- About history and production technology
- Features and properties
- Application area
- Material format
- Foam glass processing
- Mounting rules
Innovations are quickly becoming fashionable: a decade ago, foam glass was a rather exotic material, now it is already on the wide market and is in great demand. It’s time to learn how to work with him correctly: choose, cut, lay and correctly emphasize the positive qualities.
About history and production technology
The ability of silicate glass to foam from strong heating was noted in the first half of the last century. From that moment on, the development of the technology for its manufacture in Western countries was considered very promising – the material had really outstanding features. Today, foam glass is the most advanced material of mineral origin among those that have self-supporting properties and the ability to bear additional load..
In the production of foam glass, a subtle combination of physical and chemical processes is involved, requiring high-precision equipment. Therefore, the place of production of foam glass plays a decisive role for its quality. This is especially true for foam glass in large blocks: due to the low thermal conductivity, the core cools much more slowly, which is why, with insufficient annealing and rapid cooling, inhomogeneity and internal stresses may appear. Outwardly, it is extremely difficult to determine, while the material will be significantly inferior in properties to high-quality foam glass.
It is important to understand that today foam glass as a material is part of the insulation technology, which is also actively developing. At the moment, there are already systems of fastening and protection of material that have been worked out by many years of practice, as well as a very specific area of application. When the effectiveness of using foam glass is considered and specific quantitative indicators are given, you need to understand that we are talking about ideal operating conditions. These can be approached only by total adherence to the technological instructions for use and installation, since this material has already been mastered quite well..
Features and properties
Foam glass has a structure of hard but fragile cells, predominantly of a closed type. Under a static distributed load, this material does not deform, its compressive strength at the highest density (200 kg / m3) can reach 4 MPa. For more porous blocks, this figure can be up to 2–3 times lower. At the same time, foam glass is extremely susceptible to shock loads, which should be taken into account when drawing up the insulation cake.
Very often cellular glass is considered as a more technological option for porous concrete. There is a reasonable grain in this: with a similar density and strength, the only difference lies in the structure of the cells. Foam glass has zero vapor permeability, so the prospect of its use as the main building material seems extremely doubtful. But the practically absent ability to accumulate moisture is an absolute plus, which has a very favorable effect on frost resistance. When calculating the moisture accumulation of the wall cake, there are no obstacles to bring the dew point inside the insulation.
Foamed glass is an absolutely inert material chemically, it is not subject to either water or biological erosion. Deaf packing of such insulation inside building structures does not cause concern, the service life of foam glass is at least 100 years.
Foam glass cannot be called a universal material for use. The problem is not in its technical flaws, but in the cost, which is still too high for widespread use. The main criterion in determining the scope is the comparability of the service life. So, it makes no sense to use durable foam glass as a filler for sandwich panels, the shell of which will last only 25–30 years. But composite concrete slabs with a foam glass interlayer are an excellent technical solution, both materials have approximately the same service life.
Foam glass is mainly used as a heater, for this purpose it can be used in any zones of the building. The fire-fighting properties of this material are especially important – it is capable of heating up to 300 ° C without irreversible loss of mechanical properties. These qualities make foam glass a much better and safer substitute for materials such as XPS and PUR, the use of which is highly undesirable for insulating high-rise buildings. Low ability to deform under load makes it an excellent replacement for polymeric materials when working with insulated slab foundations.
There are two options for using foam glass to improve the energy efficiency of a building. In the first case, a continuous insulation belt is created from this material from the base of the foundation to the roof. In another version, porous glass blocks are used as the main filling material for enclosing structures in buildings on a concrete or steel frame.
The practice of making special products from foam glass is expanding. These are arched segments of pipe thermal insulation, and profile trays for pouring an armored belt or lintels of openings, as well as the above-mentioned composite concrete slabs. The main difficulty in using specific parts is the complexity of their production: the manufacture of the cellular glass itself is already a whole science, and giving a special shape is a technology that requires threefold investments in equipment.
The most popular form-factor of foam glass is blocks with dimensions of about 200-500×500-700 mm with a thickness of up to 200-250 mm. This is where the story about the blocks could end, if not for one important feature: the larger the format of the foam glass, the more complex the technology of its manufacture. We have already talked about the problem of uneven cooling, and so: the risk of defects in large blocks is extremely high. Because of this, it is much more profitable to use not monolithic blocks, but glued from several plates of small thickness. This has an advantage when constructing a heat-insulating circuit: bandaging of adhesive seams in different layers leads to a significant reduction in the number of cold bridges.
The second most popular format of foam glass is sintered granules of different fractions. Such foam glass is used as bulk insulation of walls and ceilings, it is also possible to use it as a filler for lightweight concrete grades. It is very advantageous to use mixed fraction granules as filler for floating floors. Foam glass is also in the same category – the cheapest form of insulation. Sale of battle is nothing more than a way to sell illiquid products, that is, blocks and fittings with manufacturing defects..
Foam glass processing
During the installation of foam glass insulation, it becomes necessary to mechanically process it. Despite the high constancy of the geometry of the blocks, to complete the rows, it is inevitable to make additions. The process of thermal protection device is considered even more complicated in a complex architecture of a building: bypassing bay windows, forming pilasters and cornices require a sufficiently high accuracy of corner undercuts.
Precise cutting of blocks is necessary to comply with the installation technology. It implies the minimum thickness of the adhesive seams, which excludes the formation of gaps in the thermal protection. There are two main stages of processing foam glass: cutting and fitting by grinding the cut end.
Foam glass in slab format (up to 100 mm thick) can be easily cut with hacksaws with fine carbide teeth, which are used for working with aerated concrete. In this case, it is recommended to apply markings on both sides and periodically turn the block over to prevent it from leaving the cutting line. Usually, the extensions that complete the row are installed with the edged end facing outward, but there are situations when an exact fit is required. In such cases, manual cutting is performed with a tolerance of 2-3 mm, after which the cut is ground with a wide abrasive bar.
If the assembly requires the manufacture of a large number of parts, manual processing methods are ineffective. The most productive way of processing on large objects is band sawing machines, which also allow making an angular shaped cut. The main feature of such equipment is a powerful dust removal system. When cutting foam glass, microscopic dust is formed, its ingress into the respiratory tract is extremely dangerous. That is why it is not recommended to process foam glass with a hand-held electric tool..
Foam glass can serve as a self-supporting enclosing structure, or perform the function of an insulating shell, taking on the load of the finishing layer. In the first case, the thickness of the wall being erected is usually at least 250 mm; as insulation, the thickness of the cladding can start from 80-100 mm.
Cellular glass blocks are glued together with a special glue – acrylic mastic. In parallel, the blocks are fixed to a solid fixed base, which can be a brickwork or a concrete panel. Since acrylic glue is designed to bond with the smallest possible joint thickness, it is better to fix the foam glass to the base with universal adhesive mixtures. In particular, compositions for expanded polystyrene, which retain elasticity after hardening, are very popular in this direction. If the blocks are used to insulate the floor or foundation, they are glued together at the ends, laying is carried out on a tightly rammed and even base.
The most preferable way to lay out the foam glass is in two layers with the bandaging of the joints in both directions. In this case, the wall cladding can be performed with additional mechanical fastening with disc dowels, which ensure fixation during the drying time of the glue. Gluing the rows together is strictly necessary, here it is also advisable to use universal adhesive mixtures or polyurethane foam.