From roof tiles in California to highway sound walls in Canada, diverse and sustainable precast concrete applications are serving to measurably clean our air and water, and conserve energy.
By Sue McCraven
In the No.1 dairy-producing region in the United States, San Joaquin Valley, Calif., palm trees sway in warm breezes and the sun always shines, but there’s something else distinctive in the air: smog.
San Joaquin Valley’s perpetual smog has long confounded scientists, because this rural area produces more intense air pollution than Los Angeles. The reason? More than 1.5 million cows reside in this bucolic valley. Recent scientific studies have found that the valley’s fermented cattle feed produces 25 tons of ozone per day compared to 14 tons from automobile emissions. When sunlight combines with fog and air pollution, smog is formed.
Technically, smog is a sunlight-induced photochemical reaction with hydrocarbons that produces nitrogen oxide and volatile organic compounds (VOCs). Innovative cement technology can help remove this polluting nitrogen oxide from the air. When nitrogen oxide is removed from the air, smog can’t form.
How photocatalytic precast reduces smog
“Smog-eating” precast concrete roofing tiles made with photocatalytic cement, produced by Boral Roofing of Stockton, Calif., have been proven to measurably reduce air pollution. A home roof covered with 2,000 sq ft of smog-eating roof tiles can oxidize the amount of nitrogen oxide equivalent to that produced from a car driven 10,000 miles.1 Precast concrete roofing tiles can add only about $900 to the cost of a 2,000-sq-ft home.
According to John Renowden, Boral’s vice president of product development, “it’s the tile’s titanium-dioxide coating that works with the sun to take the nitrogen oxide out of the air.” This chemical reaction continues year after year, because the titanium-dioxide coating doesn’t wear away. “Smog-eating tile is the first product of its kind in the nation,” said Renowden.
The sustainable attributes of photocatalytic precast concrete roofing tiles include:
• Locally sourced raw materials (sand and water)
• Long service life, little to no maintenance, fire resistance
• Energy-saving benefits of concrete’s high thermal mass and the insulating air space between the roof tile and the deck that help homeowners achieve about 20% savings in energy costs2
• Full recyclability, as it can be crushed after its service life to be used in new concrete construction (roadways and buildings)
• Measurably less air pollution
While the air-pollution reduction achieved obviously depends on the number of homes installing smog-eating tiles, “Any little bit helps,” said Brenda Turner of the San Joaquin Valley Air Pollution District.
2. Precast Design Flexibility Opens the Door for Solar Energy
Strength of typical precast concrete roof panels gave the contractor the design flexibility to add solar roof panels for a sustainable low-income housing project.
“The biggest challenge on this project was when the financing fell through,” says Mark Taylor, president of Nitterhouse Concrete Products Inc. in Chambersburg, Pa. Mark is talking about the sustainability award-winning Kent Avenue Apartments, a low-income housing project for elderly and handicapped persons in Pennsville, N.J. “Nitterhouse was 49% complete with production at the time (2007).”
Fortunately, Tri-County Real Estate Maintenance Co. of Carneys Point, N.J., took over the project. Unfortunately, the new owners were “more familiar with wood and steel-stud construction, and they were concerned that the new financing would not allow for a totally precast structure,” recalls Taylor.
Convincing project owners to opt for all-precast structure
Nitterhouse invited the new owners, Ron Rukenstein and John Bibeau of Tri-County, to its Chambersburg plant and explained the benefits of a totally precast design, including speed of construction, strength, low maintenance and energy efficiency. The words “energy efficiency” perked up the two partners’ interest as Rukenstein said, “My concern, along with the financial incentives, made our decision to be environmentally responsible of paramount importance.” Nitterhouse won the contract.
Precast construction of the five-story, 101-unit Kent Avenue Apartments was complete in 37 days. The $2.6-million precast portion of the project included: 39,237 sq ft of 12-in.-thick insulated exterior wall panels; 16,693 sq ft of 7-in.-thick interior wall panels; 85,652 sq ft of 8-in. precast hollow-core planks; and 34 precast stairs with landings.
Originally, roof-mounted solar panels were not part of the design and “were not actually considered until after the building had been designed and constructed,” said Taylor. The typical precast hollow-core roof slabs, made with 6,000 psi concrete, had the structural strength to afford design flexibility for the owners to consider a roof-mounted solar energy system for the project. The roof’s reserve structural capacity meant that the precaster could “accommodate their (the owners’) change in plans without needing to otherwise reinforce or add supplemental structural members to support the solar panels,” says Daryl Wenger, sales manager at Nitterhouse. “Not all structural systems are as accommodating as precast.”
