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- 1 picture shows Portland-composite cement, not (Ordinary) Portland cement
- 2 physical properties
- 3 NPOV lacking in this article
- 4 possible mistake?
- 5 Formula mistake?
- 6 Global warming?
- 7 Possible mistake?
- 8 Regarding composition, Standards and emision
- 9 The picture is inaccurate.
- 10 Type Ia etc. Poor choice.
- 11 History
- 12 Cement plants as alternatives to conventional waste disposal or processing
- 13 History of cement
- 14 CO2
- 15 Introduction: Use of Clay
- 16 Description of ASTM C 150 Cements
- 17 Plastic Cement
- 18 Setting Mechanism
- 19 Slag
- 20 Reorganized 11 Feb 2007
- 21 Edits 18 March 2007
- 22 Portland cement business
- 23 Bogue's Compounds
- 24 "Rawmix" → 'raw mix' etc.
- 25 suggested changes
- 26 Premix isn't the same thing as rawmix
- 27 Original Research
- 28 Rawmix or rawmeal (raw meal)?
- 29 Safety
- 30 Heat During Curing
- 31 Flux ?
- 32 Unreferenced and original research
- 33 Energy Requirements
- 34 EMC Section reads like an advertisement and is not representative of Portland cement.
- 35 ASTM and EN standards naming convention
- 36 Complex Series of Chemical Reactions Still Only Partly Understood
picture shows Portland-composite cement, not (Ordinary) Portland cement
The first picture in the article shows 'CEM II/B-M' cement, which is strictly speaking not Portland cement, but Portland-composite-cement (EN 197-1) and has a clinker content <79%. This might be confusing because the picture is placed beside the statement that Portland cement has more than 90% clinker. However, the name 'Portland cement' is sometimes used for Ordinary Portland cement only or for all cements with some Portland cement content, including blended cements/composite cements. CEM I is Portland cement with >90% clinker (so called 'Ordinary Portland cement' in the USA). —Preceding unsigned comment added by 220.127.116.11 (talk) 15:24, 9 June 2010 (UTC)
"The physical properties of concrete depend on the chemical properties and the proportions of the constituent materials. Compressive strength is usually between 2,000 and 15,000 psi, tensile strength between 100 and 4,000 psi, and shear strength between 1,000 and 10,000 psi."
I have not verified the correctness of these numbers. They are off the top of my head. If anyone can verify, please do so.
The strength of concrete depends mainly on the water to cement ratio. For a footpath concrete with a 28day compressive strength of 20 MPa is can be used particularly if the concrete contains flyash which will give added strength beyond 90 days or the cement is a blended cement containing slag which has a slower strength growth. For a driveway or garage floor one should specify a minimum 28 day strength of 30 Mpa and ensure a maximum slump of 80mm. 50-60 Mpa concrete is normally used with high rise concrete building where the concrete is pumped. Water reducing additives are used with these concretes. I have seen 120 MPa (at 28 day) concrete put down at a truck weighbridge so that it could be used after 2 days when the strength was over 40Mpa. This concrete contained a blended cement with a high proportion of ground slag and a superplastiser to reduce the water.
I believe this article lacks neutrality and requires some restructuring. The disputed second paragraph in the article reads as follows:
"Manufacture of portland cement requires the burning of large quantities of fuel, typically coal or natural gas, which along with impurities contained in the limestone can result in significant emissions of pollutants regulated in many countries, including greenhouse gases such as nitrogen oxides (NOx) and sulfur dioxide, as well as particulates (PM 10, PM 2.5), volatile organic compounds (VOCs), and carbon monoxide. Cement plants emit substantial quantities of arsenic, lead and mercury."
This paragraph initiates a discussion of pollution at the outset of the article, which is pejorative and atypical of other wikipedia articles dealing with global industries (see: Petroleum and Steel, for examples). The paragraph is factually incorrect, listing oxides of nitrogen and sulfur dioxide as greenhouse gases; they are not. The final sentence declares that "cement plants emit substantial quantities of arsenic, lead and mercury" which is not supported by fact. See the discussion of cement chemistry later in the article and note that none of these elements play any part in the manufacturing process, nor are such heavy metals typical of the limestone and shale that comprise the essential raw materials in production.
The disputed third paragraph under "Safety and health" is similarly pejorative. It reads:
"Living near a portland cement plant can have serious health consequences due to the large quantity of pollutants released by the manufacturing process, as well as fugitive emissions from related on-site activities (such as haul roads, blasting, and truck traffic). The pollutants released by portland cement industry are known to contribute to lung and circulatory problems, including asthma, bronchitis, and heart attacks, as well as cancers. Hovever, many residents in these communities consider these risks to be acceptable in view of the economic benefits. For instance, polls show the residents of Ste. Genevieve County, Missouri to be overwhelmingly in favor of the cement plant being built there beginning in 2005. This plant will be the largest cement plant in the United States."
The statement "living near a portland cement plant can have serious health consequences" is an allegation lacking any source, certainly not a statement from NPOV. Looking to the article on Oil refineries as an example, public health concerns voiced by environmental groups should be cited as such, with appropriate links. The environmental concerns must be cast as topics of public debate with the article taking a strictly neutral position.
