Sometimes, it is not clear why in some countries an application of cellular glass is allowed and in others not. In some cases, lobbying of competitive products could be the reason. In order to get a fairplay, Europe generates European Assessment Documents (EAD), which are able to overrule the local laws. They are defined as follows:

The European Assessment Document (EAD) is the documentation of the methods and criteria accepted in EOTA as being applicable for the assessment of the performance of a construction product in relation to its essential characteristics. The EAD is developed in all cases where the assessment of a construction product is not or not fully covered by a harmonised technical specification (Regulation (EU) No 305/2011).

It contains, at least,

• a general description of the construction product and its intended use (Chapter 1 – Scope),
• the list of essential characteristics relevant for the intended use (Chapter 2) and
• methods and criteria for assessing the performance of the product (Chapter 2),
• principles for the applicable factory production control (Chapter 3 – AVCP).

Recently, one appeared for cellular glass as a pdf-file, which can be download on this website.

This EAD is an extension of EN13167 with the following:

Moreover, it covers in the following paragraph the GLAPOR RDS system:

In this way, the GLAPOR RDS system cannot be blocked anymore by lobbying competition in a few countries. The RDS-blocks are typical edge modules with the same chemical composition as single boards and even the used cellular glass gravel.

Polyurea is an elastomer with a very large tensile strength (40Mpa) and elongation (500%). On top of that, it can absorb a lot of kinetic energy without damaging the underground, like illustrated in the following paper. The last property is the consequence of a glass transition of the polyurea under a high deformation rate. This (reversible) glass transition takes a lot of energy, which returns as heat after impact without remaining deformation.

The weakness of cellular glass are its dusty surface, the lower tensile / bending strength and a rather weak surface. By applying polyurea, the dusty and weak surface are completely  eliminated, while the large tensile strength / elongation eliminate the immidiate failure consequence of a crack in the cellular glass due to bending or tension. In fact, a board cellular glass, coated on all sides with polyurea behaves as an extremely robust light board. Standard polyurea is combustible with EUROCLASS F and removes an important strong point of cellular glass.

But with the addition of some flame retarders,  Epaflex has a polyurea with  Reaction to fire classification B s2 d0 today available with  10 MPa tensile strength and 280% elongation. This means no risk for flashover and no (dangerous) droplets during a fire, with limited smoke generation while the cellular glass mechanical properties are largely improved.

Indeed, on the condition of a suitable Reaction to Fire classification, polyurea and cellular glass may be a good combination. A straightforward application could be a cellular glass flat roof, built with large cellular glass boards (less joints) where the water proofing membrane is replaced by polyurea.

Polyurea coated cellular glass has indeed a huge bending strength in relation to its weight like shown in this picture. Uncoated celllular glass never takes a weight of about 500 kg in these circumstances.

Some time ago, we have written a post about the minimum thickness of a cellular glass boards in case larger dimensions are requested. In that post, we have calculated the case of 2.8m and 4m long cellular glass boards, which have to sustain at least their own weight. From the previous post, we now that cellular glass is the lightest option between a lot of materials.

For a 2.8m long board, we have calculated that a minimum thickness of 10cm is needed to be on the very safe side. But great was our surprise that some cellular glass sales engineers claim that these boards cannot be produced although this was already shown in an old post. It was even claimed that transport or handling of such  2.8m long boards are physically impossible. Therefore, we give the calculation again and also a picture of 10cm GLAPOR thick boards, 2.8m long, which are transported over at least 1250km by truck and handled on the job site.

Such false stories, told to harm others are called a hoax. It is clear that these kind of stories need a law to guarantee fair competition. But in the meantime, we use them to show the incompetence of the source like the physicist Socal once did with some post-modern sociologists.

A long time ago, cellular glass was a thermal insulation which is vapor tight and has a large compressive strength. Later on, I realized that it is a thermal insulating material which can replace bricks, it is a construction material. But recently, I learned as suggested by Michael Ashby that cellular glass is the lightest material between the ones which can support there own weight.

The following table shows a list of all kind of materials. We consider a beam with a certain span and width and allow a certain deflection under its own weight. The thickness is a free parameter. We calculate weight and also embodied energy, which is the primary energy needed to produce the beam. We have rescaled the weight by dividing by the weight of the GLAPOR PG600 beam.

