AERATED CONCRETE 2 or Dreamland

Foreword.

The appearance of the first article "What aerated concrete salesmen are holding back" in early 2005 was brought on by massive advertising of aerated concrete, which presented this product as a panacea for all problems. Cheap, warm and easy, it forms the best walls in the whole world. All that's left is for the blocks to magically jump on the foundation while covering themselves in mortar.

Meanwhile, at the real sites where technical supervision was dispatched to everything was far from being so sugary.

The article was shared on forums and websites, sparking intense discussion. The editorial team of one construction journal asked if the article could be edited for printing, but the negotiations were brought to a close quite soon, obviously. Why would the journal upset their major advertisers? Printing is a business built on readers. There is no need for attempts at education or provision of useful information.

As a response to the article online (mostly on various construction forums) along with the opinion that the facts mentioned do take place, there were a lot of claims that all of the provided information is not true, but let's say the reviewers didn't have enough "time" to refute it.

The most persistent criticism of the article comes from those specifically targeted in it - salesmen. Clients have started asking them uneasy questions.

How can GlyebGrinfeld (Aeroc), while responding to questions posed by visitors of his corporate forum, agree with the facts that make aerated concrete (hereafter AC) look bad, if he is employed by the company manufacturing AC, and his professional duties include promotion of its products, which he is paid for? It would make as much sense as bees opposing honey.

Being salesmen, Hebel - YTong staff assume fake identities online (I am sure, you understand how much sense it makes to do so) and visit numerous online forums, give nonsensical responses to participants' "difficult" questions, and even posted an anonymous article on their website, ridiculing me and the facts provided in my paper.

Special attention was paid to accusations in direct interest. Numerous posts stated that the author (that is me) sells competing products. One could read that i trade rock-wool, foam rubber, brick or sawn timber - whatever they could come up with. The only issue was that these bawlers couldn't provide a single fact that would prove I had sold any materials to anyone, no matter how persistently asked. i will repeat this one more time: I am not a construction materials salesman. I deal with design, technical supervision and construction.

When designing and providing technical supervision, I suggest to the customer only durable and high-quality solutions. The constructed building should last at least 100 years, and maintenance-free service life must be at least 25 years. But nowadays, due to extreme decrease in educational levels and the overpowering will to get as much money as possible, there is no risk of unemployment. Hardly have you finished building a house, when you have to spend all of the warranty period fixing something. Later, renovations are necessary almost every year, as something cracks here, something falls off there. So, in order to stop explaining the same thing (namely, why AC is a problematic material and does not fit the profile of "cheap, durable and maintenance-free") I have taken down all of its issues in writing, and then decided to share it with everyone interested.

Somehow an idea was ingrained in our society that we have a lot of new construction materials. People probably think so, drawing an analogy with various electronic gadgets. That is wrong. Construction is a rather conservative industry. The number of brand new building materials is minuscule. But there is so much new packaging, new advertising articles, pamphlets and slogans, as well as different combinations of conventional materials to form another "magic product". Hence, an ordinary person forms a wrong opinion about what they deem a brand new material. Now is the time of information warfare, and in most cases the material is one and the same, but its packaging and commercial hype around it become more sophisticated year after year. All for you, our dear customers!

Just keep buying it all, and buy more, and, hopefully, it will last you at least till the warranty expires. After that, it doesn't matter. The faster it falls apart, the more you will buy. But why does it fall apart? Obviously, it happens solely because you didn't follow the right technique. You will not get a different response to your claim from any company.

If you buy a product of high quality and good durability, there won't be any need for you to repair it, meaning you won't spend money in the future, which will lead to lower commodity-money turnovers for manufacturers, or their profits. The entire country's economy may stop growing. All of that will happen because of your irresponsibility. That is why you are persuaded to spend money on disposable and low-durability goods. The bigger the turnover, the higher the profits. Otherwise, if a plant has manufactured enough eternal light bulbs, what can its management do other than close it?

NB! In the articles I give links (link) to sources and additionally publish screenshots in brackets, denoting them like this - (picture). I do it because over time texts at the pages I give links to (if they are still relevant) are correct after my articles have been read.

The documentation I reference (SNiP, GOST, articles) can be downloaded in one package at the end of the paper.

Personally for the anonymous from hebelblock.ru

I will try to somehow justify myself a little bit in response to both Aeroc ("Myths...") and Hebel ("Following the footsteps of Mr. Yemelyanov's "creative work"). But attack is the best defense, which can very well be seen, for example, on hebelblok.ru.

Actually, I have noticed that I have become a sort of free "error search" for aerated concrete salesmen. They post an infinite number of different advertising absurdities and technical nonsense, I point out their blunders, voice them in articles and on forums, and they immediately and diligently correct their mistakes. At his AEROC forum G.Grinfeld has even offered 80 rubles to one good designer I know for every error found there (link) (picture). The entire "National Association of Autoclave Aerated Concrete Manufacturers" is incapable of maintaining publications and technical documentation truthfully and without overt blunders.

