Editing Concrete (section)

==Environment, health and safety==
{{main|Environmental impact of concrete}}
{{unbalanced section|date=January 2024}}

The manufacture and use of concrete produce a wide range of environmental, economic and social impacts.

===Health and safety===
{{see also|Occupational dust exposure#Construction}}
[[File:Dust emission when using electrical power tools.webm|thumb|upright=0.83|[[Concrete dust]] emission from the use of power tool]]
[[File:Crushed Concrete Granular Fill.jpg|thumb|Recycled crushed concrete, to be reused as granular fill, is loaded into a semi-dump truck]]

Grinding of concrete can produce [[hazardous dust]]. Exposure to cement dust can lead to issues such as [[silicosis]], kidney disease, skin irritation and similar effects. The U.S. [[National Institute for Occupational Safety and Health]] in the United States recommends attaching local exhaust ventilation shrouds to electric concrete grinders to control the spread of this dust. In addition, the [[Occupational Safety and Health Administration]] (OSHA) has placed more stringent regulations on companies whose workers regularly come into contact with silica dust. An updated silica rule, which OSHA put into effect 23 September 2017 for construction companies, restricted the amount of breathable crystalline silica workers could legally come into contact with to 50 micro grams per cubic meter of air per 8-hour workday. That same rule went into effect 23 June 2018 for general industry, [[hydraulic fracturing]] and maritime. That deadline was extended to 23 June 2021 for engineering controls in the hydraulic fracturing industry. Companies which fail to meet the tightened safety regulations can face financial charges and extensive penalties. The presence of some substances in concrete, including useful and unwanted additives, can cause health concerns due to toxicity and radioactivity. Fresh concrete (before curing is complete) is highly alkaline and must be handled with proper protective equipment.

===Cement ===
A major component of concrete is [[cement]], a fine powder used mainly to bind sand and coarser aggregates together in concrete. Although a variety of cement types exist, the most common is "[[Portland cement]]", which is produced by mixing clinker with smaller quantities of other additives such as gypsum and ground limestone. The production of clinker, the main constituent of cement, is responsible for the bulk of the sector's greenhouse gas emissions, including both energy intensity and process emissions.<ref>{{cite web |last1=Akerman |first1=Patrick |last2=Cazzola |first2=Pierpaolo |last3=Christiansen |first3=Emma Skov |last4=Heusden |first4=Renée Van |last5=Iperen |first5=Joanna Kolomanska-van |last6=Christensen |first6=Johannah |last7=Crone |first7=Kilian |last8=Dawe |first8=Keith |last9=Smedt |first9=Guillaume De |last10=Keynes |first10=Alex |last11=Laporte |first11=Anaïs |last12=Gonsolin |first12=Florie |last13=Mensink |first13=Marko |last14=Hebebrand |first14=Charlotte |last15=Hoenig |first15=Volker |last16=Malins |first16=Chris |last17=Neuenhahn |first17=Thomas |last18=Pyc |first18=Ireneusz |last19=Purvis |first19=Andrew |last20=Saygin |first20=Deger |last21=Xiao |first21=Carol |last22=Yang |first22=Yufeng |title=Reaching Zero with Renewables |date=1 September 2020 |url=https://www.h2knowledgecentre.com/content/researchpaper1611 }}</ref>

