Vagueness and the Aftermath - A sporadic diary

[RED-DOG]

The next time I use concrete, I swear I'm going to do my own cube test.

I'll use Chinese takeaway cartons to form the cubes, and I'll crush them in my dad's vice.

[RED-DOG]

Is it true about the concrete in the hoover dam?

Yes it is.

Please ignore Boshi, boldie & Gatso. They really are naughty boys.

[tikay]

Is WHAT true about concrete in the Hoover Dam?

Incidentally, when concrete is poured in large volumes, the process of hardening, setting, "going off", call it what you will, generates incredible amounts of heat, & that heat must be controlled, or it will cause damage to the concrete, so it has to be kept below a certain temperature.

Some amazing stats about the heat generated in the Hoover Dam exist somewhere, iirc.

Some general stuff here......

http://hooverdamtourcompany.com/build.html

And......

http://en.wikipedia.org/wiki/Hoover_Dam

And in particular, 2.4, "Concrete", which says.....

".....The first concrete was poured into the dam on June 6, 1933, 18 months ahead of schedule.[57] Since concrete heats and contracts as it cures, the potential for uneven cooling and contraction of the concrete posed a serious problem. Bureau of Reclamation engineers calculated that if the dam was built in a single continuous pour, the concrete would take 125 years to cool and the resulting stresses would cause the dam to crack and crumble. Instead, the ground where the dam was to rise was marked with rectangles, and concrete blocks in columns were poured, some as large as 50 feet (15 m) square and 5 feet (1.5 m) high.[58] Each five-foot form contained a series of 1 inch (25 mm) steel pipes through which first cool river water, then ice-cold water from a refrigeration plant was run. Once an individual block had cured and had stopped contracting, the pipes were filled with grout. Grout was also used to fill the hairline spaces between columns, which were grooved to increase the strength of the joins.[59]

The concrete was delivered in huge steel buckets 7 feet (2.1 m) high and almost 7 feet (2.1 m) in diameter—Crowe was awarded two patents for their design. These buckets, which weighed 20 short tons (18 t) when full, were filled at two massive concrete plants on the Nevada side, and were delivered to the site in special railcars. The buckets were then suspended from aerial cableways, which were used to deliver the bucket to a specific column. As the required grade of aggregate in the concrete differed depending on placement in the dam (from pea-sized gravel to 9 inch (230 mm) stones), it was vital that the bucket be maneuvered to the proper column. Once the bottom of the bucket opened up, disgorging 8 cubic yards (6.1 m3) of concrete, a team of men worked it throughout the form. Although there are myths that men were caught in the pour and are entombed in the dam to this day, each bucket only deepened the concrete in a form by an inch, and Six Companies engineers would not have permitted a flaw caused by the presence of a human body.[60]

A total of 3,250,000 cubic yards (2,480,000 m3) of concrete was used in the dam before concrete pouring ceased on May 29, 1935. In addition, 1,110,000 cubic yards (850,000 m3) were used in the power plant and other works. More than 582 miles (937 km) of cooling pipes were placed within the concrete. Overall, there is enough concrete in the dam to pave a two-lane highway from San Francisco to New York.[45] Concrete cores were removed from the dam for testing in 1995; they showed that "Hoover Dam's concrete has continued to slowly gain strength" and the dam is composed of a "durable concrete having a compressive strength exceeding the range typically found in normal mass concrete".[61] Hoover Dam concrete is not subject to Alkali-Silica Reaction (ASR) as the Hoover Dam builders happened to use nonreactive aggregate, unlike that at downstream Parker Dam, where ASR has caused measurable deterioration.[61]....."

[tikay]

Note, by the by, that the concrete in the Hoover Dam is still, 80 odd years after being cast, still gaining strength. This is true of all concrete.

I can imagine some folks eyes are bleeding, reading all this, but concrete really has changed the world we live in.

Next up, an even more fascinating, & taken for granted subject - glass.........Don't start me offf on that!

[TheChipPrince]

That the concrete in the middle won't set for 800 years.

[tikay]

That the concrete in the middle won't set for 800 years.

Well not EXACTLY, no, the term "set" is very wide, but esssentialy, it "sets" within hours.

