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Claudia Lösch | Philip Rieseberg Edited by Mike Schlaich | Regine Leibinger
Building with Infra-Lightweight Concrete Design | Detailing | Construction
Birkhäuser Basel
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Acknowledgments
This manual was created by numerous authors and with the assistance of many others. Special thanks go to Dr. Alexander Hückler, who contributed a large part of his research results on deflection measurements and the bonding, cracking, and deformation behavior of infra-lightweight concrete and made a significant contribution to this book with corrections and comments. Max Bauer and Prof. Matthias Schuler (Transsolar Energietechnik GmbH) wrote the chapter on dynamic simulations (Chapter 6.4). Dr. Arndt Goldack provided assistance with corrections and comments on Chapter 7. We would also like to thank the many members of staff, students, and tutors of the Chairs of Conceptual and Structural Design and of Building Construction and Design at Berlin Technical University who, with great personal commitment, were involved in simulations, designs, studies, test series, and the construction and testing of prototypes. Berlin, December 2017 Claudia Lösch, Philip Rieseberg, Mike Schlaich, Regine Leibinger
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Contents
Acknowledgments
5
1 Introduction
11
2 Theoretical Background
13
2.1
Definition and Classification of Infra-Lightweight Concrete
14
2.2
The Development of Lightweight and Infra-Lightweight Concrete
14
2.3
Conceptual Design Potential of the Material
19
3 Material Technology 3.1
Composition and Bulk Density Classes
3.2 Properties 4 Building Typologies
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25 26 27 31
4.1
Example Design of a Building
33
4.2
Infill Building
38
4.3
Linear Buildings
43
4.4
Single-Family House
45
4.5
High-Rise Building
49
5 Key Building Construction Details
55
5.1
Wall Construction Details
58
5.2
Floor Slab Connections
60
5.3
Balconies and Cantilevers
64
5.4
Window Connections
68
5.5 Foundations
78
5.6
86
Detail of Joint between Parapet and Flat Roof
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6 Fundamentals of Design 6.1
Table of Parameters for Initial Design Considerations
92
6.2
Infra-Lightweight Concrete in the Context of the Energy Conservation Directive (EnEV)
94
6.3
Building Physics Properties
95
6.4
Dynamic Simulation-Based Investigations
104
6.5 Eco-Balance
110
6.6 Costs
112
6.7
113
Legal Background
7 Calculation Procedures for Structural Design 7.1
Structural Design Principles
7.2 Durability
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91
117 118 120
7.3
Ductile Building Component Behavior
122
7.4
Base Values for Structural Design
123
7.5
Structural Design for the Ultimate Limit State
126
7.6
Structural Design for the Serviceability Limit State
133
7.7
Special Considerations for the Design of Components with GRP Reinforcement
141
7.8
Bonding Behavior and Concrete Cover
142
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8 Practical Construction Aspects
145
8.1
Suitable Formwork
146
8.2
Surface Design
146
8.3
Production and Building with ILC
154
8.4
Stripping Times and After-Treatment
155
8.5
Surface Protection – Water-Repellent Coating
156
8.6
Concrete Cosmetics and After-Treatment
156
9 Selected Buildings
161
9.1
Single-Family House in Infra-Lightweight Concrete, Berlin
162
9.2
Betonoase, Berlin
164
9.3
Single-Family House, Aiterbach
166
9.4
Small House I, Kaiserslautern Technical University
168
10 Appendix
171
10.1 Calculation of Design Values – Examples
173
10.2 ω-tables with Design Values
182
10.3 Editors and Authors
202
10.4 Literature
203
10.5 Index of Figures
209
10.6 Index of Tables
212
10.7 Index of Keywords
213
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1 Introduction
On the Use of This Manual This manual is the result of the interdisciplinary research project, entitled Infra-lightweight Concrete in Multistory Residential Buildings (INBIG), at the Chair of Conceptual and Structural Design of Prof. Mike Schlaich and that of Building Construction and Design of Prof. Regine Leibinger and Prof. Matthias von Ballestrem at Berlin Technical University, which received funding from the Future of Building research initiative of the Federal Institute for Research on Building, Urban Affairs, and Spatial Development (BBSR). This research project at TU Berlin focuses on infra-lightweight concrete, a thermally insulating lightweight concrete, which can be used for the construction of buildings without additional layers of insulation. A monolithic material that combines load transfer and thermal insulation can be used in robust, durable, and straightforward constructions and provides a high degree of conceptual design potential. These properties make this material a competitive alternative in terms of conceptual design, fire protection, and recyclability compared with the multilayer wall constructions common today. Infra-lightweight concrete has been the subject of research and development at the Chair of Conceptual and Structural Design at TU Berlin since 2006. During the first research phase [1], basic knowledge was established for the production and processing of the material and a first building was constructed. During the second phase [2], further significant development of the original infra-lightweight concrete was achieved, new information was obtained, and the basis for various research projects was created – such as the INBIG project. The findings from research activity carried out over a period of ten years are also included in this manual. The content is based on investigations in the context of thirdparty-funded projects, doctoral theses, and student projects and dissertations. It goes without saying that research is continuing; currently work is being carried out on optimizing the composition of the material. For this reason it is advisable to search for the latest research results when designing an actual project. This manual is aimed at illustrating the constructive and architectural possibilities of infra-lightweight concrete and at providing detailed help in the design of buildings with an envelope consisting of this new type of material.