Like can be observed, GLAPOR cellular glass is the lightest material that support its own weight but it has also the smallest embodied energy like shown in the GLAPOR cellular glass EPD. And in a near future, it will also be the cheapest material in the list.

This means that cellular glass can replace concrete in unloaded situations, when non-combustibility and water tightness are an iussue. Besides light, ecologic and cheap, cellular glass can be produced in about 10 hours while concrete takes several days.

Although this application of cellular glass is straightforward, it became only realistic after GLAPOR developed the continuous foaming process, delivering large boards upto 2.8m x 1.2m based on direct foamed recycled glass with prices below 200€/m3. The mould process and the cellular glass based on a special composition can never compete in this discipline.

In this post, I like to put the attention on more academic / laboratory contributors. Indeed, cellular glass is born on the scale of a cup of coffee and later on further extended to larger dimensions, today up to 2.8m x 1.2m.

Bernard Long, a scientist working once for St Gobain Glass, filed in 1938  patent US2337672 about the foaming of glass. He used carbon as foaming agent and describes the reduction of an oxide as the gas evolution source. I guess this is the first closed cell cellular glass patent and this foam could be used as floating device for the curtains in the harbours against submarines.

Boris K. Demidovich,  has published in 1972 a book about the production and use of cellular glass. It is the perfect description of the knowledge at that time and is the advised work to study for each cellular glass starter. It was so important that the American Army translated the work in English. Personally I was impressed by the knowledge in Czecho-slovakia, with a plant in Usti nad Labem in 1947. Sixty years later, a cellular glass plant was built in 2007 at about 80 km from the first plant.

Prof. Dr. Bernardo Enrico, a professor at the University of Padua developed the cold foaming of glass like already described in a previous blog. This open cell foam can be made from bottom ash and fly ash from waste incinerators. Up to now, open cell foams were not popular but this will change in the near future.

Prof. Dr. Lorna Gibson is a cellular solids expert at MIT. By studying her work, people become aware of the opportunities of the cellular version of a material. Glass is already extraordinary  and the cellular version extend largely the importance of that product.

Prof. Dr. Michael F. Ashby is a material engineering expert at Cambridge Univerisity, which is already mentioned in a previous blog. He described cellular glass as the most efficient  material to support its own weight. Since GLAPOR is delivering large boards by 2.8m x 1.2m, this property can be applied everywhere to replace unloaded concrete beams.

Prof. Dr. Christian Maes, Physics department of the KU Leuven, Belgium discovered that cellular  glass fails under a compressive load in a diffusive way. This important statement is probably valid for all kind of fragile heterogeneous materials. This was already discussed in a previous post.

The previous heroes were all experts with the dry powder method. The following heroes have worked or are working with the wet method (or water glass method).

Recently there was a meeting of a group of people, who will change the cellular glass world thoroughly and even a large part of the mineral insulation world. It is a combination of knowlegde, huge ecology loving capital and direct communication without any hiearchical borders.

Dr. Oleg Sharykin (second from right) is an important investor in the Russian cement industry, who believes strongly that ecology is the future for this planet. A long time ago, he recognized the assets of the GLAPOR technology and invested in the further development of that company. Today, GLAPOR has the technology (and a booming market) to produce a product of excellent ecologic quality, like shown in a GLAPOR EPD (Environmental Product Declaration), certified by the world famous IBU (Institut Bauen and Umwelt, Germany). It will be a mistery forever whether two technologies, namely gluing sand particles with cement and sintering waste glass particles belonging to the same investor is a coincidence or not. Indeed, in a lot of applications, concrete boards can be replaced by cheaper and lighter cellular glass boards.

Walter Frank (right side on above picture) is the founder of GLAPOR and took beyond any doubt the largest risk. Therefore, I would rank him as the largest cellular glass hero of all times. Walter was a sales engineer and sold for Horn Glass Industries the first float glass line in Russia, without any reference. But he was also working in the old Coriglas plant where he met cellular glass for the first time. Walter has chosen the recipe of Millcell with glycerin / water glass. He extended the cellular glass gravel process with an annealing furnace and broadend the furnaces to what was standard in the float glass industry. He immideately realized that large cellular glass boards are the future and focused on direct foaming of recycled glass to improve ecology. He did not jump into the thermal conductivity rat race, started by the polymer Pied Piper of Hamelin to hide their own important weakness, which is combustibility. Today his dream is reality, which also means that his dream is gone (is not a dream anymore). His next dream is to jump beyond the typical thermal insulation jobs and to start an entirely new cellular glass market besides the existing one. For that reason, he can not retire during the first ten years.

