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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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#1
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OT - High-mix and low-mix concrete
I just finished a book describing the building
of Boulder Dam, and there's something I don't understand. The book mentioned that two concrete batch plants were made, one to product "low-mix" concrete for the lower portions of the dam and another to produce "high-mix" concrete for the top. The two plants were not run at the same time. Any ideas as to why they needed two separate plants and what the difference in the concrete was? |
#2
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OT - High-mix and low-mix concrete
This is somewhat speculation, and some bit of foggy memory so somebody that
really is up on this feel free to disabuse me. From what I understand the engineers needed one monolithic block of concrete when all was said and done so the lower portions were blended to cure real slowly so the end result would be no seams. Also the lower part of the damn is much thicker than the upper part but the concrete mixture had to be adjusted to maintain a steady cure rate and the thinner sections having less cross section had to be a hotter mix than the lower part because the heat generated from the chemical reaction was disapated faster in the thinner sections. -- Roger Shoaf If knowledge is power, and power corrupts, what does this say about the Congress? "Jim Stewart" wrote in message ... I just finished a book describing the building of Boulder Dam, and there's something I don't understand. The book mentioned that two concrete batch plants were made, one to product "low-mix" concrete for the lower portions of the dam and another to produce "high-mix" concrete for the top. The two plants were not run at the same time. Any ideas as to why they needed two separate plants and what the difference in the concrete was? |
#3
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OT - High-mix and low-mix concrete
Roger Shoaf wrote:
This is somewhat speculation, and some bit of foggy memory so somebody that really is up on this feel free to disabuse me. From what I understand the engineers needed one monolithic block of concrete when all was said and done so the lower portions were blended to cure real slowly so the end result would be no seams. Also the lower part of the damn is much thicker than the upper part but the concrete mixture had to be adjusted to maintain a steady cure rate and the thinner sections having less cross section had to be a hotter mix than the lower part because the heat generated from the chemical reaction was disapated faster in the thinner sections. -- Roger Shoaf If knowledge is power, and power corrupts, what does this say about the Congress? "Jim Stewart" wrote in message ... I just finished a book describing the building of Boulder Dam, and there's something I don't understand. The book mentioned that two concrete batch plants were made, one to product "low-mix" concrete for the lower portions of the dam and another to produce "high-mix" concrete for the top. The two plants were not run at the same time. Any ideas as to why they needed two separate plants and what the difference in the concrete was? From a contemporary account: "On the trestle-bridge mentioned above, was placed a fifty-ton traveling crane with which to dump the concrete. The concrete was mixed in two houses, one on either side of the river, by the world's largest and most up-to-date mixing plants. It was carried from these plants to the fifty-ton crane by a traveling chain of buckets. The structure of the dam is honeycombed with thousands of pipes, the purpose of which is to cool the concrete. As the concrete hardens great heat is generated inside the structure, and it is said that it would take one hundred and fifty years for it to cool naturally, but by passing icy water through the pipes the engineers are able to reduce the temperature to normal within a month." Jim *** Posted via a free Usenet account from http://www.teranews.com *** |
#4
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OT - High-mix and low-mix concrete
I've read that the Three Gorges Dam on Yangtze River
uses over a dozen different concrete formulations depending on the task and conditions. Jim Stewart wrote: I just finished a book describing the building of Boulder Dam, and there's something I don't understand. The book mentioned that two concrete batch plants were made, one to product "low-mix" concrete for the lower portions of the dam and another to produce "high-mix" concrete for the top. The two plants were not run at the same time. Any ideas as to why they needed two separate plants and what the difference in the concrete was? |
#5
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OT - High-mix and low-mix concrete
I would suspect that the interior portions of the dam run lower strength
(less % of portland cement) mixes. Major sections of the dam are mostly filler. I did some reading years back, the "gravel" used for the dam was graded with rocks up to 6" or so. Why not, the best concrete mixes use a variety of aggregate sizes to produce the best 'fit' of small pieces next to larger pieces. Jim Stewart wrote: I just finished a book describing the building of Boulder Dam, and there's something I don't understand. The book mentioned that two concrete batch plants were made, one to product "low-mix" concrete for the lower portions of the dam and another to produce "high-mix" concrete for the top. The two plants were not run at the same time. Any ideas as to why they needed two separate plants and what the difference in the concrete was? |
#6
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OT - High-mix and low-mix concrete
Jim Stewart wrote:
I just finished a book describing the building of Boulder Dam, and there's something I don't understand. The book mentioned that two concrete batch plants were made, one to product "low-mix" concrete for the lower portions of the dam and another to produce "high-mix" concrete for the top. The two plants were not run at the same time. Any ideas as to why they needed two separate plants and what the difference in the concrete was? My speculation: Modern bath plants vary the cement content in each load in accordance with the customer's order. The plants used in building that dam didn't have the technology that we use today to vary cement content so easily, and since there was plenty of demand (round the clock pouring), it made sense to have two plants, each producing a diffent mix. -- Gary Brady Austin, TX www.powdercoatoven.4t.com |
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