The spectrum of subjects reaches from the technical introduction to the composition, manufacture, and properties of the material, through to approaches to the structural design, practical application details, and processing methods, as well as the design possibilities. The manual is conceived as a reference book and is sub divided into ten chapters. References to other chapters, external publications, and built examples help with the search for further information. The book provides a short overview of the historical development of the material and a short list of some exemplary buildings built of infra-lightweight concrete that are worth mentioning in the context of this publication. The authors’ emphasis is not on a comprehensive historical review or the compilation of all completed buildings using thermally insulating lightweight concrete for construction; instead, their aim is to include some exemplary applications of the material. The construction details illustrated are intended as a design aid and as inspiration for conceptual and construction design. These details reflect the current state of construction technology to the best of our knowledge. The practical suitability of the material for buildings has been convincingly demonstrated in several completed projects. In spite of this, infra-lightweight concrete does not – as of 2017 – have the benefit of general building control approval. As of that date, any projects require individual approval as a prerequisite for the use of the material. The approaches presented here can be used in the context of this procedure; however, in each individual case they should be checked, adjusted and, if necessary, modified to reflect the requirements of the respective building project. This manual is intended to promote the wider use of this useful building material and to make a contribution to the sustainable use of globally limited resources. The authors and publishers hope that the result of the multidisciplinary research presented here will encourage many readers to pursue similar courses of action.
11
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2 Theoretical Background
2.1 Definition and Classification of Infra-Lightweight Concrete 2.2 The Development of Lightweight and Infra-Lightweight Concrete 2.3 Conceptual Design Potential of the Material
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2 Theoretical Background
2.1 Definition and Classification of Infra-Lightweight Concrete
are limited, which is why industrially manufactured aggregates are important.
Infra-lightweight concrete is a constructive lightweight concrete with very low bulk density [1] that combines the load-bearing and thermally insulating functions of the building envelope in a monolithic material. In contrast to complex, multilayer wall constructions, building with infra-lightweight concrete results in straightforward, robust structures that are durable, require very little maintenance, and can therefore contribute to a sustainable use of resources. In spite of ever more strict energy conservation regulations, exposed concrete buildings involving sophisticated free-form designs can make a contribution to our building culture. Generally, different types of lightweight concrete (LC) are classified in terms of their structure, making a distinction between porous particulate and dense-structure (constructive) lightweight concrete. Porous particulate lightweight concrete types are characterized by a matrix of rock particles, which are bonded together with cement paste only at the points of contact; they are usually used for prefabricated components or building blocks [3]. By contrast, dense-structure lightweight concrete has a similar structure to that of normal concrete (NC). Its low bulk density is mainly achieved by using more lightweight rock particles, which can be manufactured industrially or are quarried from natural resources. Industrially manufactured aggregates include expanded clay, foam glass, and expanded slate. Natural alternatives include natural pumice stone, which does not need to be expanded – a process which does require a large amount of energy – and therefore has comparatively good properties in terms of ecology. However, natural pumice stone reserves
Infra-lightweight concrete 800 kg / m3
In addition to the dense structure and porous particulate lightweight concrete types there is also the group of porous lightweight concrete (foam concrete) and porous concrete, both of which are manufactured without coarse rock particles. The porous lightweight types of concrete use foaming agents for foaming the cement matrix, whereas porous concretes are manufactured in porous concrete works using air-entraining agents such as aluminum [4]. Infra-lightweight concrete is considered part of the group of dense-structure lightweight concretes. Owing to its low bulk density of less than 800 kg/m³, it is distinguished from the lightweight concretes defined in DIN EN 206 [5] (dry bulk densities of between 800 kg/m³ and 2,000 kg/m³). This gives rise to the prefix “ultra” (see Figure 2–1). Dense-structure lightweight concretes that have good compressive strength and low thermal conductivity and can therefore perform structural and insulating functions are referred to as insulating concretes [6]. Ultra-lightweight concrete is such an insulating concrete, which is characterized by a very good combination of compressive strength and thermal properties and, in accordance with Faust [7], is to be classified as High Performance Lightweight Aggregate Concrete (HPLWAC).
2.2 The Development of Lightweight and Infra- Lightweight Concrete Even though concrete has been used for two thousand years and modern reinforced concrete, in the last one hun-
Lightweight concrete
Normal concrete
γDR = 2,000 kg/ m3
Infrared
Heavyweight concrete 2,600 kg/ m3
Ultraviolet
[infra (Latin prefix) = beneath, under]
Figure 2-1 Classification of infra-lightweight concrete in accordance with dry bulk density ρDR [1]
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2.2 The Development of L ightweight and Infra-L ightweight Concrete
dred years, has been established as the most important building material, these developments indicate that the potential of this material has by no means been exhausted. In terms of lightweight concrete, infra-lightweight concrete can meet load-bearing and thermal insulation requirements, which have arisen as a result of the energy turnaround and the discussion on sustainability and climate change. The research at Berlin Technical University has resulted in infra- lightweight concretes with a bulk density of less than the normal bulk density of lightweight concretes, which makes it possible to build houses with exposed concrete walls without additional thermal insulation material. Below follows a short history of lightweight concretes through to infra-lightweight concrete. For the history of concrete, please refer to the specialist literature.
Lightweight Ships Interestingly, modern lightweight concrete construction started in shipbuilding: one of the early concrete structures includes a ship, the concrete barge by Joseph Louis Lambot. In order to save on expensive steel and weight, the United States started to manufacture lightweight concrete ships during the First World War. The USS Selma, a tanker, weighed about 7,500 tons and was 425 feet long! This was based on the patented idea of Stephen J. Hayde, who managed to produce lightweight rock particles from shale in the rotary furnaces used by his company, Haydite. The USS Selma was not completed until after the war, and was then successfully used for peaceful purposes for many years. These first successes led to the US Marines producing more than 100 cargo ships of lightweight concrete during the Second World War [8].
Antiquity The best-known early lightweight concrete structure is probably the roof of the Pantheon in Rome, which was started in AD 114 by Emperor Trajan and was completed about ten years later by Hadrian. In order to reduce the weight of the spherical shell, the Romans used tuff stone as a lightweight rock particulate for their opus caementicium.
