UHPC Planters - Fatma Aslan & Wilbert de Rooij

UHPC P L A N T E R S ir.

Fatma

Aslan

&

Wilbert

de

Rooij

Colophon The centrifuge Ir. Fatma Aslan Wilbert de Rooij Eindhoven, November 2015

Eindhoven University of Technology (TU/e) Architecture, Building and Planning Den Dolech 2 5612 AZ Eindhoven Faculty of Architecture Building Vertigo Pieter van Musschenbroek Laboratorium De Wielen Postbus 513, 5600 MA Eindhoven

CC-Studio Architecture and Engineering Unit 406 Nieuwpoortkade 2a 1055 RX Amsterdam

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UHPC PLANTERS

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Preface This report, UHPC Planters, marks the end of a two months research/ production process.

Hereby we want to thank all our supervisors for the guidance and support during this

The research was conducted to explore the possibilities of the Ultra High Performance

process. We want to thank Gerald Lindner and Danny van Kessel, for setting up this

Concrete. The correlation between the way it is made and the appearance was searched in

research and the freedom they gave us to do our research.

order to find the best design for a square and smooth planter.

We are especially pleased and grateful for Hans Lamers and Rien Carters, for their friendly

This report is written as part of our internship at CC-Studio in Amsterdam. From August

attitude and the offered available workplace for the production process. In the same

2015 until November 2015 we have been engaged in the research, production and writing

way, we would like to thank the other supervisors from the Pieter van Musschenbroek

of this report.

Laboratorium.

This research is written for our internship office CC-Studio and Technical University

We hope that this report can serve as a solid base for new research in the field of UHPC.

Eindhoven. The research was firstly conducted by Fatma Aslan, to establish the quality

Giving insights in the material, possible problems and phenomena to encounter, and

and possibilities of the UHPC. The research question was figured out by Fatma and both

offering explanations and solutions for preventing problems and irregularities.

internship supervisors, Gerald Lindner and Danny van Kessel.

The research and the production process was too much work in very little time. Therefore, in September 2015 Wilbert de Rooij joined the research.

The research we have done was very complicated, but eventually led us to interesting and answers and solutions for problems we encountered.

Fortunately our internship supervisor Gerald Lindner and especially the supervisors from the Pieter van Musschenbroek Laboratorium from the Technical University Eindhoven,

Fatma Aslan and Wilbert de Rooij

Hans Lamers and Rien Canters, were always ready to answer our questions. Their help is greatly appreciated.

Eindhoven, November 2015

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Table of contents Preface

Smoothness

5

Introduction

9

Production

Faces

67

Corners

71

Color

73

Air bubbles

75

Cement pockets

77

Organisation

13

Requirements

15

Ingredients

23

Excess amount of water

79

Materials

25

Synthetic flakes

81

Synthetic fibers

83

Steel fibers

85

Mixing Process

27

Pouring Process

33 Shape

Removing the mould

37

Target

91

Heat/Steam treatment

43

Corners

93

Faces

97

Mechanical Properties

103

Acquired Knowledge UHPC

105

Outer mould

45

Inner mould

49

Failure inner moulds

53

Tectonics Sources

Surface structure Target

65

Information UHPC

109

Pictures

111

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Introduction In a collaboration between the Eindhoven University of Technology and CC-Studio a study about ultra high performance concrete was done by Fatma Aslan and Wilbert de Rooij. The study focusses mainly on the relation between the appearance of the concrete and the way it was made, resulting in UHPC planters in many variations and appearances.

The UHPC planters are cubes of fifteen by fifteen centimeters with sides of one centimeter thickness. With these requirements two difficulties should be overcome. The cube shape of the planters makes it difficult to remove the innermould and to achieve corners of ninety degrees, while the thin sides increase the risk of crack formation. Further the used concrete is white and the aim is to make the surface of the planters as homogeneous and smooth as possible.

During a testing and production phase of six weeks lots of variations were made to prevent or reduce irregularities of any kind. These variations are visible in the appearance of the planters but originate from different production techniques with the purpose to prevent or reduce these irregularities.

Eventually variants and irregularities are put together and compared with each other. For the irregularities possible causes are explained and recommendations are done to prevent them in the future.

In the first part of this report the overall production process will be explained, among other things with the help of pictures. The second part of this report will elaborate on the encountered irregularities. Pictures are used to show the physical characteristics of these irregularities.

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Organisation Requirements Ingredients Materials Mixing Process Pouring Process Removing the mould Heat/Steam treatment Outer mould Inner mould Failure inner moulds

PR OD UCT IO N

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Organisation A well organised and prepared work is very essential for a good result, and is therefore a major part in the making process. Also a fast working process is important for a good result. Especially, to obtain a smooth surface and high quality end product. Good coordinated teamwork will lead to a smooth production process. A slight delay in time can lead to serious consequences on the usability of the mixed fresh concrete.1 Consequently, everything must be checked beforehand to avoid any delays in the making process.

1 CAE Nederland B.V. (2010)

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1. Working place

2. Outer mould

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3. Inner mould

Requirements A good workplace is significant to make everything right. It is essential to have the space to

14. Plastic bag

work easy and fast. Otherwise, a good organisation will suffer from it, and the production

15. Glass cups

of the planters will decrease. Furthermore, to keep the productivity in good level, every tool

16. Spades

and material should be ready to use immediately during the production of the concrete.

17. Funnel

In this way the concrete can get poured into the mould in a fluent process, preventing air

18. Whisks

bubbles and deformies as much as possible.

19. Mixer

Therefore, some tools and materials are indispensable, and are needed to achieve a good result. Below is a list of the required equipment that is needed to make the concrete

20. Libra

planters.

