role of cement & concrete in sustainable development · 2013-06-20 · kimberly kurtis school...
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Role of Cement & Concrete in
Kimberly Kurtis
School of Civil & Environmental Engineering
Sustainable Development
School of Civil & Environmental Engineering, Georgia Institute of Technology
Engineers for a Sustainable WorldNovember 15, 2012
Outline
Context– Why do we care about cement and concrete, in particular?
Case Study– Assessment and Utilization of Recycled Aggregate
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What are cement & concrete?Some common mineral cements: – portland (calcium silicate-based)– calcium aluminate
d t l d b t
– gypsum (plaster of paris)– calcium sulfoaluminate
l i ili t
Cement paste = +
M t
– some dental and bone cements – aluminosilicate
Mortar = + +
Concrete = + + +
Impacts of Infrastructure on EnvironmentAt the global level, the built environment in each country is estimated to account for:
25-40% of the energy consumption 30-40% of the material resource consumption 30-40% of the waste production 30-40% of the greenhouse gas (GHG) release
70% of raw materials consumed are used in
construction
Materials manufacture (cement, plastics, metals) currently accounts for 20-25% of
Source: http://www.ntnu.no/sustainability/crucial
Each year, 200M tons of construction wastes are discarded in landfills
worldwide energy consumption
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Why do we care about cement & concrete?The ubiquity of concrete construction presents an incredible opportunity for impact through development of innovative green technologies
With >20Bt placed each year, concrete is most widely used construction material
Ashby, 2009
Concrete ProductionEmbodied energy associated with concrete production
PCA, SN3001
~ ¼ barrel oil per yard or ~ 2 tons of concrete
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Cement Manufacture: ReviewTraditional cement manufacture:
Utilizes virgin materials: 1.5 t raw material is required for 1 t cementEnergy intensive: 6-8% worldwide fuel consumption
CaCO3 (limestone)2SiO2•Al2O3 (clay, shale)Fe2O3 (iron oxide)SiO2 (silica sand)
Kiln
Fossil fuel intensive Liberates CO2: CaCO3 –heat-> CaO + CO2 ( )
3CaO•SiO22CaO•SiO23CaO•Al2O34CaO•Al2O3•Fe2O3Clinker
intergroundFinishedcement
Gypsum +
CaO•SO3•2H2O
Kiln
CaCO3 60%
Fuel 40%
CO2 Emissions
WRI, 2005
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Cement ManufactureTremendous (40%) improvements in energy efficiency Alternatives to fossil fuel combustion would decrease CO2emissions associated with energy use– Waste fuels – Hydro (regional, enviro concerns)
N l ( i ) S l (i ffi i t)– Nuclear (enviro concerns) – Solar (inefficient)
Carbon capture??? Wet process (pre-1970’s)
Dry process (modern)
CementWater
AirFine Aggregate
65-75% of volume
Role of Aggregates? Recycled waste/by-product materials– recycled concrete
recycled tires
Coarse Aggregate
is stone & sand– recycled tires– slag…
Potential for CO2capture/sequestration– reaction with hydrated cement
in recycled concrete aggregates
– overcoming crushing energy critical for this application
Pervious concrete– control runoff– filtration
pervious concrete layer
open-graded gravel basesources: PCA; Offenburg, Conc. Int., 2005.
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Outline
Context– Why do we care about cement and concrete, in particular?
Case Study– Assessment and Utilization of Recycled Aggregate
Recycled Aggregate ConcreteAggregate extraction can contribute to: – Particulate matter generation/ release
N i ll ti
Each year, 200M tons of construction wastes are discarded in landfills;
100M tons are concrete– Noise pollution– Energy consumption (<10% of
concrete EE) – GHG emissions (<< cement)
Aggregate is a high bulk, low value commodityRecycled concrete aggregate (RCA) is primarily used low-value applications; in road base and as fill, with more limited usage in structural concrete
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Why would we want to use this as a case study? y“Scientists warned… (the earth) has not created a significant number of new rocks since the earth cooled some 3.5B years ago.Moreover, … (this supply has) been very slowlyhas) been very slowly depleting… due to growing demand for fireplace mantels, rock gardens, gravel and paperweights.”
Source: The Onion
Recycled Aggregate ConcreteRecycling concrete as aggregate makes most economic and ecological sense in regions that are:– Space constrained
Resource constrained– Resource constrained– Other (e.g., economic incentives,
abundance of recyclable material)
Increasing rates of aggregate recycling have largely stemmed from increased taxation on both mineral extraction and waste landfilling.
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Recycling Aggregate in CaribbeanThe 2010 Haiti earthquake resulted in ~20 million cubic yards of debris, enough to fill the Louisiana Superdome five times over .It is estimated that debris removal could take 20 years or more to accomplish at current removal rates. Two years following the earthquake in Haiti, reconstruction progresses slowly.
What to do with debris?In Haiti, as in other Caribbean islands:– Population density is high; landfilling debris is not a viable option– Environmental issues likely prevent use as fill or in artificial reefs– Limited natural resources for new constructionLimited natural resources for new construction
Finding a way to safely reuse the debris can have a huge positive impact on rebuilding efforts, while simultaneously minimizing the impact on the environment, and ultimately is a key to accelerating reconstruction.
Lessons learned canLessons learned can be applied in other countries and after other types of events
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Research Plan
Objective: To determine if Haitian concrete debris could be combined with other local materials to produce good quality concrete.quality concrete.Steps:– Obtain Haitian concrete and local fine aggregate; assess their
quality– Crush concrete to produce aggregate– Characterize recycled aggregate and local virgin aggregates to
obtain properties needed for mix design– Design, produce, and test concrete mixes – Assess long-term performance
Haitian Concrete QualityProportioning often done by eyeMixing performed often by hand
fcave= 1300psi
56-day strength results for cylinders batched and cast in Haiti
Low strength of debris is a significant challenge for reuse in structural concrete
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Concrete Aggregate Concrete
Concrete Strength Results
fcave= 1300psiHow can a concrete strength be greater than the strength of the
Concrete used as Aggregate
fcave= 3100psi
aggregate from which it is produced?
Recycled Aggregate Concrete
ave p
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Further Testing/Implementation
Variation with RCA source– Define limits on properties– Develop specificationsDevelop specifications
Long-term performance– Shrinkage, creep– Durability– Seismic behavior of RCA concrete
Environmental impacts– LCI/LCA– LCI/LCA– Dynamic assessment needed during reconstruction
Based upon these results Systematic recycling efforts can be developedhttp://www.statesman.com/blogs/content/shared-gen/blogs/austin/charity/entries/2011/01/10/haiti_one_year_later.html
Assessment of seismic performance of code-based and underreinforced beam-column connections, containing virgin and recycled concrete aggregate.
Further Testing/Implementation
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Questions?
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