UNIVERSITY OF HUDDERSFIELD

School of Art Design and Architecture

Department of Architecture and 3D Design

THA1240 Technology 3, Materials & Tectonics

CONCRETE FRAMES, DECORATIVE FINISHES

By Christos Iacovides 1258543

January 2015

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Concrete Frames, Decorative Finishes Introduction Concrete is an invaluable material in contemporary construction and is the

main constituent material in precast concrete frames. The key advantage of

concrete is that it can be moulded and shaped into virtually any shape; it can

be cast in-situ or cast off-site in the form of precast concrete frames.

Generations of architects have exploited this flexibility using a myriad of

different decorative finishes to create the contemporary built environment

(Newman and Choo 2003). This report explores the manufacturing and

development of concrete frames, tracing the origins of the materials to its

present day use and assessing the benefits and drawbacks of this material as

a design material in contemporary architecture.

History of Concrete

Contemporary concrete can be traced back to its origins in ancient Syria,

where in 6500 BC the material consisting of gypsum and lime to create

elements of the built environment The Egyptians also used lime and gypsum

cement and the Romans who combined this early form of cement with sand

and water to construct iconic structures such as the Parthenon (Li 2011,

Amato 2013). The birth of contemporary concrete started in 1756, when a

British engineer added a coarse aggregate and powered brick to the cement

to form a structural material. Almost 100 years later in 1824 Joseph Aspdin

developed the material further by burning ground limestone and clay together,

thus altering the chemical properties of the material and inventing Portland

cement, which ultimately dominated the concrete market (Bellis nd.). Li (2011)

points out that engineers realised the potential in this material and in 1845

Standards were developed to ensure the structural integrity of the material.

However it was acknowledged that concrete was weak in tension and the

concept of reinforced concrete was developed in 1952, combining the

concrete with reinforcement to improve its tensile strength and to exploit its

high compressive strengths.

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Exemplar Precedents and Designers The use of concrete in frames can be traced back to 1842 when Francois

Hennebique used a cast in-situ system for a flour mill in France where the

weight of the units were limited to that which could be carried by two men.

The first precast concrete frame in the United Kingdom was Weaver Mill in

Swansea in 1897 (Elliott & Jolly 2014).

Figure 1 Weavers Mill Swansea 1897 (Elliott & Jolly 2014, p.2, Figure 1.1).

Since that time, the use of concrete frames has flourished in the global

construction industry with many iconic contemporary buildings using this

system as a base structure. The versatility of concrete is demonstrated in the

22-storey O-14 office building (nicknamed the Swiss Cheese Building) in

Dubai which as shown in Figures 2 and 3 has a concrete exoskeleton.

The use of a concrete shell of O-14 as both the primary and lateral structure

in this unusual concrete frame provides an efficient structural exoskeleton,

ultimately creating a highly efficient internal space (ArchDaily 2013).

Concrete was also the preferred choice albeit in a more conventional manner

in the iconic 829.84m high Burj Dubai skyscraper, as shown in the

construction development of the building, depicted in Figures 4, 5 and 6.

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Figure 2 Swiss Cheese Concrete Building in Dubai (ArchDaily 2013)

Figure 3 O-14 Building Dubai (ArchDaily 2013)

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Figure 4 Reinforcement and formwork being prepared for Burj Dubai (Burj

Dubai 2015)

Figure 5 Concrete construction for Burj Dubai (Burj Dubai 2015)

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Figure 6 Completed Burj Dubai (Google Images 2015)

In this structure the designers used special design mixes to ensure that the

reinforced concrete building could withstand the extreme pressures of the

massive building weight. The concrete structural system is essentially a

buttressed core that provides torsional resistance of the structure, with

extending wings terminating in thickened hammer head walls at every level.

The structure also includes perimeter columns and flat plate concrete floors

complete the system (Burj Dubai 2015).

Process/manufacture

Concrete consists of engineered proportions of coarse and fine aggregates

combined with cement and water and in some cases admixtures added to

alter the setting process. The actual consistency of a concrete mix will depend

on the end-use of the concrete and is typically base don the structural

capacity of the concrete and the environment in which the mix will be placed

(Li 2011). The aggregates used for concrete can be either quarried natural

material or recycled material from other construction sites quarried (Li 2011).

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Figure 7 Schematic for Cement Production (KEMA, 2005, p. 3-2, Figure 3-1)

Cement is manufactured using a dry mix process in what the American

Cement Association (2015) describes as a controlled combination of calcium,

silicon and aluminium. The process as shown in Figure 7 starts with quarrying

ingredients such as limestone, shells, and chalk along with clay or slate, blast

furnace slag and silica sand. This material is crushed, mixed and heated at

high temperatures in a rotary kiln to form clinker. The red-hot clinker is cooled

to handling temperature while the hot air is re-circulated back to the kilns to

reduce the energy consumed and to improve the sustainability of the process.

The cooled clinker is then ground to a powder and mixed with small quantities

of gypsum and limestone.

The cement and aggregate are stored in silos at a ready mixing concrete

plant, with additional silos for sand, and additives such as plasticizers. These

components are then fed by gravity fed into a preparation bin with the

proportion of each carefully controlled by computer to ensure that the quality

of the mix and the strength of the hardened concrete will conform to the

required standards. A precise dosage of water is added to the mix and the

mixing process is continuous and consistent (VICAT 2015).

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If the frame is manufactured off site then the process involves pouring ready

mix concrete is poured into steel moulds complete with steel reinforcement

and a mineral oil coating to prevent the concrete adhering to the steel. The

mould is vibrated to ensure a good consistency and left to cure. Once the

material has cured, the form is struck and the precast units are loaded for

transport to site for use (Levitt 2007). If on the other hand the concrete frame

is cast in-situ then formwork is prepared on site complete with reinforcement

and the ready mix concrete is poured into the formwork and vibrated. The

formwork is left in place to enable the concrete to set, cure and gain strength.

