DESIGN STRATEGY FOR RECYCLED AGGREGATE CONCRETE

DESIGN STRATEGY FOR RECYCLED AGGREGATE CONCRETE

RAEng Frontiers Champion Project:

Recycled Aggregate Concrete in South East Asia

Nikola TošićUniversitat Politécnica

de Catalunya

[email protected]

mailto:[email protected]

CONTENTS

▸ Intro to CEN prEN1992 and fib Model Code 2020

▸ RAC provisions in prEN1992 and MC2020

▸ Background to RAC code provisions

▸ Implications for design and future work

1.Intro to CEN prEN1992 & fib MC2020

Intro to prEN1992 and MC2020

CEN – European Committee for Standardization

EU + Iceland + Norway + Switzerland + UK + North Macedonia ++ Serbia + Turkey


EN 1992 – Design of Concrete StructuresEN 1992-1-1:2004 Part 1-1: General rules and rules for buildingsEN 1992-1-2:2004 Part 1-2: General rules - Structural fire designEN 1992-2:2005 Part 2: Concrete bridges - Design and detailing rulesEN 1992-3:2006 Part 3: Liquid retaining and containment structures

Links to other EN standards:EN 196, EN 197 – Methods of testing cement; CementEN 206+A1 – Concrete – Part 1: Specification, performance, production and conformityEN 10080 – Steel for the reinforcement of concreteEN 12620 – Aggregates for concreteEN 13670 – Execution of concrete structures


Revision of the Eurocodes


Revision of the Eurocodes

https://eurocodes.jrc.ec.europa.eu/showpage.php?id=23

https://eurocodes.jrc.ec.europa.eu/showpage.php?id=23


Revision of the Eurocodes: prEN1992-1-1 & prEN1992-1-2

▸ CEN Enquiry: September–December 2021

▸ Target date of availability of 2nd generation EN 1992: March 2023

▸ Date of publication – national choice (National Annexes!)

▸ Target Date of Availability of last 2nd gen. Eurocodes: March 2026

▸ Target Date of Withdrawal of 1st gen Eurocodes: March 2028


International Federation for Structural Concrete – fib

Euro-International

Committee for Concrete

Comité euro-internationale du béton1953

CEB

International Federation

for Prestressing

Fédération internationale

de la précontrainte

1952

fib

David Fernández-Ordóñez, 2018


International Federation for Structural Concrete – fib



Evolution of Model Codes



Task Group 4.7: Structural Applications of Recycled AggregateConcrete – Properties, Modelling, and Design

https://www.fib-international.org/commissions/com4-concrete-concrete-technology.html

https://www.fib-international.org/commissions/com4-concrete-concrete-technology.html

2.RAC provisions in prEN1992 & fib MC2020

RAC provisions in prEN1992 and MC2020

Current basis: EN 12620 & EN 206+A1

▸ Only coarse RA▸ Composition-based classification▸ Future – performance-based classification?

https://www.gov.il/BlobFolder/reports/aggregates/en/04%20Sanchez-

%20EN%2012620%20Aggregates%20for%20concrete.pdf

https://www.gov.il/BlobFolder/reports/aggregates/en/04%20Sanchez-%20EN%2012620%20Aggregates%20for%20concrete.pdf


Current basis: EN 12620 & EN 206+A1

▸ Only coarse RA▸ Low substitution ratios▸ Assuming no change in properties/not taking into account any change


Current situation:

▸ “High collection rates of well-segregated CDW are achieved…but the market uptake of recycled materials is really low; large storage areas at treatment plants have essentially become temporary landfills”

▸ Motivation: increase the use of RA in structural applications!

[1]

[2]




MC2020 section 12

3.Background to RAC code provisions


Background: significant amount of research performed overprevious decades on all levels – from material to structural

[3]

[4]

[5]

[6]

[7]

Background documents


Fabienne Robert, 2021

Choice of main variable – N.3

▸ Definition of αRA

▸ Future: changes to EN 206?

▸ Future: LoA with more variables?

