An actual branch of knowledge has been created on the creation and uses of glulam, which has revolutionised the world of construction. The main contributions in this regard came mainly from three Italian engineers, the pioneer Franco Laner, Attilio Marchetti Rossi and Angelo Micheletti, who defined the applications of this particular type of beam in the building industry and how to design structural glulam works, building up knowledge that has clear practical influences even today.
But all this knowledge would not have existed without drying. In fact, if we bring the whole matter down to a purely practical level, the curing process is fundamental for obtaining a glulam beam: its components, in order to be glued together and to stand the test of time, must contain specific moisture levels, to which only drying can lead. Let us therefore analyse the characteristics of glulam, focusing on the importance of proper drying at its origin.
Glulam, its uses and characteristics
Glulam is a composite structural material, which is essentially made of natural wood, of which it retains the most renowned qualities (high ratio of mechanical strength to weight, slow combustion in case of fire), but which, at the same time, deriving from a technological pressure-bonding process, eliminates the most severe defects of solid wood. It is obtained by reducing the trunk into strips, i.e. wooden boards designed for structural use, with a maximum width of 20 mm, which are then glued together with opposing grain (a stratagem that gives the beam a certain uniformity in the distribution of strength). The wood species most commonly used for this purpose are the conifers (spruce, fir, larch, pine), but it is not uncommon to come across some broad-leaved trees (chestnut and oak above all).
The result of the industrial gluing process, which to all intents and purposes gives rise to glulam, is a beam with rectangular cross-sections, in which the ratio of base to height is decidedly unbalanced towards the latter. By virtue of its construction process and its particular structure, it opens up the following advantages:
- Flexural and tensile strength;
- Lightness;
- Versatility of use;
- Significant insulation capabilities;
- High tolerance to weathering and temperature changes;
- Excellent earthquake-resistant properties due to its elasticity;
- Low environmental impact and recyclability;
- Absolute fire resistance (even greater than that of reinforced concrete!).
It is clear that, with all these peculiarities, glulam proves itself to be a material capable of making a difference in many respects. In particular, the main uses for which it is intended are in construction: in this context, it can even replace reinforced concrete, combining, with its tough strength, a lightness that allows considerable savings in transport costs (it weighs 80% less than reinforced concrete!). This is why glulam is used in a wide variety of ways in the construction industry:
- for lightweight structures such as bungalows, gazebos, canopies and cottages;
- for the renovation of floors, mezzanines and roofs of various kinds;
- for low-energy housing;
- for buildings designed for civil habitation;
- for large beams for roofing large structures (sports facilities and shopping centres, schools, auditoriums, theatres, etc.);
- for the construction of lightweight fixtures and stairs.
The use of dryers to ensure quality and capacity
Glulam, in order to achieve the amazing goals it can provide, begins its journey from the same point from which any type of wood used by human beings begins: drying. This process – it is always good to remember – is the real driving force behind the wood market, because wood, as it is found in nature, cannot be used for man-made purposes: firstly much of the water contained within it must be removed, otherwise serious problems arise regarding strength and durability. Drying deals precisely with the removal of excess moisture in the various wood species.
In this sense, it is clear that dryers, machines capable of artificially implementing drying in much less time than natural curing, acquire a fundamental role. In the case of glulam, in order to make sheets with the structural requirements necessary for the subsequent industrial gluing process, the systems must treat the material in such a way as to bring it to an internal moisture content of between 7 and 16%. Then, as the moisture content is not regular within the same sheet, the strips have to be left to rest for two or three days: only then do they reach the high quality standards to be taken to the processing line.
Our drying systems
Incomac also has congenial solutions for the drying of glulam. Here are our systems that can best process this type of material:
- Icd. This machine must be fed by a thermal fluid (hot water, superheated water, diathermic oil or steam) and uses boiler heating to proceed: through this combined fluid-boiler action, the speed of the drying cycles is ensured;
- Tag. It is a direct-heating dryer with burner, which among its advantages boasts ease of maintenance and adaptability to short heat treatment cycles, thanks to the fast temperature rise in the kiln;
- Idv. It does not need any heating system to carry out the drying process, because it generates heat through a viscous dissipation process. In this way, no pollutant emissions are produced;
- Mac_Hybrid. From traditional drying systems, we move to condensation systems, with this machinery using electricity and thermal energy at maximum efficiency, reducing atmospheric emissions by 50% and thermal consumption by 30%;
- Pre. Glulam can also be treated by our pre-drying systems, which, working at low temperatures (30/35°), preserve its key properties.