After I criticized YTONG for adding rock-wool to U-blocks, when due to its properties it is not suitable for such use (it absorbs moisture from concrete, binder decomposes due to moisture, it causes an unjustified rise in cost and makes no sense for vapor permeability), voila, they added "... and polystyrene foam". As it turns out, it can be done! I suppose, they didn't know about that before. Not to mention "Technical Solutions Albums", where one can find way too many inconsistencies!

By the way, who is the author of that personal response I received on hebelblock.ru? Because it i a little awkward for me - who should I address with my answer? I suspect that message had been composed by the entire staff of YTONG-Hebel, at their team retreat in Prostokvashino:

"Dear Mr. Yemelyanov! I live well. Just wonderfully. I have my own house. It is warm. I miss you very much, especially in the evenings. Now I go shopping alone. And all the shop assistants know me. They give me bones for free. I can't even stand to look at mice now.

I only catch them for entertainment. Sometimes I use a fishing rod, sometimes I pull them out of their holes with a vacuum cleaner and take them out to the field..."

They seem to be trying to tell me that I have confused everything, that I am wrong, etc. How can I accept such addresses if they are overflowing with lies? I suppose, they don't know any better.

I am going to go through only a couple of facts, so as not to seem precarious on this picture (2 Mb!)I have highlighted the following with a pink marker and numbers:

1. Quote: "in GOST 31359-2007, implemented on 1 January 2009" - of course, this is a bit much, my psychic abilities have been highly exaggerated. When writing my paper in early 2005, I suppose, I was expected to anticipate what would be implemented in the future GOST of 2009. Actually, GOST was changed for their profit (we will speak of this later in the paper). The same goes for the "adopted in St. Petersburg in 2006...". What an interesting way of proving someone wrong. Half of this address has been built on such an amazing director's discovery as criticizing figures that were relevant at the moment of appearance of the article, so to speak, post date. The given data of 4% and 5% humidity are also taken from a GOST adopted in 2007 (highlighted further in the text). For some reason I don't find a sentence starting with "The author is wrong, as in accordance with the GOST implemented in 2057..." You should definitely add it there, please do not forget.

All of that is followed by a lot of text, all of advertising nature, of course, going on about how everything is actually wonderful. The text is overflowing with numbers, formulae, questionable calculations. I am sure you understand this is calculated to impress a reader not very well versed in construction figures.

2. Pay attention to the "cheerful pictures", so beautiful, with German words (obviously to show off and to further impress readers), how well they are showcased for you! First of all, do these numbers mean anything to you? For instance, U=0,2W(sq.m*K). The figures are not presented to you in the GOST system, but in the way used in the EU. The anonymous are obviously unable to translate them into the Russian format, the champagne at the team retreat is all out, and they are about to move on to stronger spirits. But that translation is unnecessary, really, because their aim is clear - to confuse you.

Secondly, to "show off", they first use 300 mm of AC with the density of 300kg/cub.m. Please take note that heat permeability for density of D300 (for effect) is stated at 0,08. God knows where those figures came from.

Thirdly, the calculations themselves are done completely wrong if we take into account article SP 23-101-2004 "9.1.3 Thermotechnical calculations of non-homogeneous external walling containing corners, openings and connecting elements between the outer cladding layers (arris, traverses, rod connections), through-wall and blind heat-conductive elements operate... ...where A is area of non-homogeneous walling or its fragment, sq. m, measured on the inside, including the slopes of window openings;..." The same thing is stated in GOST R 54851-2011. And what do we see in the pictures? The heat loss through window openings is not considered at all while conducting the calculation, which suggests no knowledge of conducting calculations as well as publishing of the conclusions made by the staff composing this anonymous message.

Look at how beautifully and now evenly concrete slabs are lying on thermal insulation blocks with the density of 300, which simply cannot be used as loaded elements, especially when mounted on half of the 150 mm block!!! That is, if you build based on the pictures provided by these salesmen, unfortunately, you and your family are potentially dead. But who will be the one to die is a game of Russian roulette. Would you like to try your luck? They want to kill you! I don't know their motives. Maybe they are thinking that you will have already spent the money, and to avoid your coming over to them with warranty claims, they plant these solution ideas in your head. What this is and what it is for, I do not understand. I can only laugh at the education level of these anonymous artists, so-called "professionals"! Is this the response you came up with? Go back to school, who in the world gave you your high school diplomas in the first place!? What is exceptionally sad about this situation, is that in this situation they are free of any responsibility. You and your family could be killed with such pictures, and no one would pay for it, because they obviously won't find the janitor who created them. And even if they do, they can always say that it was "just a picture", and the fact that you used it as instruction is your own decision. Democracy and freedom, ladies and gentlemen!!!

I would like to also turn your attention to the caption on the pictures. These are estimates for three options of walling - D300, D400 and D500. In the calculation figure for D500 I have highlighted a few points in the table that need to be considered.

That is, the article states that the calculations in Figure 5 have been done for the density of D500 blocks, but the table for some reason reads density of 350 kg/cub.m  and thermal conductivity coefficient of 0,09 W/(m?K), which corresponds to GOST 31359-2007 for intermediate density of 350-400 of a dry block, not a finished wall! Moreover, after the calculations for D400 and D500 are completed, we get the same thermal conductivity for both - 0.28 W/(m?K)!!! Can you see how cleverly you are being fooled? And it's like this everywhere. It is very difficult to sell honestly.

