Download - Building Materials 4
Building MaterialsBuilding MaterialsBuilding MaterialsBuilding Materials
Lecture 4
M h i l tiM h i l tiMechanical propertiesMechanical properties --continuationcontinuationcontinuationcontinuation
Abrasion resistanceAbrasion resistance• ability of a surface to resist being worn away y g y
by rubbing or friction• coatings paints floor surfaces pipescoatings, paints, floor surfaces, pipes
Abrasion resistance testsAbrasion resistance tests
• usually measured as a loss percentage based on original weight g g
Taber abraderTaber abrader• thickness loss after definedthickness loss after defined
number of rotations using standardized wheel andstandardized wheel and defined load
Amsler/Böhm testAmsler/Böhm testi i bj t d• a specimen is subjected
to stress by grinding • the abrasive grit
accumulating from this is indicated as loss of volume or thickness (abrasive loss) per test area 50 cm2
7,07 x 7,07 cm
Abrasion resistance (Amsler / Böhm)
• EN 1338, 1339, 1340 – concrete pavings• EN 14157 – natural stones• EN 13 892-3 – screeds
Adh i d h iAdhesion and cohesion
• adhesion – state in which two surfaces are held together by interfacial effectsinterfacial effects
• cohesion – ability of a material to i t i it t th h fi dmaintain its strength when unconfined
adhesion < cohesion
AdhesionAdhesion• between two materials - in compositesbetween two materials in composites
(steel + concrete, cement + aggregates )aggregates…)
Adhesive strengthAdhesive strength• between the upper layer and basebetween the upper layer and base
(plasters, coatings..)
Pull-off testPull-off test
• the circular pull-head plates are glued to the test material and upper layer is pp ycut around them
FPULL-HEADCUT
F
TESTED LAYER
GLUE
SUBSTRATE
TESTED LAYER
SUBSTRATE
Pull-off test equipmentPull-off test equipment Adhesive strength fAdhesive strength fa
F• test results: AFf u
u
f f f ffa fu fa fu
fa = fu
Moisture Moisture (hygric)(hygric) propertiesproperties( yg )( yg ) p pp p
DefinitionsDefinitions
• Moisture content - amount of watercontained in a material
• Dampness - presence of unwanted moisture in the structure of a buildingmoisture in the structure of a building,
• Humidity - amount of water vapor in the air
• Hygric - relating to moisture• Hygric - relating to moisture
Moisture contentMoisture content
• amount of water contained in a material, which can be removed bymaterial, which can be removed by drying
• any porous i l i hmaterial in the
construction is not quite dry !
Moisture typesMoisture types• production (wet• production (wet
manufacturing process)groundwater intrusion• groundwater intrusion
• rainwater leaks• diffusion through walls,
roofs, and floors • indoor moisture
(breathing, perspiration, (b ea g, pe sp a o ,cooking, bathing, and washing )g )
Water-vapor productionWater-vapor production
••
human metabolism (based on activity
50 - 250 g of water vapor/h• vapor/h
bathrooms 700 - 2600 g
•kitchens 600 -1500 g
f tlaundry drying 200 - 500 g of water vapor/h/5 kg
Moisture typesMoisture typesA di iAccording time:• initial moisture (natural, manufacturing)initial moisture (natural, manufacturing)• storage moisture• stabilized moisture (constant - after
longer period – ca 2 - 7 years)
Moisture content during time period Gravimetric water contentGravimetric water content
)(*mmmw DWOH 1002
)(mm
wDD
m 100
mD mass of dry materialmD …. mass of dry materialmW …. mass of wet materialmH2O …. mass of water in material
Volumetric water contentVolumetric water content
)(*mmVw DWOH 1002
)(V*V
wOH
V 1002
mD ..... mass of dry materialD ymW ..... mass of wet materialV l f t i t i lVH2O … volume of water in materialV ....... volume of materialV ....... volume of material
SorptivitySorptivity
• amount of water taken in by a material when immersed
• maximum amount of water, which can be in the materialcan be in the material
• volumetric sorptivity: 0 - 100 %• gravimetric sorptivity: can be higher than• gravimetric sorptivity: can be higher than
100 %
Sorptivity of materialsSorptivity of materials350
300300
350y
[%]
gravimetric sorptivity
200
250
sorp
tivity gravimetric sorptivity
volumetric sorptivity
150
100
150
80
2297
6040 45
2050
100
9 07 00
CapillarityCapillarity• ability of a liquid to flow in narrow ab y o a qu d o o a o
spaces without the assistance of, and in opposition to external forces like gravityopposition to external forces like gravity
Capillarity in practiceCapillarity in practice•
CapillarityCapillarity
MaterialBulk density in dry state
Gravimetric capillarity [kg/m3]aftery
[kg/m3] 2 hours 8 hours 24 hours
Foamed 16 1 1 1 2 1 2polystyrene 16 1,1 1,2 1,2Foamed polyurethane 35 0,3 0,4 0,4polyurethane , , ,
AAC 540 12,7 19,9 29,7
Sorption behaviorSorption behavior• ability of a hygroscopic material toability of a hygroscopic material to
absorb or release water vapor from or into the air until a state of equilibriuminto the air until a state of equilibriumis reached
adsorption(uptake of water vapor)( p p )
x desorptiondesorption
(water vapor release)
Equilibrium moisturecontent
Depends on:• air temperature pressure and humidityair temperature, pressure and humidity • pores sizes and shapes
Sorption hysteresisSorption hysteresis Sorption hysteresisp y
Sorption hysteresisSorption hysteresis Water permeabilityWater permeability
Water permeabilityWater permeability