Following the example of the articles on Petroleum and Steel, I propose to retitle the "Safety and health" heading as "Safety and Environmental Effects" and relocate the discussion of fuel usage, impurities, and pollution under that heading. I have collected some data on typical cement plant emissions to place as a data table under that heading, but for the sake of balance some examples of emissions control technology as applied to cement production might be appropriate as well.
I invite informed, objective debate on these issues…please speak here before deleting or reverting. Thanks JJackson8 20:02, 2 November 2005 (UTC)
Its sensationalist, delete it. The lights in a concete building would use 1000 times more electricity over the building lifetime, than electricity used in construction. The pollutants a re no worse than any other industrial process, and I dont see a pollution section on every manufacturing article .
There is also the sentence: "For instance, polls show the residents of Ste. Genevieve County, Missouri to be overwhelmingly in favor of the cement plant being built there beginning in 2005." (My comment: There's a cement plant near me opposite an ice cream factory. Nobody cares less about either, including pollutants.) Gtoomey 02:46, 3 November 2005 (UTC)
First, I am not an expert on the enviromental side (only on the material) and thus can't tell what's "correct" for this - but as like other ppl I am of the opinnion that I can make up my own decissions based on the presentation of documented facts. Second, the "exhaust gasses" from a cement plant will pollute alot if not cleansed - but major cleansing prosesses are used (and pollution regulated) for many countries. This is the same as for metal production, oil refining etc.
I vote for the creation of an Safety and enviromental effects section.
Oyvind 09:18, 4 November 2005 (UTC)
Noted today that WAS 4.250 moved the disputed sections without any contribution the discussion here. I have now deleted the disputed text (shown above in entirety). Based on comments here and attempted edits by several others (look to the history) there is a consensus that this text is not appropriate. I believe the burden now belongs to those who wish to insert such text to discuss it here and provide proper documentation. To consider any "data" as fact, it must be supported as being true. It is not correct to argue that we must disprove it. I will be proposing text and data to insert under the "Safety and environmental effect" heading here for discussion and improvement prior to any further edit of the article. This is the Wiki way...please participate! JJackson8 18:04, 6 November 2005 (UTC)
The environmental effects section needs a rework. As it reads at the moment, CO2 isn't a special problem of cement as compared to any other industry - the criticism is generic and noone reading the article would realise that the cement industry is a particularly significant CO2 emitter. I propose
1) a concise and factual addition to the first paragraph that underlines the specific problem that CO2 poses for the cement industry. Its the industry with the second largest CO2 emissions worldwide, and its well known for being so.
2) splitting the first paragraph (and the section itself) into problems and mitigation techniques. Its an industry that has a large environmental impact, which is mitigated to some extent. The split emphasises the size of both the environmental impact and the diversity of ways that are used to mitigate them. more importantly, it makes the structure of the whole section less choppy...it now progresses from a list of problems to a description and analysis of CO2 emission to mitigation, rather than mixing them all together due to previous editing spats. The way it reads at the moment is a testament to generations of opposing POV rather than proper consensus.
3) cutting back on the section on SO2/worker hazards. its far too large, and could be summarised in a sentence
4) cleaning up the language a bit...my cement future doesn't include thrusts of any sort, even of innovation ;)
I don't know what to do with the references. Do we need as many SO2 references as we've got, now that the section is gone? what does everyone think? Where we do need references is when the article first mentions the scale of CO2 emissions (e.g. an IPCC report or peer reviewed paper), and we need at least one for the whole CO2 source analysis. The numerical section corresponds nicely to the data found at arjournals.annualreviews.org/doi/abs/10.1146/annurev.energy.26.1.303 - this paper is old now, but the data corresponds well to that already in this WP article, and its east to read. It also demonstrates the difference between efficient and inefficient production nicely.
Here's my proposed rewrite:
Environmental effects Portland cement manufacture can cause environmental impacts at all stages of the process. These include emissions of airborne pollution in the form of dust, gases, noise and vibration when operating machinery and during blasting in quarries, consumption of large quantities of fuel during manufacture, release of CO2 from the raw materials during manufacture, and damage to countryside from quarrying. Fuel consumption and CO2 release from raw materials make cement manufacture the second largest manmade source of CO2 after power generation. In the absence of well-implemented mitigating practices worker safety may be impaired, in particular by airborne pollution.
The CO2 associated with Portland cement manufacture falls into 3 categories:
(1) CO2 derived from decarbonation of limestone, (2) CO2 from kiln fuel combustion, (3) CO2 produced by vehicles in cement plants and distribution.
