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Environmentally friendly concrete - like the one used by the Romans

An international team of researchers, led by scientists from the University of California, Berkeley, has revealed the secrets of a concrete Roman breakwater that has been in the Mediterranean Sea for 2000 years.

A core excavated from a sunken Roman concrete pier in Pozzuloi Bay. Photo: Lawrence Berkeley Laboratories
A core excavated from a sunken Roman concrete pier in Pozzuloi Bay. Photo: Lawrence Berkeley Laboratories

An international team of researchers, led by scientists from the University of California, Berkeley, has revealed the secrets of a concrete Roman breakwater that has been in the Mediterranean Sea for 2000 years.

Chemical analysis of samples taken from the concrete that makes up a Roman breakwater explains why the best Roman concrete is more effective than most modern types of concrete in terms of its durability and why its production was less harmful to the environment, and how these improvements can be utilized today. "It's not that the cement that exists today isn't good - it's so good that we use 19 billion tons of it every year," explains the chief researcher. "The problem is that the production of Portland type cement contributes to seven percent of the total amount of carbon dioxide that the industry emits into the air."

Portland cement is the source of the glue that holds most modern types of concrete together, but its production results in carbon emissions resulting from the need to heat a mixture of limestone and clay to a temperature of 1450 Celsius and the heated limestone itself. The research team found that the Romans, in contrast, used smaller amounts of limestone derived from a material heated to a temperature of only 900 degrees Celsius, which required much less energy than the methods available today. Reducing greenhouse gas emissions is one of the strongest incentives for finding more efficient ways to provide the entire world with the concrete it needs; Another incentive is the need for buildings, bridges and other structures that will be stronger and more durable over time. "In the middle of the twentieth century, concrete buildings were designed to be durable for 50 years, but today they are supposed to be durable for a period of up to 120 years," explains the main researcher. In contrast, the structures of the Roman ports have survived for 2000 years and are stable against chemical eating and the damage of underwater waves.

The Romans made concrete by mixing limestone and volcanic rock. For underwater structures, the Romans mixed limestone and volcanic ash to create plaster, and this plaster, along with volcanic tuff, was packed into rigid forms. The sea water immediately activated a hot chemical reaction. The lime stone underwent a reaction from a day - the penetration of water molecules into the structure - then this material reacted with the ash to glue the entire mixture.

The team of researchers found, using advanced equipment, a number of differences between the ancient concrete and the one produced today. One of them is the type of glue that holds the concrete components together. In concrete composed of Portland cement this compound includes calcium, silicates and hydrates (CSH). The Roman concrete, on the other hand, consists of a compound that includes the addition of aluminum and less silicon. The final compound, consisting of calcium, aluminum, silicate and hydrates (CASH) is an exceptionally stable adhesive. The results of tests with the help of X-ray spectroscopy showed that the unique transformation form of the aluminum atoms instead of the silicon atoms may be the key to the excellent adhesiveness and great stability of the Roman concrete.

Environmentally friendly concrete types already today include volcanic ash or coal ash obtained from coal burning waste in power plants as a partial replacement for Portland concrete, and their effectiveness has been proven to be good. These concrete mixes also include a CASH adhesive, but their long-term performance cannot be determined until the team of researchers can analyze them with the same equipment. The researchers found that the Roman recipe required 10% less limestone than is required today, while using a temperature one third lower than that required today. Limestone reacting with aluminum-rich plaster ash and seawater created an extremely stable concrete that could be hard and durable for days. Both the materials and the way of production of the Romans carry lessons for the future.

"Pozzolan type plaster is important due to its practical applications," explains the lead researcher. "It will be able to replace 40 percent of the world's requirements for Portland type cement. And sources for this plaster exist all over the world. For example, Saudi Arabia does not have much coal ash, but it has mountains of pozzolan."

Stronger, longer-lasting concrete produced with less energy and less carbon emissions may be the legacy of a deeper understanding of how the ancient Romans made their durable concrete.

The news about the study

9 תגובות

  1. An Israeli i-tec w company holds patents in the production of natural raw materials for cement substitutes in the world. Using these materials saves over 80% of cement production in the world, there is no need to burn raw materials at temperatures for the production of clinker.

  2. Happy holiday
    There is another method that works that has an Israeli patent, and is used in the production of concrete, in other cement substitutes such as the use of enzymes. A completely natural material.
    The role of enzymes is to increase the reaction in nature, a process that creates a nanobiological connection or adhesion of the clay materials in nature.
    We produce enzymes for various uses, soil stabilization.
    Cement substitutes.
    Using the material saves over 50% of the amount of cement in the concrete mix
    See articles or material on the subject for details

  3. We are generally in favor of construction without cement. For several years developing and building technology and using foamed concrete on a different gypsum base. Of course, gypsum undergoes a change process. But gypsum is an environmentally friendly material, harmless, non-flammable, breathable, etc. In addition, there is no healing process, weight and of course load on the foundation is reduced, etc.

  4. A. Portland cement (cement is a mixture of cement and water)
    B. There is no problem with the existence of concrete made today compared to the Roman concrete. The problems arise from the use of iron in concrete.
    third. Most of the Roman buildings did not survive. The buildings that survived are public buildings (in which they invested more), built in periods when the relative humidity was high. The reason such cements are not used today is their longer hardening times.
    d. Pozzolanic cement and not pozzolan type plaster.
    God. Of course, the amount of clinker in concrete decreases over the years. What limits the download of the clinker content is normality and not technological ability.

  5. I'm just commenting, the name of the city is Pozzuoli and not as written (at the bottom of the picture)

  6. A. Ben Ner

    Write it down for yourself. The greens don't understand anything about cost calculations. With them, money grows on trees, so it is our duty to spend it for this green green.

  7. If the lime burning temperature in Roman cement (pozzolanic cement) (about c900 ~ 1173k) is about a third smaller than the lime burning temperature in the method accepted today (Portland) (about 1450c ~ 1723k), and since the energy is proportional to the square of the temperature, then the amount of energy needed to burn the lime in the method The Roman (1173 square meters) is about half the amount of energy needed to burn the lime in the modern method (1723 square meters). We will add to that that the amount of lime needed in the Roman method is about 10% less than that needed in the modern method and we will get that the amount of energy needed to make cement in the Roman method is about 40% in relation to the energy needed to make cement in the modern method.
    On the other hand, the advantage of modern cement is the wide distribution of the raw materials; Sea sand, clay and limestone and their cheap price. This is in comparison to the raw materials of the pozzolanic cement which, in addition to the limestone, are also quartz volcanic ash or a paste of quartz rocks. These materials are less common and more expensive to process.

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