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BME Department of Mechanics, Materials and Structures Design of Reinforced Concrete Structures Impacts of modern concrete technologies on architectural design of rc structures 1

BME Department of Mechanics, Materials and Structures

Lecture 4:

IMPACTS OF MODERN CONCRETE TECHNOLOGIES ON ARCHITECTURAL DESIGN OF VISIBLE CONCRETE STRUCTURES

Draskóczy András


CONTENT

Introduction Material technology Mould technology

Concrete placing and compacting technology Curing, after treatment technology Standardized quality requirements

Relationship of climate, function and application of visible concrete Examples

-surface textures and colours -building exteriors -building interiors

-coverings -furniture, art works

-Summary, conclusions


Introduction

Concrete as life style

Unlimited possibilities of use of concrete -strong

-rough, puritan surface -clear and clean forms

-seems to be rigid, but in its simplicity can be beautiful -durable, radiates stability

-it can have variable surface textures and colours -organic forms can be fitting into any environment

-great variety of functions: load-bearing, surface covering (plinths, walls, roofs), furniture (outdoor and indoor), art works (relief, statues)

-mixed use of concrete with: wood - becomes more natural

glas – produces airy effect metal – strengthens industrial character textile, leather – become more warm

-Widespread use of white cement based coloured, fibre reinforced concrete objects poured in gypsum negative


Material technology

Concrete

1 m3 fresh concrete = appr. 350 kg cement + appr. 1,2 m3 aggregate + appr. 160 l water

Cement: Clinker: mixture of calcium carbonate (limestone), silica (sand), iron oxide and alumina (clay) melt at 1450 °C Clinker content of cement gives its binding properties Ordinary portland cement (OPC) = clinker + gypsum ground to fine powder Blended cements: OPC + supplementary cementitious materials (SCMs): blast-furnace slag, fly-ash or

silica fume or meta-kaolin Types I to V PC-s: high early strength PC, air-entraining PC, low heat of hydratation PC, sulphate resisting PC White PC used for coloured visible concrete structures

Aggregate: sand, gravel, crushed stone Strength, shape and

grading (particle size distribution)

Water water/cement ratio (W/C= 0,5 to 0,3) the smaller better, influences final strength, workability, pumpability, durability


Material technology Chemical agents and additives

Admixtures, additives: limestone flour micro-air entrainer with high freeze-thaw resistance water reducers (self-compacting concrete) bound accelerators (super)plasticizers bound retarders pore reducing agent shrinkage reducers colour intensifier/efflorescence reducing agent mass hydrophobic efflorescence minimiser colour slurry for colouring concrete

Surface primers: oil and vapour barrier

moisture barrier graffiti barrier crystalline waterproofer corrosion inhibitor adhesion promoter colour pigments for dyeing concrete aftercare treatment water repellent cleaning agent for cementicious surfaces

Mould detaching agents: fast detaching silicone mould release agents

solvent free release agents (no ventilation needed before concreting)

More info at: http://www.schomburg-ics.de/en/Concrete_Admixtures


Material technology Special concretes

Self-compacting concrete (SCC) Self-compacting concrete (SCC) is a flowing concrete mixture that is non-segregating, able to consolidate under its own weight. It shall be flowable enough to pass through highly reinforced areas. Composition: more powder content and less coarse aggregate. Shape and gradation of the aggregate are essential, rounded aggregates would provide a better flowability. Chemical admixtures: a high range water reducing admixture (HRWRA) and sometimes, viscosity-modifying agent (VMA). Beside the advantages above, better durability is essential.

Applications of self-compacting concrete

Self-compacting concrete has been used in bridges and even on pre-cast sections. One of the most remarkable projects built using self-compacting concrete is the Akashi-Kaikyo Suspension Bridge. In this project, the SCC was mixed on-site and pumped through a piping system to the specified point, located 200 meters away. On this particular project, the construction time was reduced from 2.5 years to 2 years.

This type of concrete is ideal to be used in the following applications:

Drilled shafts

Columns

Earth retaining systems

Areas with high concentration of rebar and pipes/conduits

https://www.thebalancesmb.com/world-s-highest-rail-bridge-844757

https://www.thebalancesmb.com/longest-suspension-bridges-in-the-world-4061820


Akashi Kaikyo bridge, Kobe, Japan


High strength concrete (HSC)

Characteristic cube strength between 60 and 100 N/mm2. The target water/cement ratio should be in the range 0.30–0.35 or even lower. Crushed rock aggregates (of suitably high crushing value) are preferable. Admixtures: Superplasticisers / high range water reducers are to use to achieve maximum water reduction, although plasticisers may be adequate only for lower strength HSC (C60 to C70). Silica fume (microsilica) or meta-kaolin can be used to enhance the strength at high levels (C80 and above), but is not needed generally at the lower end (C60 to C80).

Applications of high-strength concrete

offshore structures columns for tall buildings prefabricated structural members long-span bridges and other highway structures.

The main advantage is the reduction in size of compression elements and/or the amount of longitudinal reinforcement required.