Source 1 is fairly constant: minimum around 0.47 kg CO2 per kg of cement, maximum 0.54, typical value around 0.50 world-wide. Source 2 varies with plant efficiency: efficient precalciner plant 0.24 kg CO2 per kg cement, low-efficiency wet process as high as 0.65, typical modern practice averaging around 0.30. Source 3 is almost insignificant at 0.002-0.005. So average total CO2 is around 0.80 kg CO2 per kg finished cement. This leaves aside the CO2 associated with electric power consumption, since this varies according to the local generation type and efficiency. Typical electrical energy consumption is of the order of 90-150 kWh per tonne cement, equivalent to 0.09-0.15 kg CO2 per kg finished cement if the electricity is coal-generated.
Overall, CO2 generation ranges from a minimum of 0.7 kg per kg cement with nuclear- or hydroelectric power and efficient manufacturing to twice this amount. Research focuses on the reduction of sources 1 and 2 by modification of the chemistry of cement, by the use of wastes, and by adopting more efficient processes. Although cement manufacture is a very large CO2 emitter, concrete (of which cement makes up about 15%) compares quite favorably with other building systems in this regard. See also cement kiln emissions.
Equipment to reduce dust emissions during quarrying and manufacture of cement is widely used, and equipment to trap and separate exhaust gases are coming into increased use in developed countries. Environmental protection also includes the re-integration of quarries into the countryside after they have been closed down by returning them to nature or re-cultivating them.
I'll edit the article to this in three days. As most of the text is straight from the existing article, i don't anticipate much objection. i think it presents cement as it is: a great product with an annoying CO2 side effect which can be exacerbated or mitigated depending on the production method. Cool? Hardcoeur 6 September 2007
- Cool by me!! If there are other parts of the article you want to have a go at, there's plenty of scope for improvement. . . .LinguisticDemographer 14:56, 6 September 2007 (UTC)
== photo sensitive elements == Apart from that it Could be photo-electric/photo sensitive
Shouldn't the raw material be calcium carbonate (44%) not calcium oxide (44%) ?
Portland clinker (at least in N europe) consists of 45-65% (% by weight) Tricalcium silicate C3S. The finished product (cement) consist of 62-67% calcium oxide. Oyvind 09:52, 27 October 2005 (UTC)
Shouldn't "dicalcium and tricalcium silicates (C2S C3S)" be "(Ca2S Ca3S)" - i.e., symbol for calcium, not carbon?
- It doesn't matter. Some screwball, idiosyncratic jargon of a narrow field should not be used in Wikipedia without including normal, general usage as well. Gene Nygaard 23:44, 19 August 2005 (UTC)
- While I'm in agreement that the more mainstream notation should also be used, if the original CCN formulations C2S, C3S were correct, then the translations done above, and the ones done on the entry in July are wrong. C2S in CCN would be 2 CaO • SiO2 in normal mainstream notation. (see the CCN entry.)
- Cement production is a global industry, hardly a "narrow field." I agree that the shorthand cement notation is idiosyncratic, but it is in no way "screwball". This notation is used worldwide; I know of no cement plants that do NOT use this notation. A reader seeking understanding of cement production needs to be aware of this notation in addition to the formal chemistry.
"...The high energy requirements and the release of significant amounts of carbon dioxide makes cement production a concern for global warming...."
This is an opinion - the author's - and is inappropriate in this context.
Agreed. Delete it. Gtoomey 02:47, 3 November 2005 (UTC)
I have worked in construction for many years and have formulated a variety of products with PC and with other cements as well, such as calcium alumina. For every ton of PC made, you produce a ton of CO2. Think about that for a moment. A ton of PC fits on a skid. How much room does a ton of CO2 gas take up? Everybody in the business knows it. However, nobody (the public that is) cares enough to change. There are alterante inorganic binders out there. Pyrament was such an experiment. Worked great, cured fast, reliable, all that. However, it was more expensive and thus an economic failure. This sort of thing requires governmental backing and in order for government to back it, it must be an election issue for voters, which it is not. Most people will not reserve any attention span as soon as the word cement is uttered. Nobody cares, even if the alternative is THAT much better, let alone perhaps pay more in taxes to fund public highway projects? Are you kidding? Everybody wants a bargain and alternatives to great pollution are as popular and Green parties are in general elections. They don't even appear on the radar screen. So, the issue is not nearly controversial The cement industry REALLY TRIED and offered an alternative and nobody cared enough to make the alternative economically viable. The only thing controversial here is showing a generally apathetic public a mirror. That is not a sexy thing to do in politics and there the matter will rest - until we have, in the words of Captain Jean-Luc Picard: "evolved beyond the need for money".--Achim 22:17, 15 April 2006 (UTC)
What I do not understand: when the cement is cured, doesn't it absorb the released CO2 again, with Ca(OH)2 + CO2 -> CaCO3 + H2O ? It seems I have a misconception there, but I could not find a definite answer anywhere. Oku 00:32, 12 May 2006 (UTC)
That is very simplified but correct chemical equation. Ca(OH)2 + CO2 --> CaCO3 + H2O However there are two important points to consider why this reaction does not negate all of cement's CO2 emissions. 1st: Half of the total CO2 emitted from cement production is from fossil fuel combustion to produce the heat required to pyrolize limestone (CaCO3) feedstock. This CO2 is not recaptured in the first hydration reaction. CaCO3 + Heat --> CO2 + CaO 2nd: CO2 reactions with concrete mainly occur on the surface layer. Thus all of the interior material is not carbonated and thus, will not reabsorb CO2.
