Talk:Concrete

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[edit] Cracking

I changed the third sentence in the first paragraph of section 3.4 ("Cracking") from "Extending the period concrete stays damp during curing increases its strength." to "The strength of the concrete can be increased by keeping it damp for a longer period during the curing process."

I think it is easier to understand this way.

Truly confused. You say: it is both particular and *an individual*, hence occupying some space and time. But an individual as a noun refers to a person. I think you want to say that: it is both particular and individual, hence occupying some space and time. Then you expand on this and compound the confusion with: So, to say that something is concrete is to say that it is a particular *individual* that is located at a particular place and time. Are only individuals, i.e. people, concrete? I always thought my PC was concrete. I guess I had better look at it. An abstract PC will be little help in disputing this definition. Please clarify.

'Individuals' (as in P. F. Strawson's book by the title) in philosophical jargon refer not just to individual human beings but to any individual (numerically singular) thing.

A beautiful pun one of my profs made, completely unintentionally: Sometimes being concrete actually makes things harder. We need a place to put information about sidewalk-stuff, too.

:-) Hopefully, we'll be able to start disambiguating words with parentheses; then I'll direct you to concrete (metaphysics), I suppose.----

"In general, a [[concept]] is considered concrete if it is not abstract..."(from concrete)
"A concept is an abstract, universal mental entity that serves to designate a category or class of entities, events or relations."(from concept link)
I think I'm confused:)

The article mentions John Smeaton as the pioneer of the use of portland cement in concrete. John Smeaton's article, however, makes no mention of this, and both the [portland cement] and the [Joseph Aspdin] article cite Joseph Aspdin as its inventor. Can someone clarify/confirm? Uly 12:04, 12 May 2005 (UTC)

I need some help and advice on the production of cement and concrete in the 19th century. This relates to Oak Island (see entry in Wikipedia). I also have a website for collaborative study on this (some content has restricted access - pls just ask): http://oakisland.esolutionswork.com). Thanks - John Bartram

[edit] Cement versus concrete

Since cememt is redirected to concrete, could someone give the differences between the two perhaps structurally and in their uses? 69.181.82.210 06:01, 30 August 2005 (UTC)

Concrete is the complete mixture: Portland cement, water, the aggregate (for example, crushed rock), and any other additives.

Technically speaking, cement is just the Portland cement that glues the aggregate together. But it's often used colloquially (and incorrectly) as a synonym for concrete.

Atlant 14:22, 30 August 2005 (UTC)

Redirection of Cement is fixed. The Cement topic is up and running again.
Oyvind 17:09, August 30, 2005 (UTC)

Portland cement concrete is the default meaning of "concrete" in this context, but there are other types of concrete. For example, asphalt is sometimes called "bituminous concrete". Polymer concrete uses resins as the binder/cement; cultured marble, which is commonly used for bathroom sinks, is one example of polymer concrete. --Leo Schlosberg 21:07, 3 November 2005 (UTC)

If portland cement was invented in 1824, how could smeaton have pioneered the use of it in concrete in 1756?

The romans pioneered concrete even before that. You don't neet portland cement to make concrete. -- Dullfig 17:54, 27 February 2006 (UTC)

[edit] Roman Concrete

I have a book that explains the whole topic of Roman Concrete. Roman concrete was a mixture of quicklime and pozolan. Quicklime had already been used as a mortar, but when pozolan was added, the romans discovered that the resulting mixture had hydraulic properties, in other words, the concrete would set underwater. Since quicklime is more flexible than modern day portland cement, roman constructions have lasted 2000 years without the need for expansion joints.