21. Gloves 22. Lab coat

1. Working place

23. Safety goggles 24. Safety boots

2. Outer mould (existing form 15x15x15 cm) 3. Inner mould (made by us from cardboard 13x13x13 cm, thickness 2 mm)

25. Cleaning place

4. Plastic outer mould (polyester sheet, thickness 0,5 mm)

26. Spatula

5. Glue

27. Cleaning products

6. Cling film 7. Tape 8. Vaseline 9. Brush

10. Wrench 11. Screwdriver 12. Paper 13. Cotton wool 15

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4. Plastic outer mould

5. Glue and cling ďŹ lm around the inner mould

6. Tape

7. Vaseline and brush

8. Wrench

9. Screwdriver

10. Paper and cotton wool

11. Plastic bag

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12. Glass cups

13. Spades

14. A funnel

15. Whisks

16. A mixer

17. Inside of the mixer

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18. A libra

19. Gloves

20. Lab coat and safety goggles

21. Safety Boots

22. Cleaning place

23. Spatula

24. Cleaning products

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Cement

Superplasticizer

Synthetic ďŹ bres

Water

Ingredients The various ingredients are weighed precisely, and will be placed, in different spades, near the mixer. This is necessary, because from the beginning of the mixing process timing plays an important role to put the mixture as fresh as possible into the mould; it will determine the freshness of the mixture.

Furthermore, the Ultra High Performance Concrete is largely dependent on a precise composition, which can be better weighted without the pressure of time.2 Therefore, a good preparation is important in the making process, which will affect the result of the ďŹ nal product.

On beforehand the right composition of the mixture should be explored, because the composition effects the uidity of the mixture. A good viscosity is important during the pouring process. A too viscous liquid mixture can have major consequences for the using mould.

Below is the list of the recipe and the type of the ingredients, which is needed to make the 1c

right mixture for one concrete planter. The dimensions of the planters are 15 x 15 x 15 cm

m

The recipe: 2000 gram concrete

15 cm

with a thickness of 1 cm.

400 gram water 20 gram superplasticizer 2 gram synthetic ďŹ bres

15

cm

15

cm

2 CAE Nederland B.V. (2010)

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Dyckerhoff Flowstone® weiß, 25 kg

Flup®-PCE-001 Fließmittel für Dyckerhoff Flowstone, 250 g

Teijin Aramid Technora® Fibre

Tap water

Materials Water / cement.

The compressive strength of concrete has a strong link with water / cement ratio. By adding

The fibre reinforcement increased the tensile strength and elasticity of the material. This

water to the cement mixture, a hydration is started, which provides a hardened mixture.

is needed, because the tensile strength of the concrete is behind the development of the

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The ratio for a regular concrete is between 0.4 and 0.65 depending on the strength. The

compressive strength.

higher classes have lower ratios. For the UHPC pots we used ratio 0.2.

A lower water / cement ratio provides a higher density on the concrete. As a result, the

The fibres provide a great tensile strength, which influences the total strength of the

water permeability of the material will be smaller. However, a lower water / cement ratio

material. The fibres may vary in material, length and shape. The large fibres (up to 30

has a few disadvantages. First, the workability of the concrete will decrease; the concrete

mm) are suitable for the reduction of micro-cracks that eventually change into macro-

will be too dry, which makes it less fluid. Second, the hydration degree of the cement is too

cracks. Altogether, the addition of fibres increases the tensile strength and elasticity of the

low; not all the cement can react with water. Third, the temperature of the mixture will rise

concrete, while the compressive strength remains practically the same.7

rapidly; crack formations in the product may occur.4 However, by using superplasticizer it is possible to use a lower water / cement ratio. The superplasticizer increases the workability of the mixture.

Superplasticizer As said before, a low water / cement ratio increases the density and the strength of the concrete. A low ratio has consequences for the workability of the mixture. In order to avoid this process, superplasticizer is added. Superplasticizer is an auxiliary matter, which increases the process ability of the material. Furthermore, the superplasticizer ensures that the concrete mixture penetrates in inaccessible places without segregation.5

Fibres The addition of fibres in the concrete mixture improves the structural feature. The concrete without the addition of fibres would be too brittle. The fibres provide a very tough material.

Even in some designs the traditional reinforcement can be entirely replaced by fibers.6 3,4,5,6 and 7 CAE Nederland B.V. (2010)

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Four mixers: CAE Nederland B.V. (2010)

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Compulsory mixer

The best mix with a compulsory mixer

Ring mixer

Vacuum mixer

Mixing process Due to the fast curing of the concrete mixture, a fast and effective mixing method and process is strongly required.8 There are three main elements, during the mixing process, to take properly into account.

First, the temperature of the working place and the concrete mixture should be as low as possible. The high temperature of the environment and the heat development of the hydration process ensures that the concrete mixture will solidify prematurely.9

Second, an efficient mixing method is significant to mix the composition. The mixing method determines the temperature of the mixture and therefore the hydration process. Also, the type of concrete mixer is significant for this process and also influences the temperature.

Different kinds of mixers have various results. Pictures next show the influences of the various mixers. During our experiment standard whisks for the mixer were used. These whisks resemble the conventional mixer. Reduced properties must be accepted and should be kept in mind, that this is not the perfect mixer.

The mixing method is based on conventional mixer. This method must be implemented properly. Timing is significant during the mixing process, and therefore everything must be prepared before the mixing process.

8 and 9 CAE Nederland B.V. (2010)

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Preparation before mixing

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The dry mixing process takes about two to three minutes, followed by the addition of water and superplasticizer. The following mix period takes about three to four minutes, by the addition of the remaining superplasticizer.

Next, the fibres are added to the mixture. In this stage, it is important to carefully add the fibres to the concrete mixture. This prevents the formation of clusters of the fibres.