Lightweight Concrete in Building Construction The experience gained in shipbuilding led to lightweight in situ concrete being first used in the USA in the 1920s and then also worldwide in building construction. The reduction in weight of the load-bearing structure led to savings in the foundations and a reduced mass in the case of earthquakes. The first high-rise building in lightweight concrete is thought to be the Park Plaza Hotel in St. Louis dating from 1929; better known are probably the 60-story-tall towers of Marina City in Chicago. The low weight of lightweight concrete and its good resistance to frost and thawing and to frost and de-icing salt can be beneficial in bridge construction. Particularly attractive examples are the Dyckerhoff pedestrian bridge in Wies baden-Schierstein designed by Ulrich Finsterwalder in 1967 and Maintenance Hall V at Frankfurt Airport by Helmut Bomhard, a stressed-ribbon construction from 1972 that is covered with lightweight concrete. In spite of their low bulk density, modern lightweight concretes can have high structural strength. The recently completed widely cantilevering roofs of the tramway stops in front of Berlin Main Railway Station were built using LC45/50 concrete that only weighs 1,600 kg/m³.
Figure 2-2 Roof of the Pantheon in Rome
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2 Theoretical Background
Figure 2-3 Tramway stop at Berlin Main Railway Station (source: Hans Joosten)
Figure 2-5 Dyckerhoff bridge at Schierstein Rhine Port (source: Cengiz Dicleli)
Figure 2-4 Marina City Towers
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2.2 The Development of L ightweight and Infra-L ightweight Concrete
Bridges Offshore structures
Industrial buildings, roofs, stadiums TU Kaiserslautern
Buildings
TU Berlin Oil crisis 1973
HPLWAC
Modified static resistance αHP
200 180 160 140 120 100 80 60 40 20 0 1950
1960
1970
1980
1990
2000
2010
2020
Year Figure 2-6 Historical development of the performance characteristics of lightweight concrete ([9], based on [10])
The Oil Crisis and New Lightweight Concrete
Figure 2-7 Lufthansa Maintenance Hall V (source: Yoshito Isono)
Expanding clay or glass to produce lightweight rock particles requires very high temperatures and therefore a high consumption of energy. As shown in Figure 2–6, the shock of the 1973 oil crisis and rising energy prices led to an almost twenty-year standstill in lightweight concrete construction. Naturally, lightweight concrete was, and continues to be, used in building and bridge construction owing to its low weight. Interestingly though, for some years, the idea of saving energy has once again led to lightweight concrete becoming attractive for building construction. The thermal properties of lightweight concrete were primarily rediscovered by Swiss architects, leading to the increased use of lightweight concrete in residential building. In his important book Architektonisches Potential von Dämmbeton [6], Patrick Filipaj demonstrates the diversity of modern Swiss exposed concrete construction.
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5 Key Building Construction Details
5.1 Wall Construction Details 5.2 Floor Slab Connections 5.3 Balconies and Cantilevers 5.4 Window Connections 5.5 Foundations 5.6 Detail of Joint between Parapet and Flat Roof
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The often cited quote “God is in the details” has frequently been credited to the architect Mies van der Rohe, though he is likely to have borrowed it from the art historian Aby Warburg. Mies van der Rohe seizes on the statement in the sense of an architectural principle that is effective between the overall appearance of a building and its constituent individual elements. Every detail of a construction reflects the spirit of the overall building. During the design process, the architect or designer always faces the same seemingly banal question: How do I actually do that in detail? The examples presented here are intended to provide basic answers to that question. An attempt is made to reflect the basic simplicity of a building made of infra-lightweight concrete. These details reflect the current state of construction technology to the best of our knowledge.
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5 Key Building Construction Details
5.1 Wall Construction Details
ETICS, standard U = 0.27 W/(m² · K)
Curtain wall facade U = 0.29 W/(m² · K)
Poroton S10 U = 0.26 W/(m² · K)
Scale 1:20
Infra-lightweight concrete ILC600 U = 0.30 W/(m² · K) (λ10°,dr) U = 0.34 W/(m² · K)
Infra-lightweight concrete ILC800 U = 0.36 W/(m² · K) (λ10°,dr) U = 0.41 W/(m² · K)
(λ: rated value)
(λ: rated value)
Detail 5-1 Comparison of different wall constructions in accordance with EnEV 2016 (external walls with an average thermal transmittance of U = 0.28 W/m² · K)
Comparison of different wall constructions in accordance with EnEV 2016 (external walls with an average thermal transmittance of U = 0.28 W/m² · K) Whereas in Germany no fixed requirements exist regarding the thermal resistance of individual building components because the transmission heat loss H'T relating to the entire heat-transferring envelope surface is considered instead, specific values must be achieved in other countries. In those cases, the necessary U-value can only be achieved with the thickness of the external wall.
In Germany it is possible to compensate for any inadequacy in the thickness of a building component with other compo-
nents (such as windows, roof, foundation slab, exposed parts of floor slabs, etc.). In the assessment of ILC, the rated value for thermal conductivity (λrv) was chosen as the parameter. This is approximately 20 percent above the measured value of the thermal conductivity (λ10°,dr) of ILC at 10 °C in dry condition. Note: Where complex building components contain a high proportion of reinforcement, the reinforcement may have to be included in the calculation of the U-value of the external wall.
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5.1 WALL5.1 CONSTRUCTION DETAILS High-Rise Building
ETICS, standard U = 0.21 W/(m² · K)
Curtain wall facade U = 0.21 W/(m² · K)
Poroton S10 U = 0.22 W/(m² · K)
Scale 1:20
Infra-lightweight concrete ILC600 U = 0.27 W/(m² · K) (λ10°,dr) U = 0.30 W/(m² · K)
Infra-lightweight concrete ILC800 U = 0.31 W/(m² · K) (λ10°,dr) U = 0.35 W/(m² · K)
(λ: rated value)
(λ: rated value)
Detail 5-2 Comparison of different wall constructions in accordance with EnEV 2016 less 20 percent (external walls with an average thermal transmittance of U = 0.21 W/m² · K)
Comparison of different wall constructions in accordance with EnEV 2016 less 20 percent (external walls with an average thermal transmittance of U = 0.21 W/m² · K) It is likely that, with the future introduction of the new Building Energy Act, the requirements relating to the building envelope will be made more demanding. The examples in the diagram show the effects of an approximately 20 percent change which, for the external wall, would mean an average thermal transmittance of U = 0.21 W/m² · K.
