As a building material, precast concrete has an edge over other materials in many sustainability practices, but a precaster can be environmentally friendly in other ways as well.
By Joan Shirikian-Hesselton
Precast concrete manufacturing has an intrinsic environmental advantage compared with constructing similar products at a job site. Although it may be something we take for granted, this advantage has always been an important component of any precast product, and in today’s environmentally conscious world it is becoming a more important value-added component of precast concrete products.
Precast elements have many natural advantages over pouring concrete at a job site. The environmental conditions in a precast concrete facility are much more consistent and can be managed much better than at a construction site, resulting in better quality. This prevents waste from products that are rejected because of inconsistency. It also allows better control and monitoring of raw materials than when pouring at a construction site. Pouring on site also creates unexpected delays that result in wasted concrete when the ready-mix delivery has not been properly sequenced. These issues can be more easily managed at a precast facility, resulting in product that is made in a more environmentally friendly manner.
Since a manufacturing facility is a relatively stable environment, it is also better equipped to handle other elements that can be potential environmental offenders. Whatever systems are put into place, it is important to remember that there are numerous federal and local regulations regarding the control of process water runoff, air emissions and even noise.
How often do we think about the forms and beds used at precast facilities? They are certainly not single-use items. Steel forms allow for sustainable production, as all types of forms use components that can be interchanged, allowing for different-sized products. Even when specialty forms are built with plywood, they generally are used for multiple pours. At a building site, it is common to find forms that are scrapped after a single use.
In conjunction with the major environmental advantages listed above that are intrinsic to precast concrete facilities, a number of environmentally friendly initiatives can be undertaken with relatively minor changes in precast plant operations and production processes. If implemented, they will have a positive environmental and safety effect.
Less toxic materials
Form oil has traditionally been a mineral oil release agent. Mineral oil may affect workers’ health; pollute soil, water and air; is flammable; is not considered biodegradable; and, depending on quantity and condition, may require disposal as a hazardous waste. New form oils are available that contain a mix of biodegradable oils (marine ester, medical white oil and vegetable oil) and are nontoxic. Many precasters are starting to experiment with these nontoxic oils.
Muriatic acid traditionally has been used in precast concrete facilities to remove concrete and rust from forms. However, there are now biodegradable nontoxic materials that can replace muriatic acid and eliminate the environmental and safety hazards.
Many paints and sealants used on finished products contain volatile organic compounds (VOCs) that are emitted as gases and include a variety of chemicals. Some of the chemicals have short-term and even long-term adverse health effects. Many less-toxic paints and sealants can replace these products. Once again, this is not only safer for employees but it is the environmentally friendly alternative to a more toxic product. It also makes cleanup and container disposal easier and more economical while keeping
employees, the environment and the community safer.
Admixtures are used in concrete mixtures in very small quantities and therefore have negligible environmental impact. Their use is important since they provide added benefits to the concrete and to the environment. Admixtures can reduce the amount of water required without contributing to emissions; improve durability by increasing the frost resistance of concrete; and help control the setting of the concrete.
Reinforcement of precast concrete is similar to reinforcement installed at a building site. However, when the precaster prepares the steel and mesh at the precast facility there is better control than when a contractor does this on a job site. Once again, the precaster uses less raw material and consumes fewer natural resources.
Process water can also be reclaimed, treated and reused. The amount of water that can be used with each batch will depend on the reclamation system and treatment type. However, with proper monitoring and maintenance, the process can be perfected. Wash areas for equipment can allow for water capture, filtration and reuse, but it is important to ensure that process water is always handled properly.
Air emissions always need to be properly controlled. There should never be any type of visible dust cloud anywhere in or around the facility. Bag houses and filters need to be properly maintained. Roadways at the facility also need to be kept in a condition to eliminate dust. Proper speed needs to be enforced for safety and to reduce dust. It is always beneficial to have roadways paved, since this helps keep dust down, although this is not always possible. When any type of suppressant is used on yards or roadways it is essential that it is environmentally friendly.
Material Safety Data Sheets (MSDSs) must always be reviewed when making a material selection, and they need to be reviewed with employees and added to the MSDS file.
Many saws used in precast facilities are equipped with vacuum attachments to help reduce particulate emissions. Other work practices such as establishing work stations that allow product to be brought to a specific area where proper ventilation is provided can be used to eliminate emissions and exposure. In this type of situation, as with bag house systems, proper filter maintenance is essential.
Noise needs to be properly controlled. It is both a safety hazard and an environmental issue. With the introduction of self-consolidating concrete (SCC), there is less need for vibrator use. This has significantly reduced the noise level in many facilities and generally has been an improvement to the environment inside the facility.
Depending on the facility and the community, it may be necessary to consider the yard noise. Some facilities have limited operating hours or have built sound barriers to help block some of the noise to allow early morning and late evening operations without disturbing the surrounding neighborhood.
Whether the facility operates its own fleet or uses hired hauling, it is important to ensure there is proper maintenance on all vehicles so that the product is not being hauled on trucks that are emitting inappropriate exhausts.
Housekeeping is another critical component that impacts all aspects of the precast facility. Poor housekeeping will negatively impact safety, environmental issues and product quality. If housekeeping is maintained, employees will take pride in their work and the facility. It has been shown that the pride and respect good housekeeping generates will impact all the other work aspects at the facility.
The plant is not the only place for concern with the environment. Office activities should also respect the environment. Recycling is an important part of every business. There should be appropriate containers throughout the facility to allow for separation of materials for recycling. Initially it may be difficult to change people’s behavior, but with some time and encouragement and maybe some innovative introductory programs, it can be achieved.
Recycling does not just apply to paper in the office and metal in the shop. Electronic equipment can be recycled in a number of different ways (see the companion articles on sustainability in this issue). Outdated computers and cell phones can be donated to shelters or schools. Broken equipment needs to be properly disposed of to ensure it does not end up in a landfill where it can contaminate natural resources. Batteries, toner and ink cartridges, and cleaning chemicals all have safe disposal mechanisms. Many items have manufacturer-sponsored return programs. These programs not only save money but they ensure the environment is not negatively impacted by improper disposal of dangerous materials.
Another way to help preserve the environment is to encourage paperless communication when appropriate. People often print e-mails and other items even though they have no need for the printed copy. Discussions with employees can generate plans and ideas on ways to become more environmentally friendly in this area. And it will save money.
It is important that employees are familiar and compliant with all appropriate federal, state and provincial rules and regulations. Just as with most regulatory authorities, various permits may be required depending on what the plant does, what materials are used and even where business is conducted. Safety and environmental activities complement each other; however, they each require very strict record keeping, specific paperwork and reporting independent of each other.
It is important to consider all these topics on a daily basis. By conducting activities in a fashion that works to preserve the environment and keep the plant safer, production and business will be preserved for future generations.
Joan Shirikian-Hesselton is an independent Occupational Safety and Health consultant. She has more than 30 years of experience in Occupational Safety and Health in both the public and private sectors, including a decade of dedicated experience in the precast/prestressed concrete industry. She is a past NPCA Safety, Health & Environmental Committee chair, and she has worked with U.S. OSHA as a Special Government Employee.