The cement industry is one of the three primary producers of carbon dioxide, a major greenhouse gas – the other two being energy production and transportation industries. On average, every tonne of cement produced releases one tonne of CO<sub>2</sub> into the atmosphere. Pioneer cement manufacturers have claimed to reach lower carbon intensities, with 590&nbsp;kg of CO<sub>2</sub>eq per tonne of cement produced.<ref>{{cite web |title=Leading the way to carbon neutrality |publisher=HeidelbergCement |date=24 September 2020 |url=https://www.heidelbergcement.com/en/system/files_force/assets/document/7e/8c/co2-strategie_factsheets_en.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.heidelbergcement.com/en/system/files_force/assets/document/7e/8c/co2-strategie_factsheets_en.pdf |archive-date=2022-10-09 |url-status=live }}</ref> The emissions are due to combustion and calcination processes,<ref>{{cite web |title=Cement Clinker Calcination in Cement Production Process |url=http://www.cementplantequipment.com/all-the-things-about-cement-clinker-calcination-in-cement-production-process/ |website=AGICO Cement Plant Supplier |date=4 April 2019 }}</ref> which roughly account for 40% and 60% of the greenhouse gases, respectively. Considering that cement is only a fraction of the constituents of concrete, it is estimated that a tonne of concrete is responsible for emitting about 100–200&nbsp;kg of CO<sub>2</sub>.<ref>{{cite web |publisher=Portland Cement Association |title=Carbon footprint |url=https://www.cement.org/docs/default-source/th-paving-pdfs/sustainability/carbon-foot-print.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.cement.org/docs/default-source/th-paving-pdfs/sustainability/carbon-foot-print.pdf |archive-date=2022-10-09 |url-status=live }}</ref><ref name="Lehne-2018">{{cite web |last1=Lehne |first1=Johanna |last2=Preston |first2=Felix |title=Making Concrete Change: Innovation in Low-carbon Cement and Concrete |date=13 June 2018 |url=https://www.chathamhouse.org/2018/06/making-concrete-change-innovation-low-carbon-cement-and-concrete }}</ref> Every year more than 10 billion tonnes of concrete are used worldwide.<ref name="Lehne-2018" /> In the coming years, large quantities of concrete will continue to be used, and the mitigation of CO<sub>2</sub> emissions from the sector will be even more critical.

Concrete is used to create hard surfaces that contribute to [[surface runoff]], which can cause heavy soil erosion, water pollution, and flooding, but conversely can be used to divert, dam, and control flooding. [[Concrete dust]] released by building [[demolition]] and natural disasters can be a major source of dangerous [[air pollution]]. Concrete is a contributor to the [[urban heat island]] effect, though less so than [[Asphalt concrete|asphalt]].

===Climate change mitigation===
Reducing the cement clinker content might have positive effects on the environmental life-cycle assessment of concrete. Some research work on reducing the cement clinker content in concrete has already been carried out. However, there exist different research strategies. Often replacement of some clinker for large amounts of slag or fly ash was investigated based on conventional concrete technology. This could lead to a waste of scarce raw materials such as slag and fly ash. The aim of other research activities is the efficient use of cement and reactive materials like slag and fly ash in concrete based on a modified mix design approach.<ref>{{cite journal |last1=Proske |first1=Tilo |last2=Hainer |first2=Stefan |last3=Rezvani |first3=Moien |last4=Graubner |first4=Carl-Alexander |title=Eco-friendly concretes with reduced water and cement contents – Mix design principles and laboratory tests |journal=Cement and Concrete Research |date=September 2013 |volume=51 |pages=38–46 |doi=10.1016/j.cemconres.2013.04.011 }}</ref>

The embodied carbon of a precast concrete facade can be reduced by 50% when using the presented fiber reinforced high performance concrete in place of typical reinforced concrete cladding.<ref>{{cite journal |last1=O'Hegarty |first1=Richard |last2=Kinnane |first2=Oliver |last3=Newell |first3=John |last4=West |first4=Roger |title=High performance, low carbon concrete for building cladding applications |journal=Journal of Building Engineering |date=November 2021 |volume=43 |page=102566 |doi=10.1016/j.jobe.2021.102566 }}</ref> Studies have been conducted about commercialization of low-carbon concretes. [[Life-cycle assessment|Life cycle assessment]] (LCA) of low-carbon concrete was investigated according to the ground granulated blast-furnace slag (GGBS) and fly ash (FA) replacement ratios. Global warming potential (GWP) of GGBS decreased by 1.1&nbsp;kg CO<sub>2</sub> eq/m<sup>3</sup>, while FA decreased by 17.3&nbsp;kg CO<sub>2</sub> eq/m<sup>3</sup> when the mineral admixture replacement ratio was increased by 10%. This study also compared the compressive strength properties of binary blended low-carbon concrete according to the replacement ratios, and the applicable range of mixing proportions was derived.<ref>{{cite journal |last1=Lee |first1=Jaehyun |last2=Lee |first2=Taegyu |last3=Jeong |first3=Jaewook |last4=Jeong |first4=Jaemin |title=Sustainability and performance assessment of binary blended low-carbon concrete using supplementary cementitious materials |journal=Journal of Cleaner Production |date=January 2021 |volume=280 |page=124373 |doi=10.1016/j.jclepro.2020.124373 |bibcode=2021JCPro.28024373L |s2cid=224849505 }}</ref>