• roofing (ceramic and concrete tiles))• depends on the amount of capillary pores p p y p
and cracks (size 0,01 – 0,5 mm)
Roof tiles are always permeable– space under roof has to be ventilated !p
Permeability testing• measuring the time taken for a drop of water
Permeability testing• measuring the time taken for a drop of water
to appear on the underside of the roofing tile when a 6 cm thick water head is applied onwhen a 6 cm thick water head is applied on the opposite side
• measuring the volume of water that passes through a saturated roofing tile under a 10through a saturated roofing tile under a 10 cm thick water head
Diffusion propertiesDiffusion propertiesDiffusion propertiesDiffusion properties
DiffusionDiffusion• gases, vaporg , p• spread of particles through random motion
from regions of higher concentration to g gregions of lower concentration
• Important for: – vapor barriersp– radon barriers– rehabilitation renders– paints– passive houses
Water vapor transportWater vapor transport
Important properties:• the water vapor diffusion coefficient δthe water vapor diffusion coefficient δ• the resistance to water vapor diffusion
f tfactor μ• the water vapor diffusion equivalent air t e ate apo d us o equ a e t a
layer thickness Sd
Water vapor diffusion -- coefficient δ
• the amount of water vapor [kg] which diffuses through a layer of material which is 1 m thick and has an area of 1 m² at a partial water vapor pressure difference of 1 Pa in 1 hour
• units: [kg/m.h.Pa]units: [kg/m.h.Pa]
Resistance to watervapor diffusion - factor μ
• the ratio of the water vapor diffusion coefficient of the air δL to the value δmat of the building material
a measure for the vapor• a measure for the vapor tightness of a material (h ti t th(how many times greater the resistance to transmission of a layer of building material isa layer of building material is compared to a static layer of air of the same thickness)
Equivalent air layer thickness Sd
Sd = μ · s [m] d μ [ ]• the thickness of a static layer of air in meters,
which displays the same resistance to waterwhich displays the same resistance to water vapor transmission as the building material in the thickness s with the resistance to waterthe thickness s with the resistance to water vapor transmission value μ
• Sd ≤ 0.5 m => diffusion-open materials
• 0.5 m < Sd => diffusion-blocking materials
• Sd ≥ 1500 m => diffusion-proof materials
Diffusion of coatingsDiffusion of coatings Künzel’s facade protection theory:Künzel s facade protection theory:• protection and breathability of coating are influenced by water absorptionare influenced by water absorption capacity w (sorptivity) and the water vapor permeability Spermeability Sd
Soil permeabilitybili f il i d i• ability of soil to transmit water and air
• important in the areas with radon riskimportant in the areas with radon risk
Thermal propertiesThermal propertiesThermal propertiesThermal properties
Interaction heat - materialInteraction heat - material
• If the surroundings of the material has different temperature than the pmaterial, the thermal energy is transferredtransferred
1. The properties of material influence the transmission of heatthe transmission of heat
2. Thermal energy influences the ti f t i lproperties of material
Heat transportHeat transport• conduction – solid materials
– the transfer of heat within a substance, molecule by molecule
• convection - gases, liquids – heat transfer by the mass movement of a fluid in– heat transfer by the mass movement of a fluid in
the vertical direction
• radiation gases• radiation – gases– heat is transfered
through wavethrough wave energy
Heat transportHeat transport
Depends on:
• porosity• porosity• structure• temperature• material typematerial type
I th t i l th h t i• In the porous materials the heat is transferred by combination of all types f h t t tof heat transport
Thermal conductivityThermal conductivity
• a material's ability to conduct heat
λcoefficient of thermal conductivityλ• coefficient of thermal conductivity
Coefficient of thermal conductivity
• or k-value• or k-value• the quantity of heat transmitted, due to
unit temperature gradient in unit timeunit temperature gradient, in unit time under steady conditions in a direction normal to a surfacenormal to a surface
•units SI: [ W/m.K]imperial units: [Btu/hr.ft.F] (1 Btu/hr.ft.F = 1.730735 W/m·K)
•the lower λ, the better insulator (thermal insulating materials λ < 0,15 W/m.K)•range λ : 10-2 - 102 W/m.K
Material λ [W.m-1.K-1]• Copper ……………………..... ~370• Aluminium …………………... ~200• Carbon steel ………………… ~50• Concrete ~1 4Concrete …………………..... 1,4• Glass …………………………. ~0,75• Brick ~0 7• Brick …………………….. ~0,7• Water (20° C, quiet)………... ~0,60
W d 0 15• Wood ………..…………......... ~0,15• Mineral fibers ….……………. ~0,05 m
altio
ns
• Polystyrene foamed …….. ~0,035• Air (dry, quiet) ……….……. 0,025 th
erm
insu
la
• Argon (quiet) …………….... ~0,015
Thermal conductivity - comparisonThermal conductivity comparison Thermal conductivityO i t i l b tt
Thermal conductivity• Organic materials are better
insulators than anorganic m.Cr stalline mat are better• Crystalline mat. are better conductors than amorphous m.Mat with lower bulk density are• Mat. with lower bulk density are usually better insulators.Metals are very good• Metals are very good conductors.Anisotropic mat have different• Anisotropic mat. have different conductivity in different directionsdirections.
