- Technological rationality of permanent formwork
- Layering of finished monoliths
- Versatility and variability
- Practicality of fixed formwork in use
- Permanent formwork safety
- Vapor tightness of the resulting enclosing structures
In the first part of the article, we will talk about the main features of monolithic construction with the use of fixed formwork, we will figure out how relevant this technology is for the construction of a private house.
When choosing material for building their home, many Russians are seriously considering the option of using reinforced concrete and monolithic technology, which has now received a second life in the private sector. Most importantly, people are not only interested, they are actively building in this way – the houses are very durable, without seams, practically unlimited in configuration … There are many advantages, but most of all our compatriots value the regular decrease in the cost of the building at the exit and the opportunity to do everything with their own hands without attracting highly qualified specialists. At the moment, quite a lot of experience has already been accumulated, both in the nuances of construction and in the operation of cottages made of concrete.
Formwork is a fundamental element of monolithic technology. Its main task is to give the products a given configuration and geometric dimensions: it is in it that liquid concrete is formed, supported and hardened. The second point is the orientation of monoliths in different planes: with the help of formwork, not just flat scattered parts are created, but single, complex spatial structures with given coordinates. Traditional formwork consists of mold parts (panels of different materials), support elements and fixing components. It is assembled and exhibited locally, in the case of wall construction – to a limited height. After the concrete has set a sufficient “stripping” strength, the shields are removed and everything is repeated over again. But this is not always the case – there is also a technology of monolithic construction using permanent formwork.
From the name it is clear that this formwork does not need to be dismantled, it remains in place and is an additional functional element in the composition of building structures. There are several options for the implementation of such formwork systems, which differ quite significantly from each other in many respects. Therefore, let’s immediately determine: fixed formwork is not only hollow foam blocks, as many believe, it is also various external panels and internal load-bearing reinforced panels. But about structures and materials – in the second part of the article, while about this method of construction in general. So the features.
Technological rationality of permanent formwork
The “central” idea of the permanent formwork is to combine several technological operations. In this case, in a single technological cycle, we get a load-bearing wall (by the way, and not only a wall) made of metal-reinforced concrete with increased thermal insulation characteristics. In other words, it will not be necessary to separately deal with the insulation of the foundation / facade / floor / roof. And these are additional materials: dowels, adhesives, brackets, etc. And considerable labor costs: cleaning surfaces, assembling / disassembling scaffolds and scaffolding, exposing and fixing heaters. Anyone who has been insulating their home knows how difficult this is..
In some systems, if not cast blocks, but slabs are used, the formwork serves as an extreme decorative coating, for example, cement slabs can have the texture and color of natural stone, brick, wood. Indoors, slabs of permanent formwork, made on the basis of gypsum and plant fibers, with minor modifications, act as an excellent basis for finishing – you do not need to glue drywall, or, for example, you can refuse to assemble frames for lining.
It is also important that the stripping operation is abolished. Ordinary reusable shields can be difficult to remove, for example, when pouring a foundation, they are often clamped in a trench, and in this case we can even deliberately fill the slopes with soil in order to stabilize the structure. In addition, inexperienced builders often do not comply with the maturation time of concrete to a minimum strength and damage the monoliths during stripping..
Taking care of concrete looks more simplified (except for the honeycomb technology), since concrete is enclosed in a cocoon for the entire period of strength development, which does not allow moisture to evaporate too quickly. Another point is that at borderline low temperatures, it is possible not to cover the fresh monolith with insulation (fixed formwork, as a rule, has high thermal insulation characteristics by default), not to introduce special chemical additives and not to organize its forced heating.
It should be noted that the fixed formwork greatly simplifies the process of laying utility lines. This plus is, in principle, inherent in monolithic technology, but there is an opportunity, after pouring the structures, to burn out (with a hairdryer or a red-hot loop) neat grooves in expanded polystyrene. You can also spread channels and pipes inside the formwork before pouring concrete, clearly setting the output relative to the resulting planes. Of course, this work somewhat reduces the rate of construction of structures and requires the development of a clear project for all building systems, but this time spent will pay off handsomely.
Layering of finished monoliths
The structures, which include the elements of the permanent formwork, are distinguished by high insulating characteristics. This primarily concerns the resistance to heat transfer. The use of foamed and fibrous materials in most cases is included in the “basic configuration”, and if panels are used, then insulation can be inserted in various thicknesses, which will provide design insulation suitable even for the most severe climatic conditions. It is not for nothing that this technology is very popular in Scandinavian countries and in the north of the United States. At the same time, it cannot be said that insulation is an obligatory layer because of the “coldness” of reinforced concrete as a material. Calculations show that in order for a home to fully comply with modern energy efficiency standards, in our climate, walls made of any materials must be supplemented with a heat insulator.
