How monolithic domes are created – a few facts about modern construction

Published: 24-04-2018

Despite the fact that dome houses are not quite new in construction, they are still surprising and arouse curiosity. An example of the first monolithic dome is probably an igloo. Its durable construction owes itself to blocks of compressed snow, which alternately melts and freezes, creating a strong and homogeneous structure. The Igloo shows the two most important advantages of such structures, namely their high strength and excellent insulating properties. The monolithic domes owe their durability mainly to the natural strength of the arch, and good insulation is provided by the minimal surface of the spherical cross-section.

The first contemporary monolithic dome was the ice rink built in Provo (Utah USA) in 1963. Four years later it was rebuilt and transformed into a market. In this form, the first monolith structure functioned until it was demolished in 2006. In Poland, the most recognizable dome construction is the so-called “Cosmic town” in which the headquarters of Radio RMF FM is located.

Nowadays, monolithic domes are used in various architectural projects, both residential, as well as industrial and service projects. Due to their durable construction, monolithic structures may serve as warehouses in the cement, fertilizer, energy, agricultural and mining industries. They are also often used as so-called buildings that limit radiation in nuclear power plants, thanks to their structural integrity.

Stages of building a monolithic dome

Modern monolithic domes are mainly built using a method developed in the United States by three brothers: David, Barry and Randy South. The first dome was built at Shelley in Idaho in April 1976. The construction of monolithic domes using this method is based on several stages, performed in a strictly defined order.

The first stage consists of preparing the site for construction. For this purpose, a ring-shaped concrete foundation is made, reinforced with steel rebar. The bars laid out outside the foundation serve to connect the structure with the further reinforcement of the structure. This creates a monolith with high structural strength.

The second stage of the construction of the monolithic dome is the fixing of the pneumatic air to form the ring followed by air being pumped until the right form has been achieved.

In the next step, polyurethanes enter the game. Inside the dome, a layer of polyurethane foam is applied, which, after hardening, acts as insulation for the whole structure and provides further reinforcement. At this stage you can use, among others, ready-made polyurethane systems available in the PCC Group’s offer, which enable the production of high-quality insulating coatings. An example of such products are the Ekoprodur and Crossin® series. Insulating polyurethane systems ensure excellent thermal and acoustic insulation thanks to semi-rigid and rigid foam. These types of insulations have a very wide range of applications. They are applied to foundations, floors, internal and external walls, roofs and attics. Thanks to the use of Crossin® products, it is possible to achieve excellent thermal conductivity coefficients. In addition to ready-made polyurethane systems, the PCC Group’s product portfolio also includes semi-finished products, such as Rokopol® polyether polyols, flame retardants (Roflam series),  as well as  compatibilizers and emulsifiers that are used to produce high quality OCF assembly foams. All these chemical products are widely used in modern construction.

The fourth stage of construction of monolithic domes is the assembly of reinforcing steel bars on the previously applied polyurethane foam using a specially designed rim system. Small domes require bars of small diameter with wide spacing. For larger constructions it is necessary to use thicker bars located at smaller distances.

The last stage of construction of monolithic domes consists of spraying concrete on the reinforcement made in the previous stage. This layer usually does not exceed 8 cm thick and completely covers the steel rods, creating a thin-walled monolithic skeleton. After drying, the concrete creates an extremely rigid and durable construction. To improve the properties of the sprayed concrete, special modifying additives are often used, such as, for example, products of the Rofluid series (M, H, P, T). Concrete additives of this type are used as very effective concrete bond retarders that slow the set of the concrete mix. In addition, thanks to their chemical structure and low chloride content, Rofluids do not cause corrosion of steel reinforcement.

Advantages and disadvantages of monolithic domes

Monolithic domes have a number of advantages. First of all, they are characterized by excellent load-bearing and insulating properties mainly due to their shape. Their unique design gives them the ability to withstand even the greatest natural disasters, such as storms, tornadoes and even earthquakes. Monolithic buildings are therefore particularly popular in regions of the world most exposed to natural disasters.

A lack of necessity of setting load-bearing walls in monolithic constructions makes it possible to arrange the layout of rooms in a convenient way. In addition, due to the unique design, there is no need for a roof. This translates to significant reduction of investment costs, as well as saving construction time. Large savings are also obtained due to the use of lesser quantities of building materials than in standard construction.

One of the disadvantages and difficulties encountered while building monolithic domes is the need to engage experienced professional with specialist equipment. This may involve a relatively high cost of carrying out such a construction. In addition, curved surfaces in the interior of the dome require adjustment of the entire interior design and furnishings. For the optimal use of surfaces, especially those harder to reach parts, it is usually necessary to make custom-made furniture. The original appearance of this type of building can also be a disadvantage, especially in areas with traditional buildings, where monolithic domes would be too distinctive.

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