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CNY Engineering Expo 20159 November 2015
Jim D’Aloisio, P.E., SECB, LEED AP BD+CPrincipalKlepper, Hahn & Hyatt
How can we reduce our CO2 –e emissions from concrete without compromising the performance of our structures?
(keeping project costs in mind, of course)
…is this an important new design parameter?
Quantify the approximate CO2‐e emissions from concrete, based on mix design and yardage.
Realize the importance of, and potential for, reducing CO2‐e emissions from concrete.
Learn low‐ CO2‐e alternatives to traditional concrete construction systems that can be implemented with currently available technology and systems.
Identify research needs and opportunities that will help to further reduce CO2‐e emissions.
1. Rationale for this new design parameter
2. Alternatives to conventional foundations to reduce the concrete volume used
3. Use of Supplementary Cementitious Materials to offset Portland cement quantity
4. Alternatives to standard concrete slabs‐on‐grade that can reduce cement usage
5. Use of Insulated Concrete Forms (ICF) to reduce cement usage in superstructure walls
6. Voided Slab Systems (VSS) for 2‐way slabs
7. Current research on alternative cements
29% +117 PPM
Prior to 1880
Added 1880‐2014
71% 280 PPM
41% increase in atmospheric CO2 since 1880
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Source: NASA’s Goddard Institute for Space Studies
400
320
340
360
380
300
220
240
260
280
2013 CO2 Concentration: 4002013 CO2 Concentration: 400
CO2(ppmv)
180
200
800,000 700,000 600,000 500,000 400,000 300,000 200,000 100,000 0
Age (years BP)
Source: National Climatic Data Center, NOAA
Reduce CO2e of construction
PERSONAL PROFESSIONAL * POLITICAL
MITIGATION
IMMEDIATETry to use minimal
A/C
Advocate for CO2e redux
(Representative actions only)
Emergency response aid
ADAPTATION
LONG‐TERM
IMMEDIATE
LONG‐TERM
(i.e. resilience)
Reduce energy use of buildings
Design for more powerful storms
Insulate and air seal your home
Practice natural ventilation
Insulate and air seal your home
Improve codes for resiliency
Increasing help for storm victims
Advocate for pricing of CO2e
* ‐ actual response varies with the profession
Volunteer lobbyists advocating CO2 reduction
Carbon Fee and Dividend
Places a steadily rising fee on the CO2 content of fossil fuels.
Gives all of the revenue from the carbon fee back to households.
Border adjustments will discourage businesses from relocating.
It's good for the economy AND even better for the climate
www.citizensclimatelobby.org
Production of Portland cement accounts for 6 to 8%* of the worldwide anthropogenic CO2
About half is a byproduct of the chemical reaction
About half is produced by heating ‐ 2,700 ⁰F
1 ton of Portland cement produces just under 1 ton of CO2
Global production of Portland cement is increasing about 5% per year
200,000 metric tonnes of CO2 emitted by cement producers every hour
* ‐ the actual percentage is subject to debate Portland cement plant in Alpena, MI
Life‐Cycle Assessment (LCA)
LEED v4 – new Materials & Resources Category
Product Category Rules (PCRs)
Environmental Product Declarations (EPDs)
National Ready‐Mixed Concrete Association (NRMCA): EPDs for concrete mixes across USA!
See…http://www.nrmca.org/sustainability/EPDProgram/Downloads/NRMCA%20EPD%2010.08.2014.pdf
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BOTTOM LINE: Standard concrete emits
About 0.1 lbs. CO2 per 1 lbs. of concrete
About 1 lb. CO2 per 1 lbs. of Portland cement
From 350 – 800 lbs. CO2 per yard of concrete
See…http://www.nrmca.org/sustainability/EPDProgram/Downloads/NRMCA%20EPD%2010.08.2014.pdf
Approximately how much CO2‐e gas is emitted into the atmosphere from 10 yards of concrete with 500 lbs. per cubic yard of cement?
Approximately how much CO2‐e gas is emitted into the atmosphere from 10 yards of concrete with 500 lbs. per cubic yard of cement?
ANSWER:
10 X 500 = 5,000 lbs.
Source: BuildingGreen
Why overspecify strength?
Durability is not proportional to strength
More cementmore shrinkageMore cement more shrinkage
How low would you go? 2500 psi? 2000 psi?