Should we add a sepparate topic for roman concrete? -- Dullfig 19:47, 11 February 2006 (UTC)

Probably just fleshing-out the subheading would suffice. If you wanted to get really technical, you could fill a book with it (but then it wouldn't be an encyclopedia entry anymore). I did a project on ancient Roman concrete for one of my masters courses. --King aardvark 18:08, 24 February 2006 (UTC)

Roman concrete is a very important topic (I would rather know about it than all of the boring modern crap) which deserves a full section. — Chameleon 07:31, 15 August 2007 (UTC)

The Italian word for concrete is calcestruzzo, which is lime ostrich. Why do the Italians consider concrete to be lime ostrich please? Thank you for helping me to understand this. --Prospect Vale 19:47, 21 October 2007

[edit] Poured concrete, esp. for naval architecture

Does anybody know how Poured Concrete Construction is done, especially for naval artictecutre? ---User:kstephent 14:06 (EST), 09 March 2006. (By the way, did you know Hermann Georing suggested a concrete locomotive?)

If you're talking about ferrocement boat hulls, isn't that usually gunnite/shotcrete sprayed onto rebar set in a plywood form that creates the outer, smooth shape of the hull? If so, the linked article has a section on that. Or are you asking a different question when you say "naval architecture?

Atlant 19:35, 9 March 2006 (UTC)

[edit] All concrete poured?

Surly all concrete is poured unless we place a distinction between those drier materials used for road bases or machine laid pavement quality concretes which have litle workability (or consistence as now termed in European standards). Perhaps the distinction shouldbe precast as opposed insitu?

One area of confusion that is bound to occur is the difference in terminology between America concrete industy and the European counterpart.

Actually, not all concrete is poured. Certain low-tech concrete products (such as the kind you set your mailbox post into) are set as powder in the hole or mixed with earth in the hole, then watered "in place". I'm not sure, but a similar process may sometimes be used to form rammed earth construction blocks.

Closer to reality ( :-) ), shotcrete really isn't poured.

Atlant 01:02, 21 March 2006 (UTC)

At least all concrete is placed by some sort of action.. Oyvind 07:55, 21 March 2006 (UTC)

Roman concrete was pretty stiff. it was done in layers. the workers placed fist sized stones in a layer, and then the concrete was tamped into place with bars. -- Dullfig 23:57, 23 March 2006 (UTC)

Hi, yes, when one comes to think of it not all concrete is poured. The strength of concrete is determined by the water cement ratio, the less water in the mix the higher the final cured strength. We also get rollcrete used in the construction of large dams. Some mixes are very dry when placed in moulds which are rammed hydraulicly to provide required compaction. Some is pumped too. Regards, Gregorydavid 07:14, 24 March 2006 (UTC)

[edit] Glasscrete ?

Does anyone have information on substituting recycled glass for the sand and/or aggregate? I've heard it can be substituted up to 50% and can change the appearance of the finished concrete noticeably. Make it decorative and mottled, or more reflective, or more irridescent. Bill 17:53, 12 April 2006 (UTC)

[edit] Discussion pertaining to worldwide useage and practice

The examples and perspective in this article or section may not represent a worldwide view of the subject.
Please improve this article or discuss the issue on the talk page.

Is there any disagreement about anything in the article? Gregorydavid 11:18, 26 May 2006 (UTC)

Although I am not responsible for the globalisation banner I appreciate why it's there, having read the article it comes across as US biased. Out of interest do you think there are enough editors with knowledge of concrete to give this article a real improvement drive? The basis is there but still alot of work to do, ie. no references, thoughts anyone? Grahams Child 20:53, 27 May 2006 (UTC)

I know a very little about non-US concrete practice, but engineering research into concrete is international, and my impression is that basic concrete practice is similar across the world. Argyriou 23:17, 1 June 2006 (UTC)

Yes, I think there is consensus worldwide regarding what constitutes good and bad practice, ie generally accepted practice by experts. "Concrete technology" focuses on mix design and related topics while "Concrete design" relates to the structural and stress related aspects of concrete usage.

