Befriending our Existing Concrete
Shall we not squander the embodied energy*, social meaning and memories of concrete or post-industrial buildings through aesthetic biases and social stigma, perhaps we should learn to welcome and reuse the concrete that has helped frame humanity.
“First we shape our Concrete buildings, then they shape us, then we shape them again-ad infinitum”
[I added the word concrete to Stewart Brand's adaptation of Winston Churchills Quote ]
*Embodied energy is determined by the amount of labour and energy consumed in the fabrication of a building, from the harvesting of natural resources, to the manufacture and delivery of materials and installation of these materials and products etc. (It also includes the energy required to demolish and remove building components)
Let me humbly re-introduce you to the familiar, (yet often unfamiliar) material concrete, after all, the material is an integral part of our 'everyday' and has been for longer than you might think.
Concrete's Past: The history of concrete can be mapped back to the Romans however the Egyptians and Greeks were using mortar well before then. The Romans industrialised concrete mainly due to the discovery that when volcanic ash was mixed with water it allowed concrete to harden under water. The main source of the Roman’s ash was Pozzuoli near Naples. The Romans used this natural material to bind pumice [a light porous volcanic rock] and brick rubble creating an early concrete material easily fabricated using cheap or free labour. The concrete developed by the Romans was used to great effect creating impressive structures like the hemispherical dome of the Pantheon in Rome, spanning 43 metres which to this day intrigues architects and engineers from around the world. And also, the Coliseum, Rome AD82 - the foundations and structural elements of the largest and most important amphitheatre in Rome were made of dense concrete, while lightweight concrete was used in some of the arches and vaults. The Romans also experimented with adding horse hair to lessen the effect of cracking whilst hardening and adding blood to make the mixture less susceptible to frost damage. Although concrete was known to the Romans, the Egyptians and to even earlier Neolithic civilisations, after the collapse of the Roman Empire, its secrets were almost lost for 13 centuries. The last great Roman concrete construction of note was the Leaning Tower of Pisa, a 58m high leaning tower [5 degrees from vertical] with 2.7m thick walls, clad in marble which began construction in 1173.
Roman concrete arches
Concrete was rediscovered in more recent times when a British engineer, John Smeaton pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate for the construction of Eddystone Lighthouse, built in the English channel. Smeaton and a handful of French engineers began experimenting with lime based concrete and slowly reintroduced concrete to the eighteenth and ninetieth century.
Concrete’s modern development spans no more than 185 years. In 1824 a patent for the manufacture of the first Portland cement was awarded to Englishman Joseph Aspdin which proved to be one of the most important milestones in concrete's modern history. Modern ‘Portland’ cement developed by Joseph Aspdin between 1824 and1845 revolutionised the use of concrete in construction. The discovery of hydraulic cement, created at much higher temperatures than before, altered the chemistry of the material. By heating limestone [the main source of calcium] with clay, and grinding the product [clinker] with a source of sulphate, hydraulic cement could now set and harden through chemical reaction with water, which made it ideal for
construction purposes. Concrete originally used to construct lighthouses, docks and other large scale industrial buildings using hydraulic and non-hydraulic lime binders began to diversify and find new uses in construction using hydraulic Portland cement.
The next important evolutionary step on concrete’s timeline came in 1854 when William Boutland Wilkinson patented his idea of reinforcing concrete through the addition of iron hoop and iron section. Although it wasn’t until the development and resulting patent of French entrepreneur Francois Hennebique in 1892, that architecture fully embraced the potential of reinforced concrete. The Hennebique system made use of round mild steel bars for the main steel-work needed to enhance concrete’s naturally weak tensile resistance whilst complimenting its compressive strength. The ends of the bars were split and spread to form Y-shaped “fishtails” to improve mechanical anchoring. The Shear, an effect condition which tries to split a beam or slab
vertically is resisted by flat steel strips or links wrapped around the bars. Other reinforced concrete systems have been developed generally from abroad, for example the Kahn system from the United States which uses square bars with steel wings bent up to anchor the reinforcement into the concrete. The further development of pre-stressed concrete in the early 1900s was pioneered by Eugène Freyssinet, a French structural and civil engineer who helped underpin the material’s importance in the building industry. The steel reinforcement could be pre-stressed before the process of fabrication, therefore, creating a product with compressive stress that would in turn offset any tensile stress imposed once load bearing. Concrete
elements could span longer distances as a result and the architectural merits of the material grew. Architects explored their new found structural freedom and developed fresh methods of expression.
