This document discusses strategies for reducing the carbon dioxide (CO2) emissions associated with concrete construction. It outlines various components of concrete mixes and their typical CO2 contributions. Lowering the cement content and replacing it with supplementary cementitious materials like ground granulated blast furnace slag (GGBS) or fly ash can reduce CO2 by 50%. Using natural aggregates rather than synthetic ones also lowers CO2. An audit process is presented for quantifying the embodied CO2 of different building materials and construction elements. With modifications like using recycled steel frames, less ductwork, and promoting public transport, construction CO2 can be reduced by up to 40%. The overall goal is to minimize CO2 through material selection and design solutions that also

1. Sustainable Concrete Design
• ·
• Lowering CO2 in
Construction
• CO2 Construction Audit
• Elegance in Architecture
David Bennett
Architectural Concrete Consultant

2. Picture a Glass of Latte
What’s the Embodied C02?
• Raw Material
• Production
• Packing
• Transport
• Shop
• Hot Water
• Coffee Container
• Milk
• Sugar

3. Concrete and C02
It’s just like a good cup of coffee
Expresso, Americano, Latte, Macchiato,
Mocha
Insitu, Precast, SCC, GRC, Ductal, Rammed
Discuss

13. C02 and Concrete Construction
• Cement
• Aggregates
• Ready Mix
• Rebar
• Formwork /Temporary
Work
• Plant & Machinery
• Labour

17. Concrete
Cement is one sixth of concrete
kg C02/tonne
• OPC range 930 > 760
• GGBS 54
• PFA 4
• Rocktron 50

18. Persistence Works

19. Lowering Cement C02 by 50%
• Blend OPC with GGBS/PFA
• Carbonation Benefits of OPC

20. Aggregates are 80% of Concrete
Aggregates kg C02/tonne
• Natural Washed - 4
• Natural Crushed - 4-10
Synthetic Aggregates
• Lytag Sintered PFA 60
• Liapor (expanded shale) 12

21. Typical Concrete Mix
Constituents
kgC02/m3
OPC 180 kg Ribblesdale 137
GGBS 180 kg C&M 8
Sand 750 kg Lea Valley 3
Gravel 1200 kg Thames Estuary 5
Water 180 kg Thames Water 0
Admixture ignore
Embodied kg C02/m3 153

23. CO2 of Wood
Captured CO2 = 1.84 x density
Embodied CO2
Process plywood 670 kg C02/tonne
Wisa – birch phenolic faced
18mm thick 29 kg CO2/m2
(assumes the wood is carbon zero)

27. Formwork
Temporary Support/
Falsework
Disposable Items
• Form Face Ply
18mm thick
• Plastic Cones
• Tie Rods

30. The Form Face & Sustainable
Design
• Select Material for a Good Finish
• High Reuse Factor
• FSC Grade
• Re-use in Permanent Architecture
• Responsible Design

33. Rebar C02
kg C02/tonne Total
Two Stage Process
1. Coil Manufacture 422
2. Fabrication
a) Bar 63 485
b) Mesh 88 501
Celsa/ BRC Audit
includes production , staff travel and transport

39. Concrete Quality and
Aesthetic
• Visual Concrete Specification
• the choice, the mix, the form, the finish
Get it right!

40. Thrifty Beeches

42. Spedant Works

44. Kew Herbarium

46. CHUR House

47. The C02 Construction Audit
Four Buildings Assessed
two concrete, two steel
• Bill of Quantities
• Embodied C02 of Materials
• Plant/Machinery/Labour

48. Some Anomalies
Some references are distorted
• Resin, Polyurethane, Paint, PVC
resolve micron/m2
• Structural Steel
new or recycled? check
• Lightweight Lytag Concrete
high C02/m3
RECONCILE them

49. Construction Audit Examples
• Substructure
• Superstructure
• External Cladding
• Finishes
• Mechanical Ducting

50. Building CO2 Audit Summary
Element M4C3 % M4S3 % M4C7 % M4S7 %
Substructure 136 10 95 4 254 9 160 3
Superstructure 350 27 1348 59 904 31 3411 63
External cladding 263 20 267 11 532 18 545 10
Finishes 432 33 433 19 893 31 911 1
M&E: Fully air conditioned 59 4 59 3 137 5 137 3
Plant & labour 83 6 89 4 190 6 189 4
Total (av.) 1322 100 2291 100 291 100 5353 100
Tonnes CO2

52. Building CO2 Audit Summary
Possible reductions in CO2 for lean solution
Element M4C3 % M4S3 % M4C7 % M4S7 %
Frame - na -768 na -1972
All recycled steel
M&E;
a) eliminate suspended -60 na -149 na
ceiling
b) Reduce ductwork -53 na -124 na
Public transport -77 -83 -183 -182
Total CO2 reduction -190 -14 -851 -37 -455 -16 -2154 -40

57. Total C02 Design Solution
• Minimise Construction C02
• Utilise Thermal Mass for Long Term
Energy Reduction
Lower Total C02 Emissions

61. Concrete is just like a good coffee -
Make it the low C02 blend!