Advances in Building Materials

Constant time for double the amount.

\(P(t)=P_0 e^{kt}\)

\(P(t)\)  amount at time t

\(P_0\) initial amount

\(k\)  rate of growth

Shortening time for double the amount.

The utilization rate of natural resources does not exceed that of their regeneration.

The consumption rate of non-renewable resources does not exceed the rate of development of renewable substitutes.

The amount of pollution and waste does not exceed what the environment can absorb.

To preserve the environment:

• by measures to protect its quality
• by the restoration, accommodation, and maintenance of habitats essential to species
• as well as by sustainable management of the exploited animal and vegetable species

To improve social equity:

• to satisfy the needs of present and future human communities
• to improve life quality, for instance through access to quality housing

To improve economic efficiency

• to favor optimal management of human, natural, and financial resources
• in order to satisfy the needs of human communities, for instance by corporate and consumer responsibility

Environmental Performance Index

When human activities may lead to morally unacceptable harm that is scientifically plausible but uncertain, actions shall be taken to avoid or diminish that harm.

Morally unacceptable harm refers to harm to humans or the environment that is...

• ...threatening to human life or health, or
• ...serious and effectively irreversible, or
• ...inequitable to present or future generations, or
• ...imposed without adequate consideration of the human rights of those affected
• ...

Preserve the environment:

• measure and limit the emissions of trace metals
• limit the emissions of greenhouse gases
  • reducing the consumption of fossil fuels
  • recycling cementitious materials
  • capture and sequestration of emitted CO2
  • developing clinker replacements
  • researching new solutions
• Exploitation and landscaping of quarries
•  

NOT FINISHED

The conversion of waste materials into new materials.

Strictly speaking: Production of the same new material from waste material. (e.g. paper)

Recycling of waste material resulting in new material of lower quality or less functionality.

Recycling waste material resulting in a new material of higher quality or better functionality.

28% (Africa) up until 65% (Europe, Northern America)

Latin America, Asia-Pacific around 50%

• Deconstruction
• Sorting/Cleaning
• Fragmentation
• Production

Is it worth the effort? Yes, but take into account...

• Selective Deconstruction
• Energy for Transport
• Energy for Shredding
• Attainable performance
• Specific challenges for common building materials

7% Quarrying

85% Pyroprocessing

• 50% direct release from calcination
• 35% from fuel and energy consumption

5% Grinding

3% Transportation

It is used for ~10 years in new construction

Useful and important, but:

• not very efficient in terms of CO₂ emissions,
  because aggregates are recycled and not the binder.
   
• Recycled aggregates have usually higher water absorption and lower strength
  and the rheological properties are changed compared to new concrete
  (below a fraction of 25% of recycled aggregates there is no difference!)

Transport distances can be reduced as the use of natural gravels requires long transport routes.

• with aggregates containing at least 25% concrete or mixed demolition granulates
   
• Minergie-Eco: requires that at least 50% of all building elements,
  which can be produced from recycled concrete are using it.
   
• If no usable recycled concrete is situated within a radius of 25km around the construction site,
  these requirements will not be applicable.
   
• Use of recycled concrete with a higher percentage of aggregates (at least 40%)
  can be taken into account.
   
• Use of recycled gravel as filler material replacement, for foundations, etc.
  can be taken into account.

A combination of

• CO2 reduction
• resource conservation

might be possible by carbonation of aggregates before they are used again for recycled aggregate concrete.

Improvement of recycled concrete by a reduction of porosity.

The recycling rate is only around 1.5% (2015)

Main limitations for commonly used Expanded Polystyrene (EPS)

• Lacking recycling systems
• Lacking incentives for recycling
• Current installation and deconstruction practices
  (gluing to the wall leads to contamination with plaster/glue)
• Toxic flame retanrdants

Alternatives to commonly used EPS

• Foamed mineral insulation materials, produced from construction waste
• Natural fibre boards and fibrous materials such as cellulose fibers blown
  into hollow spaces in a building (avoiding adhesives)

Main limitations by:

• The use of purely natural wood is the exception
• Wood-based products are mainly produced with the aid of adhesives
• Wood coatings for retarded moisture uptake or improved UV stability
• Biocide treatments (e.g. micronized copper) for improved durability

Most of the recycled wood is used for particle board production.

Urban Mining is simply defined as the process of reclaiming raw materials from spent products, buildings, and waste.

• Lubricant - allows segments to slide easily into place during construction
• Distributes compressive/shear stresses across each joint
• Provides a water-tight seal between segments
• Prevents loss of cementitious grout at joints when pumped through cable ducts

Methods of assemblage:

• Balanced cantilever
• Segment-by-segment
• Incremental launching
• Span-by-span

Formulation is the Art to balance requirements without too much compromising on properties:

• adhesion
• mechanical properties
• resistance
• shelf-life
• application
• costs
• production ability
• ecology

Adhesion

Force between dissimilar materials at the bond line between
adhesive and substrate.

Cohesion

The internal strength of the adhesive itself.

But a rougher surface for bonding often leads to stronger bonds:

• roughness imparts additional surface area with which
  the adhesive can make contact when forming a bond
• a rough surface provides additional mechanical interlocking at the interface
• irregularities on the surface may mitigate crack propagation,
  enabling stronger, more fatigue-resistant bonds

Not always!

• necessary for the adhesive to flow into the cracks

Chemical bonds (intramolecular)

• covalent
• ionic
• metallic

Physical bonds (intermolecular)

• Van der Waals
  • dipole-dipole
  • induced dipoles
  • dispersion forces
• Hydrogen bonds

• Polyurethanes
  • 1C reacts with air moisture or 2C used in industrial assembly
• Epoxy resins
  • Typical for where high-strength bonds are needed
• Anaerobic
  • Reacts in absence of oxygen
• Cyanoacrylates
  • Instant reaction with mated surface (super glue)
• Silylated polymers
  • Excellent for elastic joints
• Silicones
  • 1C products react with air moisture
  • Mainly exploited as sealants in facades
  • 1C and 2C silicones are used for structural glazing

• Drying adhesives
  • chain coalescence due to solvent or water loss
• Contact adhesives
  • rubbery materials applied to both surfaces first
• Hot melt adhesives
  • thermoplastics applied hot and in a liquid state
• Pressure sensitive adhesives
  • Elastomeric materials permanently tacky at R.T

Rigid

• Epoxy
• Polyester
• Polyurethane
• ...

Elastic

• Rubber
• Polyurethane
• Silicone
• ...

Reactive Adhesives are Crosslinked Thermosets

--> Polymer Network Formation

Done at the lowest application temperature limit

--> Surface change due to applied pressure

Yield stress (thixotropy) test

Thixotropy = Zeitabhängigkeit der Fließeigenschaften bei nichtnewtonschen Fluiden

Done at the upper application temperature limit