===Climate change adaptation===
High-performance building materials will be particularly important for enhancing resilience, including for flood defenses and critical-infrastructure protection.<ref>{{Cite book |last=Sabry |first=Fouad |url=https://books.google.com/books?id=udiTEAAAQBAJ&dq=High-performance+building+materials+will+be+particularly+important+for+enhancing+resilience,+including+for+flood+defenses+and+critical-infrastructure+protection.&pg=PT145 |title=Translucent Concrete: How-to see-through walls? Using nano optics and mixing fine concrete and optical fibers for illumination during day and night time |date=2022-01-17 |publisher=One Billion Knowledgeable |language=en}}</ref> Risks to infrastructure and cities posed by extreme weather events are especially serious for those places exposed to flood and hurricane damage, but also where residents need protection from extreme summer temperatures. Traditional concrete can come under strain when exposed to humidity and higher concentrations of atmospheric CO<sub>2</sub>. While concrete is likely to remain important in applications where the environment is challenging, novel, smarter and more adaptable materials are also needed.<ref name="Lehne-2018" /><ref>{{Cite journal|last=Mehta|first=P. Kumar|date=2009-02-01|title=Global Concrete Industry Sustainability |url=https://www.concrete.org/publications/internationalconcreteabstractsportal/m/details/id/56323|journal=Concrete International|language=en|volume=31|issue=2|pages=45–48}}</ref>

=== End-of-life: degradation and waste ===
[[File:Tunkhannock Viaduct, NE Pennsylvania USA.jpg|thumb|The [[Tunkhannock Viaduct]] in northeastern Pennsylvania opened in 1915 and is still in regular use today]]{{Excerpt|Concrete degradation|only=paragraph}}

===Recycling ===
{{Excerpt|Concrete recycling|only=paragraph|paragraphs=2}}There have been concerns about the recycling of painted concrete due to possible lead content. Studies have indicated that recycled concrete exhibits lower strength and durability compared to concrete produced using natural aggregates.<ref>{{Cite journal |last1=Abdo |first1=Ayman |last2=El-Zohairy |first2=Ayman |last3=Alashker |first3=Yasser |last4=Badran |first4=Mohamed Abd El-Aziz |last5=Ahmed |first5=Sayed |date=2024-01-01 |title=Effect of Treated/Untreated Recycled Aggregate Concrete: Structural Behavior of RC Beams |journal=Sustainability |language=en |volume=16 |issue=10 |pages=4039 |doi=10.3390/su16104039 |doi-access=free |bibcode=2024Sust...16.4039A |issn=2071-1050}}</ref><ref>{{Cite web |title=Khoan Cắt Bê Tông |url=https://khoanphabetong365.net/ |access-date=2024-10-25 |website= |language=}}</ref><ref>{{Cite journal |last1=Abdelfatah |first1=Akmal S. |last2=Tabsh |first2=Sami W. |date=2011 |title=Review of Research on and Implementation of Recycled Concrete Aggregate in the GCC |journal=Advances in Civil Engineering |language=en |volume=2011 |pages=1–6 |doi=10.1155/2011/567924 |doi-access=free |issn=1687-8086}}</ref><ref>{{Cite journal |last=Lu |first=Linfeng |date=July 2024 |title=Optimal Replacement Ratio of Recycled Concrete Aggregate Balancing Mechanical Performance with Sustainability: A Review |journal=Buildings |language=en |volume=14 |issue=7 |pages=2204 |doi=10.3390/buildings14072204 |doi-access=free |issn=2075-5309}}</ref> This deficiency can be addressed by incorporating supplementary materials such as fly ash into the mixture.<ref>{{Cite journal |last1=Rao |first1=Akash |last2=Jha |first2=Kumar N. |last3=Misra |first3=Sudhir |date=2007-03-01 |title=Use of aggregates from recycled construction and demolition waste in concrete |url=https://linkinghub.elsevier.com/retrieve/pii/S0921344906001315 |journal=Resources, Conservation and Recycling |volume=50 |issue=1 |pages=71–81 |doi=10.1016/j.resconrec.2006.05.010 |bibcode=2007RCR....50...71R |issn=0921-3449}}</ref>