Typically after 28 days the formwork is struck and the concrete frame is

complete (Emmitt & Gorse 2010).

Figure 8 Sample of Concrete finishes (Frank 2010, p.10)

The finished texture is in part dependent on the type of formwork and

according to formwork manufacturing company Frank (2010) it is possible to

have virtually any type of finish or colour, as shown in Figure 8.

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Health, Safety and Sustainability

Although the concrete can be recycled to reduce its carbon footprint Amato

(2013) points out that the demand for concrete means that vast quantities of

cement are produced ach year contributing over 5% of all human generated

carbon emissions. These high levels of greenhouse gas emissions are

attributed to the high levels of energy required to produce the clinker, as

shown in Figure 11 (KEMA 2005).

Figure 11 Electricity Consumption in Cement Industry (KEMA 2005, p.2-2, Figure 2-1)

The industry acknowledges that these emissions are unsustainable and are

developing green forms of concrete and alternative constituent materials to

the cement mix that have lower melting points along with ways in which to

recycle the energy used in the cement production process (Amato (2013).

Working with concrete and in particular cement can cause contact dermatitis

as well as respiratory problems and as such workers should be trained in

handling these materials and in taking precautions against skin irritation

(Health and Safety Executive 2002).

Benefits and Drawbacks EFPC (2015) argue that precast concrete is durable, thermally efficient and

provides a high degree of sound insulation. In addition it is safe with a high

resistance to fire and impacts due to natural disasters such as floods and

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earthquakes. As mentioned previously concrete is an extremely versatile

material available in a wide range of finished, textures, colours and shapes.

Concrete frames are essentially manufactured off-site thus improving the

quality of the completed structure as well as reducing site time and the

disruption caused by the construction process. It requires very little

maintenance and if the mix is correctly designed, the material can last for

decades. In addition the design of concrete is controlled through a series of

British Standards and Codes to ensure that the material is fit for purpose.

Apart from the sustainability issues discussed earlier, one of the potential

drawbacks of this material is cost.

Table 1 Cost comparison Steel versus Concrete (Tata Steel 2015) The EFPC (2015) make the point that precast concrete is competitively priced

compared to other construction frame materials. However a study by Tata

Steel (2015) indicates that concrete whether it is cast in-situ or precast is

slightly more expensive than steel, as shown in Table 1.

Summary In summary concrete is a versatile material that has existed in engineering

and architectural design for centuries. The material is strong, flexible with the

capacity to be moulded into virtually any shape imaginable. The benefits of

the material include the fact that it is durable, robust, and strong in

compression and also string in tension when combined with reinforcement. It

provides an architect with a variety of possibilities with respect to structural

form and aesthetic finish. There are drawbacks to this material particularly

with respect to the high carbon footprint of the cement manufacturing process,

however the industry is seeking ways in which to development a green

concrete.

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References

Amato, I (2013). Green cement: Concrete solutions cement manufacturing is

a major source of greenhouse gases. Nature, 494 (7437), pp.300-301.

America’s Cement Manufacturers (2015). How Cement is Made. Retrieved

from

http://www.cement.org/cement-concrete-basics/how-cement-is-made

ArchDaily (2013) O-14 Building Dubai. Retrieved from

http://www.archdaily.com/273404/o-14-reiser-umemoto

Bellis, M. (nd.). The History of Concrete and Cement, Inventors. Retrieved

from

http://www.inventors.about.com/library/inventors/blconcrete.htm

Burj Khalifa (2015) Structural System. Retrieved from

http://www.burjkhalifa.ae/en/thetower/structures.aspx

Elliott, K.S., & Jolly, C. (2014) Multi-Storey Precast Concrete Framed

Structures. Chichester: John Wiley & Sons.

Emmitt, S. & Gorse, C. (2010) Barry's Advanced Construction of Buildings

(2nd Edition). Chichester: John Wiley & Sons.

European Federation for Precast Concrete (2015) 10 reasons for choosing

precast concrete. Retrieved from http://www.bibm.eu/precast-concrete/10-

reasons-for-choosing-precast-concrete?id=1058

Frank (2010) Architectural Concrete Formwork Solutions. Retrieved from

http://www.maxfrank.co.uk/media/dokumente/produkte/uk/broschueren/030-

Architectural-Concrete-formwork-solutions.pdf

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Google Images (2015) Burj Dubai. Retrieved from https://encrypted-

tbn3.gstatic.com/images?q=tbn:ANd9GcTjj-

emYSp7cAWUnz3m7ODjZ08EJhqWRA3LaPhRTFeaDg0RZLujEw

Health and Safety Executive (2002). Cement. London: Health and Safety

Executive

Publications.

KEMA (2005). Industrial Case Study: The Cement Industry Calmac Study ID:

PGE0251.01

Final Report. Retrieved from

http://www.calmac.org/publications/industrialcementfinalkema.pdf

Levitt, M. (2007) Precast Concrete: Materials, Manufacture, Properties and

Usage, (2nd Edition). Boca Raton: CRC Press.

Li, Z. (2011). Advanced Concrete Technology. Chichester: John Wiley &

Sons.

Newman, J., & Choo, B.S (2003). Advanced Concrete Technology:

Processes. Oxford: Butterworth- Heinemann.

Tata Steel (2015) Steel Construction Information-Cost Comparison. Retrieved

at

http://www.steelconstruction.info/Cost_comparison_study

VICAT (2015) Concrete Production Process. Retrieved from

http://www.vicat.com/en/Activities/Ready-mix-concrete/The-manufacturing-of-

concrete