Advances in Building Materials

• Application Areas
  • exterior wall, interior wall
  • ceiling, floor
  • roof waterproof, etc...
• Building functions
  • decorative coatings
  • waterproof, anticorrosive
  • mildew resistant, anti-fogging, fireproof coatings...
• Textures
  • thin, thick, stratified architectural coatings, etc...
• Primary Film-forming Matters
  • organic coatings (
  • inorganic coatings (chemical action)
  • organic-inorganic composite coatings
• Dispersion Mediums
  • solvent-based coatings (better for exterior)
  • water-based coatings (better for interior)

Decorative/aesthetic

• useful to change:
  • colors/patterns
  • texture (e.g. roughness)

Protective

• chemical aggressions (e.g. anti-corrosive)
• biological aggressions (e.g. anti-fungal, insecticidal)
• fire (e.g. fire-retardant intumescent coatings)
• UV irradiation
• liquids (e.g. water-/oil-repellent, omniphobic coatings)
• Fouling (e.g. anti-scratch, self-lubricating coatings)
• human impact (e.g. anti-graffiti)

"Smart"

• self-cleaning
• photocatalytic (e.g. anti-pollution)
• biocidal (e.g. anti-bacterial, anti-virus, self-sterilizing)
• photovoltaic (e.g. luminescent solar concentrators)
• electro-/thermochromic
• anti-slip (to improve safety)
• "breathable" (let moisture escape, while providing a moisture barrier)
• reflective (for "cool roofs")
• sensing, self-reporting (e.g. to highlight hazards)
• CO2-sequestrating

• Walls - anti-graffiti coatings
  • polysiloxane-based
  • highly hydrophobic coatings
     
• Walls - anti-microbial coatings
  • repelling (exclusion steric repulsion, electrostatic repulsion, low surface energy)
  • killing (biocide-releasing, contact-active biocidal)
     
• Building envelope - self-cleaning coatings
  • ETFE film (nonstick surface)
  • prone to punctures by sharp edges --> mostly used for roofs
  • working temperature range of -185 °C to +150 °C
  • very resistant to ultraviolet light
     
• Windows - optical coatings
  • e.g. low-emissivity, spectrally-selective coatings
  • to improve energy efficiency

Keeps itself free of dirt

Superhydrophobic

• can use a combination of surface micro structuration and hydrophilic polymers
• cleans by forming droplets that carry away dirt

Superhydrophilic

• surfaces are completely, homogeneously wetted by water
• this property makes these surfaces also non-fogging
• usually based on photocatalytic oxides, especially titania (titanium dioxide)
• cleans by spreading water that carries away dirt

Property improvement needed for:

• Dimensional stability (impeding cracks)
  • coatings to reduce the moisture gradient between the inner and outer parts of the wood
    --> decrease of drying cracks by retarded moisture transfer
  • wood surface hydrophobization to repel liquids (mainly water)
  • various approaches to combine surface roughness (nano-rods) and hydrophobization (coatings)
    --> self-cleaning effect on wood surfaces
     
• UV-stability
  • organic UV absorbers and organic radical scavengers
  • metal oxides
  • coatings containing nanoparticles
  • growth of nanorods
• Durability
   
• Flammability
  • fire retardant coatings
    --> avoid the spread of flame by reducing the flammability of the surface
  • intumescent coatings
    --> react to an increase in temperature by swelling and forming a thick layer of foam
     
• wood surface protection against liquids

decrease of drying cracks by retarded moisture transfer

because wood strives for equilibrium moisture content --> swelling and shrinking

variability in mechanical properties

• decreasing mechanical variability by sorting/stress grading (new opportunities by using machine learning)
• reduce variability with glued laminated timber

low dimensional stability and swelling/shrinkage anisotropy

• decrease swelling anisotropy by cross-laminates
• decrease magnitude of dimensional changes by cross-laminates
• bilayer-structures utilize dimensional changes for novel products

The arrangement of cross-laminates at the macroscale decreases the swelling anisotropy of the element and reduces the magnitude of dimensional changes.