One important issue during the mixing process is that the mixture may show a decline in liquidity.10 This will eventually disappear, and therefore new additional ingredients such as superplasticizer or water are not necessary. Otherwise, it will have consequences to the final result. Especially water may have adverse effects on the concrete.

10 CAE Nederland B.V. (2010)

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Air bubbles after mixing

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Spatula

The last main element during the mixing process is the bubble formation. It takes considerably more energy to mix a good mixture, because of the dense structure, the addition of fibres, and the low water / cement ratio. Air bubbles can appear in the mixture.11 These air bubbles have a large negative impact on the strength of the concrete. Therefore, it is important to minimize the amount of air as much as possible.

By self-compacting concrete this problem is solved by internal and external vibrations.

However, by the presence of fibres this is not possible. As a result of the vibrations the fibres will sink to the bottom (sedimentation). In this way the orientation of the fibres will be disturbed.12 It is important to remove the air bubbles as much as possible after pouring the concrete into the mould. The easiest way to do this is to carefully stir the concrete with a spatula. By doing this, air bubbles will be removed and the fibre structure will not be disturbed.

11 and 12 CAE Nederland B.V. (2010)

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The outer mould is ready for use

The inner mould is placed inside the outer mould

The plastic outer mould gets placed between the outer and inner mould

The concrete is poured into the mould and the air bubbles are removed

Pouring process After the blendingprocess the concrete will be poured into the mould. This stage is very significant and also determines the quality of the final product. During this process every action should be done very fast, careful and precise. A slight delay in time or a mistake during the pouring can have serious consequences for the usability of the concrete.

In addition, good coordinated teamwork is significant at this stage. One person should carefully pours the concrete into the mould and the second person checks the process, and intervenes when necessary. Also the second person can remove the air bubbles in the concrete directly after the pouring process.

Directly after removing the air bubbles, the moulds get covered with a piece of plastic and plastic cling film. The plastic provides a smooth and glassy effect. The cling film, prevents the concrete from dehydration. When dehydrated, the concrete can crack during the hardening process. During the first twenty-four hours the temperature rises considerably.

Therefore, the next step is to cover the whole element with cotton wool and paper as isolation. These two materials prevent a sudden fall of the temperature. It is significant that the concrete planter gradually hardens, preventing cracks during the hardening process.

The final step is to cover everything with a plastic bag to seal the entire package.

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The concrete is covered with a piece of plastic

Covering with cling ďŹ lm

The top is covered with cotton wool

The sides are wrapped with paper

The whole element is covered in paper

The ďŹ nal step is to cover everything with a plastic bag

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The mould gets carefully dismantled

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Removing the mould The concrete needs two days to completely down. It is also possible to measure the temperature of the mould. The ďŹ rst day the whole mould is warm.

The second day the mould has reached the room temperature and can be removed from the concrete. The mould should be removed carefully from the concrete. After removing the mould and the plastic, the concrete pot gets covered with cling ďŹ lm. The cling ďŹ lm protects the concrete planter against dehydration, because the foil is waterproof. This is needed because the entire hardening process of concrete takes a long time. The constructive strenght of the concrete gets normally measured after twenty eight days.13

13 CAE Nederland B.V. (2010)

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The concrete planter gets gently removed from the mould

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There is still water present inside the mold

The plastic and the cardboard get removed from the concrete planter

The ďŹ nal result

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The remainings: dismantled inner moulds, plastic and cling foil

The empty cast iron moulds

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The outer mould gets cleaned for the next pouring process

Everything will be checked for possible reuse and will be cleaned carefully

Some concrete can only be removed with a spatula

The plastic outer mold gets cleaned with a sponge

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The paper and plastic bag, which are used during the hardening process, are reused for extra protection of the pot.

The concrete pots are covered with fresh foil

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Heat / steam treatment After removing the mould from the concrete it is possible to do a special treatment. This treatment consists of heating the concrete by heat or steam. A heat treatment takes twenty four to forty eight hours to complete. The heat treatments must take place between the third and seventh day after pouring. The temperature will slowly increase to ninety degrees.

Celsius By this the mechanical properties of the concrete will improve. The compressive strength will get achieved faster and also the formation of cracks will get reduced.14

This treatment requires speciďŹ c knowledge and more information about the strength of the concrete. Also the circumstances should be ideal to realize this special treatment. For our experiment heat or steam treatment was not used.

14 CAE Nederland B.V. (2010)

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The dismantable cast iron mould

The mould is dismantable by the bolt and nut system

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The inside of the mould

Outer mould The mould for a design in concrete is very important. It has a big inuence the ďŹ nal result of the product. The mould should be durable, because of the high amount of pots. Otherwise you lose too much time and material. An other requirement for the mould is to be easy dismantable.

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Plastic

The laser cutter is cutting the vivak foil

The plastic outer mould will be placed between the outer and inner mould

Plastic outer moulds after using it a few times

The outer plastic mould gets placed at the inside of the outer mould. The plastic mould provides a very smooth surface, which is also the target of this design. Also this is possible, because the UHPC has a very ďŹ ne structure. Therefore, it is the perfect material to create very ambitious designs.

The plastic is cut with a laser cutter to make sure the plastic mould has the right dimensions.

The plastic can be used a few times, when it is cleaned and applicated carefully.

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The making of inner moulds

The deformation of the cardboard

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Inner mould The inner mould is the most difďŹ cult mould. It should be easy removable and durable at the same time. Also it should be strong enough. We tried different kinds of inner moulds and the cardboard mould was the best. The 2mm cardboard is strong enough. However, the cardboard can be used only two times. After using two times the deformations gets too big. The concrete changes the shape of the cardboard because of the forces in the concrete during the hardening process.