All materials that are used for the manufacture of fixed formwork, to one degree or another, are highly resistant to moisture, do not saturate with water and do not transport it by capillary method. A very strong connection is formed between the concrete core and the formwork (due to high adhesion), therefore the formwork improves the resistance of concrete to any types of corrosion, which is very important for buried foundations.
In addition, layering is the best way to neutralize different sound pressure ranges: some layers absorb and scatter waves, while others reflect them. In this case, harmful resonances are not formed. Exterior walls and roof effectively protect from external noise, partitions and ceilings – from air and impact noise generated inside the premises.
Versatility and variability
Most often, fixed formwork is used to create monolithic walls and foundations, however, some manufacturers offer systems that, when using temporary supports, allow the production of ribbed floor slabs. And the so-called 3D formwork technology is suitable for pouring inclined fields and complex volumetric products on which it is difficult to hold concrete: roof slopes, non-horizontal planes in pool bowls, solid flights of stairs. Circular, curved surfaces can be formed with these panels. As enclosing structures, such systems are used for high-rise construction.
Systems supplied to the consumer, as a rule, contain a complete set of all parts for monolithic construction, including: spacers, ties, plugs, lintels, connectors, corner elements, etc. In this case, the developer can often order various configuration options depending on their needs, for example, to choose the thickness of the inserted heat insulator and its location (only outside, outside and inside) or the type of external panels that can play the role of a finishing cladding, or only a technological basis for the next layer. In addition, the elements of permanent formwork are easily cut and processed, which allows the builder to create a variety of structures in terms of configuration and purpose, with different reinforcement schemes and the percentage of metal in concrete. Some companies have gone even further, they supply the customer with components and technical documentation – they offer the developer to independently produce the parts of the permanent formwork.
Practicality of fixed formwork in use
Fixed formwork is just the case when you can do everything yourself. The elements of these systems are piece and weigh very little, therefore, to assemble the formwork, you do not need to use lifting equipment, which allows you to build even in hard-to-reach places. Finished blocks are assembled together like “Lego”, preparation of “semi-finished” panel formwork is also similar to working with a designer. With a small mass, blocks and panels are rather large, which speeds up construction, they have high stability, precise geometric dimensions.
It is possible to “self-build” with a team of 3-4 people who do not have high qualifications, while the pace of construction will be, perhaps, the highest among many technologies. As we have already noted, in comparison with traditional concrete casting, the seasonality of work is expanded here. Manufacturers claim that if it is necessary to lay concrete in a permanent formwork with insulation, then it can be poured at temperatures up to -5 degrees.
Monolithic technology makes it possible to obtain a very durable building that normally interacts with soft soils, is not afraid of seismic vibrations and other power disasters. The thickness of such walls is very small (20-25 cm), and this is an additional living area. In a house of 100 m2 a 20 cm difference in wall thickness will give us at least 10 square meters of additional interior space.
In the second part of the article, we will take a closer look at what costs are borne by a developer who has chosen a monolithic technology with the use of permanent formwork. Now we just note that there is savings, and not only materials, but also time and effort.
Permanent formwork safety
Most of all, people are interested in the environmental friendliness of foam formwork. If homeowners somehow put up with the outer layer, then inside … The thermoblock really creates a layer of expanded polystyrene on the walls in the room, but for those who do not believe in the stability of polymers, there are many options without foam. Fire safety is a separate issue. Here, too, everything is fine: with mineralized slabs, it is clear that the stone burns badly, and the foam is used for building self-extinguishing, which does not support the spread of fire. Permanent formwork easily passes certification not only in the post-Soviet space, but also in Europe and the USA.
Vapor tightness of the resulting enclosing structures
This unpleasant characteristic of building structures arises as a result of the homeowner’s desire to insulate and waterproof the building as much as possible, to exclude the appearance of drafts. The problem is an increase in indoor humidity and condensation, most often on windows. All sorts of membranes have become a way out of the situation, but polystyrene and expanded polystyrene are absolutely impenetrable for moisture in both directions. Therefore, houses in which closed-cell polymers (especially double polymers – thermoblock) are used as insulation, must be equipped with efficient forced ventilation. For the sake of fairness, we note that foam polymers are used not only in permanent formwork systems.
This we discussed the functional and operational characteristics of the fixed formwork as a separate technology. In the second part, we will consider all the varieties of these systems and talk about prices..