thermal and acoustic insulation performance...

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




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

noise (>70 dB) * Source: Environmental Performance Report 2011 of HKSAR

Complaint cases

7 What should we do

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

Higher Sound absorption coefficient—Reducing noise disturbance Reducing noise reflection and diffraction

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)




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

Foam generator Dry foam Adding foam & Mixing Foamed concrete

14

Stationary Mixer

1

Prepare the slurry first in the stationary mixer

Concrete Truck

2

Drop the slurry into the concrete truck, and add foam to concrete truck.

NAMI’s Foamed Concrete

3

When foam are uniformly dispersed, the foamed concrete is ready.

Scale-up of Foamed Concrete

Technical Merits of Foamed Concrete 15

Tailored density (300-1600kg/m3) Normal concrete: about 2300kg/m3

Relatively high strength and modulus Reaching grade 35 and 15Gpa at 1500-1600kg/m3

Conventional foamed concrete: Below 15Mpa and 8GPa

Relatively low thermal conductivity (below 0.65W/m.k) Normal concrete: 1.5-2W/m.K

Relatively higher sound absorption coefficient (Above 0.2) Dense normal concrete: <0.1

Low drying shrinkage (comparable to normal concrete) Water repelling (contact angle > 90o) Green materials (including up to 70wt% industrial by-products)

How to Achieve Above Technical Merits 16

Employing suitable foaming method - Dry foam Controlled foam size and stability Controlled foam addition

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


Measurement frequency: 250-1500Hz Absorption/reflection Coefficient Transmission Loss

Cylinder specimen: 99mm in diameter

Impedance Tube


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




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

31

32

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

Frontiers of Sustainable Materials

thermal and acoustic insulation performance...

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