Otto Anton Vieli is the inventor of the wet process with waterglass and glycerin like already discussed in a previous post. This recipe is applied in a large part of the cellular glass gravel production and for the boards by GLAPOR. This recipe has a huge potential because it foams a low density with rather coarse powder and allows to work in a furnace with efficient stochiometric combustion.

In Thuringen, Germany, there was once a small cellular glass factory, VEB Schaumglas Taubenbach, producing the product Coriglas. After  “Die Wende“, the factory was first owned by Heraklith and later on by an American multinational. The last owner shut down the production exactly 50 years after it was built. The shutdown induced a brain drain to Russia (STES), Ukrain (PINOSKLO) and GLAPOR and is one reason of the current price drop of cellular glass, making it economically available for more people.

In this series of blogs, I will remember the work of some previous cellular glass workers and thinkers. They all took once a big risk to fail and were in that way important in the evolution of cellular glass. For some legal reasons, I cannot mention people, still at work in cellular glass.

Louis Troussart was an expert in the annealing of (cellular) glass as an employee of St. Gobain Glass and a cellular glass manufacturer. Some years ago, he passed away as a well respected man. The reasons for that are obvious:

• Louis was the first to find out that glass has a thermal history. Indeed, by measuring carefully the thermal expansion for different cooling rates, he proved that the physical properties of glass are dependent on the cooling history.
• Later on, he moved to cellular glass and did important published work with finite elements. He optimized for example the guarded hot plate for the measurement of the thermal conductivity.
• Many other work cannot be mentioned because it is not public domain

Charles Beerten, an exponent of accuracy was a chemist working on the glass composition. Today, cellular glass with the best thermal conductivity is produced with “his” glass composition in Europe, China and the USA. Also in his case, most of his work is not public domain. Charles became retired against his will and lives in the “Ardennen” in the south of Belgium.

Pierre Gérard, a smart and fast mechanical civil engineer was also an efficient cost cutter. Pierre understood very fast that the most efficient cost cutting was improving the process. He was an enormous support for me, especially when the tunnel seemed endless long. His father, Paul Gérard was the collaborator of Louis Troussart during the discovery of the thermal history of glass. Pierre is retired and is spending his time with travelling with his wife.

Hugo Frederix, a typical self made man, checked in hardware mode the ideas of the above and also participated to a paper about the stability of cellular glass, like mentioned in a previous post. Hugo lives in Limburg in the east of Belgium.

Jos Bellens, a laboratory chemist passed away much too early. His important R&D work is not public domain but in his second career, he became an outstanding safety engineer. I will never forget him.

Albert Van der Heyden, production engineer and self made man, was an expert in tuning a foaming furnace for the carbon black process with the necessary reducing atmosphere. Albert made once an important experiment, which ignited the continuous foaming process project. Albert is retired and lives in Meldert, Lummen as the very best grandfather.

Marc Kolenberg was about everything: electronic, electrical and mechanical engineer, software developer and most of all production manager for cellular glass. Marc did not know any limit to reach what he considered as possible. Without him, my largest project should never run. Marc is retired and lives close to Diest with his family and dogs.

Robert Havel started as a worker and became production manager of the cellular glass factory, producing the highest quality ever. After having done the startup of a cellular glass factory in China, Robert´s ambition drove him in another direction. He lives in Klasterec Nad Ohri in the Czech Republic with the lovely Jitka Havlova and their child.

Jean Melchior, a civil engineer from Luxemburg is known as an extremely strong marketeer for cellular glass. He understood very early the importance of ecology for the thermal insulation world. Not cost cutting but ecology was his drive to support me for my largest project. From him, I got the nice title “free electron”, although that property let him explode many times. Jean is retired against his will and lives in the center of Belgium, studying Machiavelli.

This sounds like energy by cold fusion, but in this case it is real.  Prof. Enrico Bernardo from the Engineering University of Padua invented a new process to foam glass below 80°C. The motivation for this invention is quite clear.

Enrico does not want to limit him self to the foaming of “easy” soda lime glass but he wants also foam glasses which are eager to crystallize. Such glasses are already crystallizing during sintering and does not foam due to the crystallization. Glasses obtained from waste incinerators (bottom ash, fly ash) are a typical example. In fact, all the efforts are based on the philosophy to recycle any waste.