So the article needs to refined a bit more..Gregorydavid 17:58, 9 August 2006 (UTC)

[edit] Removed subsection

The subsection removed in this diff was a copy and paste from the link it contained, and I couldn't see anything granting the right the GFDL the text. - Taxman ^Talk 04:12, 1 July 2006 (UTC)

I've replaced the removed section with my own paraphrase of a different source. The subsection should be included, as it's an interesting way of placing concrete, but we shouldn't be copyvio here. Argyriou 05:19, 1 July 2006 (UTC)

Great, thank you. I didn't know enough to know if it was important enough, but I figured someone here would. - Taxman ^Talk 14:55, 1 July 2006 (UTC)

[edit] Slump

I have a real problem with the rules of thumb for improving slump in this article. Slump should NEVER be increased by arbitrarily adding water - it is extremely bad practice. If concrete doesn't have the right slump then it should be rejected, and a concrete with the required slump ordered from the producer. Alternatively, if you are making the concrete yourself, you again reject the concrete and adjust the mix proportions to get the slump you want. Does anyone agree that it should be deleted? —The preceding unsigned comment was added by Kpeyn (talk • contribs) .

Increasing a slump by adding a water will increase w/c ratio, lower the strength, and increase concrete penetreability reducing thus its durability. Slump may be increased during concrete mixing by adding superplasticizers and water reducers (see eg. Concretenetwork.com). petr.konec 21 August 2006

[edit] Concrete building techniques

There should be a section of concrete building techniques containing the techniques used in building with concrete such as:

pressurized concrete
prestressed concrete
as well as other techniques

Examples could be given aswell of other techniques such as those used in bunkers to strengthen the structure (or building).

This is Wikipedia, so you know what to do: be bold and start editing!

Atlant 12:36, 10 August 2006 (UTC)

[edit] Annual concrete production

The article says: As of 2005, over six billion tons of concrete are made each year, amounting to the equivalent of one ton for every person on Earth. Shouldn't it be six billion qubic metres (instead of tons)? According to Cement statistics (pdf), in 2002 the world production of cement was 1800,000,000 tons. Assuming 320 kg cement per qubic meter concrete in average, the concrete production in 2002 was 1800,000,000 / 0.32 = 5,625,000,000 m3 concrete. Mr. Carpenter 16:16, 11 August 2006 (UTC)

[edit] AfD Nomination: Eco-cement

The article Eco-cement has been listed at Wikipedia:Articles for deletion/Eco-cement. Please consider contributing to the discussion. Thank you. Argyriou 00:43, 24 August 2006 (UTC)

[edit] Rediscovery

From Anachronism:

A good example of this would be concrete, being used in the past by various ancient cultures only to be forgotten about and then re-invented at a later time by another culture, until the present, at which point the technology is employed globally and unlikely to slip into obscurity again.

Could the history section be more concrete (hehe) about these rediscoveries?

[edit] Length

As I was reading this article, I realized that it is rather long. It goes into greater detail than would seem (to me) optimal for Wiki.LorenzoB 04:36, 22 October 2006 (UTC)

[edit] Water impermeability and porosity

I'd be interested to know about the characteristics of concrete which relate to water impermeability and porosity. Some concretes are clearly very water resistant, and can be used to create ponds and lakes, while others are less so. Some concrete structures, even ponds, are coated with water resistant surface material to reduce leakage, or water penetration. One of the failure modes of reinforced or prestressed concrete is, I think, due to failure of the metal reinforcement due to water ingress. Concrete used to create foundations could retain a significant amount of water if allowed to become wet (after curing). It'd be interesting to have a few more pointers to all this. David Martland 17:33, 30 November 2006 (UTC)

Italic textThe permiability of concrete is controlled by it's porosity. As the water/cement ratio reduces, the products of hydration occupy more space within the matrix resulting in a lower porosity. At water/cement ratios greater than 0.38, there is not sufficient volume of gel formed to fully fill the space available to it and so leaves capillary pores. At water/cemet ratios less than about 0.7 (depending on the fineness of the cement used), the capillary pores will become discontinuous so reducing permiability if the concrete is allowed to mature sufficiently by wet curing.

Corrosion of the reinforcement can only occur if the concrete has carbonated which can be a slow process in a buried foundation. The design life of the structure can be easly met by ensuring adequate cover to the reinforcement and a sufficiently low water/cement ratio.

