HG ZHU*, ZY ZHAO, CL HU, Anderson CHU, ML SHAM and PL NG Thermal and Acoustic Insulation Performance Studies of Foamed concrete Presentation for MaSTEC 2015 Materials Science and Technology in Engineering Conference Frontiers of Sustainable Materials 24 June 2015
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HG ZHU*, ZY ZHAO, CL HU, Anderson CHU, ML
SHAM and PL NG
Thermal and Acoustic Insulation Performance Studies of Foamed concrete
Presentation for MaSTEC 2015 Materials Science and Technology in Engineering Conference
Frontiers of Sustainable Materials 24 June 2015
Outline Introduction
Preparation and performance study of foamed concrete
Application exploration and related projects
Concluding remarks
2
Outline Introduction
Preparation and performance study of foamed concrete
Application exploration and related projects
Concluding remarks
3
4 A Better Living
A More Comfortable and Convenient Living
What people are pursing all the time…
Modern Societies
Others…
5 But…… In Hong Kong
Buildings consumes 98% of total electricity in Hong Kong Air conditioning in buildings consumes 30% of total electricity
and 16% of total energy *Source: Hong Kong Energy End-use data 2014
Air pollution Resource depletion Global Warming/Climate Change
6 One More Problem
In Hong Kong Neighborhood noise
Traffic noise *Over one million people in Hong Kong are exposed to excessive traffic
Improving the thermal insulation of buildings to reduce energy consumption
Improving the Sound Insulation of Buildings
Constructing Noise Barriers
Design Operation
Materials Construction
A multifunctional materials for both thermal and sound insulation?
Foamed Concrete 8
Foamed concrete – porous concrete with air inside Features: Lightweight: 400~1600 kg/m3 (c.f. concrete 2000~2500 kg/m3) Lower strength and modulus Lower thermal conductivity Higher sound absorption coefficient Lower cost
Foamed concrete Normal concrete (2300-2400kg/m3)
Problems addressed 9
Lightweight—Reducing the construction cost Lower material cost Reducing the manpower need for handling Reducing the traffic need for transportation Reducing the dead load of buildings Fastening the construction process
Low thermal conductivity—Reducing energy consumption in buildings Improving the thermal insulation of buildings
Foamed concrete: the right multifunctional materials what we need?
10
Structural and non-structural elements of
buildings
Engineered Materials Arrestor System
(EMAS)
Thermal barrier
Noise barrier
Landfilling/Backfilling
Pavement
Potential applications
Applied R&D 11
Objectives Develop foamed concrete overcoming the above mentioned
challenges Develop foamed concrete with tailored performance for diversified
applications
Foamed concrete has a vast potential market Thermal barrier, noise barrier, landfill, pavement etc.
There are still many challenges of conventional foamed concrete, which hinders the application of foamed concrete Low compressive strength (1-15 MPa) and modulus (1-8 GPa) Large shrinkage (up to 2000-3000 microstrains) Poor water resistance (serious water absorption) Scale-up manufacturing (poor foam stability/distribution and inconsistent
density)
Outline Introduction
Preparation and performance study of foamed concrete
Application exploration and related projects
Concluding remarks
12
Preparation of Foamed Concrete 13
Composition Cementitious materials, mineral fillers, functional fillers,
water, chemical admixture, foaming agent, etc. Tailorable for diversified performance requirements
Preparation procedures: Prepare the cementitious slurry Generating dry foam (physical foaming method) Adding required amount of dry foam to the wet slurry Mixing further till foam are uniformly dispersed in the slurry
Low drying shrinkage (comparable to normal concrete) Water repelling (contact angle > 90o) Green materials (including up to 70wt% industrial by-products)
Carefully designing the formulation Selection and employment of raw materials Cementitious materials, fillers, admixtures
Dosage optimization Controlled setting time Controlled workability
Carefully mixing Foam size and dispersion
Enhancing the stability and uniform dispersion of foam in binder
Density Control of Foamed Concrete 17
Foamed concrete with tailored density (300-1600kg/m3) have been developed
The density is controlled by adjusting the amount of dry foam added The more dry foam added, the lower density of foamed concrete More water and more powerful mixing are always needed when the
amount of dry foam is increased.
Wet density measurement (Right after casting)
Dry density measurement (after sufficient oven drying)
100mm cube
100mm cube
Measured density = Calculated density ± 50 kg/m3
600
800
1000
1200
1400
1600
1800
15 20 25 30 35 40 45 50 55 60 65 70
Calc
ulat
ed w
et d
ensi
ty (K
g/m
3 )
Foam content (vol%)
Density VS Foam content
Mechanical Properties of Foamed Concrete(1/2) 18
The compressive strength and elastic modulus of foamed concrete ranging from 400kg-1700kg/m3 were measured. Tested after sufficient curing (room temperature curing:
28days; Thermal curing: 6days)
ELE compression machine Strength measurement of high
density foamed concrete
MTS For modulus measurement and strength measurement of low
density foamed concrete
Flexural strength and modulus measurement of foamed concrete are on-
going.
