—can break down in as few as 50 years. But more than a thousand years after the western Roman Empire crumbled to dust, its concrete structures are still standing.
Now, scientists have finally figured out why: a special ingredient that makes the cement grow stronger—not weaker—over time.
Scientists began their search with an ancient recipe for mortar, laid down by Roman engineer Marcus Vitruvius in 30 B.C.E. It called for a concoction of volcanic ash, lime, and seawater, mixed together with volcanic rocks and spread into wooden molds that were then immersed in more sea water.
History contains many references to the durability of Roman concrete, including this cryptic note written in 79 B.C.E., describing concrete exposed to seawater as: “a single stone mass, impregnable to the waves and everyday stronger.” What did it mean? To find out, the researchers studied drilled cores of a Roman harbor from Pozzuoli Bay near Naples, Italy. When they analyzed it, they found that the seawater had dissolved components of the volcanic ash, allowing new binding minerals to grow. Within a decade, a very rare hydrothermal mineral called aluminum tobermorite (Al-tobermorite) had formed in the concrete. Al-tobermorite, long known to give Roman concrete its strength, can be made in the lab, but it’s very difficult to incorporate it in concrete. But the researchers found that when seawater percolates through a cement matrix, it reacts with volcanic ash and crystals to form Al-tobermorite and a porous mineral called phillipsite.
So will you be seeing stronger piers and breakwaters anytime soon? Because both minerals take centuries to strengthen concrete, modern scientists are still working on recreating a modern version of Roman cement.
The Importance of Rebar in Concrete Construction Projects
At C.R.I., we’ve noted that the importance of rebar in most concrete projects comes as a surprise to many DIYers. This revelation usually prompts the question of whether rebar is always necessary in concrete. Let’s take a closer look at what rebar is, what it does for concrete, and why it’s so important.
When it comes to absorbing stress in the form of compression, concrete can be very strong. However, concrete does not stand up well to tensile strength; it crumbles when confronted with pressures that threaten to tear it apart. In construction, concrete is subjected to both types of stress, and while it will hold up if weight is applied from the top, it will flex, deform, and crack when exposed to tensile stress.
Metal rods, aka rebar, are therefore used to reinforce concrete constructions. When rebar is used in a concrete project, the finished product has significantly higher strength than concrete alone. Buildings and roadways all benefit from this strength.
Every concrete project does not necessitate the use of rebar; but, as a general rule, if you’re pouring concrete that’s more than 5 inches thick, you should use rebar for strengthening.
For a non-commercial project requiring additional concrete reinforcement, fiber or wire mesh are becoming increasingly popular as a very good, and less expensive, alternative to rebar.
Concrete reinforced with rebar, fiber, or wire mesh is not only more durable, but it also reduces the number of cracks that develop over time. This can help save money on repairs and keep your concrete looking good for years to come.
There are various types of rebar from which to pick… Welded wire, expandable metal, stainless steel, sheet metal, and epoxy coated are the most common varieties. Each type of rebar is best suited for various types of tasks, so do your homework, or consult with a concrete expert, before picking the one that will be perfect for you.
Here are some guidelines…
- Stainless steel rebar is very corrosion resistant and an excellent choice for any concrete job in corrosive environments.
- Fiber-reinforced concrete contains fibrous material, such as steel, glass, synthetic and natural fibers, to increase its structural integrity. For flat work and driveways, it is much easier to use and does an excellent job.
- Sheet metal is a common choice for concrete floors, roofs, and stairwells.
- Wire mesh is a two-dimensional grid that runs the length and width of poured concrete but not the height.
- Epoxy-coated rebar is even more corrosion-resistant than stainless steel. It is the most durable, but also most costly, concrete reinforcement option.
As in any construction project, if you feel like you’re unable to make a sound, informed decision, consult a professional. If you have questions or would like a quote on a project, click here to contact us.
C.R.I. is a diversified contractor and grounds support company serving New Jersey.
When it’s a CMU!
The concrete masonry unit (CMU) has come a long way since it was first created; still, the story of how it came to be is an interesting one. An article, published in Popular Science (Apr. 2020), tells it like this…
“Your name for the venerable CMU (Concrete Masonry Unit) probably depends upon where you live, but cinder block, breeze block, and hollow block all refer to an 8-by-8-by-16-inch brick with two or three internal voids. This mainstay of construction emerged when, in 1900, Harmon S. Palmer developed a process for using coal cinders—hence the name—to create something lighter, more insulating, and easier to work with than the solid hunks of his day. The industry standardized the dimensions in the 1930s, and coal waste eventually gave way to concrete and other materials, making the items heavier and stronger.”
This durable construction mainstay is easy to install, low maintenance, and fireproof. The CMU has come a long way since it was first introduced and, as always, Colucci Realty remains on the forefront of methods and materials in construction and concrete.
Our most recent project, located at 95 River Rd Flemington NJ, began on July 28th, using 12” x 8’ x 34’ CMUs that are totally insulated with an r24 rating.
