We found an interesting article, wriiten by an Airbus collaborator about energy absorbing barriers in air planes. Especially the impact of birds is dangerous and for that reason, the air plane needs protection with all kind of energy absorbing barriers. These barries should be lightweight but still efficient.
The article also shows the load deformation curve of the perfect kinetic energy absorber. This curve is typcial for foams and indeed also for cellular glass when the compressive strength measurement is done without capping. Indeed, the typical peak at the beginning of the flat part is absent for foams but not for honeycumbs.
The article shows also a graph with the specific kinetic absorption of foams, which do and do not comply with what is needed. The typical foams of polyurethane, polyisocianate and polyethylene do not comply, even at densities of 100 kg/m³. But on the other hand, GLAPOR cellular glass reaches 2000 kPa compressive strength with 140 kg/m³ density. In that case, we have a specific kinetic energy absorption of at least 8 kJ/kg, which is close below the well known (combustible) foams for these applications. Today, PVC-foam and PMI foams have taken this market but when non-combustibility becomes an issue, GLAPOR cellular glass is a good candidate.
Cellular glass is a perfect thermal insulation for outside walls after rendering with natural hydraulic lime mortars. These kind of systems are known in Europe as ETICS (External Thermal Insulation Composite System). For each system, the building company needs to find an ETA to be able to deliver the normal guarantee.
The ETA (European Technical Assessment) was requested by Arte Constructo, Belgium and can be applied on all kind of cellular glass boards equivalent with GLAPOR cellular glass. The rendering products are Unilit 15P2, Unilit 65M and Unilit 65F. The mineral adhesive to adhere the cellular glass boards on the wall is Unilit K/2. These mortars are produced at Tassullo, Italy.
After the hygro-thermal testing, the system did not show:
- blistering or peeling of any finishing
- failure or cracking associated with joints between insulation product boards or profiles fitted with the ETICS,
- detachment of render,
- cracking allowing water penetration to the insulation layer.
As a consequence, this system became approved and is now used for several years without important complaints.
Recently, we got a leaflet from the Welsch company Ty Mawr about the use of cellular glass gravel in Birmingham Paradise. The cellular glass for this project was delivered by GLAPOR.
Also in this case, the relation strength – weight was the main reason to use cellular glas instead of ordinary soil. BELGLAS was delighted to assist in this wonderful project with a large ecologic respect.
Norway is ranked as the best democracy for several years. In that way, we are not surprised that it became impossible for the concrete lobby to stop the following invention as a consequence of the high ecologic standards, typical for the best democracies.
In previous posts, we have mentioned
On top of that, Norway subsidizes small companies by giving them cheques for testing in official laboratories instead of cash. Such an important test facility in Norway is Sintef where all kind of tests are free of charge possible for small companies, inducing a lot of innovation. The following pdf mentions an innovation for cellular glass between a lot of other innovations. This subsidizing system (free tests without cash) is really working.
FOAMROX builds all kind of shapes from cellular glass with a coating to make it more robust. These shapes are used in the 750 km tunnels in Norway and are replacing the 7 times more heavier concrete in several cases. Cable trays, fire fighting chambers, heat resistant walls , … are now built from cellular glass. The thermal conductivity of this cellular glass is not important and for that reason directly foamed recycled glass can be used to improve ecology. To reduce labour cost, larger dimensions up to 2.8m x 1.2m are very well come. Today, GLAPOR is the only manufacturer who is able to deliver this kind of cellular glass but I guess this situation will change very fast. Hereunder, you find a picture of the proud inventors, who understood the lessons of Michael Ashby very well.
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.