“After Iron, reinforced concrete is probably the most important invention in the realm of materials, perhaps the most important of all because reinforced concrete possesses all the properties that are missing in iron – and because the properties of stone and iron are united in the building material. For what has now become possible in principle? No more and no less than the construction of surfaces without seams, walls
without joints. On a stone wall that was only possible after plastering it, not before, and moreover this enabled the straight span between two supports spaced at practically any distance. So it has become technically feasible to construct the two most important elements of architecture – wall and the member spanning between supports – with almost any dimensions. In addition, there is the unification of floor and ceiling, also as a complete unit, and again in all possible sizes. This building materialis a technical triumph over the difficulties caused by all the building materials produced up to now” [1922 Dutch Architect Hendrick Petrus Berlage]
Unfortunately concrete over the last few decades of the twentieth century has acquired a bad reputation. This, (despite the liberation the material afforded architects and designers), was mainly due to the general practice of ill considered and badly executed social projects in the 1960s and 70s. Concrete was being abused in the construction industry; new materials were used before research into their long term properties and characteristics could be fully understood. This rushed and uneducated use of concrete resulted in the short life span of many buildings or at the very best a premature need for major repair. Many buildings were demolished not only due to poor workmanship but also due to the concrete’s poor weathering properties, unsightly staining and the misnomer of concrete cancer.
What is it ? In its simplest condition, concrete is a magical but complicated substance that when set hard has the compressive strength and durability of stone but when initially mixed, has a low viscous consistency which allows the substance to be plastic in nature, malleable and easily cast in a multiplicity of conditions. Although the concrete fabrication process is fairly sophisticated nowadays, concrete has a relatively basic mixture of paste and different size aggregates [coarse and fine stone]. The paste is composed of cement [formally lime] and water which coats the surface of the fine and coarse aggregates. The mix, through a chemical reaction called hydration, hardens and gains strength to form the rock-like substance known as concrete. It is within this hydration process that the key to concrete’s remarkable dual characteristics lie. These unique properties have intrigued and seduced the construction industry for over eighteen centuries and explain why concrete, can be used to build furniture, skyscrapers, bridges, sidewalks, houses, dams and even lighthouses.
A wee bit of detail: Although the word concrete derives from the Latin word “concretes” meaning hard, concrete is often referred to as, “reconstructed stone” or “reconstituted stone” which acknowledges the fact that concrete is an artificial fabricated stone like substance, with characteristics resembling those of natural stone. For example, most sedimentary stone such as limestone and sandstone comprise of small sized stone aggregates or sand grains that have been bound or cemented together naturally over time. Concrete too, is comprised of smaller stones and sand held together by a binding cement which sets to produce a solid material.
Concrete is one of the most widely used construction materials in the world fuelling a $35 billion industry and employing over two million industry related workers in the United States alone. There are many types of concrete in circulation today ranging from the widely used concrete masonry used mainly in wall, floor and foundation construction to tilt-up concrete, where walls are cast in the horizontal position and then tilted to the vertical. However it is the ready-mix concrete that accounts for nearly three-fourths of all concrete used. Ready-mixed refers to concrete that is batched for delivery instead of being mixed on site. Each batch of ready-mixed concrete is delivered to the contractor in its plastic condition, usually by road.
Reinforced concrete was developed to address concrete’s low tensile strength and revolutionised the construction industry when realised. The unique potential of reinforced concrete derives from the complementary virtues of its two constituents: steel in tension and concrete in compression. Steel is set into the concrete. They bind together creating a material high in both tensile and compressive strength. Concrete is an extremely versatile substance and can be cast on site [insitu] or pre-cast off site in a more controlled fabrication environment. The process of pouring concrete is governed by a set of key actions. The
main actions are compacting and curing the concrete. When initially pouring the concrete into formwork it is important to compact the freshly poured concrete. This will expel unwanted air bubbles and ensure that the mixture fills the formwork to achieve the required profile and ensure the correct coverage depth when working with steel reinforcement. Consolidation [external or internal artificial vibration] will compact fresh concrete to help mould it to the forms and around embedded items such as reinforcement bars. This will help eliminate stone pockets, honeycomb, and entrapped air too. When concrete is vibrated it behaves more like a liquid and slowly settles into the forms under the action of gravity. In this condition the larger entrapped air pockets rise more easily to the surface. As soon as vibration stops the concrete continues to set naturally.