Together these two points explain why concrete does not reabsorb all of the CO2 released during its production. The cement industry is the second largest CO2 polluting industry behind power generation. See the latest IPCC report.
There is third reason why it is impossible for concrete to reabsorb all of the CO2 evolved during the cement-making process. Ca(OH)2 is only one reaction product of cement hydration, the rest of the calcium is tied up in calcium silicate hydrates. For example when C3S reacts fully with water the reaction is;-
2(3CaO.SiO2) +7H2O --> 3CaO.2SiO2.4H2O + 3Ca(OH)2
So, at best, only half of the CaO in C3S can ever be converted to Ca(OH)2. For C2S, this ratio is even smaller... only one quarter of the CaO in C2S can be converted into calcuim hydroxide during hydration. Ted Krapkat [Cement Australia] 18.104.22.168 (talk) 03:13, 26 July 2010 (UTC)
Under "Types of Portland Cement" the comment "Note: Type II cement is not really used any more in industry." appears under the heading for Type IV. Is it out of place, or should it be referring to Type IV?
Eitherway, type II cement is used almost exclusively in Northern California. And if the comment is referring to Type II it is a definite mistake.
In the US, rather more than half Portland cement consumption is Type II. On the other hand, no Type IV has been made in the last 30 years or so, because low heat concrete is normally now made with Type II and a large addition of ground granulated blastfurnace slag (ggbs).LinguisticDemographer 15:33, 27 September 2006 (UTC)
Regarding composition, Standards and emision
- ASTM C150 and EN 197 are the two major standards for Portland Cement - ASMT used in America+ and EN used in Europe+. Both are definitly notable ;) and just covering one of them is a one-sided and "protectionistic".
- As there are more than one standard the composition of cement and clinker differs - there is a larger span for the composition. To give the composition with aproximate 44% etc is to "coarse" as the spread is larger than can be coverded by the word "Aproximate"
- As to emmisions - lets settle that on this page and try to stay avay from an revert-war between different POV's. Keep it clean and simple, pleace.
Oyvind 09:41, 2 November 2005 (UTC)
I agree -- and yet, I see that emmisions is indeed an issue here and if it's an issue, it's an issue. There is no issue about whether paddling a canoe and greenhouse gasses. Whereas to create Portland cement one must use lots of fuel. I find that to be a fact and therefor worth mentioning. I find it a kind of political motive to want to Not mention it.
I don't feel it's neutral to say "there is debate about mentioning greenhouse gasses in relation to Portland cement production." I feel that if this debate should be mentioned at all, it would be "there is debate about mentioning facts or instead letting political viewpoints gloss over the fact that this production uses sufficient energy to question it's use by many."
Another way to share my view is that "there is discussion on the Talk Page to gloss over the high fuel/energy usage under the guise of NPV." *smile*
Michael Walsh 09:41, 2 November 2005 (UTC)
The picture is inaccurate.
The picture is wrong, as it shows two men making 6"x12" compressive strength TEST CYLINDERS.
Test cylinders are used to test CONCRETE, not CEMENT (cement is used to MAKE concrete)
2x2 TEST CUBES are used to test CEMENT.
Type Ia etc. Poor choice.
Not sure what the author means niggers with the statement that the grinding of cement with an air entraining agent is a poor choice. Please elaborate on this statement. I believe that if it is infact a poor choice either this product would have been replaced by better choices or would have disappeared from the market.
=* This logic doesn't work for me ("neoliberal" logic?)-- following this logic, heroin is a "good choice" since even armies can't stop it's use. I LOVE the NPV being most important here -- some day all these industries will have comments regarding the fuel/energy/greenhousegas usage. Whereas some are here advocating deletion of comments because other industries don't have greenhouse gas comments. Fact is, if indeed the generation of a ton of portland cement creates a ton of CO2, then yes, this ought be mentioned here. This is not "topical" it is as relevant as the formulii or ecomonies -- the greenhouse gas facts are indeed important.
- Would a history of the invention of Portland Cement be appropriate in this article?
I think the history is appropriate, the name says it too, and where did you say it comes from? Gregorydavid 08:09, 30 March 2006 (UTC)
- Indeed it is appropriate. I failed to see it and looked for it at the bottom of the page. I made no statement other than my question, which unfortunately gave the impression that I was questioning the inclusion as it stands.
- Very complete and well written article as it stands.
Cement plants as alternatives to conventional waste disposal or processing
This section was obviously written by a shill for the cement industry. Cement is one of the most energy intensive products in the world, and manufacturers are seeking out any means of reducing their energy costs. The practice of incinerating hazardous and nonhazardous waste is extremely controversial. For example, one Lafarge plant at St. Constant in Quebec, Canada is producing stratospheric (and increasing) amounts of dioxins as a result of incinerating scrap tires.
All I'm saying is that this particular section is far from neutral. It reads like propaganda from the cement industry.