Precast panels handle added weight of solar panels
The addition of 462 solar panels to the roof of the precast structure added 61,000 lbs of loading, making the housing project one of the largest solar panel collection systems in New Jersey. This additional weight of 30-plus tons was no problem for the 8-in.-thick, 4-ft-wide, 32.5-ft-long hollow-core roof planks. The precast panels themselves each weigh in at almost 8,000 lbs.
“Building design is increasingly incorporating alternate energy sources such as solar panels,” said Wegner. “Designers view the building rooftop as the preferred location for mounting the panels, adding substantial loading to the roof structure. Precast hollow-core plank provides the capacity necessary while maintaining excellent free-span characteristics. Today’s designer is looking to incorporate every sustainable ingredient possible in the design. Total precast design also offers benefits in local, natural material selection and in thermal mass quality.”
According to Goff Sun Power, N.J., the company that built the system, within the solar panels’ life span, the system will produce 2.7 million kilowatt-hours of electricity and reduce 1,450 tons of CO2 emissions, the equivalent of planting 19,725 trees or 2.2 million miles not driven in a car. Because of the combined energy efficiencies achieved, the owner was able to eliminate 101 gas meters, making these units much more affordable than comparable housing. The average monthly heating cost for residents is about $40.
The upscale-looking Kent Avenue Apartments complex won the 2008 Governor’s Housing Conference Award for the most sustainably built building in New Jersey.
More than 750 of the oldest U.S. cities still have 19th-century sewer systems that result in CSOs (combined sewer overflows) wherein human and industrial waste and dirty stormwater are discharged together into a single collection system. This means problems often come with the pouring rain. In some cities, even moderate rainfall flowing into these outmoded underground pipes exceeds the sewer system’s capacity. As a result, these CSOs dump environmentally toxic wastes into streams, rivers and lakes, causing serious water pollution and risks to human and aquatic health.
Meeting Clean Water Act requirements
In Cleveland, a 24-ft-diameter tunnel constructed with precast segmental tunnel liners manufactured by CSI/Hanson-JV of Hudson, N.H., will be built 200 ft below the bed of Lake Erie, part of the 18,200-ft-long, $198-million Euclid Creek Tunnel project. “Construction of the Euclid Creek Tunnel is part of the consent agreement with the EPA and other state and federal agencies to reduce CSOs into rivers that flow into Lake Erie,” said Doug Gabriel, district construction program manager at the Northeast Ohio Regional Sewer District (NEORSD). “The consent agreement by NEORSD is intended to meet the requirements of the federal Clean Water Act.” Euclid Creek Tunnel is one of seven underground tunnels, totaling 20 miles in length that will be constructed under NEORSD’s Project Clean Lake program (http://neorsd.org/cleanlake) at a cost of $3 billion over 25 years.
Production of 24-ft-diameter precast ring segments
Production of the precast concrete segmental liners, reinforced with steel fibers, started in early 2012. Six segments make up each 24-ft-diameter ring, and there are more than 21,000 precast concrete segments to be produced for the project by CSI/Hanson-JV at its segment plant in Macedonia, Ohio. About 100 segments are produced each day, and delivery of the product to the construction site began in April 2012. The precision precast concrete segments are manufactured with mold tolerances of 0.018 in. to 0.040 in. Tunnel boring for the Euclid Creek portion is expected to begin in late 2012. McNally/Kiewit ECT JV is the prime contractor for the tunnel.
The purpose of the project is to catch and temporarily retain sewer overflows during rainstorms. Sewage collected from a 31-square-mile area, a portion of the Cleveland metropolitan area, will be pumped to a treatment plant and then returned as purified water to Lake Erie. The underground precast concrete pipe will be part of a sewerage containment system that, when completed, is expected to reduce the total volume of raw sewage and other pollutant discharges into Lake Erie by more than 90% annually.
4. Canadian Precast Sound Walls for Cleanest Roads in North America
University will measure a material innovation in creating cleaner air along urban highways.
Along Highway 401 in metropolitan Toronto, a high-volume traffic route, precast concrete sound walls are being monitored by air-quality recording equipment. The University of Toronto, beginning in summer 2012, will be testing the effectiveness of precast concrete sound walls made with photocatalytic cement to remove pollutants from the air. Today, as transportation officials across North America consider sustainability in project cost/benefit analyses, it becomes necessary to obtain a scientifically proven measure of positive environmental impacts. So, precast concrete sound walls in Toronto, Ontario’s provincial capital and Canada’s largest city, are the new “specimens” for scientific analysis.
When precast concrete products incorporate photocatalytic cement, their surfaces can improve air quality. Because of its cost, photocatalytic cement is often used just on the surface of structures. Production considerations, however, led precast producer Armtec/Durisol of Mitchell, Ontario, to use this special cement “uniformly throughout the mix used for the 54 sound wall units,” according to Ron Galloway, Armtec technical sales representative. Individual precast wall panels are 10 ft long and 20 in. high and may be stacked one upon the other. At the Highway 401 test site, the area under surveillance is 14.5 ft high and extends 60 ft.
