The ancient Romans will forever be known for their exceptional military, political, and social institutions and for conquering vast parts of Europe and Northern Africa. But they were also brilliant engineers and builders who created a dazzling array of magnificent structures, such as the Pantheon and Colosseum, that are still virtually intact today. But how did they do it?
As it turns out, a material developed by the Romans was a form of concrete known for its fantastic durability and longevity. Although its exact composition and properties have remained a mystery for millennia, scientists have finally chipped away at how the Romans did it.
Also called opus caementicium, Roman concrete’s three main ingredients were volcanic ash, lime, and water. The mixture helped them build structures that included, among other marvels, public baths, temples, aqueducts, and bridges unlike any being constructed at that point in history. Because the concrete could harden underwater, it was also perfect for building breakwaters and harbors to house their impressive fleet of military and trade ships.
In addition to changing the composition of cement as we know it, researchers, environmentalists, and engineers now believe that the Roman formula also has the potential to not only pave the way for the modern use of a replicated version of this ancient mixture but will have a positive impact on the global environment.
“It is exciting to see the recent trends of concrete durability grounded on the history of ancient Romans, particularly the iconic construction such as the Pantheon close to 2000 years showing remarkable structural integrity,” said Dr. Ana Evangelista, a Course Coordinator and Lecturer at the Engineering Institute of Technology (EIT).
Worldwide, concrete is the most widely consumed civil construction material and is used in almost every type of construction, including homes, buildings, roads, bridges, airports, and tunnels. Dr. Evangelista noted that over the last decade, Pozzolanic materials (such as volcanic ash, pumice, opaline shales, burnt clay, and fly ash) had been added to concrete mixes to increase strength and durability. In different countries, they can be obtained from a variety of sources.
Although the original name, Pozzolana, refers to the Italian city of Pozzuoli, the region of a natural pozzolana from volcanic dust and ash, nowadays, by-products from burning coal in thermal power stations, smelting processes in the silicon and ferrosilicon industry, agro-waste products, and municipal solid waste are promising alternatives available worldwide.
However, Dr. Evangelista, who has been investigating the properties of recycled concrete and eco-friendly building materials, points out that pozzolanas have little cementitious (glue) value. Hence, their chemical reaction requires an alkali activator (slaked lime).
“To improve the pozzolanic reaction aiming for more durable and strong concrete, researchers are targeting not only the ingredients but the concrete mixing procedures, testing the “hot-mixing" technique with quicklime rather than traditional slaked lime,” she said.
The impacts of cement and, thus, concrete production on our environment is significant, considering a mean value of 0.948 kg CO2/kg Ordinary Portland Cement (OPC) for the life cycle CO2 footprint of OPC. But there’s a light at the end of the concrete tunnel.
Research from the Global CO2 Initiative in 2016 revealed that significant progress in CO2 has been made from 2011 to 2016, with many technologies shown to be scalable. Momentum is especially favorable for four major markets: chemical intermediates, fuels, polymers, and building materials such as cement.
To become more sustainable, the concrete industry uses industrial waste by-products such as fly ash (from coal combustion) and blast furnace slag (from iron manufacture) to constitute a portion of the cement used to produce concrete. Additionally, incorporating solid wastes, such as construction and demolition, and tire rubber to replace natural aggregate are eco-friendly alternatives.
Green concrete uses waste material as at least one of its components, requires less energy for manufacture, and produces less carbon dioxide than conventional concrete. However, the climate benefit of a CO2U (carbon dioxide utilization) product depends on how much CO2 the product contains and the amount of CO2 emitted in making the product.
Sustainable technologies in civil engineering, including green or sustainable concrete, become even more critical now when population growth, continuous industrial development, and infrastructure construction create vast amounts of construction and demolition waste. With this in mind, the construction engineering industry is taking the lead in innovating sustainable building practices to address and meet the UN sustainable development goals.
For example, one of Australia’s significant developments in the green/sustainable concrete frontier is the Green Cement Transformation Project. Backed by the Hallett Group (the most extensive integrated supplier of building and construction materials in South Australia), the project is estimated to be the largest carbon reduction innovation project in Australian history.
Hallett Group aims to construct a sovereign manufacturing capability to process and distribute three streams of Australian-generated industrial waste by-products into low-carbon green cement products. The project will reduce Australian CO2 emissions by 300,000 tons annually, approximately 1% of Australia’s 2030 CO2 reduction target.
But it’s not just the engineering industry carrying the torch for change and introducing more sustainable products in the civil engineering arena. Tertiary institutions are also proponents of green engineering innovations, whether in classrooms or webinars.
For instance, an EIT webinar in June 2022 titled: Current Trends on Concrete as Construction Material to Capture CO2 discussed the technologies that can support engineers, architects, and construction professionals seeking efficient, advanced solutions that conserve non-renewable resources and reduce carbon dioxide emissions.
Presented by Dr. Evangelista, three key takeaways from this webinar included:
● Overview of the Construction Engineering sector and UN sustainable development goals.
● Alternatives to mitigate CO2 emissions in the manufacturing process of concrete.
● A recent trend in research and commercial interests in carbon capture concrete is that of the CO2 consumed during the curing and mixing of concrete.
“There is no doubt that learning from the past is a way to face the modern challenge to enhance the efficiency of the use of by-products (pozzolanic materials), as it guarantees the use of fewer natural resources and the reduction of solid waste generated by the construction industry, which directly impacts the environment,” said Dr. Evangelista.
A 2,000-Year-Old Roman Engineering Secret Could Make Today’s Buildings Greener
We Finally Know How Ancient Roman Concrete Was So Durable
Current Trends on Concrete as Construction Material to Capture CO2
The Growth of Sustainable Concrete
Green Cement Transformation Project
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