[edit] External links

It seemed to me that the external links were mostly WP:SPAM. I pruned them, but may have deleted something useful. If so, it would be good to make it a WP:FN, instead of an WP:EL. --Walter Siegmund (talk) 04:28, 23 October 2006 (UTC)

[edit] Severe vandalism

There has been severe vandalism by anon ip users to this article. [1] [2] [3] [4] --Parker007 02:52, 21 January 2007 (UTC)

[edit] Chemistry

Maybe there should be a section wtih the general chemistry in it... Sikkema 10:45, 22 January 2007 (UTC)

[edit] Mix Ratios and Yields

I have scowered many web site and tech manuals but have failed to come up with a good description of how to mix concrete given the proper ratios of cement/sand/aggregate(gravel)/water. Many web sites work with either Metric or Pounds (Mass). These are not practical for the person who is preparing the mixture and is interested in Volume i.e.: How much cement/sand/aggregate(gravel)/water will produce how many m³ or ft³ etc.. Note that a sack of cement bought in the USA = 1ft^3 = 94 lbs = 42.6 kgs = .02832 m^3 while a sack of cement bought in Mexico = 1.17ft^3 = 110 lbs = 50 kgs = .03321m^3

The average (non-commercial) work site does not have a scale, but does have shovels, buckets, usually a mixer and a wheel barrow used to prepare and measure porportions.

Sam@leapofaith.net 02:20, 1 February 2007 (UTC)

Wikipedia is not an instruction manual. If you're mixing concrete on your jobsite, you should get a scale, or have a reasonably good idea of the bulk density of your sand and gravel, and do the volume conversions ahead of time based on some standard volume measure the jobsite will have, like 5-gallon buckets. Αργυριου (talk) 00:33, 4 May 2007 (UTC)

I agree that the wikipedia entry for concrete should have some basic information or examples of concrete formulas, such as the percentage (by weight) of cement, sand, and stone to make a typical batch. While it is said that the strength of a batch is determined by the w/c ratio, what is not mentioned is the c/a ratio (cement to agreggate ratio) or the sand/stone ratio. I make a typical batch as follows:

Cement: 23 lbs Stone (1/2" or 3/4"): 88 lbs Sand: 59 lbs

This gives a c/a ratio of 15.6%, and a sand/stone ratio of 67%. —Preceding unsigned comment added by 65.93.89.28 (talk • contribs) 04:19, 26 July 2007 (UTC)

[edit] Smeaton/Portland cement

Since Portland cement was invented in 1826, John Smeaton couldn't have used it in 1756. Smeaton used various limes in mortar and concrete, and noted that the more argillaceous limes were more hydraulic. He also compared the color of his concrete to "good Portland stone", and so may have inspired Joseph Aspdin to name his 1826 product "Portland cement". But Portland cement, which was initially an ultra-fast setting stuccoing material, was not used in concrete until the modern, hard-burned product was introduced by William Aspdin in the 1840s. Click the links for more info on this. . . . LinguisticDemographer 22:18, 17 July 2007 (UTC)

[edit] Cement trucks

Hi, I wonder if someone could answer a couple of trivia questions: 1) Is there something preventing concrete from hardening in those rotating cement mixer trucks, or are they just hoping that they'll get to their destination in time? 2) What happens if it does harden in there? Do they just discard the barrel, or is there some way to deconstruct it and get it off the concrete plug? Thanks! --Sean 20:56, 10 August 2007 (UTC)

The concrete has to be delivered and poured within a certain time. You can add additives that make the concrete dry quicker, slower, more dense, to make air bubbles, more fluid (SCC), ect… ect…

If the concrete has dried to much (still liquid) by the time it reaches a building site, the barrel will have to be emptied, back at the mixing plant (or in extreme cases where it stands).

