4.461: Building Technology 1 CONSTRUCTION AND MATERIALS

FALL TERM 2004 SCHOOL OF ARCHITECTURE AND PLANNING: MIT

Professor John E. Fernandez

Stadelhofen Station Zurich Santiago Calatrava Valls Image courtesy of Per Waahlen, photographer, and Structurae

Concrete and Composites

concrete and composites 1. Introduction practice research 2. Concrete Issues ductility CO2 generation durability 3. Improved Structural Materials substitution dematerialization technology transfer 4. Material Selection and Evaluation (CES) multi-objective optimization material indices/ CES software 5. New and Emerging Materials new concretes composites 6. Architectural Form and Research Priorities research development: NFRC design

concrete and composites 1. Introduction practice research 2. Concrete Issues ductility CO2 generation durability 3. Improved Structural Materials substitution dematerialization technology transfer 4. Material Selection and Evaluation multi-objective optimization material indices/ CES software 5. New and Emerging Materials new concretes composites 6. Architectural Form research development: NFRC design

concrete and composites

ductility

Stress - Strain Curves Not To Scale

ela sti cz on e

full plasticity metals

Stress, σ

brittle ceramics

∆σ

∆δ

Stress, σ, P/A

partial plasticity reinforced concrete

Strain, δ

E = ∆σ/∆δ

brittle

plastic flow

viscous flow elastomer

Strain, δ, ∆L/L

Stress, σ

extensive cold drawing plastic

ductile

Strain, δ

Image by MIT OCW.

concrete and composites

ductility

Failure strain, Єf Figure X

Єf - measure of the deformation of the material at final fracture stress

Material concrete, unreinforced (compression) concrete, reinforced

Ceramics

soda glass

Fracture and failure is unpredictable

0 0.02 0

low-alloy steel

0.02-0.03

mild steel

0.18-0.25

carbon steel

Probability function

εf

0.2-0.3

stainless steel, austenitic

0.45-0.65

stainless steel, ferritic

0.15-0.25

cast irons

0-0.18

iron

0.3

aluminum

0.5

copper brasses and bronzes natural rubber

0.55 0.01-0.7 5.0

Tensile Ductility, εf (except for certain materials such as concrete, unreinforced)

Fracture stress (ceramic)

Images by MIT OCW.

concrete and composites

Toughness, Gf , and Fracture toughness, Kc measures of energy absorption potential through resistance to crack propagation. Gf ( toughness), Kc (fracture toughness) both material properties. Gf = energy per unit of crack area Various ways of measuring depending on the material. Therefore, search for materials that have high resistance to cracks that are formed through loading or other lifecycle stresses. Sometimes toughness is also referred to as the area under the stress-strain curve.

ductility

Silicon Nitride (Glass ceramic)

Aluminium Nitrides (Glass ceramic) 10

Alumina Fibre

Fracture Toughness (ksi.in^1/2)

Granite

Carbon Fibre

Limestone 1

Normal Density Concrete Machineable Glass Ceramic

Ice (H2O) 0.1

Aerated Concrete

Low Density Refractory Brick Ceramic foam (carbon)

Lightweight Concrete 0.01

1

10

100

1000

Price per density

10000

100000

1e6

concrete and composites

Ecological Issues Concrete production contributes 8% of world’s total CO2 emissions. Research in building materials for the developing world is a moral obligation. Issues •

Poverty allevation

•

Safety

•

Health (IAQ, toxicity)

•

Resource Management

Cultural Issues •

Form (resonance with place)

•

Process (acknowledges local skill set)

•

Material (regional resources)

CO2 generation

Carbon Steel 100

Alumina

Diamond

Tungsten - High Alloy (<89%W)

Concrete (High Performance) Cement (Super Sulphate) Sandstone(2.35)

10

Common Hard Brick

Granite(2.63) Carbon Matrix Composite Plaster of Paris

Marble(2.7)

Young's Modulus (10^6 psi)

1

Epoxy SMC (Carbon Fibre)

Low Density Refractory Brick

0.1

Concrete (Insulating Lightweight) Medium Density Aluminium Foam (0.24-0.48) Insulation Board, perpendicular to board

0.01

1e-3

Ultra Low Density Wood (Transverse) (0.09-0.22)

Natural Rubber (NR), unfilled

1e-4

1e-5

1

10

100

Production Energy (kcal/lb)

1000

10000

100000

concrete and composites

Concrete Need for durable reinforcing and water impermeable concrete matrix Especially for freeze/thaw climates

durability

concrete and composites 1. Introduction practice research 2. Concrete Issues ductility CO2 generation durability 3. Improved Structural Materials substitution dematerialization technology transfer 4. Material Selection and Evaluation multi-objective optimization material indices/ CES software 5. New and Emerging Materials new concretes composites 6. Architectural Form research development design

concrete and composites

dematerialization, substitution, technology transfer

P 9

8

C S(n) A B S(r)

7

W(r) G R

10

10

10

W(n)

6

B

4

10

3

10

Projection

S(r)

5

10

W(n)

W(r)

P

A

S(n)

G C

2

10

1

10

R

Year

Image by MIT OCW.

2020

2025

2000

1975

1950

1925

1900

1875

1850

1825

1800

1775

0 1750

Quantity (tons)

10

concrete and composites

dematerialization, substitution, technology transfer

Concrete Dematerialization: a decrease in the material input per unit service Is occurring in certain industrial sectors but ‘ecological rucksack’ needs to be accounted for Substitution: substituting concrete best in situations in which safety is at high risk of compromise Technology transfer: best employed in situations in which to lengthen lives of existing building stock (such as infrastructure refurbishment using carbon/epoxy reinforcing) Percentage of Total (weight)

100 80

Projection

60 40 20

2020

2010

2000

1990

1980

1970

1960

1950

1940

1930

1920

1910

1900

0

Year

Image by MIT OCW.

Measurement of Percentage of Renewable Versus Nonrenewable Materials Consumption in the US

concrete and composites 1. Introduction practice research 2. Concrete Issues ductility CO2 generation durability 3. Improved Structural Materials substitution dematerialization technology transfer 4. Material Selection and Evaluation (CES) multi-objective optimization material indices/ CES software 5. New and Emerging Materials new concretes composites 6. Architectural Form research development design

concrete and composites

multi-objective optimization

concrete and composites

multi-objective optimization

Carbon Steel

100

10

Young's Modulus (10^6 psi)

1

0.1

Normal Density Concrete

0.01

1e-3

1e-4

1e-5

0.1

1

10

Thermal Expansion (µstrain/°F)

100

ceramics • Glass ceramics Machineable, good fracture toughness

• Very HPC (Ductal) Ductile concrete

• Ceramic foams Lightweight, structural material

• New laminated glasses Laminated glass (Dupont SGP interlayer)

concrete and composites

new concrete

Ductile concrete Steel whisker reinforcement Increased toughess Increased water impermeability (few micropores)

60

ductile concrete

Bending strength, MPa

50

40

30

20

10

normal concrete

0 0

300

600

Displacement, microns

Image by MIT OCW.

900

1200