The project is at the finish-to-suit stage; completion will be 90-120 days after lease signing, depending on the fit out needed.
If you are interested in leasing the building, call us at 908-797-2305.
CRI is a diversified contractor and grounds support company serving New Jersey. Contact us for information and quotes related to concrete and asphalt work, water management (including sewer, water, and drainage projects), water recharge system installation, management and delivery of all phases and requirements of site-work, and professional dismantling services.
Although the terms cement and concrete are often used interchangeably, cement is actually an ingredient of concrete. Concrete is a mixture of aggregates and paste. The aggregates are sand and gravel or crushed stone; the paste is water and Portland cement.
Cement comprises from 10 to 15 percent of the concrete mix, by volume. Through a process called hydration, the cement and water harden and bind the aggregates into a rock-like mass. This hardening process continues for years meaning that concrete gets stronger as it gets older.
Portland cement is not a brand name, but the generic term for the type of cement in virtually all concrete – just as stainless is a type of steel and sterling a type of silver. Therefore, there is no such thing as a cement sidewalk, or a cement mixer; the proper terms are concrete sidewalk and concrete mixer.
CRI provides a large portfolio of services that includes, but is not limited to, concrete and asphalt work, commercial snow removal, water management (including sewer, water, and drainage projects), water recharge system installation, management and delivery of all phases and requirements of site-work, and professional dismantling services.
For information, please call us at 908-797-2305, or submit an online form to request an estimate or receive answers to general questions.
Colucci Realty was recently contracted to remove a landscaped island that prevented trucks from getting into the loading dock.
To begin, we removed and disposed of the concrete curb, along with the trees and fill contained within the island.
Once the construction site was cleared and prepped, 4″ of DGA (dense grade aggregate) stone was installed and compacted. On top of that was layered 4″ of I-2 base asphalt mix, which is a compacted mixture of both aggregates and asphalt cement.
Finally 2″ of I-5 top asphalt mix was installed and the area was coned off, as shown in the photos below.
For information on installing, repairing, or removing asphalt or concrete, call CRI, at 908-797-2305, or submit an online form to request an estimate or receive answers to general questions.
Curious about the pros & cons of concrete vs. asphalt? Check out our post Comparing Concrete vs. Asphalt.
Higher concentrations of carbon dioxide in our atmosphere accelerate the deterioration of concrete. As CO2 penetrates a structure, it reacts with already present moisture and calcium hydroxide, progressively eating away at the layer of cement covering steel reinforcements, leaving them vulnerable to rust.
Fortunately, an environmental scientist in the Netherlands has invented a self-healing version. The concrete is embedded with nitrogen, phosphorous, calcium lactate, and a limestone-producing bacteria.
The additives lie dormant until a fissure emerges, admitting air and moisture. At that point, the bacteria activate, feed on the calcium lactate, and convert it into limestone to seal the split in the concrete.
For information on installing, repairing, or removing concrete, call CRI, at 908-797-2305, or submit an online form to request an estimate or receive answers to general questions.
The Palazzo Italia, in Milan, is the first concrete building in the world to effectively improve the quality of the air around it. The facade of the building consists of 900 biodynamic panels made with photocatalytic concrete and titanium dioxide.
The technology was invented by accident, by Luigi Cassar, a chemist at cement manufacturer Italcementi. While trying to create a construction material that keeps a bright white color even in polluted conditions, he hit upon a method called “photocatalysis”, which uses the sun’s energy to zap away dirt.
To his surprise, when the air around the treated concrete was tested, it contained up to 80% less nitrous oxide, which meant the concrete was cleaning the air as well as itself.
The material is also suited for use in road construction and roofing tiles.
From the repair of cracked, damaged, and broken concrete, to full concrete slab replacement, CRI can tackle concrete repair and removal jobs of any size. Call us, at 908-797-2305, or submit our online form to request an estimate or for general questions.
In our last post, we showed a video depicting a very creative construction crew moving cement from the mixing site, up one floor, to the installation site. But what if you need to move the cement even higher and, more importantly, safely and consistently?
The video below, titled “Concrete Pumping–The Future of Concrete Construction”, posted by the American Concrete Pumping Association (ACPA), demonstrates the economic, environmental, safety, and productivity benefits of concrete pumps.
The projects shown in the video employ truck-mounted concrete pumps with placing booms and stationary pumps. The video details the many uses of concrete pumps. Environmental benefits are also illustrated with footage of concrete pumping near rivers and streams, where precision placement and enclosed pipelines protect the surrounding area.
We’re not sure what country is home to this construction project but know for a fact that it’s not the U.S.A. – OSHA would shut down this operation in a heartbeat.
OSHA notwithstanding, this construction crew shows amazing skill and creativity… No concrete pump truck? No problem for this construction team; using skill, strength, and coordination, they quickly and efficiently move cement from the mixing site to the application site.
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