--LJ 13:29, 12 September 2007 (UTC)

The concrete in the truck is usally a dry mixture, which cannot harden. The water is stored in a tank, which is behind the drivers cabin and is only added 15-20 minutes before the mixture is used up (so it can be mixed well). Should the concrete harden in the barrel, then workers can climb in through the small hole in the sid (which is usally sealed off) and break it up with a jackhammer. It's a hard job, but the truck is worth it. Hthomasxx (talk) 20:17, 9 December 2007 (UTC)

This is not commonly the case in California - concrete is batched wet and poured into the truck. Argyriou (talk) 05:55, 10 December 2007 (UTC)

Concrete is mixed in the drum. Water is not added once they get to the job. You have moisture in the sand so you already have a product where hydration has started. The mix is measured in what concrete producers call slump. Once the load is put into the truck the driver has to go straight to the job. Hoping there are no delays. Depending on the outside tempurature concrete is usually good for 90 minutes. But if it gets hot inside the drum the last edit is what can happen and that is not fun. —Preceding unsigned comment added by 214.13.3.165 (talk) 09:57, 15 January 2008 (UTC)

[edit] environmental issues

I have heard a couple of times that concrete is rather environmentally unfriendly and came here hoping to find out more. The article seems a bit lacking in this respect, apart from part of a sentence in the History section. This isn't meant as a complaint but as a suggestion for expansion.81.174.226.229 (talk) 10:01, 8 January 2008 (UTC)

If concrete is not used with common sense in the plastic state it can be a hazard to the enviroment. But once it sets it is used a protection layer for the enviroment. Do some searching on Pervious concrete. It is being used for alot of stormwater runoff. —Preceding unsigned comment added by 214.13.3.165 (talk) 10:01, 15 January 2008 (UTC)

I was referring more to quarrying and to the energy used (and carbon dioxide released) in its production.81.174.226.229 (talk) 10:20, 16 January 2008 (UTC)

I just watched a program (grand designs) that said the concrete industry created more co2 than the airlines and gave the frightening statistic of something like a ton of co2 per ton of concrete, however a quick search comes up with the website http://www.sustainableconcrete.org.uk/ which instead says The embodied carbon dioxide (ECO2) of a tonne of concrete varies with mix design and is in the range of: 75-176kg CO2/tonne to complete the topic the enviormental aspect has to be coveredBack ache (talk) 23:24, 27 March 2008 (UTC)

An alternative to concrete is Trass, its ecologic and feautures about the same strength/feautures as concrete (some advantages over concrete too as quicker hardening (3x quicker), elasticity, water density, drying, less skin-aggressive, ... ; include in article.

Thanks, KVDP (talk) 07:11, 13 May 2008 (UTC)

[edit] What I'm doing

As those of you that may have been watching the history may have noticed, I'm attempting to slowly beat the article into a more readable, concise shape.

My current plans are more or less to smash most of the 'types of concrete' heading into one comparatively easy to understand at a glance table, listing major constituents (water, cement, aggregate, special features, uses) with a new types of concrete or similar article.

concrete failure modes swallows much of the cracking and environmental damage sections, with a short sentence or table detailing each of the failure modes.

Perhaps instead a concrete engineering practice entry, covering in a little more detail some aspects of this article, and also add more on crack control, stopping short of a full blown concrete-textbook.

Also more clearly separate cementatitious concrete from others in this article, highlighting differences and commonalities.

--Speedevil (talk) 05:41, 28 January 2008 (UTC)

[edit] Concrete vs Mortar

As it is defined now in this article there is no difference between mortar and concrete (check mortar article) other than usage when in reality mortar and concrete are different preparations. Mortar has only fine granulometry aggregate while concrete has both fine and coarse granulometry aggregates. Without the coarse aggregate the preparation is mortar not concrete. —Preceding unsigned comment added by 80.36.158.120 (talk) 02:54, 17 April 2008 (UTC)

[edit] Geopolymer green concrete

I added this section: I was surprised it wasn't mentioned here already as it seems to be the green-est concrete going. According to the manufacturer anyway. I moved the reference to the company to a footnote so as not to appear like an advertisement. But given that is where mostly the info came from and a tele-documentary, and, as they are they only ones making it commercially and not just academically, as far as I am aware, I think the footnote should stay. So by all means edit it but please dont DONT edit it out otherwise readers wont know where to go to find out more. (BTW: I have absolutely nothing whatsoever to do with the company or even the industry for that matter. (Although I would like to buy some of their stock ;-)) ) Regards, 122.148.173.37 (talk) 11:43, 22 May 2008 (UTC)

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