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The inner mould with the inner construction

The bottom plate and the inner mould are glued together

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The inner mould is greased with vaseline and is ready to use

The inner mould is a box without a top. The dimensions are 13 x 13 x 14 cm, because we want a thickness of 1 cm for the sides of the concrete planter. The cardboard sides get taped to each other, to form a dismountable inner mould. It is significant to remove the inner mould very easy.

The next step is to cover the inner mould with cling film, because the poured concrete is a liquid material. Also the cling film makes it easy to remove after the hardening process, and make it possible to use the inner mould twice.

Next, the inner construction will be placed in the mould. After that, a rectangular bottom piece of plastic gets glued to the open top of the cardboard box. To make the fixation extra strong and to have a nice smooth edge, the bottom plate and the box will be taped together.

The final step is to grease the inner mould with vaseline. It is important to spread the vaseline over the entire surface, especially at the corners and edges.

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Vacuum forming of a plastic sheet

MDF inner mould

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Vacuum forming machine

Failure inner moulds The ďŹ rst inner mould was made of Medium Density Fibreboard (MDF). The idea was to remove the entire inner mould after the hardening process at once. For an easier removal the mould was shaped conical.

After making the mould from MDF, a cover of plastic was made. The shape of the plastic was made by vacuum forming (thermoforming). A plastic sheet is heated to a forming temperature, placed above the mould, and pulled around the mould by the use of vacuum.

The aim of the plastic was to cover the MDF mould from the concrete; otherwise the MDF mould would absorb water from the concrete leading to cracks in the mould.

Unfortunately, the shape of the vivak was not made properly. During the vacuum forming the pleats arise around the corners. To prevent the pleats, the shape must be lower and the angle of the corners smaller. This will lead into a very heavy concrete pot, and a small place to put a plant. Therefore the cardboard inner mould was prefered.

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The resulting pleats

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The conical shape

The corners are the weakest areas of the thermoformed plastic sheet

The pleats are ďŹ xed in the concrete; therefore the inner mould can not be removed

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The formwork sides are ďŹ xed in the concrete

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The second inner mould was made from formwork plates. The inner mould consists of ďŹ ve sides which were taped to each other. Unfortunately, the sides got stuck inside the concrete. The sides become ďŹ xed in one position and were therefore very difďŹ cult to remove. The concrete planter cracked when trying to remove the sides. Another reason the cardboard inner mould was prefered over this variant.

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The glue was too weak to hold the bottom plate and inner mould together

The inner mould floats upwards, because the concrete flows into the inner mould

The result after removing the inner mould

The final result after the hardening process

The preferred and final inner mould is the mould made from cardboard. First we only glued the cardboard to the plastic bottom plate. This was very risky, because the cardboard did not stand for long after pouring the concrete into the mould. The glue was simply too weak to hold everything together. This was improved by the addition of tape after gluing everything together.

Sometimes the inner construction placed in the middle of the box collapsed. This resulted in very thick sides and ugly undersides. Sometimes it was necessary to pour the concrete planter twice. The final result was not perfect, because the transition between the old and new concrete was clear visible. Also creating a smooth surface became very difficult. From now on the inner construction was taped to the sides, so the sides could not collapse anymore, preventing thick and imperfect sides.

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A collapsed inner mould

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The inner construction collapsed, resulting in thick sides

The transition between the old and new concrete is clearly visible

The ďŹ nal result after pouring for the second time

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TEC TO N IC S

Target Smoothness Color Air bubbles Cement pockets Excess amount of Synthetic flakes Synthetic fibres Steel fibres

SURF A CE S T RU CTU RE

water

1. Smooth homogeneous reecting surface

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2. Detail reecting surface

Target During the production process of the planters, there are a lot of possible imperfections that

Excess amount of water

can occur on the surface structure. These encountered imperfections will be named and

In this subtopic there will be explained what happens if there is an excess amount of water

explained one by one. As a result recommendations are done to prevent the imperfections

added to the cement.

as much as possible, originated from goal to make the perfect planter.

Synthetic flakes The encoutered imperfections are the subtopics for this section and are defined as:

Smoothness The amount of smoothness or roughness of the surface of a planter will not only make

The surface of the planters to which synthetic flakes are added will be explained.

Synthetic fibers The surface of the planters to which synthetic fibres are added will be explained.

a difference in feel, but also determines the amount of light that will be reflected by the surface. This causes that a rough planter will be experienced in different way than a smooth planter.

Color

Steel fibers The surface of the planters to which steel fibres are added will be explained.

As said this section will name and explain imperfections that occur during the production

As easy as it sounds to make the planters completely white, the planters often are not.

process. The question may be whether it is possible or realistic to exclude all this

Various influences can cause different shades from white to grey or can even cause a part

imperfections of a handmade object. Maybe these imperfections can even be interesting

of the surface to be red.

as a hint to the way it was made, so they don’t have to be negative per definition.

Air bubbles Air bubbles are present on almost every planter. This is a difficult imperfection to counter and has various manifestations.

Cement pockets This is a phenomenon that occurs when on a certain area on the surface there is not enough water to react with for the cement.

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3. Rough cracked surface

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4. Pattern concrete from roughly cleaned mould

Smoothness Faces

Image 3 shows a phenomenon that can be found on the underside of many planters. The

The ultra high performance concrete has no coarse additives, what gives it the ability to

smooth face of the underside changes towards the corners in a rough cracked surface, that

follow the shape and texture of the mould in very ďŹ ne detail. This makes that the cleaning

is also brownish. The cracks may indicate dehydration of the concrete. This dehydration

marks of the outer plastic mould can be seen on the surface of the planter. After the

may be a result of uneven drying of the concrete. Although during the process the surface

formwork removal of these planters the cleaning procedure was changed to using water

was covered by several layers of plastic, the surface at the corners apparently did dry

with a soft scrouring pad, instead of the dry usage of a putty knife. As a result the next

faster.

planters had smooth faces again.