W/C and workability: water reducers vs cement
STANDARD OPTIMIZED FLOWABLE FILL(100 lbs/cy cement)
7.7 sf concrete 5.0 sf concrete 4.0 sf conc; 3.5 sf flowable fill
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DEEPDEEP‐‐TRENCH TRENCH FLOWABLE FLOWABLE FILLFILL
FROST‐PROTECTED SHALLOW FOUNDATION
2.6 sf concrete
2.7 sf conc; 7.0 sf flowable fillStandard: 7.7 sf concrete
Strategically placed rigid insulation and drainage fill
Reduces depth of excavation backfillexcavation, backfill, foundation material
Schemes for both heated and unheated buildings and elements
Source: National Association of Home Builders - www.nahb.com
Industry‐standard design guides available
Required to be used by some large clients
Can save money, time, and GWP gas emissions (in several ways)(in several ways)
Watch the type of insulation used!
Highly detail‐ and construction‐sensitive
Name three advantages to using frost‐protected shallow foundations over conventional spread footings.
Name three advantages to using frost‐protected shallow foundations over conventional spread footings.
ANSWERS:
Less concreteLess CO2‐e emissionsLess deep excavationFaster constructionCheaper
Fly AshByproduct of coal‐fired electric and steam generating plantsType C and Type F ‐ both used for concrete15 ‐ 25% cement replacement, typical
Ground Granulated Blast Furnace Slag (GGBFS)Ground Granulated Blast‐Furnace Slag (GGBFS)Co‐generated during the refinement of iron from iron oreMust be ground to cement‐grain finenessEffect on concrete is similar to Fly Ash25 ‐ 50% cement replacement, typical
Silica Fume (aka Microsilica)Produced in the refining of silicon metal or ferrosilica alloysVery fine particles. Increases water demand. “Sticky” concreteIncreases strength, adhesion, decreases permeability7 ‐ 10% cement replacement, typical
Others ‐ Rice Hull‐ Ground Glass‐More
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The use of fly ash in concrete:Reduces permeabilitySlightly delays strength gainSlightly reduces shrinkageReduces heat of hydrationIncreases workabilityI i t t ASRIncreases resistance to ASRSlightly higher ultimate strengthReduces and delays bleeding
Other EffectsReduces the amount of CO2 generatedReduces the amount of waste disposed in landfillsMay reduce cost!
How can fly ash reduce the amount of CO2‐e emitted from concrete?
How can fly ash reduce the amount of CO2‐e emitted from concrete?
ANSWER:
If the amount of Portland cement is reduced 1:1, then it reduces the CO2‐e that would have been emitted from that amount of cement.
Typical Concrete Slab Strength: 3000 psi
3000 lbs./in 2 X (12 in./ft.)2 = 432,000 psf
Typical Floor Live Loading: 100 psf
432,000 psf / 100 psf = 4,320 use a 2.0 FoS….
* Most concrete slabs on grade are at least 2,000 times stronger than their required strength! *
STANDARD ALTERNATIVE5” standard concrete on compacted subbase
4” low‐strength concrete with superplasticizer on compacted
subbase w/ 3/8” underlayment topping
Concrete Type, Amount of Cement
CO2‐e per SF
4000 psi, 450 lbs./CY 6.9
3000 psi, 350 lbs./CY 5.4 (22% redux)
3000 psi, 20% SCM, 280 lbs./CY
4.3 (38% redux)
Concrete Type, Amount of Cement
CO2‐e per SF
2000 psi, 50% SCM, 150 lbs./CY
1.8 (70% redux)
500 psi, 50% SCM, 50 lbs./CY
0.62 (91% redux)
Inherent air barrier system / no convection currents
Concrete has high thermal mass
Block Panel & Plank s stemsBlock, Panel, & Plank systems
Over 20 brands in North America
Can be used for
Residential and nonresidential
Basement and above grade walls
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Structurally – reinforced concrete walls and beams
Connections penetrate inner insulation layer
l l bRemove inner insulation at slabs at retaining walls
Inspection during concrete placement is critical
Can use high volume fly ash concrete
Boys and Girls Club of Binghamton
Completed 2009
Worcester CSD
Completed 2013
How can the use of ICFs reduce the CO2‐e emissions from a project?
How can the use of ICFs reduce the CO2‐e emissions from a project?
ANSWER:
The amount of SCM can be increased in the concrete, with a 1:1 reduction of CO2‐e.
It reduces the energy usage of the building due to thermal mass, air barrier, and good insulation
Voids in concrete at non‐structurally critical areas
Reduces concrete, Portland cement, and weight
Increases span capacity and/or reduce depth
Design methodologies based on flat slab design
http://www.crsi.org/index.cfm/engineering/floor
30 – 35% typ. reduction in cement and CO2‐e!
