In this article we share some projects and concepts related to the design of structures that are intended to be apparent with the use of “architectural concrete”, a concrete that, in addition to its usual structural characteristics and functions, incorporates functions of final finishing and coating, exposed concrete.
Structural Concrete
Concrete is one of the most chosen construction resources in the world, and it will hardly be possible to find another construction material with a greater impact on the built environment. It is a practically unavoidable material in construction, particularly in its structural component, with application in a wide range of constructions ranging from infrastructure to building projects of the most diverse types.
The great prevalence and widespread use of concrete is related to its relatively low execution cost associated with the properties of mechanical resistance and structural performance, as well as integrity and durability in the face of bad weather and aggressive environmental agents.
On the other hand, the use of concrete offers a high degree of freedom of form thanks to its moldable characteristics. Concrete is capable of acquiring the shape and texture of almost any temporary mold that contains it, whether it is made of wood, metal, paper, plastic and even textiles. Being poured as a fluid mixture, when it gains value, the concrete acquires the shape of its container, also manifesting the surface characteristics of its formwork, as if it were an impression. For this reason, over the years, many architects have experimented with different aesthetic possibilities and construction forms that take advantage of exposed concrete, exploring the diversity of possible compositions, innovating in the use of different types of formwork or incorporating colored pigmentation in the concrete composition .
Structural Concrete
Some of the projects that we have developed over the last few years together with the Pedra Líquida Architecture atelier are an example of this type of exploration of exposed concrete as a simultaneous vehicle of architectural expression and structural function.
Located on Rua da Natária, in Porto, this small building intended for single-family housing stands out for its use of exposed concrete as an architectural element that is simultaneously the structure and final finish of the work. The textured exposed concrete facades are simultaneously supporting structural elements and a distinctive feature of the building’s architecture with Architectural Design and Construction of the Work ensured by the Pedra Líquida Architecture Atelier. In terms of the design of the structural project developed by STUCCO, in addition to the “primary” objective of ensuring the necessary overall stability of the building, the need to incorporate a high degree of detailing that would allow defining not only the building’s geometry and of its constituent structural elements, as well as accurately characterize the courettes and negatives for technical installations. It should be noted that many of the infrastructures were embedded in the concrete itself, thus forcing a rigorous interdisciplinary coordination work developed in 3D, taking advantage of the BIM modeling of the structures.
As this is a work in which structural concrete is also the final finish on extensive surfaces and interior compartments.
In the design of structures, special care was taken in evaluating the behavior of structures in service, in particular with regard to the control of surface cracking with the adoption of adequate minimum reinforcement and specification of special procedures for concreting and curing the concrete.
Colored Concrete
Although concrete in its natural state has a shade of gray, or white in the case of white concrete, the use of pigments especially intended for surface coloration is increasingly common.
The project developed on Avenida Brasil in Porto, together with the architecture atelier Pedra Líquida is a recent example of the use of exposed colored reinforced concrete structures in one of the projects developed by STUCCO. This project includes two buildings of a different nature: the first, the mansion, underwent extensive rehabilitation and restoration, as well as expansion with an additional recessed floor and respective coverage; the second corresponds to a new 7-storey building with an irregular structure in reinforced concrete for which the finish was defined taking advantage of colored exposed concrete with the addition of yellow pigment.
In another area of the city, on Rua Alvares Cabral, another building for housing is under construction, with a green colored exposed concrete structure. In another collaboration between the Pedra Líquida, responsible for the Architecture and Construction project, and STUCCO that developed the Foundations and Structures project, this project characterized by the use of a green structural concrete, which in addition to pigment also incorporates the addition of the use of recycled glass as an aggregate.
The insertion of pigments during the manufacture of concrete allows the creation of a very varied color palette that includes shades of red, yellow, green, black and cobalt blue. Without significantly affecting the mechanical characteristics of the concrete, the new tones can be achieved by incorporating pigments into the mixture while they are still dry, in the proportion between 0.2% and 10% of pigment per kilogram of mixture.
The definition of the pigment dosage very sensitively conditions the color to be achieved, and it must be fine-tuned experimentally until reaching the desired color. On the other hand, the combination of the various types of pigment with the use of white cement or gray cement allows to broaden the chromatic possibilities available, with the use of white cement allowing to achieve lighter and more luminous colors and the use of gray cement resulting in colors darker and less bright.
The study and refinement of the composition of the concrete is a crucial procedure to achieve high quality results in which the concreted pieces have a finish and appearance of the structures that is compatible with their use with exposed concrete structures. It is therefore essential to develop compositions that result in very opaque and compact concrete, and that are rich in fine elements such as cement or filler, in order to achieve perfectly opaque and homogeneous surfaces where the pigments are able to be distributed in a balanced way. minimizing irregular concentrations of color.
In addition, it should be noted that the successful use of exposed concrete as a vehicle of architectural expression requires a careful articulation, not only in terms of engineering and architecture projects, but also with regard to construction procedures and planning and execution of the work, where the judicious location and treatment of concreting slugs is of particular importance, and this is a topic to be developed in a next post.