Roman concrete or opus caementicium was invented in the late 3rd century BC when builders added a volcanic dust called pozzolana to mortar made of a mixture of lime or gypsum, brick or rock pieces and water. The seawater would then hydrate the lime and trigger a hot chemical reaction which hardened the concrete.

600 BC – Rome: Although the Ancient Romans weren’t the first to create concrete, they were first to utilize this material widespread. By 200 BC, the Romans successfully implemented the use of concrete in the majority of their construction. They used a mixture of volcanic ash, lime, and seawater to form the mix.

They found that the Romans made concrete by mixing lime and volcanic rock to form a mortar. To build underwater structures, this mortar and volcanic tuff were packed into wooden forms. In addition to being more durable than Portland cement, argue, Roman concrete also appears to be more sustainable to produce.

Scientists Have Figured Out How Ancient Rome’s Concrete Has Survived 2,000 Years. “Contrary to the principles of modern cement-based concrete, the Romans created a rock-like concrete that thrives in open chemical exchange with seawater,” lead author Marie Jackson from the University of Utah said in the journal.

Roman concrete was based on a hydraulic-setting cement. It is durable due to its incorporation of pozzolanic ash, which prevents cracks from spreading. By the middle of the 1st century, the material was used frequently, often brick-faced, although variations in aggregate allowed different arrangements of materials.

Roman recipe lasted 2,000 years thanks to strengthening reactions with seawater. Instead of Portland cement, the Roman concrete used a mix of volcanic ash and lime to bind rock fragments. …

As it turns out, not only is Roman concrete more durable than what we can make today, but it actually gets stronger over time. This aggregate has to be inert, because any unwanted chemical reaction can cause cracks in the concrete, leading to erosion and crumbling of the structures.

It turns out the ancient Romans had the perfect recipe for water-resistant concrete. The material, called opus caementicium by the Romans, is made from a hydraulic cement, meaning it can set underwater or in wet conditions.

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. Because both minerals take centuries to strengthen concrete, modern scientists are still working on recreating a modern version of Roman cement.

Around 3000 BC, the ancient Egyptians used mud mixed with straw to form bricks. Mud with straw is more similar to adobe than concrete. However, they also used gypsum and lime mortars in building the pyramids, although most of us think of mortar and concrete as two different materials.

Is cement stronger than concrete? Cement is not stronger than concrete. On its own, in fact, cement is prone to cracking. When combined with aggregate materials and water and allowed to harden, however, cement—now concrete—is extraordinarily strong.

If you had time to complete the finishing process and the concrete has stiffened (typically 4 to 8 hours after mixing), rainwater may cause little if any damage. In fact, once concrete sets, water on the surface is actually beneficial because it aids in hydration and curing.

DO spray new concrete with water. One of the most common methods for curing concrete is to hose it down frequently with water—five to 10 times per day, or as often as you can—for the first seven days. Moist-cured concrete can be up to 50 percent stronger than concrete that was cured without being dampened!

Concrete typically takes 24 to 48 hours to dry enough for you to walk or drive on it. However, concrete drying is a continuous and fluid event, and usually reaches its full effective strength after about 28 days.

Regardless how fast the concrete was poured, contractors realized that by using traditional processes, it would take 100 years for the dam’s concrete to cool and cure. And once it did cool, the concrete would crack, rendering the dam useless.

Your new concrete is designed to reach 90% of its full strength potential after 7 days, so feel free to drive your personal vehicle on it then. It will take additional time before you can drive or park heavy equipment or machinery on your newly poured concrete, so make sure to wait at least 30 days.

From above table, we see that, concrete gains 16 percent strength in one day, 40 percent in 3 days, 65% in 7 days, 90% in 14 days and 99% strength in 28 days. Thus, it is clear that concrete gains its strength rapidly in the initial days after casting, i.e. 90% in only 14 days.

TIL that even after 78 years, the cement in the Hoover Dam is still curing. As far as I know, concrete curing is a reaction that could potentially be occurring for thousands of years. The more it cures, the slower it cures, meaning it might never finish curing, it would just approach an extremely slow rate.

So, there are no bodies buried in Hoover Dam. The question about fatalities is more difficult to answer, because it depends in a large part on who is included as having “died on the project.” For example, some sources cite the number of deaths as 112.

Blast the dam loose from the rock on both sides, and Hoover will just sit there while the water squirts around the sides where the rock was damaged. It would be very, very hard to significantly damage Hoover with a quake of any possible magnitude.

In 2004, a regional security manager for the bureau told the Las Vegas Review-Journal that about 30 people had jumped to their deaths from the dam since it opened in 1936.

An unnamed source stated that since 1936 when the dam was completed and open for tours, approximately 100 people had perished by suicide. Another official places that number in the “20’s.

New York City, New York, U.S. Evelyn Francis McHale (September 20, 1923 – May 1, 1947) was an American bookkeeper who took her own life by jumping from the 86th-floor observation deck of the Empire State Building.

Three Gorges Dam

The Quatinah Barrage or Lake Homs Dam, located in Syria, is the oldest operational dam in the world. The dam was constructed during the reign of the Egyptian Pharaoh Sethi between 1319-1304 BC, and was expanded during the Roman period and between 1934 and 1938.

• Kariba Dam, Zimbabwe. Kariba Dam is the world’s biggest dam based on water storage capacity.
• Bratsk Dam, Russia.
• Akosombo Dam, Ghana.
• Daniel Johnson Dam, Canada.
• Guri Dam, Venezuela.
• W.A.C Bennett Dam, Canada.
• Krasnoyarsk Dam, Russia.
• Robert-Bourassa Dam, Canada.

China

The first constructed dams were gravity dams, which are straight dam made of masonry (stone brick) or concrete that resists the water load by means of weight. .” Around 2950-2750 B.C, the ancient Egyptians built the first known dam to exist.

The World’s 10 Largest Hydroelectric Dams

• Longtan Dam. Hongshui River, China.
• Grand Coulee. Columbia River, United States.
• Xiangjiaba. Jinsha River, China.
• Tucuruí Tocantins River, Brazil.
• Guri. Caroní River, Venezuela.
• Xiluodu. Jinsha River, China.
• Itaipu Dam. Paraná River, Brazil/Paraguay.
• Three Gorges Dam. Yangtze River, China.

List of largest dams