Another point we need to address is why D300 density even used for effect in the German brochure if YTong and Hebel don't manufacture such blocks? To make a greater impression. Only this great impression leaves an unpleasant aftertaste - this is clearly a sham.

Thermal resistance is estimated with an apparent salesman's touch. It is all crammed into one line, a mass of required coefficients have been omitted, the phrase that mounted facades use flexible joints simply left me dumbfounded. People that believe they are working in construction when all they do is sell building materials have no idea not just about construction on the whole, but even what can be done with their magic blocks. On the Internet such militant ignorance is greeted with "go kill yourself".

This is the manner in which the entire concoction is done - filled with manipulations and distortions. The numbers and formulae in their entirety prove false when examined closely. I have highlighted more major absurdities in the text and don't want to waste my or your time on this corporate heresy.

"AERATED CONCRETE 2 or Dreamland"

We have amazing laws in Russia. But we have even better proverbs.

Federal law of December 30, 2009 N 384-FZ "Technical Regulations on Safety of Buildings and Structures"

Article 1. Purpose of the adoption of this Federal Law

This federal law is adopted with the view of:

• protection of life and health of citizens, property of individuals or legal entities, public or municipal property;
• protection of the environment, life and health of animals and plants;
• prevention of actions that mislead purchasers;
• ensuring of energy efficiency of buildings and structures.

But the severity of laws is offset by the fact that they can be disregarded by certain stakeholders. And if certain individuals are not interested in obeying certain regulations, I will dare remind them in 2012 a few purposely hushed up things, guided by Article 1 of the Federal Law № 384 (especially paragraphs 3 and 4).

Massive and often false advertisement of aerated concrete posted on websites and forums by manufacturers and salesmen continues to present it as "the best". Evidence suggests that it is, in fact, far from that, but I am sure you all know all these commercial tricks involving words like "the best", "number one", "better than the rest". All this list is lacking is the phrase that used to be so popular in the 90s - "buy it now before we're out".

I do not tread this path of lies and fabrications, so I will simply pick a country whose climate is similar to ours, specifically in St. Petersburg and St. Petersburg region - Finland, use a link to an agency that collects statistical data, and look up the information on the year 2010. Traditionally, there are plenty of frame structures, and if we look strictly at stone houses, the percentage is as follows (picture):

• concrete blocks of different designs - 53 %
• LECA blocks - 30%
• aerated concrete blocks - 11%
• brick - 4%

Yes, the message "The whole of Europe is built of aerated concrete" is based on a market share of only

11%, and 11% of just "stone houses" at that. If one were to take into consideration the fact that stone structures take up only about 14% of the whole, then aerated concrete makes up only 1.4%."The whole of Europe"?Really?

As an example, let's consider the information provided on the YTONG website (picture), where the technical properties section holds a figure for thermal conductivity of some abstract block - 0.09W/sq.m?°C.

Many people are familiar with the formula, can apply it in practice without going into further details, knowing the rated value of thermal resistance for Moscow (3,14sq.m?°C/W), we use the advertised figure to calculate the required wall thickness.

?=R??

As we can see, everything is fairly simple. We multiply 3,14 x 0,09 and get 0,283 meters. The closest block size is 300mm. This figure allows salesmen to state that 300mm of aerated concrete is enough for your walls as far as regulations are concerned. Only it's not.

Firstly, the brand of the blocks is not specified. This allows for fraud in terms of brands and density.

Secondly, the figures we are given are characteristic of dry material, which is unacceptable for estimation, as in operation materials have a certain moisture equilibrium.

Thirdly, the impact of seams is not taken into account, and since the material comes in blocks, which are laid with the help of adhesive mix, their impact isn't negligible, as you are told.

Fourthly, the effect of various heat-conducting elements and reveals needs to be taken into consideration. Please don't forget that a separate GOST R 54851-2011 was created and adopted just for that.

Such provision of information leads to fraudulent ways of inducing a potential client to buy materials and lets salesmen reduce the information on heat resistance of the wall to one line, manipulating the data to their advantage.

Of course, an ordinary consumer, a private developer, is competent and can calculate according to formulae, but he can't and doesn't have to figure out if the coefficients provided are correct, as, when paying for good and services, he is expecting that product properties have been presented objectively.

Do you remember my writing about the tricks used in the response to my article on hebelback.ru where all the data was reshuffled to form a pretty picture?

The AEROC company website (picture) provides more information on heat loss. For instance, one may read that if D400-500 blocks were used to make a wall even just 120mm thick (which, obviously, cannot be done due to load requirements, but the salesmen decided to fantasize a bit to awe their customers), it would still be comfortable!

I have conducted a computer calculation of the inner surface temperature, which at the temperature of +20°C inside a house in the worst understanding of this claim (D500 120mm) would equal +13,95°C (picture), and under the best conditions - +15,79°C (picture). Neither of these figures complies with the regulated value of temperature difference based on SNiP 23-02 (no more than 4°C), meaning that it cannot be considered comfortable (!).

5.8 Design temperature drop Dt0, °C between inner air temperature and inner surface temperature of a walling construction should not exceed rated figures Dtn, °C, determined in Table 5.