I agree - there is on-going opposition to the use of wastes in cement kilns, which were not designed for the job, and much data which suggests that they are not as good at burning everything up with no emmissions than is suggested by the industry. In addition, cement companies are not properly set up for the collection and storage of such wastes, and this introduces further complication. Even burning normal fuels, such as coal, results in dangerous emmissions of mercury, and of green-house gases.JaneH 13:00, 5 July 2006 (UTC)
History of cement
The section on the history of Portland cement duplicates thatin the "Portland cement" article, but has a different emphasis, giving greater credit to the Aspdins. Ideally the general history should be in the cement article, and the complicated evolution of modern Portland cement in the more specialised article. I missed an explanation of how cement sets at the microscopic level.
very confusing usage
Wait, so portland cement was invented by a guy who didn't invent portland cement? I think what the article is trying to say is that the cement originally named "portland cement" is not the stuff which is today called "portland cement" (sort of like the concept that tinfoil is actually aluminum and pencil leads are made of graphite) but I'm not entirely sure. Someone who knows should fix here, and in the Aspdin article... -- Akb4 05:20, 31 August 2006 (UTC)
Joseph Aspdin (the father) coined (and patented) the term "Portland Cement" because, when set, it looked like Portland stone. However, his product was a hydraulic lime, and not the product recognized today. Portland cement, as currently understood, is characterized by containing substantial amounts of alite ("C3S") and Joseph Aspdin's cement contained none of this. William Aspdin (the son) noted that by increasing lime content, and burning hotter, a slow-setting but high-strength product was produced. This is "Portland cement as we know it", and differs in application from his father's product: the earlier cements were used primarily for fast-setting stuccos, whereas the new product could be used for (relatively) high-strength concrete. Modern concrete production starts at this point. He subsequently set up in business on his own, and in 1842, produced the modern product commercially for the first time at Northfleet, Kent. This is much earlier than the date given in the article. He subsequently moved to Germany and commenced production at Lagerdorf in 1863. The cited source "A J Francis" describes this sequence of events although it is poor on technical detail. The latter can be supplemented with R.G.Blezard "The History of Calcareous Cements" in "Lea's Chemistry of Cement and Concrete: 4th Ed" Arnold 1998. The question arises; why did William Aspdin not give his new product a new name? It would appear that WA believed, probably correctly, that if he brought out a new patent, and disclosed his manufacturing techniques, the patent would be infringed by all and sundry almost immediately, and he would spent years fruitlessly suing his competitors. He therefore decided to claim that his product was his father's product - and protected by his father's patent - and resorted to various bizarre measures to prevent his secrets being stolen. This bought him about 2 years free from competition, until I C Johnson (at Swanscombe, Kent) found out how to emulate the product.LinguisticDemographer 15:02, 27 September 2006 (UTC)
I have pasted my initial respose to this into the Environmental section, since it appears to read OK.LinguisticDemographer 17:38, 30 September 2006 (UTC)
"Overall, with nuclear- or hydroelectric power and efficient manufacturing, CO2 generation can be as little as 0.7 kg per kg cement" What is the correct amount of CO2 generated, in the context of this passage? 0.07kg maybe? Kibblesnbits (talk) 22:32, 11 October 2008 (UTC)
Introduction: Use of Clay
In the introduction, it is stated that the wet process is no longer used, and that as a consequence clay is no longer used, because (among other reasons) it contributes too much alumina. This is all incorrect. (1) The wet process, although much less used, is still in operation. Wet and semi-wet process still accounts for more than 10% of UK production. In the US it's still around 20%. In some countries it's 100%. (2) Clay usage is not restricted to wet process: many dry process plants use clays. (3) Clays are in no way chemically distinct from shales; high-alumina shale are just as common as high-alumina clays.LinguisticDemographer 16:28, 27 September 2006 (UTC)
- Please feel free to make the appropriate edits, particularly if you have references for your assertions. See WP:BOLD Argyriou 16:42, 27 September 2006 (UTC)
Description of ASTM C 150 Cements
This section appears to be based on texts written 50 or more years ago. The typical composition data is out of date. There was a survey of North American portland cements in the mid 1990s (Gebhardt, R. F., "Survey of North American Portland Cements: 1994," Cement, Concrete, and Aggregates, December 1995, 145-189). The following mean compositions come from this: Type I: 55% (C3S), 18% (C2S), 8% (C3A), 9% (C4AF), 2.0% MgO, 2.8% (SO3), 1.3% Ignition loss, and 1.0% free CaO. Type II: 54% (C3S), 20% (C2S), 6% (C3A), 11% (C4AF), 2.2% MgO, 2.7% (SO3), 1.2% Ignition loss, and 1.0% free CaO. Type III: 55% (C3S), 17% (C2S), 9% (C3A), 8% (C4AF), 2.2% MgO, 3.5% (SO3), 1.3% Ignition loss, and 1.3% free CaO. Type V: 55% (C3S), 20% (C2S), 4% (C3A), 13% (C4AF), 2.5% MgO, 2.3% (SO3), 1.0% Ignition loss, and 0.8% free CaO. The description of Type III states that it is made by raising the C3S and C3A in the mix. This was the practice in the 1930s, but nowadays, very few manufacturers deliberately make a different mix for Type III, and this fact is born out by the above data - Type III is typically almost identical to Type I in chemistry. Type III is differentiated from Type I by finer grinding: typical Blaine fineness (m2/kg): Type I: 377 Type II: 374 Type III: 547 Type V: 370 Although not specified in this way in ASTM standards, Type III is bought and sold on the basis of its 1-day strength (or even 16-hour strength), which is proportional to the fineness and the C3S. Clearly, the modern 50% boost in early strength given by Type III can't be achieved by tweaking C3S content. Main uses are in pre-cast concrete and in pre-stressed units, where fast mould turn-around is called for. The usage text given fails to address this and appears to describe the situation 50 years ago. In general Type III can not be used in contact with ground waters!!