Fiber-reinforced concrete (FRC) Concrete containing fibrous material, which increases its structural integrity. It contains short discrete fibers that are uniformly distributed and randomly oriented. Fibers include steel fibers, glass fibers, synthetic fibers and natural fibers – each of which lend varying properties to the concrete Polypropylene and Nylon fibers can: Improve mix cohesion, improving pumpability over long distances, freeze-thaw resistance, resistance to

explosive spalling in case of a severe fire, impact resistance, increase resistance to plastic shrinkage during curing

Steel fibers can: Improve structural strength, reduce steel reinforcement requirements, improve ductility, reduce crack

widths and control the crack widths tightly, thus improving durability, Improve impact– and abrasion–resistance, freeze-thaw resistance

Applications of fibre reinforced concrete

-industrial flooring

-precasting applications are controlled with laboratory testing to confirm that local design code requirements are met, which may impose minimum quantities of steel reinforcement within the concrete.

-tunelling projects using precast lining segments reinforced only with steel fibers.

-vertical walls designed with micro REBARS (reinforcing bars)

http://en.wikipedia.org/wiki/Fiber

http://en.wikipedia.org/wiki/Fiberglass

http://en.wikipedia.org/wiki/Fiberglass

http://en.wikipedia.org/wiki/Synthetic_fiber

http://en.wikipedia.org/wiki/Natural_fiber

http://en.wikipedia.org/wiki/Polypropylene

http://en.wikipedia.org/wiki/Nylon

http://en.wikipedia.org/wiki/Spalling

http://en.wikipedia.org/wiki/Steel

http://en.wikipedia.org/wiki/Ductility


High-Performance Fiber Reinforced Concrete (HPFRC)

by addition of micro steel fibers

-To increase resistance to cracking

-Strain-hardening up to several percent strain, resulting in a material ductility of at least two

orders of magnitude higher when compared to normal concrete or standard fiber-reinforced concrete.

Unique cracking behavior when loaded beyond the elastic range, HPFRC maintains crack width to below 0,1mm, even when deformed to several percent tensile strains.

https://en.wikipedia.org/wiki/Ductility


Comparison of composition of traditional concrete and one C60 HPFRC concrete

traditional concrete C60 HPFRC concrete1

Cement kg/m3 350 462 Fly ash kg/m3 138 Lime stone filler kg/m3 139 Water l/m3 160 208 Super plasticiser l/m3 16 Aggregate kg/m3 dmax mm fine sand 2,35 99 river sand 4,75 697 crushed marble 12,5 503 gravel-sand mixture 32 1,2 m3 steel fibre kg/m3 90 l= 33 mm l/d= 65 fyd= 1100 N/mm2

1: F. Soltanzadeh et al.: Shear Capacity of HPFRC Beams Flexurally Reinforced with Steel and Prestressed GFRP Bars


Mould technology

Mould technology applied at the construction of S. Calatrava's Tenerife auditorium during the 1990-ies

Timber formwork to support the mould of one of the shells of Felix Candela in Mexico built during the 1940-ies


Mould technology

Subway moulded by use of Alkus Alu reinforced multilayer plastic Aula of the Media tower, Elbelstadt, Germany moulding tables, which can be welded together, simply or doubly curved Cement plug to close the wall moulds connector hole Moulding tubes for special column sections. Material: poly-styrene interior, inside and outside cardboard coated with hard and soft PE foil inside and outside respectively


Placement technology,

Concrete placement on Candela's shell, 1940-ies Way of placement of ready-mixed concrete today

No vibration by self-compacting concrete!

Placing of prefabricated curved visible concrete wall panel


Curing, after treatment technology

Keep concrete wet during the first week by sprinkling water and covering by PE foil!

After treatments of visible concrete surfaces (concrete cosmetics) -polishing with 120 or 180 sand-paper in 2 weeks age at summer, 4 weeks age at winter in circular movements -surface improvements with cement based repair-mortar or with concrete glaze -two layers mineral concrete pigments paint: vapour permeable, good covering power, crack filling, stuffing, sealing, 2 to 3 mm deep infiltration -impregnation: 0,03 mm thick colourless film layer, frost re- sistent, oil proof, hydrophobic -


Visible concrete standardized quality requirements

Preparation of trial surfaces – sample pieces by prefabrication – is advisable Surface evenness, dimension tolerances acc. to MSz EN 14992, curvature along 1 m: max. 3%o Lengths: ≤2 m: 3‰, >2 m: 2‰, thickness: ≤3 cm: ±3 mm, >3 cm: ±4 mm Working gap, joint: surface dimension difference max. 3 mm Use of corner batten acc. to chamfer design. Notches along vertices: max. 2 places, max. 5 mm width Crack width: 0,1 to 0,4 mm acc. to MSz EN 1992-1-1:2008 Surface texture: uniformity, max. width of cement liquid outflow 3 mm, depth: 5 mm Max. porosity: on 50 cm x 50 cm surface max. 0,3% (>2 mm, <15 mm) Colour uniformity: no discolouration due to corrosion Shade of colour only between different parts of building allowed

