Concrete
Concrete is an essential product used in a variety of construction, infrastructure and industrial applications. Ready-mixed concrete is Canada's most widely used construction material, accounting for about 70% by volume of all construction materials. Up to two thirds of Canadian concrete is estimated to be used in residential and commercial foundations or basements. Concrete is also used in the construction of municipal and transportation infrastructure including roads, bridges and sidewalks.
Concrete is made by mixing Portland cement, water and coarse (stone) and fine (sand) aggregates and may include the addition of admixtures (chemicals to control setting properties). The reaction between cement and water results in the hardening of the mixture, producing concrete. Cement accounts for only 9-13% by weight of the finished concrete. Supplementary cementing materials (SCMs) may also be used to replace a portion of the cement. SCMs used include fly ash (byproduct of coal-fired power generation), ground blast furnace slag (byproduct of metals smelting) and micro silica (silica fume).
The concrete manufacturing process releases the following substances declared toxic under the Canadian Environmental Protection Act, 1999 (CEPA):
- PM10 (Respirable Particulate Matter less than or equal to 10 microns in diameter)
- Sulphur Oxides (SOx)
- Nitrogen Oxides (NOx)
- Volatile Organic Compounds (VOC)
- Ground-level Ozone (O3) (generated as a result of chemical reactions between NOx and VOCs)
Other pollutants associated with this industry are:
- Total Particulate Matter (TPM)
- Carbon Dioxide (CO2)
- Carbon Monoxide (CO)
- Methane (CH4)
- Nitrous Oxide (N2O)
The following table demonstrates the comparison between the concrete manufacturing industry and National Total Industry Emissions for 2000.
| Emissions (tonnes) | |||
| Pollutant (Criteria Air Contaminants) | Ready-mixed concrete | Total Industrial Emissions | Ready-mixed Industry's Contribution to National Industry Emissions |
| Total PM | 10,292 | 637,000 | 1.6% |
| PM10 | 3,142 | 305,000 | 1.0% |
| PM2.5 | 1,068 | 213,000 | 0.5% |
| NOx | 112 | 681,000 | 0.0% |
| VOC | 6 | 1,037,000 | 0.0% |
| SO2 | 134 | 1,972,000 | 0.0% |
| CO | 89 | 2,192,000 | 0.0% |
Source: ICF Consulting Canada, Multi-pollutant Emission Reduction Analysis Foundation (MERAF) for the Canadian Ready-Mixed Concrete Sector, Final Report, 2002.
(URL: http://www.ccme.ca/assets/pdf/rdy_mix_cncrte_smmry_meraf_e.pdf)
Particulate matter is the main substance of concern released from this sector, accounting for about 1.6% of Total PM from Canadian industrial sources. Particulate matter is mainly released through fugitive emissions during materials handling and storage activities. Small amounts of other substances are formed from the combustion of natural gas and distillate oil used in mix water heating.
Canadian Context
Concrete is manufactured across Canada in about 700 facilities. Because ready-mixed concrete cannot be transported for long distances, production is concentrated in urban regions with the highest demand from manufacturing and construction activities. The sector is mostly composed of small regional suppliers employing less than 50 workers per establishment.
Emission Management Practices and Regulations
Federal Government
- The Canadian Environmental Protection Act, 1999 (CEPA 1999)
- National Pollutant Release Inventory (NPRI)
- National Ambient Air Quality Objectives (NAAQOs)
- Management of Toxic Substances, Environment Canada
Canadian Council of Ministers of the Environment (CCME)
Provincial Governments
Substance Release Regulation (Alta. Reg. 124/93)
Alberta Ambient Air Quality Guidelines (pdf)
Regulation 164/88 (pdf)
Air Pollution Regulation (Environmental Protection Act R.R.O 1990, Reg. 346)
Point of Impingement Standards, Point of Impingement Guidelines and Ambient Air Quality Criteria (AAQCs)(pdf)
Regulation Respecting the Quality of the Atmosphere R.R.Q.A. 1981, c. Q-2, r.20
Règlement sur les attestations d'assainissement en milieu industriel (RAMMI)
Air Quality Regulations (pdf)
Municipal Governments
Greater Vancouver Regional District (GVRD):
Emission Regulation for Ready Mix Concrete and Concrete Products Industries (pdf)
History
Concrete was first used in large-scale construction by the Egyptians around 3000 B.C. Production of hydraulic cement began in Canada in 1830. Ready mixed concrete was first produced in 1913 in Baltimore, Maryland, USA.
(Source: dee Concrete Accessories, http://www.deeconcrete.com/concretehistory1.html)
Take Action
Consideration should be given to the application of Best Available Techniques (BAT) for the prevention and control of emissions in the ready-mix concrete manufacturing process. Whenever possible, prevention of substance formation should be the preferred option. Process technology is being constantly improved to reduce the generation and release of emissions.
There are many opportunities to take action and reduce pollution.