The whole section really needs a re-write from scratch.LinguisticDemographer 16:55, 27 September 2006 (UTC)
I deleted the section on Plastic Cement, because it is not a Portland cement, since it contains components that are prohibited in the Portland specification. It is covered under cement, although the item might need a little expansion.LinguisticDemographer 16:57, 29 September 2006 (UTC)
I have a problem with the existing text which implies that setting is due to calcium aluminate hydration. This really isn't true. C3A causes flash-set if not controlled by sulfate addition. Addition of sulfate causes formation of a very limited initial amount of ettringite, which forms an insoluble crust over the C3A surfaces and prevents further hydration. The normal set occurs as a result of initial hydration of C3S. Pure C3S, in fact, sets in a manner similar to well-controlled Portland cement, after a delay of an hour or two. The ettringite layer passivating the C3A subsequently redissolves quite slowly to form Afm after the C3S-based set is well established. LinguisticDemographer 00:31, 9 October 2006 (UTC)
- May I suggest that you edit the article along the lines you propose above? Adding references and/or footnotes would be welcome, also. For guidelines, please see WP:RS and WP:FN. In particular, citation of a standard textbook would be very helpful to our readers. Best wishes, Walter Siegmund (talk) 02:44, 9 October 2006 (UTC)
Reference to slag as a raw material should not be confined to ggbs, since the physical state of the slag is irrelevant when it is used as a raw material. Furthermore, slags other than blastfurnce slag are also in use. . . .LinguisticDemographer 14:55, 25 January 2007 (UTC)
- Thanks for not reverting without comment. Gracious of you.
- It's not the physical state that matters, I think but the ubiquity of GGBFS as a pozzolan in the industry. I've never seen reference to ground slag being anything but blast-furnace slag, i.e. FHWA, Portland Cement Association, Slag Cement Association, ASTM C989 and AASHTO M302, or my various concrete materials and design texts. I seriously doubt that the total combined smelting of copper, bauxite, lead, etc. makes up a noticeable fraction of iron, and I'd really be surprised if GGBFS isn't as ubiquitous in the UK and EU as it is in North America.
- Now bauxite is smelted in significant quantities in Australia, Brazil, Venezuela, and Guyana relative iron ore. Do they use ground bauxite slag in significant quantities that you know of? (Australia seems a very likely candidate.) Can you provide references or standards?
- Even so, this article should link to GGBFS as that article is much closer to the point; and your latest version says blast furnace slag. The Slag article is off the point of cement admixtures, but is linked to in the first line of the GGBFS article. MARussellPESE 16:45, 25 January 2007 (UTC)
I think there is a misunderstanding here. Various raw matereials (and this entry is in the raw materials section of the Portland cement article) are used in formulating rawmix. The resulting Portland cement clinker may then be ground on its own to make Portland cement, or interground with pozzolans (such as flyash) or materials with incipient hydraulic activity (such as ggbs) to make Blended Cements. Materials used in the rawmix are selected purely for their chemistry, since their physical state is annihilated in the burning process. These materials include raw slag, ggbs (although because of relatively high cost, this is not favored), steel slag (in VAST quantities in the USA), basic oxygen furnace slag, and slags from the non-ferrous industries, which are used not for their own qualities, but because cement manufacturers are paid to dispose of them. Bauxite is also used, but, of course, not as a Blended Cement component. Thus, it may be appropriate to include this reference (and I thought it was already included) in the article on Cement (NOT Portland cement). I agree that there is no good article on blast furnace slag in general, but then, this is Wikipedia. Maybe someone should write one. It doesn't need to be any good! I can't write it myself because I don't know much about the iron industry. But I know an awful lot about cement manufacture. Incidentally, VASTLY more ggbs is used in Europe than in North America. In countries such as Belgium and the Netherlands, PBFC is practically the only cement on the market. . . .LinguisticDemographer 12:39, 26 January 2007 (UTC)
- I finally get the article's point. While the article is about PC and this section discusses its manufacture (I was reading: "use"), the text in this spot was very unclear. I hope this fixes it. Completely agree with you on the manufacturing and raw materials. Since "slag" really does mean more than GGBFS here, I've changed the list to read "Slag". Hopefully the new reference is of use.