This means that 120mm do not comply with SNiP. They just wanted to awe. But it didn't work. They are unable to calculate and don't know regulations. Customers don't either, but they really don't have to. And that is what salesmen are hoping for, because then they can entertain customers with fun tricks.

That is, and I quote their statement, "Understanding this is vital". Lord knows, who writes these texts, but this reminds me of some sort of sectarianism (we will speak about it later). You just have to "understand", or, rather, "believe it is so".

If somebody feels that "computer calculation" that is acceptable according to p.15.4 SP 23-101-2004 is not reputable, let's check it based on the regulations stated in the aforementioned p. 5.8 of SNiP 23-02-2003:

?t=n*(tint-text)/(Ro * aint)

where n=1, aint =8,7 W/(m2 ? °C), tint=20°C, text = -28°C;

RoD400=0,126 - thermal conductivity coefficient of D400 - 0,117 according to GOST 31359-2007 considering thermal engineering homogeneity coefficient 0.93 for laying blocks on adhesive 2 mm thick with block thickness of 120 mm.

Thus, we find that the temperature of the inner surface of the wall is:

?tD400=4,97°C

?tD500=6°C.

As a result, the calculation also shows that the comfort officially declared online is a lie.

Conclusion:

1. managers and the technical department of Aeroc are totally ignorant

2. if paragraph 1 is not true, then the managers and the technical department of Aeroc are very knowledgeable in the field of scamming customers*

*after the publication of the calculation data and the claims about advertising statements this message magically disappeared from the Aeroc website, so all that is left is a screenshot.

Very often construction and technical terms are confuse or provided simply incompetently, for instance, YTONG boasts "the lowest coefficient of heat penetration". Personally, I am not familiar with this term and I have never seen it in any construction regulations. This must be another case of a purely philosophical "Understanding this is vital"! Understand it, and, more importantly, buy it! If one were to read through all the statements, they would find a ton of false and unfounded claims, which would take too long to describe or analyze. I will delve into the major ones:

Frost resistance.

SNiP II- 22 -81* specifies requirements for materials to be used for exterior designs in p. 2.3. project marks on frost resistance of stone materials for the exterior parts of a building (12 cm thick) and foundations (full thickness), built in all construction climate zones, depending on the intended service life of structures, but no less than 100, 50 and 25 years are given in Table. 1* and p.2.4* and p.2.5.

As a rule, intended service time of residential buildings is set at a minimum of 100 years and according to the data given in the table if the structure has humid rooms, frost resistance should be no less than F35.

In the canceled GOST 25485-89 "CELLULAR CONCRETES. Technical Specifications" Table 1 provided figures for physical and mechanical properties of different types of concrete. In this table brand D400 was considered thermal insulation concrete and therefore was not rated according to frost resistance, while brand D500 was rated at F15-F35.

In the new GOST 31359-2007 paragraph 4.12 determines frost resistance for all products regardless of other properties.

It was very important for aerated concrete manufacturers to lobby this new interpretation of frost resistance definition, as the one that had been in effect before automatically prohibited use of brands under D400 and D500 (depending on the value of frost resistance F)for exterior layers of buildings (with thickness of no less than 120 mm)on the basis of the aforementioned p. 2.3. ofSNiP II-22 -81.

At the moment, everything is fine with frost resistance of aerated concrete and it can be used. There are brands like F50, F100 and even F200. Has aerated concrete become better? No. The methods for estimation of frost resistance have been altered to benefit manufacturers.

This should not surprise you, because there is no financing for stand-alone studies or development of standards, therefore manufacturers spend their own money on lobbying nomination regulations that are beneficial to them. Let's take a look at who took part in creating this new GOST:

1. DEVELOPED by the Research, Project Design and Technological Institute of Concrete and Reinforced Concrete - branch of the FSUE "SRC Construction" featuring V. A. Kucherenko Central Research and Project Experimental Institute for Complex Issues in Construction and Structures, MGRS, VGASU (Voronezh), JSC "LZID" (Lipetsk), OJSC "NLMK" (Lipetsk), Ltd. "Aeroc" (St. Petersburg), JSC "LKSI" (y Lipetsk) Ltd. Reftinskoye association "Teplit" (Sverdlovsk region), JSC "Glavnovosibirskstroy", JSC "Cottage" (Samara), FSUE "211 KZHBI" (Leningrad region).

And now let's see who developed the old GOST 21520-89:

1. DEVELOPED by the Research, Project Design and Technological Institute of Concrete and Reinforced Concrete of the State Committee for Construction of the USSR, V. A. Kucherenko Central Research and Project Experimental Institute for Complex Issues in Construction and Structures of the State Committee for Construction of the USSR, Research Institute of Construction Physics of the State Committee for Construction of the USSR and State Construction Committee of the ESSR.

Not a single AC manufacturer listed among developers, unlike "the most modern" one.

Now, let's read carefully:

The current GOST 31359 describes the method for frost resistance testing separately - Appendix B.