Precast sound walls improve air quality for urban highways
When activated by ultraviolet rays from sunlight, titanium dioxide acts as a catalyst to accelerate the oxidation process that converts nitrogen oxides (and other smog components such as fine particulate material, carbon monoxide and sulfur dioxide) to less harmful compounds (see the illustration of this process in the story “Precast Concrete Versus Dairy Cows”).
The project’s initial intent was to conduct a 12-month-long sound wall test to verify other studies done throughout the world. This project scope, however, was not feasible due to time restraints and logistical complications. The Ontario Ministry of Transportation (MTO) is conducting a scaled-back test to confirm previously published results. For the field test, MTO partnered with Armtec, the University of Toronto and photocatalytic cement producer Essroc Italcementi Group. Published data from European and Asian demonstration studies have shown that photocatalytic cement applications can improve air quality by 20 to 70% and that about 10 sq ft of treated concrete can remove 2.1 x 10-3 ounces of nitrous oxide per day. Effectiveness depends on wind (strong winds perpendicular to the precast sound wall are optimal), intensity of sunlight, concentration and location of air pollution (more is better) relative to the treated concrete and other factors. “European research shows that photocatalytic concrete placed in an area the size of a soccer field can remove emissions equal to approximately 190,000 km (118,000 miles) per year,” says Shawn Smith, project engineer at MTO Provincial Highways Management Division.
Precast concrete with photocatalytic cement is also used to keep its surfaces clean. “The surface-cleaning capabilities of the material are a bonus,” says Smith. “The concrete is self-cleaning, depending on conditions. It doesn’t do big stuff like graffiti or gum, but it will remove many of the compounds that form on it, relying to some degree on the rain to wash them away. Many structures in Europe use the product to keep buildings looking white.”
What is MTO’s long-range goal? To have the greenest roads in North America.
Bell’s Brewery of Galesburg, Mich., a regional craft beer brewery, employs more than 100 people and distributes 24 brands in 18 states. In 2011, the brewery opted for an 85-ton geothermal heat-exchange system3 of high-density polyethylene tubing as a sustainable energy source for the facility. About 100,000 ft of tubing was installed 8 ft underground (at an 8-ft depth, the earth stays at a steady temperature of about 52 F), and spread in a close-looped coils design covering two acres. The tubing holds a solution of 20% propylene glycol and 80% water that transfers geothermal energy from the earth to the facility. The brewery’s geothermal system will provide heating, cooling and power for a 42,000-sq-ft office extension.
“Geothermal is one of the most proven renewable energy sources,” said Evan Meffert, sustainability manager at Bell’s Brewery, “and there are decent business cases to be made for this technology in Michigan, where sun and wind (solar and wind power) may not be as abundant as in other states.”
A precast concrete valve vault houses the business end of 48 pipes and the inflow and outflow piping. Advance Concrete Products Inc.4 of Highland, Mich., fabricated and installed the 9- by 13- by 7-ft custom valve vault for this geothermal project. “We needed a custom design for the vault that involved moving the reinforcing steel to make room for the tube openings,” said Marcus Delong, president and owner of Geothermal Loop Pros LLC, Jenison, Mich.5 “The precaster was easy to work with, and there was no problem coring the 1.25-in. openings for the tubing.”
50% energy savings
A geothermal installation can provide more than energy savings for a company – it can also be a smart capital investment. By installing the $150,000 geothermal project, the brewery was able to take advantage of the 2009 federal stimulus package,6 which meant a tax credit of 10% up front on the total investment and 100% depreciation against company profits in the first year. In 2012, companies can claim a bonus 50% depreciation the first year, on top of an accelerated five-year 100% depreciation. Many states offer additional incentives.
“Michigan utilities offer incentives for energy-efficient projects,” said Meffert. “The funds we were able to secure helped in the effort to present a solid business case for the system.”
A geothermal system has a lot to say about a company’s commitment to sustainability, the environment and the community. With a geothermal system, Bell’s Brewery foresees a 50% reduction in energy costs over the long term.
1 PICADA: Photocatalytic Innovative Coverings Applications for De-pollution Assessment, Europe, 2004.
2 Steep-slope Assembly Testing of Clay and Concrete Tile, Oak Ridge National Laboratory. The results vary based on the profiles of the tiles installed.
3 1 ton is equivalent to 12,000 BTU
4 See July-August 2012 issue of NPCA’s Precast Inc. magazine for a company profile on Advance Concrete Products
5 Visit www.geothermallooppros.com
6 2009 American Recovery and Reinvestment Act
Sue McCraven, NPCA technical consultant and Precast Solutions editor, is a civil and environmental engineer.