Correct compaction techniques are essential if the concrete is to meet its intended strength and durability. For each one percent of entrapped air, concrete can reduce strength by six percent and its ability to protect the reinforcement and resist frost action will be severally compromised over time. Curing is the second action when working with concrete. Curing the concrete aids the chemical reaction called hydration. The concrete surface is kept moist which extends the curing / setting period which will improve durability, strength, water tightness, abrasion resistance, volume stability, and resistance to freezing and thawing and de-icer salts. The process of hydration will still take over 30 years to complete which means the material will gain in
strength long after the structure is in use.
Example:
St. Peter’s College Seminary in Cardross a Grade `A` Listed Building near Dumbarton, was designed by the Scotland based architectural practice, Gillespie, Kidd and Coia in the 1960s. The priests and students of the original fire damaged St. Peter’s college in Bearsden Glasgow waited patiently for a new college. The Bearsden College was destroyed in 1946 and in 1966 they took ownership of a new modern seminary built primarily in reinforced concrete rather than a traditional stone construction, but by creating a rough finish to the concrete similar to a harl finish, the building is recognisably Scottish in nature. The building’s inability to adapt to the Scottish climate was in the end its downfall. The building struggled to remain watertight from the outset and after a 14 year battle against the elements, it closed. Currently it stands in a ruinous state of decay, ironically making the structure more Scottish in nature, standing as so many castles stand: ruined, and yet iconic as a part of Scotland’s cultural history. The architects modified their contemporary Scottish architecture to the surrounding landscape by introducing
arches, staggered terraces, curved surfaces and a variety of form. By using large amounts of manmade materials the architects delivered a Brutalist, modern concrete building. But by softening the exterior, staggering the facade and reducing its impact on the landscape the building seems comfortable in its surroundings. The Cardross seminary building successfully relates to, and reflects the nation’s autonomous ambitions at that time. The architects, mindful of the independent nature of the brief, have designed an aesthetically defiant structure from which to teach Scottish catholic priests, with an independent connection to the Vatican in Rome.
The construction’s £486,010 original estimate grew to a final cost of £609,800 and on St. Andrew’s day 1960 the site was blessed and the first sod was cut. However, due to bad weather conditions construction was hampered and rescheduled for the spring. In April work on the massive ferro-concrete retaining walls began, ending in November. The construction schedule was contested by the client group director, Bishop Ward, who was unhappy with the two and half years estimated by the project’s architects and surveyors. The eventual main contractor agreed to do the build 6 months quicker and was given the job but many believed the contractor to be inexperienced in reinforced concrete construction. The client went with the Glasgow
based contractor against advice from other professionals on the project. The foundations were completed in April 1963. The staff and students of St. Peter’s took possession in 1966 only to be met by flood waters on their arrival to the chapel. Once in use heating was a problem as was acoustics but above all there were persistent problems of water ingress, the extent of which was revealed in an independent report. In February 1974 the building was reported to be “no longer proof against wind and water”. In 1979 the decision to abandon Cardross Seminary was taken. Father Fitzsimmons a resident of the seminary recalls, “Visually, I loved the building. It was brilliant - but utterly useless”. [Interview with Father Fitzsimmons, Walters, p67]
In its ruinous state, the building and in particular the main block, is still easily read. The main block part of the site is symmetrically arranged. The standard dimension of the concrete frame for the main block began with 2.5 metre wide student cells which informed the architectural appearance and scale of the entire block. The load bearing structure constitutes a series of reinforced concrete frames and upper cross-walls, placed in situ at 2.5 metre centres and supported on concrete columns at ground level. There are also a set of double cantilevered beams housing vaulted non-load bearing vaults, plaster finished on a steel lath system. The architects specified that all concrete should be exposed and the marking from its shuttering should remain rather than be polished out. The ground floor programme was a refectory [to the north], and the chapel to the south with a central hall dividing the two. The hall housed the central concrete stair which provided the main circulation to the upper accommodation levels which were cantilevered into the end voids situated at the north and south of the project. The cells were separated by load bearing concrete walls and the plaster ceilings were vaulted. Each room had access to a continuous balcony which was concrete and clad in heavy, exposed aggregate–faced precast units. The ground floor chapel and recessed nave is flanked on the east and west by ten silo shaped chapels of brick construction which support insitu concrete semi domes. At the south end of the main block sits the “Sanctuary Block” a load bearing deeply curved exterior wall with concrete ramp running within, leading to the cloister and crypt level. The sanctuary level was double height
and top lit. The curved load bearing wall continually curves to meet the main block at the south end. The main block is floored by a patented screed floor panel layout in dark grey.