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5 Key Building Construction Details
5.2 Floor Slab Connections
Scale 1:10
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6.1
Table of Parameters for Initial Design Considerations
47
6.2
Infra-Lightweight Concrete in the Context of the Energy Conservation Directive (EnEV) 51
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6 Fundamentals of Design
6.1 Table of Parameters for Initial Design Considerations 6.2 Infra-Lightweight Concrete in the Context of the Energy Conservation Directive (EnEV) 6.3 Building Physics Properties 6.4 Dynamic Simulation-Based Investigations 6.5 Eco-Balance 6.6 Costs 6.7 Legal Background
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6 Fundamentals of Design
Infra-lightweight concrete is a very lightweight concrete used in construction that resembles conventional lightweight concretes in many ways but also differs significantly with regard to some properties. These properties must be taken into account in the design. In addition to load-bearing capability, construction details, and durability, this also affects building physics (thermal insulation, sound insulation, fire protection, etc.) and other issues such as the formwork striking time and of course costs. The next two chapters are intended to provide approaches to the design with infra-lightweight concrete. The information given here largely relies on ILC-specific findings that are research results from TU Berlin. Where no explicit results have yet been obtained for infra-lightweight concrete, we have relied on relevant literature as a source of design details. Infra-lightweight concrete is neither covered by the currently applicable standard nor has general building control approval been obtained for it. This means that all design approaches shown here must be checked, adjusted and, if necessary, adapted to the respective building project as part of a procedure for individual building control approval.
6.1 Table of Parameters for Initial Design Considerations When starting the design of a building with monolithic infra-lightweight concrete walls, many designers always face the same questions. For example, one of the architect’s first questions will be what wall thickness is required for meeting structural and building physics requirements. When this information is not readily available, the architect, structural engineer, and energy consultant need to spend a considerable amount of time in the quest for this information and relevant details. Often this lack of basic experience and the associated extra work input required are important reasons for both client and designer to avoid infra-lightweight concrete as an option for the envelope of a building. In order to fill this information void, at least in parts, several sample designs for residential buildings have been established, including the relevant structural calculations and building physics details, in accordance with the current state of knowledge (see also Chapter 4). The results of this study have been compiled in a table of parameters that is aimed at helping designers make initial decisions for the design of future buildings. It goes without saying that the table only provides a starting point for the continuing work and the details cannot be summarily applied; rather, the full design process needs to be carried out for each project. The table includes the possible number of stories of a building when using different bulk density classes of infra-lightweight concrete with wall thicknesses of 50 and 60 cm, taking the example of the freestanding apartment building described in Chapter 4.1. In view of the fact that the number of stories possible largely depends on the design and structural concept of a building, the details given should only be understood as guide values. More stories in a building are also feasible if the structural system and other design features are adjusted accordingly, for example, applying different ILC bulk densities across the height of the building.
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6.1 TABLE OF PARAMETERS FOR INITIAL 6.1 DESIGN TableCONSIDERATIONS of Parameters
7
7 6
6
6 5
5 Number of stories
Possible number of stories in the sample building for wall thickness d = 50 cm* Possible number of stories in the sample building for wall thickness d = 60 cm*
4 4
4 3 2
2 2
2 2
ILC650
ILC600
* Calculated on the basis of the boundary conditions of the sample building in Chapter 4.1, calculation of stress in concrete for centrally applied compression
1 0
ILC800
ILC750
ILC700
Figure 6-1 Number of possible stories in the sample building in Chapter 4.1 for different classes of ILC
The next diagram shows the U-values of the external walls for different bulk density classes and wall thicknesses. This information is based on the rated value for thermal conductivity (see Chapter 6.3.1).
0.45
0.45 ILC800 0.42
Thermal transmittance U W/(m 2·K)
0.40
0.39 0.36
0.35
Finally, the table of parameters shows the possible effects on a concrete project, taking into account the requirements resulting from EnEV 2016 [26].
0.34
0.41 ILC750 0.38 0.35 0.33 0.30
0.30
0.37 0.35
0.34
0.32
0.32
0.30
0.30
0.28
0.28
ILC700
ILC650 ILC600
0.26 0.25
0.20
45
50 55 Wall thickness d [cm]
60
Figure 6-2 U-values for different wall thicknesses and ILC classes (based on the rated value for thermal conductivity, see Chapter 6.3.1)
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6 Fundamentals of Design
Selected construction method
Proportion of window area
U-value, wall W/(m² · K)
U-value, window W/(m² · K)
U-value, roof W/(m² · K)
H'T permiss. EnEV 2016 W/( m² · K)
H'T permiss. Reference build. W/( m² · K)
H'T existing W/(m²· K)
Thermal bridge correction factor
Ratio of surface- to-volume A / Ve
Primary energy factor Heating + HW
4.1 Example of building type Free-standing building
ILC800 ILC700 ILC600
60
7
In situ concrete/ prefabricated part
34%
0.34
0.88
0.14
0.50
0.56
0.47
0.05
0.32
0.7
4.2 Infill building, free-form
ILC800 ILC700 ILC600
50
7
In situ concrete
44%
0.41
0.87
0.14
0.65
0.50
0.46
0.10
0.23
0.7
4.2 Infill building, loggia facade
ILC800 ILC700 ILC600
50
7
Prefabricated part + in situ concrete
36%
0.41
0.96
0.14
0.65
0.48
0.48
0.10
0.19
0.7
4.3 Linear row of buildings, Rear wall in ILC
ILC800 ILC700 ILC600
60
7
In situ concrete
30%
0.30
0.95
0.14
0.50
0.54
0.50
0.10
0.31
0.7
4.4 Single-family house Villa
ILC800 ILC700 ILC600
60
3
In situ concrete
22%
0.34
0.95
0.14
0.50
0.61
0.49
0.10
0.53
0.7
4.5 High-rise building with bar walls
ILC800 ILC700 ILC600
60
17
Prefabricated part + bar wall
34%
0.30
0.67
0.14
0.50
0.62
0.48
0.10
0.24
0.7
Project / Parameter
Formulation
Selected number of full stories
Thermal insulation details/Requirements as per EnEV 2016
Selected wall thickness ILC [cm]
General parameters, ILC
Table 6-1 Table of parameters for sample buildings designed using ILC [27]
6.2 Infra-Lightweight Concrete in the Context of the Energy Conservation Directive (EnEV) Infra-lightweight concrete has both insulating and load-bearing properties. The lower the bulk density of a lightweight concrete, the lower its thermal conductivity, but as a rule its compressive strength is also reduced. This implies that thermal conductivity through concrete can only be avoided to a certain degree, because a certain degree of load-bearing capability must also be ensured. Even though the development of the material has by no means reached the end of the road, such a material implicitly cannot compete with non-load-bearing thermal insulation that has been designed for insulation only. In wall thicknesses of 55 to 60 cm, which
are just about still acceptable, this results in U-values above those for common multilayer wall constructions such as composite thermal insulation systems. In contrast to other EU countries, Germany does not impose special requirements for individual building components, which means that the relatively “poorer” values of an external infra-lightweight concrete wall can be effectively compensated for with other building components. Following the introduction of the Building Energy Act (GEG) [28], which as of 2017 has been submitted to the respective German Federal Ministry, new requirements for residential buildings are likely to apply in Germany from 2021. In particular, the stationary consideration of the transmission heat loss H'T regarding the heat-transferring building envelope will be omitted. From then on, the requirements for the reference building will apply.
