Environmental groups have settled litigation against the Metropolitan Water Reclamation District of Greater Chicago (MWRD) over pollution from...
Roads covered in concrete may produce safer results, higher visibility
Last summer, the Fort Bend County Toll Road Authority (FBCTRA) opened the Fort Bend Parkway, a 6.2-mile-long toll road serving residents traveling to and from Houston. Connecting State Highway 6 and Beltway 8 in the eastern part of Fort Bend County, the Parkway features two lanes in each direction, with four interchanges, one mainline toll plaza and ramp tollbooths at two locations.
This first-class roadway meets a need for area residents and takes advantage of the safety-enhancing benefits of white-cement concrete. The material was used on about three-quarters of a mile at the north end of the toll road on outer barriers, which were extended to heights of 6 to 8 ft to act as noise barriers. White cement also was used to create bridge rails on five bridges, each approximately 300 linear ft.
One reason the county chose white cement was to create a safer roadway. Research shows that white-cement concrete offers higher reflectivity than conventional gray-cement concrete, and in municipalities across the country, the material is used to create safer infrastructure components.
Aesthetic concerns also drove the decision. White cement—particularly when used for architectural details on bridge railings—helped contribute to a better-looking project, a high priority for the FBCTRA.
“We want to support the quality-of-life features and current developments already under way in the area by adding aesthetically pleasing artistic details to the parkway that will represent the Fort Bend County history and lifestyles,” said Charles Rencher, FBCTRA board member, during the planning process. White cement helped make that happen.
White cement is portland cement, just like the more conventional gray portland cement. Essentially the same material, they are different only in color; both offer the same performance characteristics when used in concrete. The process of manufacturing white cement is tightly controlled to achieve correct, consistent color, primarily by minimizing raw materials containing metal oxides like manganese and iron.
As a portland cement, white cement, like its gray counterpart, is manufactured in accordance with ASTM C 150 Standard Specification for Portland Cement. According to the Portland Cement Association (PCA), Type I, II, III and V white cements are available, with Types I and III being the most common. Placement and finishing of white-cement concrete are the same as with conventional concrete.
As when creating any concrete mix design, working with white-cement concrete requires careful specification of each component. Cement, aggregates, water, admixtures—all have an impact on the color of the finished material. So it is essential that in specifying, and later in construction, all members of the construction team are clear on the requirements for maintaining equipment and materials to create the best outcome.
Of all those involved in the construction process, ready-mix concrete plants face the biggest challenge when using white-cement concrete. Many smaller ready-mix plants have only two silos, one for gray cement and one for a supplementary cementitious material like fly ash. For a smaller plant, working with white cement might mean cleaning out an entire silo to store the white cement or using bagged product in addition to dedicating trucks and full plant operations. (Or, scheduling white cement operations for the first part of the day, when trucks are already clean from the previous day.)
“You can’t just haul gray cement concrete and come back and haul white. You have to clean out the trucks and plant first, or, as an alternative, break bags into trucks,” explained James Gohlke, technical sales representative for Lehigh White Cement Co., which supplied the white cement. “Working with white cement may be easier for larger companies with multiple plant locations, which typically have the flexibility to easily make it work. But in reality, any ready-mix concrete operation can work with white cement.”
Safety was a major concern for the FBCTRA. Research has shown that white-cement concrete offers a more reflective surface than gray-cement concrete. In its study, “Effects of Composition and Exposure on the Solar Reflectance of Portland Cement Concrete,” the Lawrence Berkeley National Laboratory found that “white-cement concretes were on average significantly more reflective than gray-cement concretes. The albedo of the most reflective white-cement concrete was 0.18 to 0.39 higher than that of the most reflective gray-cement concrete, depending on the state of exposure.”
This high reflectivity helps make median barriers, curbs and other structures stand out more in both day and night conditions. Gohlke said during normal daytime conditions, white-cement concrete is twice as reflective as gray. In rainy weather or nighttime conditions, it is three times as reflective. “Median barriers made with conventional gray concrete really blend in when they’re wet,” he said.