Although easily read in regards the architectural and design intent, the first impression of the building’s current state is one of extreme decay. The site is completely open to the elements. Running water is flowing from the landscape into and around the building and there has been damage due to fire on every floor. The widespread acts of vandalism are evident externally and especially internally. The timber detailing and most fixings have been removed, glazing, lighting and partitioning destroyed.
Despite the site’s ruinous appearance most of the damage is superficial and the main core structural elements are fit for purpose after some remedial care and steps are taken to arrest water ingress. There are countless examples of concrete spalling, cracking, water damage and steel reinforcement corrosion which have been identified in ‘Historic Scotland’s Avantire report’ which can be found on line at www.historicscotland. gov.uk/index/news/indepth/stpeters/stpeters-avantireport.htm .
The main areas of concrete decay can be found in the ‘Sanctuary’ block due to fire, vandalism and water ingress; the external stair at the north end of the main block due to exposure and poor construction techniques and the main block and central stair due to vandalism and water damage. The key signs of decay in Cardross seminary are; staining and discolouring on concrete surfaces due to the steel reinforcement bars corroding and weeping rust coloured moisture. Fractures to concrete edges, these breaks in the concrete’s structure expose the integral reinforcement bars to the climatic elements. Chloride attack, due to the absorption of the localised flood water and the sea breeze which the area receives frequently, indicating that salt has penetrated the concrete cover and is attacking the steel reinforcement. Steel tendon tracks in the concrete surface indicate that the concrete coverage is too shallow and isn’t providing the correct amount of protection to the reinforcement. The steel is already showing in places and has begun to corrode. Blackening of the concrete surface is due to localised fire damage and superficial cracking and spalling through vandalism
The concrete in its current condition will continue to deteriorate relatively quickly. Without action in addressing the key issues of climate, water and vandalism the building will be lost to the nation. The building is a fine and rare example of early Scottish modernism and signifies a brave, and at time naive architectural engagement in a relatively new building material and its possibilities. The project is culturally significant, reflecting in many ways, a national struggle for independence and autonomy; the concrete used undoubtedly symbolised a stark non compliant attitude and a solid resolute ambition for change. The material created some of the most spectacular yet subtle interior spaces and manipulated the light beautifully. However the material was in its infancy with regards fabrication knowledge and techniques. The acoustics of the space were extremely poor, due to the material’s ability to reflect sound and the poor concrete junctions and detailing meant that the building leaked heavily from the very start. The shallow concrete coverage of the reinforcement was insufficient and the contractor was relatively inexperienced in this kind of concrete construction.
Proposal
“As the twenty-first century unfolds and we reflect on the twentieth century questions as to whether and how its most significant architectural achievements are to be conserved and protected are attracting an increasing amount of public and professional discourse”. Mills, E. D [1996]
The Cardross proposal for conservation has been hotly contested over the last ten years with parties lobbying for the site’s demolition, while others want it restored to its original glory. In Scotland, nothing of significance in the so called modern style appeared before the early 1930s and therefore this building and many like it are becoming desperate for a clear resolution to the debate. The Burra charter may be the key to the final outcome for the St. Peters seminary. “Conservation means all the processes of looking after a place so as to retain its cultural significance. It includes maintenance and may according to circumstances include preservation, restoration, reconstruction and adaptation and will be commonly a combination of more than one of these” [icomos, Australia, The Burra Charter, Article 1.4, 1981].
The important question is, has the project ‘cultural significance’ and in what part of the building fabric is that most evident. The Netherlands had much the same debate with regards the Zonnestraal Sanitorium in Hilversum built by the Dutch modernist Jan Duiker. In this case DoCoMoMo [the international working party for the documentation and conservation of buildings, sites and neighbourhoods of the modern movement], initiated in 1988 by Hubert- Jan Henket proposed a restoration and reuse solution. The DoCoMoMo Hilversum scheme was an interesting example of a building conceived to facilitate the suppression of tuberculosis within the country. Jan Duiker the original architect responsible for the Zonnestraal Sanitorium, true to Dutch modernist philosophy delivered a build with a relatively short lifespan, perhaps indicating that the building’s temporary nature should reflect the fact that it should last only as long as its original programme was required. However the architectural merit, cultural significance and historic context of the building posed a conflict of ideals and ethos.
“After years of discussion and countless proposals, it was decided that the complex would be converted.
Work on recovery of the decaying buildings began in 1998, on the basis of a project by Wessel de Jonge and
Hubert-Jan Henket, and was completed in the summer of 2003.