10 mm increase of concrete cover Clean mould surfaces and reinforcement cages Positioning of mountings: tolerance max. ±10 mm Concrete consistency: F3 or F4 (fluid) 20-40 dm3/m3 cement paste supersaturation required Aggregate diameter max. 16 mm by stone-like shaping of surfaces Max. 1 to 1,5 m concrete fall Limited concreting speed Placing finish max. 1,5 hours after mixing Compacting should be finished before beginning of bound Finish vibration at appearance of cement paste on surface, and no more air bubbles appear Use steel smoother for top surface of concrete! Protect concrete from sun, rain, wind and frost during bound! Heat ripening by vapour or hot air under controlled temperature. No direct contact with vapour allowed Formwork removal after controlled achievement of adequate strength Protect fresh concrete from drying out! Keep concrete surface between 0 and 65 °C! Make quality control report! (Fill product quality certificate!) Surface cosmetics, colour paint, impregnation, graffiti protection see above!


Relationship of climate, function and application of visible concrete reinforcement canopy slab heat insulation floor slab outdoor space indoor space


Examples surface textures and colours

The past

and possibilities of the present kitchen tiles


Examples surface textures and colours

textures of exposed aggregate


Examples surface textures and colours Washed concrete surface Washed concrete surface Metro line 4 stairs of the Museum of Fine Arts Matrix design for imprint pictures Possibility of use of photogravure technology!

Matrix material: poly-urethan elastomer or silikongum Company logo in visible concrete


Examples building exteriors, civil engineering constructions

Széchy sports swimming pool Budapest Margaret Island

MO highway northern Danube bridge: Megyeri bridge


Examples building exteriors

(earlier) Laposa winery Badacsony

The heat insulated building is covered with rc crustal panels on the façade and the roof and fits well into the

trend of minimal architecture of the present

fibre reinforced fine concrete façade panels: crustal panels corrosion free steel connectors rc. crustal panels monolithic reinforced concrete wall and roof slab monolithic rc heating cables


Prescriptions of facade crustal panels:

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1 cm 0,6 1,2 - In and out screw (visible), glued on load-bearing wall

2 1,5 2,0 - In and out screw (visible)

3 2,5 2,3 One layer In and out screw (visible), cantilevered (hidden)

4 3,5 2,6 One layer In and out screw (visible), cantilevered (hidden) max 2 m2

5 4,0 3,0 One layer In and out screw (visible), cantilevered (hidden) max 1,5 m2

6 6,0 3,4 Two layers In and out screw (visible), cantilevered (hidden) max 1 m2, supported and hidden positioned

8 9,0 4,2 Two layers In and out screw (visible), supported and hidden positioned, Halfen-Deha suspension

10 12 5,0 Two layers Supported and hidden positioned, Halfen-Deha suspension


Wien University of Economics Central library and learning building by Zaha Hadid


Examples building interiors

Semmelweis University Education Centre

Pavement colouring project


Examples building interiors Metro line 4 Budapest, Fő-vám square


Examples building interiors Metro line 4 Budapest, structural solution

Section of Fő-vám tér station

Section of Kálvin square station

A system of disorderly arranged horizontal monolithic rc beams equilibrate the huge earth pressure acting on slurry walls of the about 20x20x20 m sized trench box of the metro stations producing a vibrating impression, which can be considered as architectural expression of the inevitable con- fusion people become victim when entering public transport. (Structural need is turned into architectural expression tool)


Examples building interiors Metro line 4 Budapest, structural solution

Reinforcement of crossing beams supprted by the soil, which is then excavated after hardening of concrete of these beams and thus the beams begin to function as horizontal struts equilibrating the earth pressure acting on the surround- ing trench walls by the effect of outside soil masses.


Examples building interiors Zaha Hadid Wien University of Economics CLL

building


Examples surface coverings

pavements polished surface coloured polished surface

Coloured pavement tiles set


Examples furniture


Examples trans lucent concrete Litracon® -mixture of fine concrete and optical glas fibres Invention of Áron Losonczi Hungarian architect


Examples art works

Thalia Theater Kassa Rácz bath reconstruction, Budapest

Dialogue with Ré by Ferenc Csurgai


Summary, conclusions Thanks to the developments of concrete technology, the application of a great variety of concrete admixtures and coatings became

available such improving characteristics of concrete like workability, durability, surface texture and colour etc., so that the visible appearance of this artificial „superstone″ beside „being inexhaustible source of static and construction ideas and plastic

possibilities″ – as P.L. Nervi has stated – has remained the most powerful expression tool of architectural design. Under continental climatic conditions, the most problematic point of application as visible and load-bearing rc structure is the

necessity of heat insulation. This is the reason why - in Middle, Western and Northern Europe – visible monolithic concrete is rarely used on facades of buildings, but in interiors, in civil engineering works or as material of objects like furniture, art works, coverings.

An example of organic arquitecture: biomorph visible rc columns hold the fan-shaped arranged struts of the timber roof of the Pancho Arena, Felcsút, Hungary

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