Is concrete in the Hoover Dam still curing?
Actually, the Hoover Dam is already cured. “The Hoover Dam concrete would cure in 125 years by conventional or natural methods. Crews, however, used some innovative engineering methods to hasten the process.
Now we are all vaguely aware that concrete heats and contracts as it cures, but that isn't usually a problem on any of our jobs. For the Hoover Dam, however, it was calculated that, make it in a continuous pour, and it would take 125 years to cool and would crack and crumble!
Scientists still don't 100% understand what's going on inside cement when it's setting. In chemistry labs this remains hotly-debated territory. Also intriguingly, it keeps on curing long after it's apparently set. The Hoover dam is still curing nearly a century after being built!
That's almost a quarter of a mile. At its base, the dam is a whopping 660 feet thick. That's longer than two football fields stretched end-to-end! At its top, Hoover Dam is 45 feet thick.
How was chemical heat caused by setting concrete in the dam dissipated? By embedding more than 582 miles of 1-inch steel pipe in the concrete and circulating ice water through it from a refrigeration plant could produce 1,000 tons of ice in 24 hours. Cooling was completed in March 1935.
Does concrete take 100 years to cure? No, this is a bit of a myth with the concrete industry. While concrete does continue to harden indefinitely, pore moisture has to drop below a certain level at some point and this isn't typically 100 years.
If Lake Mead were to run out of water, the Hoover Dam would no longer be able to generate power or provide water to surrounding cities and farms. The Colorado River would essentially stop flowing, and the Southwest would be in a major water crisis.
LIFE-SPAN OF DAMS AND COMPONENTS
The service life of a well-designed, well-constructed and well- maintained and monitored embankment and concrete dams can easily reach 100 years. Hydromechanical elements such as gates and their motors have to be replaced after 30 to 50 years.
It would cost well over a billion dollars, more than double what the U.S. government spent, in today's money, to build the dam in the first place.
The Dam Future
While the dam is expected to last for centuries, engineers predict the structure could last for more than 10,000 years, surpassing most remnants of human civilization if humans were to disappear from the earth.
How deep is the deepest part of Hoover Dam?
| Hoover Dam | |
|---|---|
| Maximum length | 112 mi (180 km) |
| Maximum water depth | 590 ft (180 m) |
| Normal elevation | 1,219 ft (372 m) |
| Power Station | |
The deepest point is now around 400 ft (122 m) below the surface. As of 2021, the overall water level dropped to an elevation of 1,071.56 ft (326.73 m) above sea level, which is about 140 ft (43 m) lower than the historical average. The lake's volume is around 44% of its capacity.
The dam tapers from 660 feet thick at its base to 45 feet thick at the top, which supports a road and sidewalks running across it. And get this: there is no rebar or other reinforcement in the entire dam – it's all concrete.
To divert the Colorado River's flow around the Hoover Dam construction site, four 56-foot-diameter tunnels were driven through the walls of Black Canyon, two on the Nevada side and two on the Arizona side. Their combined length was nearly 16,000 feet (more than three miles).
A major problem with a structure as large as the Hoover Dam was the cooling of the concrete. Engineers calculated that the massive amount of concrete would take over one hundred years to cool; when cool the dam would crack, rendering it useless. To avoid this, the dam was poured in rows and columns of blocks.
This means water levels at the largest man-made lake in the U.S., Lake Mead, are rapidly declining. While the wet weather has had some short-term benefits, it is unlikely to help the dire situation of Lake Mead's water levels.
About 60% of the area still is in drought. It would actually take six more years of heavy rainfall in a row to refill the Lake Mead reservoir completely. Time is ticking to solve the problem before future droughts dry up the lake completely.
Experts we spoke with agreed the feat would be astronomical. Still, it's physically possible. “As an engineer, I can guarantee you that it is doable,” Viadero said. “But there are tons of things that can be done but aren't ever done.”
Concrete is typically believed to last forever. While it may have ancient durability, its life span doesn't usually exceed 100 years. Architects recognize concrete as a stone-like, hom*ogeneous material, a mix of limestone and other rock.
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. Here are some of the basic facts regarding the question of concrete drying and curing time.
Does spraying water on concrete help it cure?
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. Known as “moist curing,” this allows the moisture in the concrete to evaporate slowly.
Three states and the country of Mexico uses water from the lake. Mack explained they all get a different allocation, a legal entitlement. “California, it gets the largest share. 4.4 million acre-feet of water is available to California.
If the Hoover Dam ever breaks, it would also wreck many dams downriver. The rushing water from Lake Mead would overwhelm the Davis Dam located 67 miles downstream, overtopping and possibly destroying the structure. There would be no way to stop all that water from moving as it continued south.
Curing times for concrete
Technically, concrete never stops curing. In fact, concrete gets stronger and stronger as time goes on. But, as far as we're concerned, to reach a practical strength, most industrial concrete mixes have a 28 day curing period.
A technique known as “wet-curing,” for example, involves laying special curing blankets across a concrete slab, dousing the blanketed surface with water, and keeping it constantly wet for 28 days.
In 1995, the Bureau of Reclamation's Materials Engineering and Research Laboratory completed a testing program to evaluate the long term properties of the Hoover Dam concrete. Compressive strengths at this time were found to average 7,230 lb/in2.
Your concrete should be solid enough to walk on, without leaving footprints, after anything from 24 to 48 hours. By seven days, your concrete should be cured to at least 70 percent of its full strength.
The concrete curing time takes about 28 days to be fully cured. Differences in weather, mix, and other items can slightly change the timeframe of the curing period. The general rule of thumb for concrete drying is 28 days to dry for every 1 inch of slab thickness.
Moist curing is a common method of concrete curing. It involves wetting the concrete slab often with water (5-7 times per day) for the first 7 days. This method ensures your concrete slab will be extremely strong and durable, because it allows the moisture to evaporate slowly, preventing cracks and shrinks.
HOW DOES RAIN AFFECT CONCRETE? Rain falling on top of freshly laid concrete can damage the surface and compromise a level and floated finish.
What happens if you don't water cure concrete?
Concrete that is not moist-cured at all dries too rapidly, and reaches less than half its potential design strength. It will also have a greater number of shrinkage cracks.