The main cause of this faster drying process at the corners will probably be an increased contact with the air in relation with the face further away from the corners. The water vapor releasing the concrete has little resistance in the corners, resulting in a dehydrated surface.

This pheonomenon emphasizes the importance of sealing the surface of the poured concrete watertight.

Image 4 shows the adaptability of the concrete to the texture of the mould. The plastic outer moulds that are placed in the cast iron outer moulds are used several times. After every use they have to be cleaned. In the beginning of the project this was done by using a putty knife. By doing this the putty knife left its marks on the relative soft plastic outer mould.

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5. Irregular surface plastic foil and petroleum jelly inside planter

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6. Detail irregular surface inside planter

The images 5 and 6 show a different expression of the adaptability of the concrete to the texture of the mould. The cardboard inner mould is wrapped with plastic foil, taped on speciďŹ c places to ensure the plastic foil stays in its place, and ďŹ nally greased with petroleum jelly. These steps are done to make sure the cardboard stays dry and can be used again, and to ensure the mould can be removed easily from the concrete.

Every inside of the planters show the crinkles from the plastic foil, the very smooth surface between the wrinkles from the petroleum jelly, and at some places an impression of a piece of tape. Therefore the inside of the planters reveal a lot about the way the planters were made. Since the planters will contain soil and plants, the insides will not be visible from the outside.

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7. Detail corner woodglue

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8. Detail corner woodglue

9. Detail corner universal glue with tape

Corners

The upper corners of the planters reveal a lot about the way the cardboard inner mould is glued to the plastic base cover. At ďŹ rst woodglue was used to glue the inner mould tot the base cover. The woodglue however does not constitute a strong binding with the plastic.

During the process this became clear by the inner mould drifting upwards in relation to the base cover. This was probably caused by realeased air from between the wrapped plastic foil and the cardboard inner mould. The woodglue was not strong enough to withstand this force.

Universal glue constitute a much stronger binding with the plastic base cover. Combined with a strong waterproof tape the phenomenon of the upward drifting inner mould did not occur anymore.

The uppercorners of the woodglued inner mould are ninethy degrees and reveal the texture of the woodglue. In contrast the uppercorners of the planters where universal glue and tape are used, are rounded and have a more homogenous surface.

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10. Differences color depending on covering plastic foil

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11. White corner

Colour Image 10 shows the differences in color depending on the positioning of the covering

This results in a faster drying process that explains the whiter color. When the framework

plastic foil. Over the white samples the plastic foil is stretched tightly over the surface of

is removed it also becomes clear that the longer the time is the planter has been removed,

the concrete. The leaving water vapor during the drying process now gets no chance to

the whiter the planter gets. This makes it possible the whiter corners will eventually

leave the concrete, resulting in a more gradual drying process.

disappear again.

In contrast to the white samples, the plastic foil is not stretched tightly over the surface

The white corners did not turn brownish as seen in earlier examples. A possible explanation

of the concrete. There is a space between the drying concrete and the foil. This gives the

is that the small cuts of the folding line are big enough to let the concrete get in contact

water vapor leaving the concrete during the drying process the chance to leave te concrete.

with the air, but are not big enough to let the water vapor leave.

When you look closely to the surface of the foil, you can see water drops hanging. The concrete of this sample dries faster and gets a brownish color. This color corresponds to the color of the superplasticizer. A presumption can be made that the faster drying process through the leaving water vapor from the concrete results in a different reaction between the cement and the superplasticizer, resulting in a brownish color of the concrete.

Image 11 shows a white corner, a phenomenon that can be recognized in a lot of planters that are made using a lasercutted plastic outer mould. During the production process two types of mould were used. Moulds that were handcut an moulds that were lasercut.

The advantage of the lasercutted moulds is that the size ďŹ ts perfectly in the cast iron outer moulds. However the corners of the plastic outer moulds are folded from a strip.

The handcut moulds are folded along a constant folding line. The lasercutted moulds howevere are not, they are folded along a line of small cuts.

The difference in color at the corners can be explained by the possibility that air can reach the concrete through the small cuts of the folding line made by the lasercutter.

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12. Air bubbles in smooth face

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13. Air bubbles in rough face

Air bubbles Image 12 shows air bubbles on the smooth face at the underside of a planter. Image 13 also shows air bubbles on the face at the underside of a planter, but this face is not smooth. There is a different cause for these air bubbles.

The air bubbles shown in image 12 originate from the pouring phase. The face around the air bubbles is mirror-like smooth and the air bubbles appear in the entire face. After the pouring process the surface of poured concrete gets covered by a piece of plastic.

Apparently there was still some air present between the poured concrete surface and the piece of plastic. This can be difďŹ cult to avoid because you sometimes can not see the air bubbles when you cover the surface with plastic.

The air bubbles shown in image 13 originate from the drying process. It is a form of dehydratation of the concrete in a mild form of the cracks as seen earlier. During the drying process it was possible for water vapor to leave the concrete resulting in this surface structure. Again this is an example that emphasizes the importance of sealing the surface of the poured concrete watertight.

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14. Cement pockets in corners

15. Mechanical fault line through cement pockets

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Cement pockets Images 14 and 15 show cement pockets that mainly occur in corners of faces. The most likely explanation for this pheonomenon is the leakage of water from the mould. In the beginning of the production phase there were malls that leaked. Later on the leaking moulds were not used anymore.

Image 15 also shows the reduced mechanical properties caused by the cement pockets.

The concerned planter is a planter from the beginning of the production process without ďŹ ber reinforcement. Later on synthetic ďŹ bres were added to absorb possible fault lines caused by the shrinking process. Image 15 shows that the face at the cement pockets is weakened and a fault line goes right through it. Not only from tectonic points of view but also from mechanical points of view it is very important to prevent cement pockets.