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6.3 Building Physics Properties
In this context, the use of active wall insulation systems powered by renewable energy would appear the most sensible solution in order to fulfill the often stationary requirements for building components in other EU countries or to comply with generally increased insulation standards. The infra-lightweight concrete mixtures available at the time of the publication of this manual already have a significantly lower thermal conductivity than conventional lightweight concrete mixtures. We can assume that the values currently being achieved for thermal conductivity can be further improved in future by optimizing the formulation (see also [15]).
6.3 Building Physics Properties 6.3.1 Thermal Conductivity / Thermal Transmittance Requirements In the current EnEV, the U-value for the external walls of the EnEV reference building for target temperatures in heated rooms of ≥ 19 °C is stated as U = 0.28 W/m² · K [26]. However, as explained in the previous section, in contrast to other EU countries, in Germany no special requirements are stipulated for individual building components (as of 2017). This means that the specified U-value of 0.28 W/m² · K is not mandatory but should be understood as a guide value. Instead, the requirements relating to transmission heat loss and to primary energy for the building as a whole must be met.
Test Values and Calculation Basis The thermal conductivity of infra-lightweight concrete was determined by KIWA GmbH, an approved inspection body in Berlin, using the guarded hotplate method [29]. As part of this process, the test specimen was first dried and then tested at a temperature of 10 °C. The measured value is expressed as λ10°,dr. The test was carried out for ILC800, ILC650, and ILC600 and the values for ILC700 and ILC750 were calculated by linear interpolation. In real-life conditions, it is common for building components to have a certain moisture content, which increases the thermal conductivity compared to the dried test specimen and
thereby reduces the insulating effect. In order to be able to take real-life conditions into account, the measured value λ10°,dr is converted into the rated value for thermal conductivity λrv in accordance with DIN EN ISO 10456 [30]. The conversion also takes into account the statistical quality of the measured data, allowances for temperature and for moisture content, as well as for aging. The calculation of the rated value λrv was carried out for ILC800 in accordance with the composition in Table 3-2 as an example, and the calculated increase over the measured value λ10°,dr was then adopted for the other ILC classes. The following should be noted regarding the calculation of the rated value of ILC800: nn The statistical quality is taken into account via the number
of measured values obtained (here n = 3). It may be possible to achieve an improvement, that is, a reduced allowance, by carrying out further testing to increase the number of measured results. This has been planned as part of the ongoing research activities at TU Berlin. nn The conversion factors for temperature and moisture content were determined for an ambient temperature of 23 °C and 80 percent relative humidity. For this condition, DIN EN ISO 10456 states a moisture content of u = 0.03 kg/kg for lightweight concrete with expanded clay aggregate. This value was confirmed in experimental investigations with ILC800, which means that the values in the DIN can be used for ILC. nn There is no clear definition of the effects of aging. The standard does not contain any references to conversion rules. In this respect, no long-term data is as yet available for infra-lightweight concrete. From what we know to date, we assume that ILC is not subject to significant aging processes that affect thermal conductivity. We therefore propose to use the factor of 1.0 for aging. We would like to point out here that, where other compositions than those in Table 3-2 are under consideration, the rated value has to be determined separately on the basis of the respective test results for thermal conductivity, and that the allowances/ values listed here are not transferable. As an alternative to the calculation of the rated value, it is possible to carry out a test at the appropriate test levels, that is, at an ambient temperature of 23 °C and 80 percent relative humidity. 95
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6 Fundamentals of Design
For the composition shown in Table 3-2, the rated values λrv listed in the following table have been established, as well as the associated thermal transmission values for wall thicknesses of 50 to 65 cm. The U-value was determined using the following formula: U=
1
Rsi +
d rv
+ Rse
[W/(m2 K)]
(2)
whereby Rsi = 0.13 [m² · K/W] internal heat transmission resistance with a horizontal flow of heat [31] Rse = 0.04 [m² · K/W] external heat transmission resistance [31] d: wall thickness [m] λrv: rated value of thermal conductivity [W/m · K]
Conclusion The current EnEV (as at 2017) does not stipulate mandatory limit values for the thermal transmittance of external walls. The U-value of ILC walls measuring between 50 cm and 65 cm in thickness lies between 0.41 and 0.24 W/m² · K. This means that, in most cases, the external ILC walls exceed the guide value of U = 0.28 W/m² · K of the EnEV reference build-
Property
ing. However, this can be effectively compensated for with other building components.