The main building is to be used as a conference centre and the other buildings as a rehabilitation centre. The
'De Koepel' service building will become visitors’ and welcome centre. The Dutch have managed to settle the
issue of restoration of buildings designed by architects who had no intention of constructing monuments and
solve the contradictions involved”. Mills, E. D [1996]
The building’s tool value was deemed a key aspect and therefore opened the site to other tool value
proposals which seemed to satisfy all the parties involved.
“A response to the conflict of interests is the pursuit of architectural alteration within a modernist building
which would facilitate new programmes adhering to the modernist’s commitment to progress and engaging in
the fundamental value of modern building which is that of the `tool value`”. Mills, E. D [1996]
Eventually a scheme was proposed to reuse the site whilst returning the building’s original fabric and aesthetic to its original intent. The detailing and repair was modernist in nature with slender steel window frames replaced and the concrete repaired and strengthened. Once the repair was complete the restoration began with regards the building’s aesthetics. The key element in the repair of the concrete, was the use of a white paint finish which concealed the work done to the concrete.
The finished Project - click here
This is also a fundament difference to the Cardross project in that the original design was of fair faced concrete with no finish and with none of the formwork polished out either. Despite the obvious differences the Hilversum project could be a valid precedent and one that has increasing similarities to the Cardross project. Indeed the Cardross building has recently been bought by ‘Urban Splash’ – a company which specialises in the reuse of buildings. The new owner has appointed ‘Gareth Hopkins’, one of Scotland’s leading architects and the engineers ‘David Narrow Associates’ to propose a reuse for the site.
“Over and above these empirical considerations, it may be contended that even an architectural movement predicated on the idea of transience on route to a better future cannot uniquely escape history but is also a cultural expression of its own period, and such deserves to be safeguarded, at least in its most significant manifestations for later generations, just like the greatest achievements of previous periods A key theme in the origins and development of modernism was the determination to address contemporary social needs by exploiting new materials and construction techniques” Mills, E. D [1996]
It must not be forgotten that a defining characteristic of the Modern Movement in architecture was its international scope and that the Modern Movement arrived later in Scotland than the rest of Europe. Is Cardross then a true Modern Movement building, with all the characteristics of the style? And if it is, then surely the modernist ethos applies too. “To attempt to preserve an authentic early modernist building, so it has been argued, is thus to misunderstand the most fundamental premise of modernism, to subvert and dishonour the intentions of its authors and to fall victim to the same `museum culture` that has produced the acres of themed experience and ersatz history that increasingly characterised our towns and cities in the name of heritage, and that the self-professed successors of original moderns so vociferously deplore” Lion, E. [1982]tbc
“The interesting paradox of seeking to prolong the life of a building, whose design intentions and physical fabric were purportedly determined solely by its operational programme. To one school of thought at least, modern architecture’s defining `raison detre` in contradistinction to all preceding traditions was its commitment to the idea that buildings should not be conceived as monuments, rarefied artefacts defying time and change, but as functioning tools valuable only for their capacity to serve the social requirements or economic processes that caused them to be built in the first instance”. Lion, E. [1982]tbc
Perhaps then by this logic, the only consistent response to the question of what to do with modern architecture in decay like Cardross, is to salute its destruction and consign it to terminal neglect. Or is there a compromise to be had in the fact that the significant elements of the project are not in its architectural merit but in its use of concrete, its location and the structure’s internal spaces and their natural light qualities which are unique, in which case a proposal would be to strip the structure of anything other than the concrete. Repair to the original concrete should be done by cutting out the infected concrete, treating and recovering the reinforcement bars, and strengthening through the use of concrete collars. The site should be properly irrigated and drainage within the building upgraded. The surrounding woodland cutback by at least
200 meters and security measures taken to ensure no further vandalism takes place. The entire site like the Hilversum project should be coated with a tinted protective coat and perhaps painted white. In this way you will still be able to appreciate the formwork, its special condition and marvel in its natural light qualities. This action will also serve to cover the repair work but not entirely, it is still important to read the building’s historic layering.
Once the concrete has been preserved, repaired and treated, the site drained and secured, the structure can be left as a castle ruin might stand: a monument to a particular architectural ethos, style and material exploration, which reflects the nation’s individuality and approach to a new modern culture. Once this has been established then within and around the building, practical architectural elements may be introduced. Smaller buildings which don’t touch or interfere with the structure in any way but merely share the space internally and or externally would service the original building and site, but more importantly serve to draw the public to the area and help engage and educate the visitors in the merits of Scottish Modernism, thus developing its economic and educational value.
we need concrete castles in our lives - we are getting good at treating stone ones, like this one below.
Σχόλια