We already have written a post about Permafrost. Although this Permafrost is unknown in our regions, a lot of people have to make their lifes on such an underground. In the Northern Hemisphere, 24% of the ice-free land area, equivalent to 19 million square kilometers,is more or less influenced by permafrost. Most of this area is found in Siberia, northern Canada, Alaska and Greenland.
The basic problem to live on Permafrost is the stability because there is an active layer, which is melting every summer. Building on this layer makes that the building is continuous sinking into the underground.
Above on the left, a standard building is “sinking” into the underground while at the right, the building is put on concrete pillars, deep into the permafrost with a concrete slab on top of this pillars to support all bending forces of the building. The havier the building (more concrete), the deeper the pillars are put into the permafrost (more concrete). Between the ground and the building, we have an airlayer, which avoids that building heat is penetrating into the permafrost, creating even more instability.
The new system replaces the active layer (about 1.5m) by cellular glass. Cellular glass is weight light, can support the building and 1.5m cellular glass avoids perfectly that building heat penetrates into the permafrost. Another advantage is that a climate change hardly influences the permafrost under the building. In that way a lot of concrete has been avoided.
For this application, we don´t need cellular glass with the lowest thermal conductivity, which means that cellular glass, directly foamed from recycled glass will satisfy. This cellular glass can be prefabricated from large boards of 2.8 x 1.2m, today only produced by GLAPOR cellular glass. This can be done with the help of polyurea, like already done for flat roofs. Cellular glass gravel is less suited because it absorbs water, which freezes and increases the weight. I guess that the new construction is a better approach (more stable) and price competitive.
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.
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.