Before, frost resistance of a material was determined according to the requirements listed in GOST 12852.4-77, when a sample was saturated with water in a tub and then alternately frozen and thawed, much like the other construction materials (brick, heavy-weight concrete). The following procedure was described in Appendix 3, GOST 25485-89. This explains such low figures for frost resistance of aerated concrete in Table 1 GOST 25485-89 (physical and mechanical properties).

For comparison, here are the old GOST 25485-89 procedure for saturation of samples for frost resistance testing:

3.6. Saturation is performed by immersing the samples in water (ensuring conditions that preclude their ascent) by 1/3 of their height and leaving them for 8 hours, followed by immersion by 2/3 and their remaining in this state for 8 hours more. Then samples are to be completely immersed and kept in this condition for another 24 hours. All the while the samples should be surrounded by a layer of water no thinner than 20 mm.

4.1. Core samples are loaded into the freezer at -18 ° C...

I.e., the samples are saturated with water and immediately frozen.

The new GOST 31359-2007 (currently in effect) regulates the following test procedures:

B.2.4 Core and control samples are saturated with water at the temperature of (18±2)°C to (35±2)% humidity (calculated by weight) before frost resistance testing.

Saturation of the samples is carried out by immersion in water for 1/3 of their height, preventing its ascent, for 8 hours, followed by immersion for 2/ 3 of their height for another 8 hours, after which the samples are totally immersed in water for 24 hours. At full immersion samples must be completely surrounded by a layer of water at least 20 mm thick.

Actual moisture content of the saturated samples is determined in accordance with GOST 12730.2

B.2.5 Depending on the value of actual moisture content, determined by B.2.4, the samples are dried at a temperature of (20±2)°C or moistened to the humidity of (35±2)% by capillary pumping. Samples are moistened through immersing them in water at a depth of 30 mm.  The samples are weighed every 30 minutes, with measure of inaccuracy of no more than 0.1%.

After drying or moistening the samples are placed in a sealed dry container for 24 hours for equalizing moisture content throughout their volume.

B.2.6 Control samples prepared in accordance with B.2.4 and B.2.5 are not exposed to alternating freezing and thawing, are kept in a thawing enclosure maintained at a (18+2)°C temperature and a (35±2)% humidity during the time corresponding to the number of frost resistance test cycles.

B.3 Procedure

B.3.1 Core samples, prepared in accordance with B.2.4 and B.2.5 are placed in a freezer at -18°C in order to determine their density and mass loss after alternate freezing and thawing.

Thus, the samples are not saturated fully (that is, let to absorb as much water as possible from the container they are immersed in) as they were before, and as the other materials are tested, but only up to 35% of their mass. The stated method is sparing to the samples and leads to high values in frost resistance.

Let's take a look at competing materials, for example, brick and the methods for its frost resistance testing.

GOST 7025-91 "Brick and Ceramic and Silicate Stones.Methods for Determining Water Absorption, Density and Frost Resistance".

7.2.2. Samples are saturated with water in accordance with Sec. 2 or 3.

2.3.1. Samples are arranged in a row (by height) and with at least 2 cm gaps between them. They are placed on a grid in a container with water at a (20±5)°C temperature and submerged at the depth of 2-10 cm.

 

2.3.2. Samples remain submerged in water for  48+1 hrs.

7.3.1. Air temperature in the freezer before samples are loaded should be no higher than -15°C, and after loading should not exceed -5°C. The freezing starting point is considered to be the moment when the temperature in the freezer decreases to -15°C. The temperature in the freezer should be between -15°C and -20°C throughout the freezing process.

That means that frost resistance of the sample is tested at full saturation for 48 hours (this is how it used to be with aerated concrete and other materials).

That is why now you can come across a F35 brick and a F100 aerated concrete block and  argue with your fingers crossed that aerated concrete has higher frost resistance.

This is how aerated concrete manufacturers quietly changed the GOST to fit their benefits and without changing the quality of the material improved its technical specifications are at least 5 times.

This is very much like that joke: "This is our snake and we will measure it however we want!"

They also added an extra point about operational humidity levels of 4% and 5%, because SP 23-101-2004 contains a regulation placing mass ratio of moisture in a material under conditions A and B at 8% and 12% respectively, which doesn't suit their interests.

 

Durability.

Aerated concrete salesmen claim many years of experience in application.

Here is a quote from a company's handout:

Xella appeared on the market in 2003 through the merger of Haniel-BauIndustrieGmbH (Duisburg, Germany), YtongAG (Munich, Germany) and Fels-WerkeGmbH (Goslar, Germany). Despite the company's relatively young age, the beginning of the story of its current success came to be in 1924, when cellular concrete was made for the first time in a small Swedish town of Yxhults. The dicovery was made by architect Axel Eriksson. Five years later, in 1929 Carl August Carlen began inductrial manufacture of cellular concrete.

This historical information on early production of aerated concrete allows for talking about "perennial" or "decades-long" application, always with a note that during all this time it has been closely observed. These facts have been interpreted in various ways and used in articles and brochures.

Let us clarify one very important thing: as of today manufacturers offer brands D400, D500 and D600 as one-layer constructions. They also claim that these brands of aerated concrete have been used for a very long time.