6.3.2 Resistance to Frost and Thawing Requirements As a rule, infra-lightweight concrete is used as an external building component, the vertical surface of which is exposed to rain and frost; in accordance with the informative examples of EC2 [20], this would mean exposure class XF1 (moderate water saturation without deicing agent). Exposure class XF3 refers to environmental conditions that lead to high water saturation without deicing agent. With respect to normal concrete, EC2 mentions the informative example of horizontal surfaces directly exposed to the weather. The latter is not very likely / should be avoided when using infra- lightweight concrete in construction. However, it should be noted that, in accordance with findings to date, ILC tends to retain water for longer than normal concrete owing to its structure, which can also lead to a higher degree of saturation in vertical building components. Therefore it may be worth considering whether ILC used in a vertical external wall directly exposed to the weather should be classified as XF3 rather than XF1.
Test Result and Allocation to Exposure Classes In order to investigate in detail the frost-thawing resistance of infra-lightweight concrete, experiments [32] were carried
ILC600
ILC650
ILC700
ILC750
ILC800
Thermal conductivity λ10°,dr [W/m)]
0.141
0.153
0.166*
0.178*
0.193
Rated value of thermal conductivity** λrv [W/m · K]
0.160
0.174
0.189
0.202
0.219
U-value for 50 cm wall thickness [W/m² · K]
0.30
0.33
0.35
0.38
0.41
U-value for 55 cm wall thickness [W/m² · K]
0.28
0.30
0.32
0.35
0.37
U-value for 60 cm wall thickness [W/m² · K]
0.26
0.28
0.30
0.32
0.34
U-value for 65 cm wall thickness [W/m² · K]
0.24
0.26
0.28
0.30
0.32
*by linear interpolation **allowance for ILC800 calculated and for ILC600 to 750 adopted
Table 6-2 Thermal conductivity and thermal transmittance of infra-lightweight concrete for different compositions as per Table 3-2
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6.3 Building Physics Properties
out with ILC800 and ILC600 in accordance with DIN CEN/ TS 12390-9:2006 [33]. The results showed that ILC800 fulfills the acceptance criterion for XF3 as modified in accordance with Faust [7] via the dry bulk density, which is why ILC800 can be considered suitable as XF3 and XF1. However, the results for ILC600 were significantly above the acceptance criterion for XF3. It is not possible to make a statement regarding XF1 because no recommendation for an acceptance criterion was given [32]; however, the fact that XF3 was clearly exceeded suggests that XF1 is not achieved without protective surface coating. Property Weathering (mean value) [g/m²] Acceptance criterion for XF3 in acc. with [32] [g/m²]
ILC600
ILC800
1,620
262
275
374
Table 6-3 Frost-thawing resistance of ILC600 and ILC800 in accordance with the composition in Table 3-2, based on [32]
DIN 1045-2 specifies minimum requirements for lightweight concretes for different exposure classes, such as cement content, water/cement value, etc. For example, the minimum cement content for XF1 is 280 kg/m³ and for XF3, 300 kg/m³ (270 kg/m³ in each case when aggregates are taken into account) [34]. As can be seen from the composition in Table 3-2, the cement content of ILC600 to ILC700 inclusive is under 270 kg/m³; only that of ILC800 is over 300 kg/m³, and that of ILC750 is 296 kg/m³. Assuming the transferability of the criteria to infra-lightweight concrete, it follows that ILC600 cannot be assigned to exposure class XF1 (ILC800 fulfills the requirements for XF3, which is borne out by the test results of the frost-thawing test). When assessing the results of the frost-thawing investigations, note should be taken of the fact that the tests were designed for normal concrete and its behavior during the capillary absorption of moisture. By contrast, in accordance with findings to date, ILC will absorb water over a longer period of time, which is why a higher degree of saturation must be assumed especially toward the end of the test, which would indicate more severe damage. Whether such an increased degree of saturation occurs in practice depends on the boundary conditions of the installation, such as the application of water-repellent coating.
Conclusion ILC800 in the composition as listed in Table 3-2 fulfills the requirements of exposure classes XF1 and XF3 also when directly exposed to the weather, that is, without surface protection. By contrast, ILC600 as listed in Table 3-2 should not be used where directly exposed to the weather, but should be given an appropriate surface protection coating. As was also shown in the tests regarding exposure to direct rain in Chapter 6.3.6, water-repellent coating generally makes sense for external ILC building components of all ILC classes. This would result in a significantly reduced risk of frost-thawing damage. Further experiments should be carried out to prove this point.
6.3.3 Water Absorption and Depth of Penetration Requirements Regarding the penetration of water, a material can be assessed using two different parameters: the water absorption coefficient that describes the capillary absorption capability, for example during continuous exposure to rain or driving rain, and the water penetration depth that takes into account penetration under pressure. Standards and regulatory instruments with specific requirements for the classification of water penetration depth are not available. Examples are available for waterproof concretes, with limit values of 50 mm (see, for example, [35]). However, this criterion should not be used for ILC since it is not possible to preclude the water penetration depth progressing over time.
Testing for Water Absorption and Depth of Penetration During internal research work, the water absorption coefficient for ILC800 and ILC600 as per the composition in Table 3-2 was tested in accordance with DIN EN ISO 15148 [36].