However, it continues to gain strength almost infinitely. I have no idea for how long, "800 years" sounds like a bit of guesswork, but for sure, it will gain strength for a very long time.

In the glass department, another oddity was reported in Bryson's ASHONE.

He said that the stained glass in some 600 year old Cathedral was thicker at the bottom than the top, because, over the centuries, gravity caused the glass to move downwards. I think we can allow Gatters to call BS on that one, but who knows?

[boldie]

From the Bureau of Reclamation;

If the heat produced by the curing concrete could have been concentrated in a baking oven, it would have been sufficient to bake 500,000 loaves of bread per day for three years.

http://www.usbr.gov/lc/hooverdam/History/essays/concrete.html

[RED-DOG]

That the concrete in the middle won't set for 800 years.

Well not EXACTLY, no, the term "set" is very wide, but esssentialy, it "sets" within hours.

However, it continues to gain strength almost infinitely. I have no idea for how long, "800 years" sounds like a bit of guesswork, but for sure, it will gain strength for a very long time.

In the glass department, another oddity was reported in Bryson's ASHONE.

He said that the stained glass in some 600 year old Cathedral was thicker at the bottom than the top, because, over the centuries, gravity caused the glass to move downwards. I think we can allow Gatters to call BS on that one, but who knows?

Note: I wasted a considerable amount of time and lost a large chunk of my dignity searching for a book called ASHONE by Bill Bryson.

[gatso]

He said that the stained glass in some 600 year old Cathedral was thicker at the bottom than the top, because, over the centuries, gravity caused the glass to move downwards. I think we can allow Gatters to call BS on that one, but who knows?

ooh, this one's easy

olde style glass manufacture wasn't as good as nowadays, you'd have thicker bits and thinner bits so obv you put the thicker bit at the bottom when you're fitting it. common sense really

got stuff to do now. can people hold off posting nonsense while I'm away?

[RED-DOG]

He said that the stained glass in some 600 year old Cathedral was thicker at the bottom than the top, because, over the centuries, gravity caused the glass to move downwards. I think we can allow Gatters to call BS on that one, but who knows?

ooh, this one's easy

olde style glass manufacture wasn't as good as nowadays, you'd have thicker bits and thinner bits so obv you put the thicker bit at the bottom when you're fitting it. common sense really

got stuff to do now. can people hold off posting nonsense while I'm away?

That's the best time to post nonsense surely....

[AndrewT]

Please don't post any more facts on this thread unless gatso is online to vet them.

If this thread was on QI it would break the klaxon.

[tikay]

He said that the stained glass in some 600 year old Cathedral was thicker at the bottom than the top, because, over the centuries, gravity caused the glass to move downwards. I think we can allow Gatters to call BS on that one, but who knows?

ooh, this one's easy

olde style glass manufacture wasn't as good as nowadays, you'd have thicker bits and thinner bits so obv you put the thicker bit at the bottom when you're fitting it. common sense really

got stuff to do now. can people hold off posting nonsense while I'm away?

That fits, for me, I'll buy that.

[RED-DOG]

Please don't post any more facts on this thread unless gatso is online to vet them.

If this thread was on QI it would break the klaxon.

'Klaxon' is a name that does not belong to one of Santa's reindeer. Fact!

[outragous76]

maybe only tony will appreciate this, but "cube testing" of concrete gave me my 2nd biggest sweat of my professional career!

As tony mentioned you test cubes every 7 days to ensure they have reached the specification. Its not often that you get past 14 or 21 days before confirmation.

I once had failed tests right the way up to 42 days (6 weeks)!  In the mean time superstructure was up, roof on, wall cladding complete and we were due to commence the internal fit out on the Monday! Oh, and this was of a 100,00sq ft industrial unit. The problem being that if the cube test fails, the remedy is to rip the floor out and re-pour. Now although the subcontractor would be at fault, as a project manager it isn't ideal!

Cube day 42 squeaked past and we cracked on! There wee many visits to the toilet that sunday night!

[outragous76]

and Tom, to continue your concrete education, Im sure you are aware of how a traditional reinforced concrete slab would be constructed with steel mesh

well google "steel fibre concrete reinforcement"

Imagine the time saved on these huge steel portal frame sheds you see everywhere, and just marvel in the genius of it! (it is not without problems thou!)