Earlier in the article I have cited GOST's that used to regulate physical and mechanical properties of aerated concrete and its products. According to the current GOST and SNiP regulations brand D400 was allowed for walling construction only on January 1, 2009 (GOST 31359-2007). Earlier, since the adoption of GOST in 1989, D400 was in a marginal position of application/non-application, which meant ambiguity and high risk of its use in walling, and since at that time doubtable solutions were not considered, this brand remained unused till 2000, when new requirements for thermal insulation took effect, and this property became more sought after. D500 has also not been used in walling constructions till recently, approximately 1977, when GOST was implemented. Therefore we cannot speak of extended (decades-long) experience in aerated concrete application when discussing D400 and D500.

Credible experience in use of brand D400 starts in 2000.

So where did these "years of experience since 1929" come from?

Actually, when I was studying at the Department of Industrial and Civil Construction, my teachers always said that AC was originally manufactured to accelerate economic growth and was meant for building barns and pigsties.

Now, turn your attention to a remarkable book - Silayenkov E. Durability of Cellular Concrete Products Stroyizdat, 1986, which aerated concrete manufacturers and salesmen use to fish out only the facts that suit them, which they cite on their websites:

On page 3, which presents data on different volumes with reference to dates and specific manufacturers, density of aerated concrete of 700 kg/m3 is used.

Citations:

1984 - 99 enterprises functioning, 5.9 million m3 products manufactured.

Growth in production of cellular concrete products was 3% per year in 1970-1985. Unit capital investment in production of cellular concrete panels with average density of 700 kg/m3...

etc.

It should be clarified that foam concrete, which the USSR manufactured in large volumes, is also considered to be cellular concrete. But process physics and chemistry of foam and aerated concretes in  operation is the same, which I have already talked about in the first article.

foam concrete, already written in the first article.

Another statement from Aeroc:

From 1960 till 1990, about 15 million square meters of housing with single-walled aerated concrete walls were built in Leningrad.

The plant finish of aerated concrete panels (manufactured by Integrated Home-building Factory #3 in Avtovo) was done with cement paints.

No plaster, no waterproofing or any other methods of "moisture protection" were used.

Simply because such "protection" is unnecessary.

Moistening of the concrete by slanting rain does not exceed depth of 2-3 cm.

The density of AC used in construction has been well-advisedly left out. Depth of rain penetration really was stated in the book, but it was attributed to brands with much higher density. Since D400 and D500 are very porous, penetration will be deeper.

The book indicates that a group of scientists have conducted a study of the lifetime of aerated concrete used at many construction sites and lists the main problems connected with aerated concrete, which caused the initiation of this study.

Pages 8, 9 and 10 provide a list of sites under study, with exact addresses. It should be noted that the buildings that were investigated were built with aerated concrete with density of 700-1000 kg/m3. Only in one case 500 kg/m3 panels were used - at the experiment base of UralPromstroyNIIProekt (Sverdlovsk), which can be considered the first attempt at using 500 kg/m3 density as an experiment on the base of the Research Institute (Reminder: this book was published in 1986).

The author states, "In total about 100 industrial and civil structures with operating life of 40 years were studied" (p. 6).

The main problems with aerated concrete listed are:

Page 4 reads that cellular concretes have their own specific set of distinctive features, and when property assessment characteristic for heavy-weight concretes was applied to them, cellular concretes showed low durability. That is, the author argues that for calculating lifetime of cellular concretes, their specific properties should be taken into consideration.

Page 7 indicates that 40-year-old  one- and two-story buildings in Riga were examined. No significant damage to the blocks left without decoration was found. P. 8 explains what happened to the paints, which leads to a conclusion that paint does not prevent cellular concrete from cracking.

On page 12 the results of the assessment of plastered surfaces of aerated concrete are explained (it should be noted that the author uses correct terms - cellular concrete or foam/aerated concrete). The following observations were made specifically concerning small-block aerated concrete:

• Peeling of complex solution plaster of 10-15 thickness occurred between 10-23 years of life of buildings.
• Plaster withstands 10 years of operation.
• Cracks develop faster on the plaster on walls laid with large blocks.
• Increased cracking on large blocks is due to the fact that with increasing size of the base the influence of its deformation on the finish layer increases.

On page 18 a conclusion is made based on the observations. Equilibrium moisture content is reached faster when the finish layer is made of materials with high vapor permeability or when finishing layers are absent. Plaster layers slow down the reduction in moisture content of the structure when its construction is over.

On page 21 we see a conclusion that a continuous drizzle has increased moisture content of the blocks from 7-9% to 10-12% (by weight) in 48 hours, and it wasn't stated that the drizzle hit the blocks directly. Under the conditions of slanting rain the amount of water absorbed by the open surface of cellular concretes can equal 150-180 g/dm2. The blocks' moisture content changes abruptly during the rainy season (a graph is given).

On page 23 a conclusion is made that as the size of blocks and panels is increased, cracking increases as well.

Page 50 reads that experiments show that there is not enough data on frost resistance of cellular concretes with density lower than 500 kg/m3. However, a separate point is made that reducing density of blocks has a future (please, do not forget that this book was published in 1986).

The main reason for cracking of blocks and slabs is shrinkage. The shrinkage depends not only on moisture content but also on carbonation (p. 51). Autoclave concretes have high shrinkage compared to non-autoclave (p. 69).

