The development of formwork technology is closely linked to the development of concrete construction as such. Already in the first century AD concrete was known as a building material. The use of larger, load-bearing concrete buildings was made possible many centuries later with the invention of ferroconcrete, the predecessor of reinforced concrete, in 1849. Another one hundred years later, the reconstruction work after World War II was the triggering point for rapid development – both regarding the development of concrete as a building material as such and also regarding formwork technology.
Formwork means the device that provides fresh concrete with shape and structure. Until the concrete building is completely hardened, the formwork has to withstand the weight and pressure of the concrete and all other materials and built-in parts. The scaffolding or ambient influences like wind and weather are also criteria that have an impact on the formwork. Until about 1930, mostly simple wooden boards were used as formwork which were kept in place with timber props. Parallel to increasing concrete production and further development of concrete as a construction material after World War II (1939 to 1945), from about 1950 on new methods for the improvement of formwork and streamlining formwork construction were discovered – the beginning of the formwork industry.
Modern types of formwork are not only characterized by higher load-bearing capacities and surface qualities. The utilization of large-size formwork and system components which can be used flexibly several times and which were load-optimized and geometrically adjusted, have increased the quality and speed for the construction of buildings. At the same time, the continuously increasing safety requirements are taken into account. And the construction cost are also influenced by the new systems, for instance by the fact that the time spent for assembly and disassembly has been clearly reduced.
Apart from the overhead and operating expenses, the expenses for a reinforced concrete shell construction include the material expenses for formwork material, construction machinery and building materials. About half of the overall expenses, however, are made up by labor costs, of which the greatest share can be attributed to labor costs for forming operations– several times the costs for the formwork material as such. In a sample calculation for considering the costs for the construction of a simple concrete wall, this becomes particularly evident: The formwork costs here make up the biggest share of more than 60 per cent. With a share of more than 50 per cent, the labor costs for forming operations amount to almost five times the amount for the formwork material costs. As a complex and the largest of all trades, forming operations therefore have enormous significance from an operational and economic point of view.
The fundamental production factors of work input, equipment and material should be considered in combination when analyzing the costs for system formwork by comparing not only the costs for formwork material but also the costs for the forming operations. Since labor costs are determined by the time spent on forming operations, this now leads to a sound basis for making a decision. With a good system, the savings in labor costs can even clearly exceed the investment costs over the lifetime of the formwork.
Therefore two considerations are dominant in order to optimize the costs for formwork – and thus the overall construction costs: On the one hand the selection of a formwork system as efficient as possible, on the other hand the minimization of forming labor costs.
The individual elements of the formwork are only of particular efficiency when they are comprehensively used and when they are adjusted to both the construction task and to one another in the best possible way. Minimizing labor costs and labor time remain the decisive criteria. A formwork system which, due to its system logic, simplifies and so accelerates the application has its obvious advantages here: The more efficient a formwork system can be used, the more the work spent on forming operations and thus the labor costs are reduced. In many cases this even reduces cost-intensive work at night. The numbers of different parts which have to be built in, for instance, are one aspect with an effect on the time and work spent. The lower the number of variants, the less time is required for compiling the parts and for the erection and dismantling. The same is true for movable parts such as connectors or formwork ties. The fewer that have to be installed, the lower the time needed for assembly and disassembly.
In this context, PERI system formwork is characterized by particularly high efficiency and under real conditions it proves itself through innovative technical design, intelligent mechanic features, high quality and longevity. It is designed to guarantee advantages in handling, simplifying work and offering high safety standards, and to save costs at the same time.
Before considering the costs in more detail, first the basic question for the selection of a formwork system has to be asked: Which type of structure do you want to build? This determines how complex the task is and which special requirements have to be taken into account. As said before, the costs are an extremely important criterion for the selection of the right formwork. And they are again closely connected to the planned construction progress, which on the one hand is defined by a given time slot for the construction of the shell structure and on the other hand by the time required for shuttering and striking, which then again means that it is a question of deadlines and costs. Also a forecast on how often individual formwork elements can be used, for example for climbing formwork, is important for cost considerations, and also the project assessment as regards construction production technology. Another aspect influencing the decision is of course also the question of whether the formwork should be rented or bought.
Further decisive criteria are for example the desired concrete surface, to the extent this can be influenced by the selection of the formwork system and the formlining. Also the situation at the jobsite, for instance the storage capacities or the infrastructure for lifting and transportation devices affects the decision. Environmental influences, such as the common climate at the jobsite or the weather to be expected during the building process, have to be considered, too.
Formwork systems can be classified according to different aspects. One example is the classification according to essential technical design aspects. Here we differentiate, for example panel formwork, this means firmly welded frames including formlining, and girder formwork, where system elements can be assembled by using formwork girders. Alternatively, formwork types can also be classified according to their application (for example wall formwork, slab formwork, column formwork, circular formwork), according to the specific type of building structure (for example tunnel formwork, bridge formwork) or according to the material used (for example plastic formwork, aluminum formwork). PERI’s product range encompasses the complete portfolio from plywood up to complex systems. Here a basic overview:
Wall formwork was originally made from squared timber and boards. This evolved into modular-type systems which are characterized by manifold utilization options and long service lives.
Their technical design specialty is the circumferential frame of the formwork elements which protects the edges of the formlining. Nowadays, this is the type of formwork most commonly used, with a market share of more than two thirds.
Girder formwork types are the most versatile formwork elements as regards their design. Their supporting structure consists of wooden or metal formwork girders which are held by steel walers.
Curved walls principally can be manufactured by polygonal approximations to the desired geometry. Continuous bending radii of 1 meter to about 20 meters are possible.
Slab formwork mainly consists of a horizontal support structure which holds the formlining and transfers the forces into a load-bearing scaffold.
For the concreting of columns (round and square shapes), the formwork has to be designed to withstand a relatively high fresh concrete pressure because the pouring takes places quickly for this rather small cross-section.
PERI’s product portfolio offers solutions and systems in the areas of foundation formwork, climbing formwork, tunnel formwork, bridge formwork, aluminum formwork, plastic formwork, special and freeform formwork, handset formwork, formwork girders, plywood and formwork panels and formwork solutions for fairfaced concrete of the classes SB 1, SB 2, SB 3 and SB 4.