Open source software: octave

logo_smallOpen source software was always a point of interest for BELGLAS. Semi professionals work together and generate an equivalent of commercial software. In this case, we discuss GNU Octave, which is an alternative of MATLAB.

100px-Gnu-octave-logo.svgBoth products are used to solve mathematical problems with numerical methods. Everything is based on matrices but standard programming, like done with C and FORTRAN is also included. It is a script language, which means that every command is first interpreted and then executed , contrary to FORTRAN or C, where compiled programs are executed.

downloadDeveloping a solution for a problem goes much faster with this software but execution is slower than with FORTRAN. If a certain solution works well with Octave but execution is too slow, reprogramming partially or completely is an option. The plotting software is also very easy to use and writing or reading data to/from a file is straightforward. A lot of Octave programs are already available in all kind of technical disciplines.

For the interest reader, there is the official website, where you can download the program and I found a tutorial on the internet. Even a more complete handbook could be found next to the official octave manual.


Acoustic absorption with cellular glass

logo_smallAcoustic absorption is a typical open cell foam application like nicely explained in this handbook for acoustics or in this wikibook. In some cases, fibrous materials like mineral wool are not allowed and an open cell foam is chosen. But if also combustibility is an issue, we have to work with a mineral foam. A typical example (and maybe the only one today on the market) is Reapor.

In the datasheet, I found the following absorption spectrum.


absorberThis means that 1m² of this material is equivalent with an open window of 1m² for the noise in a room, which is almost perfect. In another post, we found what was already possible in 1963. In this case, we reach 70% to compare with 100% for the Reapor product.  This means we the 1963 product, you have to install 30% more to obtain the same result. The composition on the Reapor datasheet discloses that the material is in fact foamed bottle glass.

Both products are two steps process. Reapor starts from foamed glass granules, which are sinterd to obtain a irregular structure of small and larger pores. The 1961 process starts from closed cell cellular glass. The cells are opened with hydro-static pressure and the holes are introduced on both sides to improve the absorption.

If a material could be foamed in large boards with 100% open cells and an irregular hole pattern could be introduced during the finishing, we have a one step process, which should be competitive. But today, such a process is still not public domain. Typical (one step) open cell foams have about 70% open cells.


A new cellular glass gravel plant in the USA

logo_smallA new cellular glass gravel production line was built in Eddystone PA, USA by SGGC, Germany for the company Aeroaggregates. A second line will be built in the near future. They use SiC as foaming agent, which means they are using the dry process.

I found some remarkable facts on their website.

logotmlowresGlass is a fully recyclable material that can be recovered in a closed loop over and over again. This is particularly true for glass bottles which, on average, have a recycling rate of only 34% in the United States in 2013 (according to the U.S. Environmental Protection Agency).  Today, there is a limited number of glass processors to accommodate the entire glass stream that is generated in the United States.

awardAeroAggregates LLC is the first vertically-integrated, U.S.-based company to produce lightweight aggregates from 100% recycled glass. Our manufacturing capabilities include the ability to make several types of foamed glass including both open and closed cell aggregates.


The founders of AeroAggregates realized the need for a sustainable solution for lightweight construction materials due to increased design or constructability requirements. Today’s civil engineering challenges include construction on soft soils, lateral load reduction behind retaining walls and structures, insulating subgrade and backfill, and the protection of underground utilities. AeroAggregates provides an answer to most of these challenges by supplying a lightweight material with a high friction angle that is also insulating, free-draining, non-absorbent, rot-, acid-, and chemical-resistant, noncombustible, and a beneficial reuse for glass containers.

It is clear that the founders are aware about the opportunity to recycle and also understand that foamed glass is much more than thermal insulation. They also consider open cells besides closed ones. I wonder when they start to produce boards.

Replacing concrete by cellular glas in Permafrost regions

logo_smallWe 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,[9]is more or less influenced by permafrost. Most of this area is found in Siberia, northern Canada, Alaska and Greenland. 

active layerThe 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.

cellhouseThe 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.

GLAPORlogoFor 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.

Kinetic energy aborption in air planes

logo_smallWe 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.


load deformationThe 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.

kinetic_graphThe 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.


ETA for rendering on cellular glass

logo_smallCellular 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.

medusa-3The 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.


Walking on cellular glass

logo_smallRecently, 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 replacing concrete by cellular glass

logo_smallNorway 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

imagesOn 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.

DownloadFOAMROX 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.


More applications allowed for cellular glass in total Europe

belglasSometimes, 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:

logo-blueThe 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:


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


RDSIn 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.

Cellular glass and polyurea: a good combination?

logo_smallPolyurea 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.

polyurea formulaThe 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.

reaction to fireBut 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.

polyureaIndeed, 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.

autoPolyurea 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.