The full process is described in a paper. The alkali-activation method (geopolymers) is used to create a gel. Air is introduced in this gel (foaming) by mechanical stirring. The resulting foams are hardened at 75°C. After this step, the foam has already all its properties like compressive strength, thermal conductivity, ….. To eliminate leaching out or to make the foam chemically stable, a temperature step at 700°C (firing) is needed. Because the foam is formed, crystallization in this last step is not a problem anymore.

The foams are open celled, which opens a new market for cellular glass, based on “real” waste and as a consequence at very low cost. I think now on a cheap alternative of low and high density gas concrete. But if the foam can be evacuated to low pressures (0.1 Torr) and packed, a low thermal conductivity of the order of 0.025 W/mK can be reached.

Michael F. Ashby is a Cambridge University professor about new (and old) materials. By accident, I found his textbook about engineering materials Vol. 1  on research gate.

The textbook describes the important physical properties and physcis behind these properties. But also the availability and price are given some attention.

The book is of course illustrated with case studies. Hereunder we cite the case study about the support of a large telescope mirror.

Introduction
The worlds largest single-mirror reflecting-telescope is sited on Mount Semivodrike,
near Zelenchukskaya in the Caucasus Mountains. The mirror is 6m (236 inches) in
diameter, but it has never worked very well. The largest satisfactory single-mirror
reflector is that at Mount Palomar in California; it is 5.08 m (200 inches) in diameter. To
be sufficiently rigid, the mirror (which is made of glass) is about 1 m thick and weighs
70 tonnes.*
The cost of a 5m telescope is, like the telescope itself, astronomical – about UKE120 m or US$180 m. This cost varies roughly with the square of the weight of the mirror so it rises very steeply as the diameter of the mirror increases. The mirror itself accounts for about 5% of the total cost of the telescope. The rest goes on the mechanism which holds, positions and moves the mirror as it tracks across the sky
(Fig. 7.1). This must be so stiff that it can position the mirror relative to the collecting system with a precision about equal to that of the wavelength of light. At first sight, if you double the mass M of the mirror, you need only double the sections of the
structure which holds it in order to keep the stresses (and hence the strains and deflections) the same, but this is incorrect because the heavier structure deflects under its own weight. In practice, you have to add more section to allow for this so
that the volume (and thus the cost) of the structure goes as M2. The main obstacle
to building such large telescopes is the cost. Before the turn of the century, mirrors were made of speculum metal, a copper-tin alloy (the Earl of Rosse (1800-18671, who lived in Ireland, used one to discover spiral galaxies) but they never got bigger than 1 m because of the weight. Since then, mirrors have been made of glass, silvered on the front surface, so none of the optical properties of the glass are used. Glass is chosen for its mechanical properties only; the 70 tonnes of glass is just a very elaborate support for 100 nm (about 30 g) of silver. Could one, by taking a radically new look at mirror design, suggest possible routes to the construction of larger mirrors which are much lighter (and therefore cheaper) than the present ones?

At the end, it is summarized in a material index, which is calculated for a few materials.

The following conclusions are taken:

The optimum material is CF’RP. The next best is polyurethane foam. Wood is obviously
impractical, but beryllium is good. Glass is better than steel, aluminium or concrete
(that is why most mirrors are made of glass), but a lot less good than beryllium, which
is used for mirrors when cost is not a concern.

But at the end, we find the inventive step:

The most obvious obstacle is the lack of stability of polymers – they change dimensions with age, humidity, temperature and so on. But glass itself can be foamed to give a material with a density not much larger than polyurethane foam, and the same stability as solid glass, so a study of this sort can suggest radically new solutions to design problems by showing how new classes of materials might be used.

Indeed, with low density cellular glass, we arrive at a material index = 0.1, which is the best value. However, with the usable dimensions of cellular glass (60 x 40 cm), the idea of building a large mirror cannot be realized with cellular glass. But the continous glass foaming technique as developed by GLAPOR allows dimensions up to 3.2 m. Even wider up to 6m (like for float glass) is possible in case there should  a market for this large product. Indeed, light structures built from foamed recycled glass have a certain future.

Also Engineering Materials vol2 is available in pdf on nanotech. This book contains a nice chapter about glass and the production of glass articles. Also ceramics and more particular concrete are mentioned with a lot of data to be used for the calculation of an order of magnitude.