The main processes that contribute to the aging of concrete are carbonation and drying. Moisture loss is a prerequisite for stabilization of concrete volume (p. 92). During carbonation durability may decrease by 20-30 %.

Pages 101-102 describe the need for waterproofing cellular concrete. When protective layers are applied, due to big differences between the structure and properties of polymeric coating and concrete their application on concrete directly leads to tension in the contact area, shrinkage and deformation of the film coating.

Page 126 contains a basic requirement for surface finish for facades made of brick and dense concrete, that is ornamentality. A different approach is needed to finish products for cellular concrete.

Finishes for facade surface made of cellular concrete products must meet a broader range of requirements than those designed for brick and dense concrete walls. High porosity of cellular concrete, while giving it a range of advantages over other materials, also makes it more prone to deformation in use, gives it high moisture content, as well as vapor, moisture and gas permeability. Autoclave processing dramatically decreases concrete's ability to prevent corrosion of steel reinforcement.

Thus cellular concrete surface finish products, apart from regular requirements like aesthetics and long life, must meet technical requirements of vapor permeability, grip on concrete and waterproofing qualities.

Page 128 reads that since finish performs not only decorative but also protective functions, the level of protection must be maintained throughout the life of the structure. Cement paint finish is of low durability.

A table on page 131 contains experiment results, where coatings made with cement (even solutions containing cement and polymers and applied through spraying) have a very short maintenance-free lifespan of 5-8 years, 10 years at maximum.

Page 144 reads that lifespan of cellular concrete is the longest when screen finish is used.

In Conclusion on page 161 the following is stated:

- In the aging process (caused by insufficient durability of hydrosilicates in the cement stone)autoclave aerated concrete when in contact with carbon dioxide undergoes changes in its chemical makeup and full reconstruction of its microtexture. Aging occurs in the entire structure in a short period of time (15-20 years) and is accompanied by changes in durability (usually reduction) and shrinkage, which is a few times more intensive than shrinkage caused by changes in its moisture content.

- Total shrinkage in the operating conditions depending on the type of concrete equals 1.2 - 2.2 mm/m, maximum drawability does not exceed 0.2 mm/m, so the formation of cracks in the product is a natural process.

- Studies done by Ural Promstroy Research Institute Project research showed that in the series of measures ensuring durability of cellular concrete structures significant amounts of attention should be paid to their facade surface finish.

Based on the synthesis of technical data and research results we can make the following conclusions concerning aerated concrete:

The phrase "long-term studies of lifespan" are applicable only to the material with the density of 700-1000 kg/m3.Nowadays  mainly blocks with densities of 400-600 kg/m3 are produced. In 1986 there was no reliable data on observations of brands with density that equals 500 kg/m3 or lower. Therefore, claims made by manufacturers and salesmen that these products have been manufactured since 1930s, as well as citation of various data received in these studies in connection with modern products are deliberate lies.

During a relatively short period of time (15-20 years) aerated concrete undergoes carbonation which leads to a 30% decline in its durability. Therefore, when designing constructions it is necessary to account for extra 30% of grade durability, which is hardly ever done nowadays.

Carbonation is a chemical reaction of cement paste with carbon dioxide CO2 and water to form ordinary chalk. Have you noticed how old AC walls become chalky and how finish falls off of them?

Speed of carbonation is reduced by finish layers applied to blocks, but to avoid moisture accumulation and cracking due to low vapor permeability of finishes aerated concrete manufacturers recommend against using any finishes (as Aeroc proudly informs us). Only that leads to faster carbonation. Since porosity and, obviously, gas and vapor permeability of modern blocks is higher, carbonation and aging happen much faster than the 15-20 years defined in Mr. Silayenkov's study of brands 700-1000 kg/m3 dense.

In AAC corrosion of steel reinforcement is much faster. All reinforcement recommended in "Albums..." are short-lived due to high porosity of aerated concrete and adhesive mixture, unlike heavy concrete where reinforcement has a very long lifespan.

In order to ensure a long lifespan for aerated concrete one needs to protect the material from excessive moistening. This means protection from precipitation and condensation that occur during its life. According to research, coatings containing cement have lower vapor permeability and therefore flaked off after 5-8 years when used on aerated concrete base.

The importance of proper selection of finishing layers and the need to protect aerated concrete from moisture are constantly emphasized in speeches made by professionals in the area.

For example, in the article "Problems of Operational Reliability of External Walls of Buildings Based on Autoclave Aerated Concrete Blocks and Their Possible Protection from Moisture " stated that:

 

 

The issue of protection of an outer wall made with autoclave aerated concrete blocks... can be resolved... with a decorative and protective system. Such a system should have waterproof qualities that would ensure that no moisture can be absorbed from slanting rain or condensation that accumulates on the surface of the wall during transition periods.Adhesion of the system to AAC should be at the level of aerated concrete base's durability to strain... For concrete of average density of 400-600 kg/m this corresponds to a range of adhesion properties of 0.15-0.4 MPa. Elements of the protective system should have minimal shrinkage, increased drawability and frost resistance. Materials in protective systems must be vapor permeable to prevent walls from excessive moisture content on two criteria: non-accumulation of moisture in the walling for a period of one year, and restriction of moisture content during periods with negative average monthly outdoor temperatures AWau. These conditions should be consistent with a high vapor permeability coefficient of highly porous aerated concrete (m=0.23-0.17mg/(mh-Pa) for cellular concrete with an average density of 400-600 kg/m3) and low resistance to vapor permeability of the wall (for wall thickness 400mm Rup=1,74-2,35m2-Pa/mg).