- My references were totally off-track and belonged in the Concrete article. I fixed that to discuss mineral admixtures and blended cements. I'll update Cement with these, which is where they belong.
- Cheers, MARussellPESE 18:32, 26 January 2007 (UTC)
Reorganized 11 Feb 2007
I have changed the order of the article to give (I hope) a more logical read. I have also eliminated one or two redundancies (see "Setting mechanism" above), and have added a bunch of text which I think is probably valuable. This also seeds two new articles: rawmill and cement mill. I'm on the lookout for good photos for these. The wiki server was playing up as I pasted this, and there may be a few typos, errors etc. Please fix if you get to it before I do.
LinguisticDemographer 17:56, 11 February 2007 (UTC)
Edits 18 March 2007
I changed a section that seems to be based on a very old text, in order to reflect modern usage. There are many repeated and circular wikilinks: I have taken out some of these. Is there some sort of "bot" that does this automatically? . . .LinguisticDemographer 15:08, 18 March 2007 (UTC)
Portland cement business
The current section 4 needs to be relocated to the "Cement" article. The text refers explicitly to "hydraulic cement", on which the world production is based. A large proportion of this is strictly non-Portland, as is the large majority of the Chinese production. I'll move it if there are no objections. . . .LinguisticDemographer 19:04, 24 April 2007 (UTC)
The notional compounds C3S, C2S, C3A and C4AF are informally referred to as "Bogue compounds", and the process of calculating their amounts is referred to as "Bogue analysis", because this calculation was first proposed by Bogue. The actual minerals present in Portland cement clinker (alite, belite, tricalcium aluminate and calcium aluminoferrite) differ substantially from the notional Bogue compounds in composition, so that the calculated Bogue compound composition is often very different from the true mineral composition. For this reason, and because direct methods of mineralogical analysis are now available, "Bogue analysis" is now gradually going out of favor. . . .LinguisticDemographer 11:02, 27 May 2007 (UTC)
"Rawmix" → 'raw mix' etc.
"Rawmix" does not seem to be the usual term. Relevant sources show that the normal term is 'raw mix'. Likewise for "rawmill"/'raw mill', etc.. Here are a couple of examples:
-  — official industry site calls it "raw mix"
-  — UN document uses "raw mix" almost exclusively throughout, except for a singe instance (which might be a misprint).
— DIV (22.214.171.124 08:26, 22 June 2007 (UTC))
I'm not unsympathetic to this edit. Rawmix may be two words in Australia (obviously the industry doesn't have an "official" website), and it's certainly not used at all in Britain. I'm not sure about other parts of the English-speaking world - e.g. India. But in North America, it's usually (not always) written as one word. Also rawmill. I have reverted the edit because it has been done without regard to proper capitalization and updating of links, and generally makes the article look unprofessional. If anyone would like to make this change in a disciplined manner, it's fine by me. . . .LinguisticDemographer 10:18, 23 June 2007 (UTC)
Okay ...I didn't notice I'd messed up any of the capitalisation — sorry if that was the case. I acknowledge that I hadn't simultaneously revised the rawmill article, but the links did still all work (as far as I know) after my edits, so I'm not sure exactly what you're referring to. In any case, the discussion is here, and hopefully someone will spend the time to modify the article according to consensus. As I say, most of the stuff I saw online used separate words for the two terms. By the way, I thought it would be clear I intended the first link to be read as "an official industry site". —DIV (126.96.36.199 10:18, 5 July 2007 (UTC))
Rawmix blending; please define alite and belite here. How about a section in rawmix about deleterious elements, e.g. Mg, F, P, also problems of sulphides in feedstock and alkalis in cement
What do people think of a section on cement aggregate reactions, such as alkali silica, alkali-dolomite reactions, also some info on sulphate attack of cementitious materials? I can do an outline if necessary, but I'm not top of the field in either area at present.
Rawmix blending; please define alite and belite here. How about a section in rawmix about deleterious elements, e.g. Mg, F, P, also problems of sulphides in feedstock and alkalis in cement
What do people think of a section on cement aggregate reactions, such as alkali silica, alkali-dolomite reactions, also some info on sulphate attack of cementitious materials? I can do an outline if necessary, but I'm not top of the field in either area at present.
Premix isn't the same thing as rawmix
When I go to the hardware store to buy cement, I've been told to ask for something called 'premix'. In what way is 'premix' different from 'rawmix'? I'm not an expert on this sort of thing, and I thought I'd go to Wikipedia to get an answer on the matter. 188.8.131.52 (talk) 23:31, 10 August 2008 (UTC)
- Premix is cement mixed with sand or sand and gravel: it's really mortar or concrete in a "just add water" form – useful if you only need a little. Rawmix is a stage in the manufacture of cement, so it's not at all the same thing – it's like the difference between wheat and cake-mix. By the way (and I don't in the least mean to sound unfriendly) WP isn't really meant to be a Q&A site – try one like www.answerbank.com. Richard New Forest (talk) 14:08, 11 August 2008 (UTC)
Substantial parts of this article were written by me. I am a well known researcher in this field. I hereby assert that all those parts of the article that were written by me and are not provided with references are the results of my own original research. Wikipedia rules state that information that is the result of original research is prohibited, and where such information is unambiguously present in an article, it is the duty of every editor to remove it forthwith. LinguisticDemographer (talk) 21:56, 15 April 2010 (UTC)
Rawmix or rawmeal (raw meal)?