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8 Practical Construction Aspects
8.1 Suitable Formwork 8.2 Surface Design 8.3 Production and Building with ILC 8.4 Stripping Times and After-Treatment 8.5 Surface Protection – Water-Repellent Coating 8.6 Concrete Cosmetics and After-Treatment
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8 Practical Construction Aspects
8.1 Suitable Formwork The properties of formwork have a significant impact on the result of exposed concrete quality. In practice, wood-based shuttering panels are frequently used, in particular for in situ concrete construction. Many different products are available that differ in strength, quality, and coating, etc. One property that has a significant impact on the appearance of exposed concrete is the suction behavior of the shuttering material. As a rule, shuttering with open-pored surfaces (allowing suction) results in darker, slightly rough surfaces that have few pores and air voids. By contrast, shuttering without suction results in smooth, lighter surfaces. In order to identify suitable shuttering material for infra-lightweight concrete, various shuttering panels have been tested with different coatings and suction behaviors [100]. The release agent used was a partially synthetic universal release agent that does not mix with water and does not contain solvents [101]. The results were in line with expectations: for example, a plywood panel consisting of birch wood with a special film coating on one side allowing slight suction resulted in a slightly rough surface with few pores and air voids. On the other hand, a plywood panel consisting of birch wood with phenolic resin film coating on both sides allowing no suction resulted in a smooth surface with an even distribution of pores (see Figure 8-1).
Conclusion Where the surface of an infra-lightweight concrete component is intended to have few pores, the use of shuttering panels with a degree of suction is recommended (alternatively it is also possible to use fleece; see Chapter 8.2). The tests carried out with ILC800 produced satisfactory results.
8.2 Surface Design This chapter contains a systematic listing of the different surface design options for infra-lightweight concrete. The measures taken into consideration are the use of matrix formwork, textured shuttering surfaces achieved with a range of materials, and the use of pigment additives. Options for after- treatment of completed surfaces, such as sanding, oiling, waxing, etc., are dealt with in the following chapter.
Some Basic Aspects of Infra-Lightweight Concrete Surfaces As in normal concrete mixtures, the outer exposed surface of infra-lightweight concrete is formed from the fine cement matrix. The surface qualities resulting from the use of a wide range of shuttering materials were tested as secondary results in the context of several research projects and student works. The result of these investigations allows the conclusion
Figure 8-1 Examples of ILC800 surfaces achieved using shuttering with special film coating with no suction (left) and with birch plywood panel shuttering allowing slight suction (right) [27]
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8.2 SURFACE DESIGN
Figure 8-2 Infra-lightweight concrete prototypes and surfaces; left: ILC800, right: ILC600
that – provided the correct ILC formulation for higher bulk densities is used – similar surface designs are possible to those achieved with normal concrete. The popular formulations of about 800 kg/m³ allow the widest design range, because the surfaces tend to be more uniform and have fewer pores. The very lightweight concrete formulations below approximately 700 kg/m³ in particular are highly porous and therefore tend to result in more irregular-looking surfaces, which may require more extensive after-treatment. The prototypes of a wall component with window shown in Figure 8-2 were produced with different concrete formulations. The formulation with 800 kg/m³ results in a contiguous exposed concrete surface (in this case the visible lines are the result of the small concrete batches being poured), whereas the formulation with 600 kg/m³ resulted in a very uneven surface, even though the shuttering had been optimized for infra-lightweight concrete, that is, it had a high-suction surface.
Using Nonsuction Concrete Matrix Formwork Made of Plastic The use of nonsuction matrix formwork made of plastic delivered a very convincing result in terms of surface quality. This formwork was tested in a dedicated series of studies on the subject of surface quality of infra-lightweight concrete using several uniform test specimens measuring 50 cm × 50 cm × 10 cm. In infra-lightweight concrete too, the surfaces of smooth textures (ribs, waves, and studs) remain smooth, closed, and almost free from faults. Shuttering patterns with more pronounced profiles also showed convincing results, which is partly due to the self-compacting property of the ILC. Very sophisticated reliefs (timber imitation or photoengraving) showed small concentrations of pores in areas with pronounced patterns.
These results can be transferred directly to the surfaces of textured formwork patterns; here too the more lightweight concrete formulations result in similar effects.
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8 Practical Construction Aspects
Figure 8-3 ILC component with ribbed surface
Figure 8-4 ILC component with wood-plank-textured surface achieved with plastic matrix formwork
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8.2 Surface SURFACE Design DESIGN
Figure 8-5 ILC component with photoengraved surface
The strength of infra-lightweight concrete is less than that of common normal concrete of lightweight concrete formulations. Shapable, flexible formwork suits the material well, particularly when the shuttering geometry is complex, because the risk of breakage and spalling at the more sensitive edges is reduced. We can therefore state that special matrix formwork consisting of flexible materials is particularly suitable for infra-lightweight concrete.
Use of High-Suction Formwork – Wood, Fabric, and Organic Materials When using natural formwork materials such as wooden boards, chipboard, or OSB (oriented strand board), it is important to use separating oil in the precise formula for the respective material and to observe the correct point in time for stripping the formwork. Generally it can be said that, similar to shuttering panels commonly available in the market, here too the high-suction surfaces result in the reduction of air pores and velvety but smooth surfaces (see also Chapter 8.1).
If insufficient separating oil is applied to the geometrically uneven high-suction surfaces, too much water is taken out of the concrete during the curing process; this means that the surface becomes too soft and bits of concrete remain attached to the formwork. However, if too much separating oil is applied, the concrete surface will be discolored unevenly. When using natural wood it is therefore recommended to test the correct application of separating oil for the respective surface using prototypes. With building materials that have very irregular and heavily patterned surfaces, such as OSB, it is common for parts of the concrete to remain attached to the shuttering boards, particularly in places where the concrete runs behind the shuttering material.
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9 Selected Buildings
9.2 Betonoase, Berlin Architecture: Gruber + Popp Architects, Berlin Structural design: schlaich bergermann partner sbp GmbH, Berlin
Figure 9-5 Youth center in Berlin (photo: Alexander Blumhoff, Berlin)
Figure 9-6 Youth center in Berlin, cross section (source: Gruber + Popp Architects)
Key material parameters of the outside walls in monolithic infra-lightweight concrete: nnDry bulk density: 700 kg/m³ nnAverage compressive strength: 9.4 MPa nnThermal conductivity λ10°,tr: 0.166 W/m · K nnExternal walls: 50 cm nnGalvanized steel reinforcements
The new leisure center for young people, Betonoase, was constructed in Berlin Lichtenberg in 2017. The target group for the venue are children and youths from eight to eighteen
years. In order to do justice to the complexity of the brief, the architects produced an understated design in terms of appearance and construction, which nevertheless has its inherent quality. The load-bearing single-story walls consist of monolithic infra-lightweight concrete. A special feature is the projecting concrete canopies, which are back-anchored to the concrete walls without additional decoupling details. In accordance with the client’s wishes, the new building is intended to exemplify the basic idea of sustainable building with optimized energy conservation.