A vast majority of manufactured mixtures called "filler" or "plaster" are not suitable as finish for aerated concrete walls, as they have lower vapor permeability. For finishing aerated concrete walls one needs to use plaster mixes and paints with high vapor permeability, designed specifically for aerated concrete.

"Moscow Center" - Central Administrative District Newspaper (link):

Elena Orekhova, Moscow, VerkhniayaKrasnoselskaya St., 9:

- Our house is in trouble: its facade is falling off. Not so long ago a huge chunk of it fell on my car and dented its hood. Facade renovations were initially planned for this year, but due to the financial crisis it has been postponed. They say that now they are planning to work on it in 2014. But if the destruction continues at this pace, I am afraid, the facade will completely fall off by then.

Response by Galina Chupakhina, Head of the Krasnoselskiy district Council:

I know the issues in your house very well. It was built by a Turkish company with co-investors in the first half of 1990s, and very serious breaches of technology were made. As of now, unfortunately, the facade is not the only problem, internal communications are in a bad state as well. What can be done? On the one hand, the building is in dire need of renovations. On the other hand, it is only 15 years old and is not eligible for the city apartment buildings overhaul program. We have discussed this question numerous times in the Central Administrative District prefecture. Renovations of the facade only will cost 22 million rubles, and the district is unable to allocate such a sum of money. We have asked the city for assistance and hope that the money will be allocated, although, as you know, city budget has been cut dramatically. If we manage to receive at least partial funding, we will start the renovations this year.

 

"Serious breaches of technology" - that is what they call lack of knowledge and no wish to obtain it. Once again, someone will be swindled, "it's no one's fault", the facade will be renovated with the same "serious breaches", so that in the near future there is more work and more opportunities to make some more money.

Or maybe everything is very primitive - no one needs competent and high-quality construction, and all this showing off with expressive gestures, beautiful presentations, tons of advertising and sleek managers in suits and ties that we see at construction expos and offices are nothing more but a setting for commonplace moneymaking "here and now".

You see, manufacturers' managers for the most part are unfamiliar with construction, having only memorized a few pages of commercial advertisement. They have no time to go through it thoroughly, when sales targets are in danger. Technical professionals may have a more substantial idea, but that rarely happens.

Then where are designers, who are obligated to be well-versed in technology and should not fall for managers' sweet talk? We are running out of them too. Soon they will go extinct.

This is happening because a new trend is on the rise. Construction material manufacturers are teaching students in technical schools and higher educational establishments now. Can you imagine what they will teach the poor kids based on their financial interests?

That is why, while there is a huge number of unsolved issues and distorted properties and numbers going around, you, as an aerated concrete purchaser, have to know that no one but you is interested in obtaining and proper implementation of truthful information. Therefore, you are the only one who has to do everything in your power to protect yourself. Please remember that the main conclusions that can be drawn from the information provided are as follows:

1. misleading of consumers regarding the use of AC continues

2. only specialized facade finish materials with high vapor permeability must be used, as ordinary store-bought ones most of the time are not suitable for AC

3. when calculating loads in construction it is vital to use a lowering coefficient of 1.3, that is, to design loaded AC walls with a 30% stress reserve, which is omitted and is not regulated anymore.

When looking at all these advertising slogans about aerated concrete, which, much like endless reality shows on MTV, are poured into the society's consciousness in a steady stream, I come to a conclusion that all those involved in manufacturing and selling AC have joined one huge sect.

(Wikipedia) Sect (Latin secta - school, doctrine, from Lat. Sequor - follow) - definition (term) used to refer to a religious group that has separated from the main religious school or points to an organized tradition that has a founder.

In some sources the term "sect" is interpreted more widely. The definition is used to name any group (religious or non-religious, separated or new) that has its own doctrine and practice, which are different from the dominating church or ideology.

There are obvious signs that:

• there are groups with the doctrine of "aerated concrete" and "foam concrete", that have their own devotees and ideologists
• the "cellular concrete" doctrine is separate from general building regulations
• AC manufacturers on the whole work within laws, breaking them only in places that are contrary to the basic ideology of promoting their doctrine
• AC manufacturers have their own flock that supports their doctrine regardless of the circumstances
• numerous actions and objects in the doctrine are given not from a clear position of science, but from the standpoint of faith only (do you remember the phrases "Understanding this is vital", that is, "Believing in this is vital"?)
• cellular concrete is an object of worship and a source of income for sectarians
• the school of aerated concrete is experiencing a dissension. Even  religious wars are fought between the sect of foam concrete and the sect of aerated concrete

It appears to be that when dealing with aerated concrete we are dealing with a sect :)

Author: Gennady Yemelyanov

based on the materials at www.wdvs.ru