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16. White drop pattern on surface

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17. Detail drop pattern

Excess amount of water Images 16 and 17 show the faces of a planter where to an excess amount of water is added.

A drop pattern along the faces is clearly visible. This drop pattern makes this planter different than the smooth more homogeneous looking other planters, but can be found beautiful in its own way.

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18. Model with excess amount of synthetic akes

19. Detail marmoreal underside

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20. Detail leathery upside

Synthetic flakes For preventing shrinking cracks three types of reinforcement were tested. Images 18,19 and 20 show the sample of concrete reinforced with synthetic flakes. During the pouring process the concentration of the synthetic flakes appeared to be too high. This resulted in a very dense structure of tangled together balls of synthetic flakes. It became impossible to pour it in the shape of a planter explaining the appearance of the sample shown in image 18.

Image 19 shows a detail of the underside of the sample. The surface is very smooth and the flakes can be recognized, giving it an almost marmoreal appearance.

Image 20 shows the difference in appearance between the underside and upside of the sample. The underside is poured into a mould, making the surface very smooth and reflecting. In contrast the surface of the upside is not limited to the shape of the mould, the material can live its own live with regard to its shape and surface structure. The synthetic flakes can also be recognized in the upside, but in a complete other appearance than the underside. The surface has a almost leathery appearance with bumps of tangled together balls of synthetic flakes.

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21. Detail synthetic ďŹ bres

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22. Model with excess amount of synthetic ďŹ bres

Synthetic fibres Image 21 shows the surface of the underside of the planter were to synthetic fibres were added as reinforcement. The synthetic fibres only appear visibly at the undersides of the planters. This is caused by the fact that the synthetic fibres float on the poured surface of the concrete. Since the planters are poured upside down this phenomenon only appears at the undersides of the planters.

Image 22 shows a sample were to an excess amount of synthetic fibres is added. This sample was made in an early phase in the production process when the planters were not poured upside down, explaining the cement pockets at the underside. Apparently at the underside there was still some air present. In combination with the excess amount of synthetic fibres, the concrete was not able to spread evenly over the surface of the underside of the planter.

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23. Detail protruding synthetic ďŹ bres

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24. Detail concentration synthetic ďŹ bres in corners

Image 23 is an example of a planter from the early production process. The cardboard inner mould was glued with woodglue to the plastic base cover. Air between the wrapped plastic foil and the cardboard inner mould wanted to escape, causing the innermould to brake loose from the base cover and to float upwards. This caused the concrete to get into the inner mould.

The downside of the planter as shown in image 13 is in fact formed by a piece of cardboard from the inner mould. Because of the lack of concrete the way the synthetic fibres are normally placed in the concrete becomes visible. A more horizontal placement of the synthetic fibres in the picture can be recognized.

A more extreme example of synthetic fibres placed in the same direction and in a high concentration can be seen in image 24. During the pouring process the fibres were not spread evenly through the surface of the surface. The concrete gets poured in the middle of the mould causing the synthetic fibres to float to the corners of the surface of the planters.

Through the high density of the fibres the space between the fibres is not filled completely with concrete. When looked from the side of the planter the synthetic fibres are visible and the lower edge of the planter is not straight.

After this planter was removed from the formwork the pouring process got chainged.

During the pouring process the synthetic fibres get spread evenly through the surface using a spatula.

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25. Detail steel ďŹ bres corners

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Steel fibres Image 25 shows a planter where steel fibers were used as reinforcement. The steel fibres are much smaller than the synthetic fibres, but are also very sharp. At some corners the steel fibres extrude making it dangerous to hold the planter. Another difference with the synthetic fibres is that the steel fibres are visible as small dark lines on every face of the planter.

The image also shows most of the steel fibres are oriented vertically and that they can be seen mainly at the upper side of the faces. Where the synthetic fibres float during the pouring process, this proofs that the steel fibers sink.

When shrinking cracks appear, the cracks are oriented vertically. For the reinforcement thereby it is important to be orientated horizontally as much as possible. During a production process in a factory the steel fibres can placed in a specific orientation using a magnetic field which can fix this problem. For the production of planters on this scale however using magnetic fields is not a feasible option.

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TEC TO N IC S

Target Corners Faces

SH APE

26. Almost perfect ninethy degrees angle

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Target The encountered imperfections during the production process with regard to the shape will be named and explained in this section. These imperfections manifest themselves in for example patterns, cracks and edges, but now as a result in shape instead of surface structure. Further recommendations are done to prevent the imperfections as much as possible, originated from goal to make the perfect planter.

The encoutered imperfections are the subtopics for this section and are devided in: Faces Corners

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28. Concrete between outer cast iron mould and plastic mould

27. Place of closure outer plastic mould

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29. Concrete between outer cast iron mould and plastic mould

Faces Image 27 shows three phenomenons as a direct result of irregularities from the outer

The second cause is the deviation of the outer cast iron moulds. The sides of the cast iron

mould. These three phenomenons are the result of a displaced outer plastic mould.

mould get attached to each other by screws and little pins. However some pins moved

The place of closure of the outer plastic mould is a critical area. In the beginning of the

while attaching the sides causing the mould often to be a little bit smaller. When the

production process this place of closure was not taped to ensure it stayed in position, later

outer mould is smaller than the inner mould it is obvious that the inner mould will fold

on in the process this was changed.

somewhere. Later on in the production process the pins were inspected closely before adding the plastic moulds to prevent this phenomenon.

In the case of image 27 the two endings of the outer plastic mould have been slided along each other. This causes the corner not to be a ninethy degrees angle and causes the adjacent face to be skewed. The protruding edge at the upside of the face also tells the two endings of the outer plastic mould did not slide along each other in a straight way, making it possible for the concrete to get under the plastic mould.