[8]


Choice of main variable – MC2020

▸ τTRA (=αRA) and τRCA

▸ MC2020 does not rely on EN 206


Density

• volumetric vs. mass replacement ratio

Δ𝜌RAC = 𝜌ag ∙ 𝑉ag − 𝜌ag ∙ 𝑉ag ∙ 1 − 𝛼V,RA + 𝜌c ∙ 𝑉ag ∙ 𝛼V,RA = (𝜌c−𝜌ag) ∙ 𝑉ag ∙ 𝛼V,RA

𝛼RA =𝜌c ∙ 𝑉ag ∙ 𝛼V,RA

𝜌ag ∙ 𝑉ag 1 − 𝛼V,RA + 𝜌c ∙ 𝑉ag ∙ 𝛼V,RA=

𝜌c ∙ 𝛼V,RA

𝜌ag ∙ 1 − 𝛼V,RA + 𝜌c ∙ 𝛼V,RA

𝛼V,RA =𝜌ag ∙ 𝛼RA

𝜌c + (𝜌ag − 𝜌c) ∙ 𝛼RA

𝜌RAC = 2.50 − 0.22 ∙ 𝛼RA[9]


Compressive strength

• Input parameter in the code!

• No observed difference in statistical distribution vs. NAC

• <= C50/60 (~fcm,max = 60 MPa)

[10]


Modulus of elasticity

• 𝐸cm = 𝑘E ∙ 𝑓cmΤ1 3

• 𝐸cm = 𝑘E − 𝑘E − 𝑘RA ∙ 𝛼RA ∙ 𝑓cmΤ1 3

• Experimental database

• prEN1992: 𝐸cm = 𝑘E ∙ 1 − 0.25 ∙ 𝛼RA ∙ 𝑓cmΤ1 3

• MC2020: 𝐸cm = 𝑘E ∙ 1 − 1 −7100

𝑘E∙ 𝛼𝑅𝐴 ∙ 𝑓cm

Τ1 3

[9]


Tensile strength

prEN 1992: 𝑓ctm = 0.3 ∙ 𝑓ckΤ2 3 = 0.3 ∙ 𝑓cm − 8 Τ2 3; for concrete strength class ≤ C50/60

and 𝑓ctm = 1.1 ∙ 𝑓ckΤ1 3; for concrete strength class > C50/60

MC2020: 𝑓ctm = 1.8 ∙ ln 𝑓ck − 3.1 = 1.8 ∙ ln 𝑓cm − 8 − 3.1; for all strength classes

𝑓ctm = 𝑎 ∙ 1 − 1 −𝑏

𝑎∙ 𝛼𝑅𝐴 ∙ 𝑓ck

Τ2 3

Experimental database

For low RA content no change!

[9]


Stress–strain relationship

•𝜎c

𝑓cm=

𝑘∙𝜂−𝜂2

1+ 𝑘−2 ∙𝜂

• 𝜀c1 = 0.7 ∙ 𝑓cmΤ1 3 ≤ 2.8‰

• 𝜀cu1 = 2.8 + 14 ∙ 1 − Τ𝑓cm 108 4 ≤ 3.5‰

• Increases for RAC observed in experiments

• 𝜀c1 = 1+ 0.33 ∙ 𝛼RA ∙ 0.7 ∙ 𝑓cmΤ1 3 ≤ 2.8‰

• 𝜀cu1 = 1 + 0.33 ∙ 𝛼RA ∙ 2.8 + 14 ∙ 1 − Τ𝑓cm 108 4 ≤ 3.5‰

[9]


Fracture energy

• prEN 1992: not treated

• MC2020: 𝐺𝐹 = 85 ∙ 𝑓ck0.15

• Experimental database:

• 𝐺𝐹 = 1 − 0.4 ∙ 𝛼RA ∙ 85 ∙ 𝑓ck0.15

Shrinkage

• Strong increase for RAC!

• RECYBETON: 𝜀cs,RAC 𝑡, 𝑡𝑠 = 1+ 0.82 ∙ 𝛼RA ∙ 𝜀cs 𝑡, 𝑡s

• Tošić et al. 2018: 𝜀cs,RAC 𝑡, 𝑡s = 𝜉cs,RAC ∙ 𝜀cs 𝑡, 𝑡s =100∙𝛼CRA

𝑓𝑐𝑚

0.30∙ 𝜀cs 𝑡, 𝑡s ≥ 𝜀cs 𝑡, 𝑡s

• 𝜀cs,RAC 𝑡, 𝑡𝑠 = 1+ 0.8 ∙ 𝛼RA ∙ 𝜀cs 𝑡, 𝑡s


[11]

[12]

[12]

[9]

Creep

• Strong increase for RAC!