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9.2 BETONOASE, BERLIN
Roof construction: – Extensive roof greening – Vegetation layer, 7 cm – Drainage layer, 3 cm – Bitumen roofing membrane, DIN EN 13707 (V13), 2 mm – Extruded polystyrene 025 – Bitumen roofing membrane, DIN EN 13707 (V13), 2 mm – Concrete C 30 / 37, 32 cm, reinforcement content: approx. 125 kg/m³
Floor construction: – Asphalt screed in 2 layers, ground, 7 cm – Mineral insulation (heat-resistant), 15 cm, PP membrane, ≥ 0.05 mm – Floor slab, nonreinforced concrete C16/20, 20 cm – Extruded polystyrene 035, 20 cm – Layer of gravel, 5 cm Strip foundations: – Concrete C16/20, 80 × 45 cm, nonreinforced, normal compaction of base of trench – Extruded polystyrene 035, 5 cm
+–0.00 = 36.65 above MSL (prev. 36.75)
–0.39
–1.05
Figure 9-7 Youth center in Berlin, section through facade (source: Gruber + Popp Architects)
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10.7 Index
10.7 Index
A after-treatment 155 air void content 28, 154
exposed to weather 156 exposure class 96 exposure to the weather 97
B
F
balcony 36, 64ff. Baroque 21 bar wall 51 bending 129 bonding behavior 142 building component –– slender 122 –– nonreinforced 119 building component behavior, ductile 122 Building Energy Act 94 building height 34 bulk density class 26
facade 40 fatigue strength coefficient 119 finishing treatment 156 fire safety, fire protection 101 flat roof 86ff. floor slab connection 60ff. formwork 146ff. framework model 128 freeform 40 foundations 78 foundation slab 79, 81
C
general building control approval 113 global warming potential 111 GRP reinforcements 121 GWP (global warming potential) 111
carbonation 112, 120, 156 color additives 153 compaction 28, 154 composite creep 125 concrete cover 122 concrete surface mark 154 corrosion behavior 120 cosmetic treatment of concrete 156f. costs 112 creep 139 creep coefficient 124 cross section value, notional 123
D deflection 136, 140f. deformation 135, 141 deformation model 137 degree of shrinkage 126 dimension of opening 35 discontinuity area 128 driving rain 100 drop height 154 dry bulk density 27 ductility 141
E eco-balance 110 Energy Conservation Directive (EnEV) 94
G
H heat capacity, specific 99 high-rise building 49 hydration heat 28
I INBIG 11, 18 individual building control approval 112, 114, 118 infill building 38 insulating concrete 14 interaction diagram 129
L life cycle costs 113 lightweight concrete 14 –– dense structure 14 –– porous particulate 14 limitation of crack width 133 linear buildings 43 load assumption 126 load-bearing capability 126 loggia 52 longitudinal compressive force 127
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10 APPENDIX
M
T
material safety coefficient 119 minimum concrete cover 101 minimum reinforcement 133f., 143 mixing process 154 modulus of elasticity 27
temperature development 28 tension stiffening 139 thermal bridge 108ff. thermal bridge loss coefficient 108 thermal insulation, active 104 thermal insulation, in summer 104 thermal transmittance coefficient 95 timber construction 44 torsion 132
N number of stories 92f.
O object, epistemic 20
U U-value 93, 94
P parapet 86ff. poché 21, 46 pressure from uneven distribution 128 proportion of window area 52
R reinforcements 121 relative humidity 107 research 18 resistance to frost and thawing 96
V villa (freestanding residence) 45
W wall, nonreinforced 127 wall construction 58 water absorption 97 water-repellent treatment 100, 120, 156 water vapor diffusion 99 water penetration depth 97 window connection 68ff.
S sanding 157ff. self-compacting 28 self-weight 126 service life 112f. shear force 132 silica fume 27, 110 simulation –– hygric 107 –– thermal 104 single-family house 45, 162, 166 sizing diagram, general 131 slenderness 129 slump flow 27 solidity coefficient 125f., 129, 134 sound insulation 102 sound insulation value 43, 102f. standard 118 stress-strain curve 123 stripping time 155 story 34 serviceability 119, 133 surface design 146
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Translation from German into English: Hartwin Busch Copy editing: Keonaona Peterson Project management: Alexander Felix, Nora Kempkens Production: Amelie Solbrig Typesetting: Sven Schrape Paper: Magno Volume, 135 g/m2 Printing: optimal media GmbH, Röbel/Müritz Library of Congress Control Number: 2019957284 Bibliographic information published by the German National Library The German National Library lists this publication in the Deutsche Nationalbibliografie; detailed bibliographic data are available on the Internet at http://dnb.dnb.de. This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, re-use of illustrations, recitation, broadcasting, reproduction on microfilms or in other ways, and storage in databases. For any kind of use, permission of the copyright owner must be obtained. ISBN 978-3-0356-1925-6 e-ISBN (PDF) 978-3-0356-1926-3 Original German Edition: © 2018, Infraleichtbeton. Entwurf, Konstruktion, Bau by Fraunhofer IRB Verlag, ISBN (Print): 978-3-8167-9881-1 © 2020 Birkhäuser Verlag GmbH, Basel P.O. Box 44, 4009 Basel, Switzerland Part of Walter de Gruyter GmbH, Berlin/Boston 9 8 7 6 5 4 3 2 1
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