Image 28 shows what happens when the concrete gets poured between the outer cast iron mould and the plastic mould. This happens when the outer plastic mould does not ďŹ t perfectly in the outer cast iron mould. A fold is created which gives the concrete the opportunity to enter the space between the plastic mould and the cast iron mould.

There are two possible causes the plastic mould does not perfectly ďŹ t in the cast iron mould. The ďŹ rst cause is that this phenomenon mostly occured at plastic moulds that were handcut. Logically the probability of deviation of these moulds is bigger than the probability of deviation of the lasercutted moulds.

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30. Thick sides through collapsed inner mould

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31. Uneven thickness sides

Image 30 shows what it looks like when the inner cardboard mould collapse. A cross shaped framework is placed in the cardboard mould to prevent it from collapsing. In the beginning of the production process these frameworks were not taped to the sides of the cardboard mould. This made it possible when the inner mould was turned upside down and placed in the outer mould to move. When the cross shaped framework is moved it does not support the sides of the cardboard mould anymore, making it possible to collapse through the pressure of the concrete. Later in the production process the framework got taped to the side of the inner mould to prevent this.

Image 31 shows the main reason to pour the planters upside down. In the beginning of the production process this was not the case. First the concrete was poured in the outer mould. Then the inner mould was pushed down in the outer mould to form the inside of the planter. During this pushing process it is very difďŹ cult to position the inner mould in a good way, making it very difďŹ cult to get planters with sides of an even thickness.

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32. Detail cracked corner

33. Detail protruding edge

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Corners The surface of the cracked corners as seen earlier generate the side view as shown in image 32. The underside of the planter is not straight and the cracks can be seen from the side.

Image 33 shows a protruding edge at the upside of the face. This happens when the outer plastic mould does not connect well to the base cover, making it possible for the concrete to get under the plastic mould and to form a protruding edge. The main reason the outer plastic mould did not connect well to the base cover is that the plastic mould does not ďŹ t perfectly in the outer cast iron mould. This phenomenon got explained on the basis of image 27.

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34. Detail wave pattern corner

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35. Detail cracked plastic outer mould

Image 34 shows a corner of a planter poured in a lasercutted plastic outer mould. The lasercutted moulds are folded along a line of small cuts instead along a constant line.

These cuts can be recognized in the shape of the corners of the planter.

Image 35 shows a detail of a cracked platic outer mould. This problem often occurs at the lasercutted moulds. The small cuts that were made to create the folding line also weakens the corners of the mould. After being used a couple of times the corners break and sometimes crack. The plastic outer moulds can only be used a limited amount of times.

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Mechanical Properties Acquired Knowledge UHPC

UH PC

37. Added concrete

36. Shrinking crack near corner planter

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38. Detail added concrete

Mechanical properties Image 36 shows shrinking cracks of the concrete that will occur at every planter when no

Packing concrete watertight

measures are taken. This problem can be prevented by various methods. Some methods

This is an important measure to prevent the concrete from getting dehydrated during

will be more effective than others. To reduce the risk of getting shrinking methods it is

the drying process. When the concrete is dehydrated differences in color, air bubbles and

recommended to use as many of these preventative methods as possible.

cracks can appear.

Using reinforcement

Protecting concrete against temperature variatons

The easiest preventative method to prevent shrinking cracks is to add reinforcement to the

During the pouring phase and drying phase it is important to protect the concrete against

concrete. There are many types of reinforcement available. For this experiment steel fibres,

temperature variatons. During the drying process the concrete first will heat up after which

synthetic flakes and synthetics fibres were used. Eventually synthetic fibres were found to

it will cool down again. Making concrete is an exothermic process. Cooling down too fast

be most useful for the final product.

will increase the chance of getting shrinking cracks. It is important to protect the concrete

The synthetic fibres can only be seen at the underside of the planters and are not visible

against these temperature variations by insulating the mould right after pouring. During

at the faces. During the pouring process it is important to spread the fibres out over the

this experiment this was done by using cotton wool as insulation material.

surface and avoid the fibres to accumulate at the corners, preventing the corners to have inconsistant shapes.

Images 37 and 38 show a planter where after two days of drying concrete was added.

Synthetic flakes are another viable option when the right concentration is chosen. When

During the pouring process the inner mould did float upwards causing the concrete to get

this does not happen it results in a very dense structure of tangled together balls of

into the mould. Therefore there was not enough concrete available to form the underside

synthetic flakes, making it impossible to pour in the right shape.

of the planter. Later on this was done by adding concrete to the already dried planter. A clearly visible dividing line is the result of this. From mechanical point of view the strength

Steel fibres can be useful for a production process in a factory, using a magnetic field to

of this connection can be questioned between the two parts of concrete poured with two

give the fibres the preferred orientation. Without using a magnetic field the steel fibres will

days in between.

sink into the concrete in a vertical orientation. For preventing shrinking cracks horizontally orientated reinforcement is required, proving the necessity of a magnetic field to prevent shrinking cracks. Another property of this type reinforcement is that the reinforcement is visible at the faces.

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39. Ability UHPC to follow shape of the mould in high detail

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40. Symbolic image experiment UHPC planters

Acquired knowledge UHPC Properties of the material Image 39 shows the ability of the UHPC to follow every shape of the mould in high detail.

Because the used UHPC contains no gravel it can follow almost any possible form of the mould. For the experiment of the UHPC planters image 40 is a symbolic image. It shows the amazing properties of the UHPC, but also always reveal the way it was made.

The properties of the material can be enumerated in the following way: Follows every shape but also imperfection of the mould, making it possible to make mirror-like surfaces, but also requires perfect moulds.