• RECYBETON:𝜑RAC 𝑡, 𝑡0 = 1 + 0.9 ∙ 𝛼RA ∙ 𝜑 𝑡, 𝑡0

• Tošić et al. 2019a: 𝜑RAC 𝑡, 𝑡0 = 𝜉cc,RAC ∙ 𝜑 𝑡, 𝑡0 = 1.12 ∙100∙𝛼CRA

𝑓cm

0.15∙ 𝜑 𝑡, 𝑡0 ≥ 𝜑 𝑡, 𝑡0

• 𝜑RAC 𝑡, 𝑡0 = 1 + 0.6 ∙ 𝛼RA ∙ 𝜑 𝑡, 𝑡0


[11]

[13]

[13]

[9]

Durability

• prEN 1992: If Exposure Resistance Classes (ERC) are not used, “traditional” cover

recommendations are given

• ERCs not envisioned by MC2020

• Qualitative literature review:

• Carbonation – cmin,dur,NAC + 5 mm

• Chloride ingress – cmin,dur,NAC + 10 mm


Flexural and shear strength

• Basing calculations on fcm – no need to modify flexural strength models

• For shear there is a need to increase γC!

• Members not requiring shear reinforcement:

• 𝜏Rd,c ≥ 𝜏Rdc,min ⟹0.66

𝛾C∙ 100 ∙ 𝜌l ∙ 𝑓ck ∙

𝑑dg

𝑑

Τ1 3

≥11

𝛾C∙

𝑓ck

𝑓yd

𝑑dg

𝑑

• 𝑑dg = 16 mm+ 𝐷lower ≤ 40 mm for 𝑓ck ≤ 60 MPa

• 1 − 0.2 ∙ 𝛼RA ∙0.66

𝛾C∙ 100 ∙ 𝜌l ∙ 𝑓ck ∙

𝑑dg

𝑑

Τ1 3

≥ 1 − 0.2 ∙ 𝛼RA ∙11

𝛾C∙

𝑓ck

𝑓yd

𝑑dg

𝑑

• ddg limited to 16 mm


Deflection control

• Decrease modulus; increase creep and shrinkage – not enough

• Decrease tension stiffening (Tošić et al. 2019b)

• 𝑎 = 𝑎1 ∙ 1 − 𝜁 + 𝑎2 ∙ 𝜁; 𝜁 = 1 − 𝛽tRA ∙𝜎sr

𝜎s

2

• 𝛽tRA = 1.0 for single, short − term loading

• 𝛽tRA = 0.25 for sustained or repeated loading

• Expression for L/d can be used as long as modulus, creep and shrinkage are considered


[14]

Bond and anchorage/lap lengths

• No differences observed relative to NAC


[9]

4.Implications for designand future work

Implications for design and future work

Example: 6-m one-way slab in a residential building, As for ULSShear strength:

Deflection control:

[15]

0.0

1.0

2.0

3.0

4.0

15 17 19 21 23 25

VR

d/V

Ed

L/d

NAC RAC 0.2

RAC 0.4

C25/30

0.0

1.0

2.0

3.0

4.0

15 17 19 21 23 25

VR

d/V

Ed

L/d

NAC RAC 0.2

RAC 0.4

C50/60

0.0

0.5

1.0

1.5

2.0

15 17 19 21 23 25

a/a

lim

L/d

NAC

RAC 0.2

RAC 0.4

C25/30

0.0

0.5

1.0

1.5

2.0

15 17 19 21 23 25

a/a

lim

L/d

NAC

RAC 0.2

RAC 0.4

C50/60

[15]

Implications for design and future work

Directions for future work

Punching: critical for RAC use in residential and office buildingsExisting research scarce or not fully representative

Carbonated RA: easier mix design, improvement of RAC fresh-state and hardened properties; structural behaviour?

Prestressed RAC: existing research scarce

Innovative reinforcements/concretes: FRC, FRP, 3DPC, etc.

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THANK YOU FOR YOUR ATTENTION!

RAEng Frontiers Champion Project:

Recycled Aggregate Concrete in South East Asia

Nikola TošićUniversitat Politécnica

de Catalunya

[email protected]

mailto:[email protected]

Documents

DESIGN STRATEGY FOR RECYCLED AGGREGATE CONCRETE