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Hybrid cement
Alkali cementsAlkali‐Activated Cements (AAC)
Aluminosilicate‐based alkaline cements
Geopolymer cements
Sulfur cement
Fly ash cement
Calcium sulfoaluminate‐based cements
Gypsum cements
BASE CASE
50,000 sf, two story rectangular building, 25,000 sffootprint, 100 ft X 250 ft., with 12’foot high walls
2nd floor – 2‐way concrete slab, 25 foot spany p
1st floor – concrete slab on grade
Perimeter walls 1st‐2nd floor – 8”concrete
Conventional spread footings
Roof framing – steel beams, joist, and roof deck
MODIFIED CASE
25% SCM in all concrete, unless otherwise noted
2nd floor – 2‐way concrete voided slab system
1st floor lo strength concrete slab on grade1st floor – low strength concrete slab on grade with high‐strength flowable fill topping
Perimeter walls 1st‐2nd floor – 8” ICF, 50% SCM
Frost‐protected shallow perimeter foundations
Roof framing – steel beams, joist, and roof deck
SYSTEM 50,000 sf, 2‐story bldg, 25,000 sffootprint – no SCM in concrete
2nd floor – 2‐way concrete slab, 25 foot span – 8” thick, 4000 psi
t fl ” l b
CO2‐e EMISSONSAssume 3000 psi conc 350 lbs., 4000 psi conc. 450 lbs.
(25,000 X 8/12) X 450 = 278,000 lbs.
( / )/ )1st floor – 5” concrete slab on grade, 3500 psi
Perimeter walls 1st‐2nd floor – 8” concrete, 4000 psi
Conventional spread footings –say 3’ deep X 16” wide fd’nwalls, avg. 3’ wide, 1’ deep footings, 4000 psi.
(25,000 X 5/12)/27) X 350 = 135,000 lbs.
[(2 X 100 + 250) X 12 X 8/12]/27 X 450 = 93,000 lbs.
700 X [(3 X 16/12) + 3]/27 X 450 = 82,000 lbs.
TOTAL CO2e = 588,000 lbs. (12 psf)
SYSTEM 50,000 sf, 2‐story bldg, 25,000 sffootprint – 20% SCM u.n.o.
2nd floor – 2‐way voided slab, 25 foot span – 8” thick, 4000 psi
t fl ” h
CO2‐e EMISSONSAssume 3000 psi 350 lbs., 4000 psi. 450 lbs., 500 psi 75 lbs.
(25,000 X 8/12) X .65 /27 X (.75 X 450 = 135,000 lbs.
[ ( / ) ( /1st floor – 4” 500 psi conc. with 3/8”, 750 lbs./cy topping
Perimeter walls 1st‐2nd floor – 8” ICF concrete, 3000 psi
Frost‐protected shallow foundations – say 1’ deep X 16” wide fd’n walls, avg. 3’ wide, 1’ deep footings, 3000 psi.
[25,000 X (4/12 X 75) + (.4/12 X 500)] / 27 = 46,000 lbs.
[(2 X 100 + 250) X 12 X 8/12]/27 X 450 X .5 = 47,000 lbs.
700 X [(1 X 16/12) + 3]/27 X 350 X .75 = 42,000 lbs.
TOTAL CO2e = 270,000 lbs. (5.4 psf)
200,000
250,000
300,000
BASE CASE
MODIFIED
Lbs. CO2‐e from Concrete Elementsfor 50,000 sf Building
0
50,000
100,000
150,000
Perimeter Foundations
1st Floor Slab 1st Floor Walls 2nd Floor Slab
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Approximately` how much CO2‐e is emitted per square foot, from a 5‐inch thick, 3500 psi slab, with no SCMs?
Approximately` how much CO2‐e is emitted per square foot, from a 5‐inch thick, 3500 psi slab, with no SCMs?
ANSWER:
11 psf
Do not over‐specify concrete strength
Use SCM as much as possible
Consider flowable fill to reduce concrete volume
Minimize foundation concrete area
Consider use of FPSFs, ICFs, VCSs when appropriate
Consider alternative slab systems
Encourage use of EPDs, CO2‐e tallies of projects
Stay tuned for future research results!
Questions?
What have you learned?
What will you do?
Jim D’Aloisio, P.E., SECB, LEED AP BD+C
Klepper, Hahn & Hyatt
East Syracuse, NY
CNY Engineering Expo27 February 2015