19
1
3
5
7
9
11
13
15
0
10
20
30
40
50
60
300 500 700 900 1100 1300 1500 1700El
astic
mod
ulus
(Gpa
)
Com
pres
sive
stre
ngth
(Mpa
)
Density (kg/m3)
Strength
Modulus
Compressive strength and elastic modulus of foamed concrete
0
5
10
15
20
25
30
0 20 40 60
Elas
tic m
odul
us (G
pa)
Compressive strength (Mpa)
Foamed concreteNormal concrete
Elastic modulus comparison between normal and foamed
concrete
E = 3.46(fcu)0.5 + 3.21)
Strength and modulus reduces with decreasing density, but the rate is higher when density is above 1000kg/m3
Strength and modulus are affected by the foam concrete, pore size and binder performance
Though the strength of foamed concrete could reach the strength level of normal concrete, the modulus of foamed concrete is about 50% lower than that of normal concrete
Mechanical Properties of Foamed Concrete(2/2)
20 Shrinkage of Foamed Concrete The shrinkage of conventional foamed concrete is always large,
even reaching 3000 microstrains, due to lack of aggregate Leading to crack formation in foamed concrete elements
0
300
600
900
1200
1500
1800
2100
0 240 480 720
Mic
rost
rain
s
Time (hrs)
Shrinkage of NAMI'sFoamed Concrete
Shrinkage of ConventionalFoamed concrete
Maximum Shrinkageof Normal Concrete
Foamed concrete with Low shrinkage (1500-1600 kg/m3, about 500 microstrains) are developed
Drying Shrinkage Comparison
21 Water Repelling Performance of Foamed Concrete
Conventional foamed concrete is always hydrophilic Water absorption->Pores filler with water->Density
increase and insulation performance degradation Hydrophobic foamed concrete (water contact angle > 90oC) has
been developed
105.7o 122.8o Water contact angle measurement of hydrophobic
foamed concrete Hydrophilic foamed concrete
Hydrophobic foamed concrete
Thermal Conductivity of Foamed Concrete 22
The thermal conductivity of foamed concrete ranging from 400kg-1700kg/m3 were measured. 100mm cube specimens: Curing->Drying->Cooling->Measuring
Quick Thermal Conductivity Meter (QTM-500)
Probe
Specimen
0.15
0.25
0.35
0.45
0.55
0.65
0.75
500 700 900 1100 1300 1500 1700
Ther
mal
cond
uctiv
ity (W
/m.K
)
Density (kg/m3)
Mix 1
Mix-2
Thermal conductivity VS Density
Thermal conductivity of normal concrete is 1.5-2W/m.K
Lower density, lower thermal conductivity Affected by both density (porosity) and binder
Thermal Insulation of Foamed Concrete 23
5oC reduction of the indoor temperature can be achieved by using NAMI’s foamed concrete.
24 Acoustic Insulation Performance of Foamed Concrete (1/3)
Pore structure of foamed concrete is beneficial to the sound absorption and sound insulation
Low modulus of foamed concrete is beneficial to reducing the impact noise generation
However, few studies on the acoustic insulation performance of foamed concrete have been conducted. Impedance tube Effect of porosity (density) and thickness on acoustic performance
25 Acoustic Insulation Performance of Foamed Concrete (2/3)
Measurement frequency: 250-1500Hz Absorption/reflection Coefficient Transmission Loss
Cylinder specimen: 99mm in diameter
Impedance Tube
26 Acoustic Insulation Performance of Foamed Concrete (3/3)
Some Preliminary Results
Lower density is beneficial to sound absorption, while higher density is
beneficial to transmission loss.
Transmission loss increased with
increasing specimen thickness.
0.00
10.00
20.00
30.00
40.00
50.00
60.00
200 600 1,000 1,400 1,800
Tran
smis
sion
Los
s (d
B)
Frequency (Hz)
40mm
75mm
98mm45dB
Density: 400kg/m3
Density Effect
Thickness Effect
Outline Introduction
Preparation and performance study of foamed concrete
Application exploration and related projects
Concluding remarks
27
On-going Projects (1/2) 28
Public Sector Trial Scheme: High performance cementitious materials for the construction of external wall with enhanced thermal insulation
Objectives: Partner with the Housing Department of HKSAR to Verify the scale-up capability of foamed concrete Verify the heat insulation performance of foamed concrete
Status: On-going
Two 2.5m*2.5m*3m enclosures will be constructed with NAMI’s foamed concrete and normal concrete
1-year field trial will be conducted with on-site continuous temperature monitoring
29
Site Trials of NAMI’s Foamed Concrete in Public Housing NAMI is now partnering with the HA to conduct trial applications of the NAMI’s
foamed concrete in Public Housing to To determine the effectiveness of noise reduction and heat insulation by foamed
concrete in public housing To verify the viability and engineering feasibility of application of foamed concrete
in public housing
Scope of Trials
160mm concrete slab
20mm In-situ foamed concrete for sound
insulation
Sound Insulation: Floor of 4 apartments 0/20/30/40mm foamed concrete layer Generating impact sound Measuring noise in beneath apartment
Heat Insulation 3 RC refuse collection house 1: Control; 2: with FC roof topping; 3: with FC
external skin on the westerly-faced wall Temperature measuring in hot and shiny
summer
West
1 2 3
RC FC
FC
RC: Reinforced concrete; FC: Foamed concrete
On-going Projects (2/2)
Other Applications Exploration 30
Development of a lightweight fire-resistant internal wall system
Structural use of foamed concrete in low-rise buildings
Foamed concrete block for internal wall
Other potential applications
Noise reducing foamed concrete pavement
Engineered Materials Arresting System (EMAS)
Concluding Remarks Foamed concrete is a multifunctional material with
some unique features which normal concrete doesn’t have
This material has about 100 years history can be innovatively used to improve the living condition of human
To widen and promote applications of foamed concrete, more applied research efforts are still needed to overcome the present limitations of foamed concrete
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NAMI’s foamed concrete technology has won the
Certificate of Merit
Green Innovations Awards of the 2014 HKAEE
Thank You!
Materials Science and Technology in Engineering Conference