Many times, looking at the work currently under way on the Sagrada Família, visitors wonder what Gaudí would have done without reinforced concrete. One could even think that the architects today, with all this reinforced concrete, are cheating because Gaudí only used stone. And that would be a grave mistake.
The fact is, reinforced concrete has been key to building the Temple, but it shouldn’t be a surprise that it is used. Gaudí had always planned for it.
CEMENT, MORTAR, CONCRETE AND REINFORCED CONCRETE
Concrete has several basic ingredients, the most important of which is undoubtedly cement. The rest, gravel, sand and water, are much easier to get and are much easier to handle than the main component of the agglomerate, the glue that sticks it all together: cement.
Water is only needed to kick off the reaction of the cement so it will start to set. There should be a minimal amount of water, since, with the reaction, part of it evaporates and that causes the number of holes in the result to increase. which is counter-productive as we want the final product to be as dense as possible.
When the mixture only contains cement, sand and water, it is called cement mortar. It is only when you add gravel to make it more compact for structural functions that it is called concrete, which is nothing but man-made rock.
Concrete, like any rock, can be very strong when compressed, but doesn’t stand up as well against tensile stress. So, to make up for this weakness and create a material that can stand up to all types of stress, steel is put into the concrete. This steel is called the reinforcement of the concrete and it allows the concrete to resist tensile and bending stresses.
WHEN WAS THIS CEMENT FIRST USED?
Building with cement and concrete may seem like a modern invention but these materials were used in Roman times. Of particular note is Pozzolanic cement, used by Roman engineers to build water channels, piers and watermills after they discovered this material can harden underwater. The name comes from the town of Pozzuoli, on the slopes of Mount Vesuvius in Italy, and the most well-known example of building with this type of cement is the Pantheon in Rome, from 123 AD. Its lightness without sacrificing strength is another great quality of this material, which is why it was used to build the great dome: with its diameter of 43.3 metres it is still the largest made of un-reinforced concrete in the world to this day.
It took nearly two millennia to surpass this size and was made possible by innovations in reinforced concrete, first used by Italian architect Pier Luigi Nervi in the 1960s.
THE FIRST CEMENT FACTORY IN CATALONIA, OWNED BY EUSEBI GÜELL
Eusebi Güell, Gaudí’s protector and patron, was the Catalan industrialist who promoted the first factory to extract and produce Portland cement in Catalonia and Spain, in 1901. It was the Ciment Asland factory, in Castellar de n’Hug, near the source of the Llobregat River.
Gaudí’s close relationship with Mr Güell, also in terms of this company, can be clearly seen in his works that remain in the county, including the house in Catllaràs for the engineers heading up the extraction of the coal needed to fuel the ovens in the cement factory. With little wagons and funiculars, they brought the material down from the Catllaràs mountains to Clot del Moro, where the factory was located. This house designed by Gaudí has undergone several refurbishments to suit its various uses over the years, but now there is a firm commitment to restoring it to its original state.
Nevertheless, Eusebi Güell isn’t the only person around Gaudí who had ties to concrete. Domènech Sugranyes, who was one of Gaudí’s close collaborators and even became his right-hand man from 1914, did too.
Sugranyes became a professor at the Escola del Treball in 1923. There he gave classes in Construction, Basic Mechanics and Geometry with great enthusiasm, and the notes he made up for his classes show how, using graphic calculations, he not only passed on to his students what he had learned in Gaudí’s workshop regarding the funicular load transfer in calculating arches and vaults, but also pushed this knowledge forward and used the same tools (straight edge and compass) to develop graphic calculations for reinforced concrete.
GAUDÍ, PIONEER IN REINFORCED CONCRETE
Given everything discussed above, his proximity to the first cement factories and quarries in the country and having experts in calculating cement in his workshop, the supposition that Gaudí was a pioneer in our country in using reinforced concrete makes perfect sense. The descriptions of Joan Bergós, Gaudí’s biographer, and those in the Sagrada Família magazine paint an in-depth picture of Gaudí using concrete structured with metal elements on the Pedrera, the pavilions at Park Güell and the auxiliary buildings for the workshops at the Sagrada Família, among many other examples. César Martinell, another great Gaudí biographer, also says he abandoned the original idea of building the Sagrada Família vaults with paraboloids and turned instead to hyperboloids when he became aware of the growing possibilities that reinforced concrete had to offer.
The most obvious example of reinforced concrete at the Sagrada Família is terminals of the towers on the Nativity façade. The southernmost bell tower, dedicated to Barnabas, was built by Gaudí and finished by Christmas of 1925, half a year before his tragic accident. For this tower, he used a notable metal casing that was then covered in pre-fabricated concrete pieces with the characteristic Venetian-glass mosaics.
Gaudí, moreover, proposed using concrete to build the nave vaults, as has been done, which can be seen in the conference on the structural system for this project that Sugranyes gave at the Association of Architects of Catalonia in 1923. In his talk, he went into great detail regarding the verticality of the geometry and that the transfer of the loads would leave only small horizontal components remaining. He said he trusted that they would be absorbed by the reinforcements in the concrete on the three levels of superimposed vaults and roofs on the nave.
THE REINFORCED CONCRETE OF TODAY, AND AT THE SAGRADA FAMÍLIA
Although it is clear that Gaudí himself was using reinforced concrete, it was a far cry from the material today. Technology has progressed so much that the concrete Gaudí used might as well have been from the Palaeolithic era compared to what is used today.
One example is its resistance to breaking under simple compression forces. This resistance has been obtained through many, many trials with concrete and the characteristic strength must guarantee it stands up to it in at least 95% of tests. Around the 1970s, in the construction sector, it was common to use cement with a characteristic strength of 175 kg/cm2, especially for foundations, but soon after regulations began requiring values of 200 kg/cm2 for any structure. Today, civil works must guarantee at least 250 kg/cm2 for any cement structure.
For the Sagrada Família, however, cement with 350 kg/cm2 is used for less important structures and with 600 kg/cm2 for important ones. Laboratory results often confirm that we know how to make cement that is four times stronger than the conventional type. Plus, as it is more compact and denser, it is also more resistant to erosion and deterioration due to atmospheric agents.
This concrete has been made possible by collaborating with university research centres, which have introduced new formulas for its composition.
So, the reality is that regulations have regularly increased the requirements for structures, and the extraordinary increase in our needs has also made it essential to improve the cement commonly used, above all taking into account that the work must last for years and will be exposed to the salt air over this time. In this regard, boosting the strength of the concrete used was the only alternative to meet the new requirements, regarding seismic activity and wind, as the size of the structural elements (the diameter of the columns, the width of the walls, etc.) could not be altered and still remain true to the plans and svelteness of Gaudí’s original designs.