In choosing the design, the FBCTRA considered the aging population that now drives our roadways, added Gohlke, “A lot more of us are over 50 years old, and our eyesight is worse at night. Anything we can do to make median barriers stand out is a big plus.”
Richard Fields, P.E., partner with the transportation engineering firm Aguirre & Fields LP, helped develop aesthetic scheme guidelines and details for structures on the parkway. He said that in doing his research he found white cement would definitely offer greater visibility.
“I was impressed with the photos that James Gohlke had showing the distinction between the white-cement concrete and the gray-cement concrete, contrasting photos that were quite impressive, especially in the rain,” said Fields. “I knew that was what the toll-road authority wanted.”
Pretty without the makeup
The initial cost of using white cement is higher than gray cement, sometimes double, according to Gohlke. But Jim Spackman, P.E., project director with general engineering consultant Turner Collie & Braden (parent company: AECOM), said using white cement did not have an adverse effect on costs for this project. While the firm adjusted approximately $1 per ft in its construction estimate to account for the material, “Our bids on all of the barrier that we used came in a good bit below our estimate,” he said. “It didn’t actually cost us anything more to add the white cement.”
Typically, the cost of white cement is higher than gray (sometimes twice the price, in fact), but the payoff is often worth it: the initial cost is often made up for in savings on maintenance.
“White cement is a little more expensive, but the durability of the finished product, and not having to paint it or maintain it . . . the maintenance savings are a big deal.” This from Mike Stone, director of construction for the FBCTRA.
Stone, a former construction manager, was a FBCTRA board member who resigned to take on the full-time consulting job of handling projects for the county. He said durability was a key factor in the decision-making process; typical barrier construction in the area is to cast jersey-style barriers in gray concrete and paint them.
“The problem with that is, particularly here in Houston, it can be 100° and 100% humidity and it’s really difficult to keep those coatings on the rails and looking good,” said Stone.
And the bonus, he added, is obvious: “It just looks so much better on the road.”
White cement “gave the project an enhancement,” Spackman said. “It definitely looks unique. The toll-road authority was pretty conscious of wanting to build a facility that had a bit of a unique look that didn’t look like just another road out there. They took pains to make this a more attractive facility, and the white cement was part of that.”
Stone said he sees a future in using white cement to create more architectural details in infrastructure applications. White cement helps make architectural details stand out, and he said that with all of the bridge columns that the Texas DOT erects there are plenty of opportunities for exercising creative license.
“TxDOT uses form liners and puts architectural detailing in columns, then goes back and paints these in different colors,” he explained. “What would be really nice would be to do them with white cement. Then, instead of painting the entire column, just paint the recessed architectural details with a darker color. I’d like to give that a try,” said Stone.
Worth a try
White cement is being used all over the U.S. to create a wide variety of infrastructure components. In Pennsylvania, the turnpike commission specified white-cement concrete parapets for bridges, primarily to increase visibility in dark and rainy conditions. In Chicago’s high-traffic and pedestrian-heavy Old Town neighborhood, white-cement concrete was used to create curbs and nosings at median terminations to increase visibility.
White-cement concrete also can be used to increase visibility and safety near train tracks at grade crossings or to construct curbs and medians in busy areas. And some municipalities take the process a step further, using white cement to create brightly colored concrete components. Blending white cement with colored pigments can achieve almost any color imaginable for use in creating yellow safety striping or markers, multicolored walkways or decorative planters. Concrete made with white cement and colored pigments can offer both increased safety and beauty.
Stone said the experience using white-cement concrete was definitely positive, and one that the FBCTRA will repeat. “It’s a good thing,” he said. “People who see the finished results all voice the same sentiment.
“I don’t know how many folks have ever tried working with it, but I think it’s one of those things where until you try to use it and see how big a difference it can make in the appearance of something, you really don’t know what you’re missing.”