...but, they do not decrease the magnitude of swelling/shrinkage of wood

The wood structure (cell walls) needs to be modified by:

• Thermal treatments
• Chemical modification

Wood modification via heat treatment

• temperature at least 160°C
• atmosphere without oxygen
• Parameters:
  • wood type; initial moisture
  • sample size and geometry
  • treatment temperature and duration
  • pressure, medium

Property changes:

• + reduced equilibrium moisture content
• + improved dimensional stability
• + improved duraibility
• + darker color
• - reduction in strength
• - increased brittleness

Modification of cell lumina

• Lumina filling usually with resins
• --> increase in density
• --> limited impact on wood properties
• can affect some mechanical properties (e.g. hardness)
• water adsorption can be slower, but no absolute change in the sorption behavior

Cell wall modification

• cell wall components are chemically affected
  --> chemical bonds are changed or modified
• water adsorption and thus durability and dimensional stability can be influenced
• functionalization of the OH groups (Acetylation)
• Cross-linking treatment (DMDHEU)
• Spruce - insertion of flavonoids into the cell wall

"Bulking" modification - cell wall and lumina

• generally changes the sorption behavior of the wood and the swelling and shrinkage can be reduced
• Disadvantage: the density of the wood is increased

Insertion of calcium carbonate in the wood structure

• lowers heat release rates and smoke production
• Process 1: decomposition of dimethyl carbonate (DMC)
• Process 2: mineralisation by alternating salt solutions

Polymerization of pyrrole in fir wood cross-sections

• Polymerization: process to form polymer chains or three-dimensional networks
• Pyrrole:  organic compound

Polymerization of aniline in pine veneers

• Aniline:  organic compound
• Pine veneers: a "paper thin" cut of wood that is attached to a panel of fiberboard or particleboard

Metalized wood (wood filled with tin-bismuth alloy)

Electric conductivity by laser-induced graphitization of wood

• graphitization: the process of heating amorphous carbon
  --> rearranging the atomic structure to achieve an ordered crystalline structure

Formation of superparamagnetic iron oxide particles

Directional water transport for autonomous fog collection

• Fog collection: harvesting water from fog

--> Janus wood membrane

• asymmetric wettability on two sides
  --> hydrophobic and hydrophilic side

Delignified wood

• Delignify:  the process of extracting lignin from plant sources
• Uses:
  • transparent wood (as optical lighting material)
  • thermal insulation
  • cooling purposes (scattering solar radiation)
  • enhancing piezoelectric properties

Densified wood

• obtained by delignification and hot-pressing
• good waterproof and excellent dimensional stability
• higher compressive strength

Moldable wood is a strong and flexible cellulose-based material. Moldable wood can be folded into different shapes without breaking or snapping. The patented synthesis is based on the deconstruction and softening of the wood's lignin, then re-swelling the material in a rapid "water-shock" process that produces a wrinkled cell wall structure. The result of this unique structure is a flexible wood material that can be molded or folded, with the final shape locked in by simple air-drying.

Early age

• Rheology

Intermediate age

• Early strength --> time to demolding
• Main heat released --> thermal stresses after demolding
• plastic shrinkage

Late age

• Final compressive strength
• Drying shrinkage
• Duariblity
• Creep

Carbonation depth refers to the average distance from the surface where CO2 reduces the alkalinity in concrete or mortar, leading to neutralization of the protection for reinforcing steel.

Limestone Calcined Clay Cement

Calcined clay and limestone are already commonly used as Supplementary Cementitious Materials (SCMs).

The major innovation in LC3 is to combine the use of abundantly available low-grade kaolinite clay with a further 15% of limestone, which together have a synergetic effect and reach a similar performance as OPC - CEM I.

C  -  CaO  (Calciumoxide)

S  -  SiO₂  (Siliciumdioxide)

A  -  Al₂O₃  (Aluminiumoxide)

F  -  Fe₂O₃  (Iron(III)-oxide)

C'  -  CO_{2  (Carbonoxide)}

S'  -  SO₃  (Sulfurtrioxide)

Portlandite (CH)

Calcium silicate hydrate (C-H-S)

Ettringite (AFt)

AFm