Ability to be made very thin. The ďŹ ne structure of the concrete makes it possible to be manufactured at thicknesses from two millimeters thick.

The porosity of the concrete can be composed as desired. The planters as made in the experiment are even waterproof.

Possible other applications For buildings higher strengths than normal concrete are reached, making it possible to reduce the amount of concrete needed. This can be a sustainable improvement in the current cement industry.

The ability to make the surface very smooth in combination with the ability to be waterproof UHPC can be an interesting alternative for porcelain in some cases. Examples could include bathroom applications, but also façades.

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Information Pictures

UHPC

SO UR C ES

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Information UHPC 1 CAE Nederland B.V. (2010) Serie; de productiemethode van elementen in vvUHSB. Retrieved at 26 October 2015, from http://www.uhsb.nl/?p=449

11 CAE Nederland B.V. (2010) Serie productie – deel 2; het mixen van vvUHSB. Retrieved at 5 November 2015, from http://www.uhsb.nl/?p=488

2 CAE Nederland B.V. (2010) Serie productie – deel 5; referenties productiemethode. Retrieved at 2 November 2015, from http://www.uhsb.nl/?p=597

12 CAE Nederland B.V. (2010) Serie productie – deel 2; het mixen van vvUHSB. Retrieved at 6 November 2015, from http://www.uhsb.nl/?p=488

3 CAE Nederland B.V. (2010) samenstelling deel 1; De water/cement ratio. Retrieved at 3 November 2015, from http://www.uhsb.nl/?p=209

13 CAE Nederland B.V. (2010) Serie productie – deel 4; nabehandeling (warmte-/stoombehandeling).

Retrieved at 6 November 2015, from http://www.uhsb.nl/?p=579

4 CAE Nederland B.V. (2010) samenstelling deel 1; De water/cement ratio. Retrieved at 3 November 2015, from http://www.uhsb.nl/?p=209

14 CAE Nederland B.V. (2010) Serie productie – deel 4; nabehandeling (warmte-/stoombehandeling).

Retrieved at 6 November 2015, from http://www.uhsb.nl/?p=579

5 CAE Nederland B.V. (2010) samenstelling deel 2; Hulpstoffen. Retrieved at 3 November 2015, from http://www.uhsb.nl/?p=248 6 CAE Nederland B.V. (2010) Serie; De samenstelling van vvUHSB. Retrieved at 3 November 2015, from http://www.uhsb.nl/?p=34 7 CAE Nederland B.V. (2010) samenstelling deel 4; Vezels. Retrieved at 3 November 2015, from http:// www.uhsb.nl/?p=278 8 CAE Nederland B.V. (2010) Serie; de productiemethode van elementen in vvUHSB. Retrieved at 4 November 2015, from http://www.uhsb.nl/?p=449 9 CAE Nederland B.V. (2010) Serie productie – deel 5; referenties productiemethode. Retrieved at 4 November 2015, from http://www.uhsb.nl/?p=597 10 CAE Nederland B.V. (2010) Serie productie – deel 5; referenties productiemethode. Retrieved at 5 November 2015, from http://www.uhsb.nl/?p=597

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Pictures Wrench, page 13 Manutan. (2015) Steeksleutel per stuk serie 44. Retrieved at 26 October 2015, from http://www. manutan.nl/nl/mnl/steeksleutel-per-stuk-serie-44

Models different mixers, page 22 CAE Nederland B.V. (2010) Serie productie – deel 2; het mixen van vvUHSB. Retrieved at 5 November 2015, from http://www.uhsb.nl/?p=488

Screwdriver, page 13 Datona. (2015) Platte schroevendraaierset 6-delig - KTG. Retrieved at 26 October 2015, from https:// www.datona.nl/platte-schroevendraaier.html

Remaining pictures Made by Fatma Aslan and Wilbert de Rooij

Gloves, page 16 Horeca J en P. (2015) Latex handschoenen. Retrieved at 26 October 2015, from http://www.horecajenp. nl/latexhandschoenen-p-13689.html Safety goggles, page 16 EHBO winkel. (2015) UVEX veiligheidsbril Astrospec Optidur NCH. Retrieved at 26 October 2015, from https://ehbo-winkel.nl/product/uvex-veiligheidsbril-astrospec-optidur-nch/ Lab coat, page 16 Reinke bedrijfskleding. (2015) Labjas De Berkel Hamar. Retrieved at 26 October 2015, from http:// www.reinkebedrijfskleding.nl/labjas-de-berkel-hamar Safety boots, page 16 Werkman Oost. (1938) Grisport veiligheidsschoen 70416 S3. Retrieved at 26 October 2015, from http://www.werkmanoost.nl/Grisport-veiligheidsschoen-70416-S3--p-18212.html Glass cup, page 18 A star. (13 May 2015) Great moments in science: mysterious killer chemical. Retrieved at 26 October 2015, from http://astar.tv/post/great-moments-in-science-mysterious-killer-chemical/ Superplasticizer, page 20 Amazon.de (2015) FLUP Betonfließmittel (PCE). Retrieved at 26 October 2015, from http://www. amazon.de/FLUP-Betonflie%C3%9Fmittel-PCE/dp/B009JRZKVO/ref=pd_bxgy_60_img_2/2778662366-1252536?ie=UTF8&refRID=0WCTFXKD8JKMKNJ3CJV4 Tap water, page 20 PeterReekmans.be (24 September 2009) Ook stijgende drinkwaterprijzen variëren enorm van streek tot streek in Vlaams-Brabant. Retrieved at 26 October 2015, from http://peterreekmans.typepad.com/ peterreekmans/2009/09/ook-stijgende-drinkwaterprijzen-vari%C3%ABren-enorm-van-streek-totstreek-in-vlaamsbrabant-.html

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