The article talks about 'rawmix' or 'raw mixture', but not 'raw meal'. In both wet, semi-wet and dry process kiln systems the terms 'rawmix'(raw mix) or 'raw mixture' invariably refer to the heterogeneous mixture of the unground raw materials which are fed to the raw mill. However, the homogenous powdered material which comes out of the raw mill in a dry process kiln (or the dried powdered slurry in a semi-wet process) is generally referred to as 'raw meal'. For clarity, I suggest that this convention also be observed in the article. Ted Krapkat (Cement Australia) 184.108.40.206 (talk) 01:17, 27 July 2010 (UTC)
In the Safety section, it says:
- As of 2010, however, the development of formulations of cement that include fast-reacting pozzolans such as silica fume as well as some slow-reacting products such as fly ash have allowed for the production of comparatively low-alkalinity cements (pH<11) that are much less toxic and which have become widely commercially available, largely replacing high-pH formulations in much of the United States. Once any cement hydrates, the hardened mass loses chemical reactivity and can be safely touched without gloves.
- Low-alkalinity cements have been available since before 2010. I've changed that.
- There needs to be a citation for low-alkalinity formulations "largely replacing high-pH formulations in much of the United States."
- The loss of chemical reactivity occurs after the cement sets, not hydrates. I've fixed that.
Heat During Curing
I understand that the curing process of Portland cement generates heat, and that for very large castings, measures must be taken to prevent heat damage. Perhaps this is worth mentioning in the article. — Preceding unsigned comment added by Mohanchous (talk • contribs) 16:18, 6 March 2011 (UTC)
The article has a link to flux_(metallurgy), which is confusing. I had hoped to correct the link, but the Flux_(disambiguation) page did not enlighten me either. Some more explanation would be useful.Brinerustle (talk) 11:05, 25 April 2011 (UTC)
Unreferenced and original research
There is a problem with this article: certain sections have been marked as "unreferenced" for two years, during which time no attempt has been made to supply references. The author of these sections freely admits that they are Original Research. Original Research is absolutely prohibited in Wikipedia. Accordingly I have deleted them. Do not restore them - you are absolutely forbidden by Wikipedia rules to restore them - unless you also supply valid references from a reliable - i.e. peer reviewed - source. — Preceding unsigned comment added by 220.127.116.11 (talk) 11:55, 24 November 2011 (UTC)
"Typical electrical energy consumption is of the order of 90-150 kWh per tonne cement, equivalent to 0.09-0.15 kg CO2 per kg finished cement if the electricity is coal-generated."
This is FLAT wrong and out by an order of 1000!!!!!!!!!!
See, table at page 4 of http://www.wbcsdcement.org/pdf/CSI%20GNR%20Report%20final%2018%206%2009.pdf
- Jono2013, the reference you cite, p 14, declares that about 5000 megajoules of energy are used per tonne of clinker. Does clinker mean cement? There are 3.6 MJ per kilowatt hour, so 5000 MJ is about 1400 KwHr. But why quote KwHr? Energy quoted in MJ makes sense because fossil fuel and combustible waste are used for heating the kiln. When electric power is mentioned, does this mean that cement kilns are electrically heated? DavidJErskine (talk) 06:22, 7 March 2014 (UTC)
EMC Section reads like an advertisement and is not representative of Portland cement.
The linked entry under the EMC section is tagged for deletion, for apparently good reason. This product most definitely doesn't belong on the Portland cement entry page. — Preceding unsigned comment added by 18.104.22.168 (talk) 06:35, 4 May 2013 (UTC)
ASTM and EN standards naming convention
ASTM itself identifies its standards with no space between the letter and numbers (for example, ASTM C150). Even the page ASTM International identifies a page without the superfluous space. I realise that it is fairly common usage to insert a space. But the space contributes nothing to readability or clarity. I think that the nomenclature by which an organisation identifies its own standards should prevail. EN apparently identifies its standards with a space. So EN 197-1 is the canonical form. "EN197" and "EN-197" are not in proper form. Whatever the organisation's preferred form is, that is what we should use. 22.214.171.124 (talk) 03:26, 1 July 2013 (UTC)
Complex Series of Chemical Reactions Still Only Partly Understood
Can it really still be true that the most important property of one of the central and widespread materials of 20th and 21st century civilisation, tightly and widely formulated, and composed only of inorganic molecules, is still, more than 150 years after its formulation, only partly understood?
That's what it used to say in my chemistry books when I was growing up in the 60s. The books were probably repeating what was known in the 30s. That's the 1930s. If this statement is true, what use the scientific century? Atconsul (talk) 10:18, 2 September 2013 (UTC)