Coefficient of thermal conductivity
Depends on:• chemical composition• structure• structure • porosity (bulk density)p y ( y)• moisture• temperature
Porosity influencePorosity influence
• AIR = 0,025 W/m.K
• the higher the amount of air in the material (porosity), the lower bulk (p y),density and thermal conductivity is
• size of pores is limited (best 0,1 – 1 mm)
Moisture influenceMoisture influence app 25 x higher than water app. 25 x higher than air
i t i ifi tl d th th l• moisture significantly reduces the thermal insulating ability of materials
• very small pores are liable to wetting (capillarity) – the best size of pores in ( p y) pinsulating materials: 0,1 – 1 mm
Temperature influenceTemperature influence• increases with rising temperature increases with rising temperature
t0025,00t (for t = 0-100C)
Thermal insulating materialsThermal insulating materials• fibrous - mineral and glass fibersfibrous mineral and glass fibers
- wood wool (excelsior) cellulose fibers- cellulose fibers
- recycled paper fiberst (b l l )- straw (bales, loose)
• porous particles- expanded clay aggregate e pa ded c ay agg egate- expanded perlite- ash- cinders
Thermal insulating materials
shaped li ht i ht t ( ith
Thermal insulating materials
• shaped - lightweight concretes (with lightweight aggregates,
i t d t )pervious c., aerated concretes)- insulating brick blocks- diatomite
• foamed - foamed polymers (PU,PS, h li f )phenolic foam)
- cellular glass
Thermal insulating materialsThermal insulating materials
• other - cork (expanded)- wood- wood-based materials (fiber board particle board)(fiber board, particle board)- lamb wool
Best insulation?Best insulation?
• vacuum• „VIP“ = Vacuum Insulated Panel„VIP Vacuum Insulated Panel• a nearly gas-tight enclosure surrounding a
rigid core from which the air has beenrigid core, from which the air has been evacuated
0 007 W/ K• = 0.007 W/m·K
Thermal conductivity ymeasuring
• steady-state methods - the temperature of the measured material does not change with timewith time
• transient (non steady-state) methods -( y )a measurement during the process of heating up
Steady state - a situation in which all variables are constant in spite of ongoing
th t t i t h th Fprocesses that strive to change them. For an entire system to be at steady state, i.e. for all state variables of a system to be constantstate variables of a system to be constant, there must be a flow through the system
Thermal conductivity ymeasuring
Steady-state methods:• Guarded hot plate• Guarded hot plate• Divided bar
Hot box• Hot box
Transient methods:• Hot wire• Plane source• Needle probeNeedle probe• Laser flash method
Thermal conductivity imeasuring
Thermal conductivity determination
• Steady state method:
dq Q T-Td q
21
AQq
T T 21 Aq….. of heat passing through a unit area of the
sample in unit time [W/m2]sample in unit time [W/m ]d …. average thickness of sample [m]T1 .... temperature of warm side of the sample [K]1 p p [ ]T2 … temperature of cold side of the sample [K]Q .... quantity of heat passing through a base area of y g g
the sample [W]A ..... base area of the sample [m2]
Guarded hot plateGuarded hot plate• placing a solid sample of fixed dimension
between two temperature-controlled plates • one plate is heated while the other plate is
cooled, and their temperatures are monitored until they are constant
Thermal resistanceR-value
• directly proportional to the thickness ofR = d / [(m2 .K) / W]
directly proportional to the thickness of the materialf i i l• for construction, not material
• can be used for masonry blockscan be used for masonry blocks
R = 0 65 (m2 K)/W
• the reciprocal of R-value is thermal
R = 0,65 (m2.K)/W
the reciprocal of R value is thermal conductance [W/m2.K]
Thermal resistance• multi-layered construction : the R-
Thermal resistancemulti layered construction : the Rvalues of the individual layers are addedadded
Rtotal = Routside air film + Rrender + Rinsulationtotal outside air film render insulation+ Rbrick + Rplaster + Rinside air film
Thermal transmittanceU-value
• the measure of the rate of heat loss through a materialthrough a material
• incorporates the thermal conductance of a structure along with heat transfer due tostructure along with heat transfer due to convection and radiation
U-value = 1/R[ W / m2 .K ]
U-value in EuropeU-value in Europe Heat lossesHeat losses