The Concrete Choice

Whether it’s paving a small side street or building a country’s complex highway system, engineers have major considerations to keep in mind. Among the most pressing concerns are how they can make roads safer for drivers and stronger for heavy transport, which material to use to make the roads last longer and, of course, how to get the best value for the money they spend.

In the Philippines, the status of roadways is a prime concern for traffic and safety planners. According to the Asian Development Bank, seventy-five percent of government expenditures on transport infrastructure go to the road system. Still, motorists endure large potholes which often result in accidents and the traffic congestion for which Metro Manila’s streets have become world renowned.

One way to address the pothole problem is the selection of appropriate construction material. Many roads in the Philippines are built using asphalt, which is brought hot to the site, poured into a paving machine, and spread in 50 to 100-millimeter thick layers.

A greater number of roads are made of concrete, a hard and strong construction material made from a mixture of cement, gravel and sand. It is either mixed in ready-mix plants and delivered to the site by transit mixers, or batched at the construction site.

The Cement Manufacturers’ Association of the Philippines (CeMAP) recommends the use of concrete due to its proven superiority over asphalt in road construction applications. “A concrete road’s rigid structure allows it to spread the load over a wide area, reducing the stress on the sub-base beneath the road. Despite heavy loads passing over it, concrete resists the formation of potholes. Asphalt is flexible, making it more susceptible to wear and tear,” says CeMAP President Ernesto M. Ordoñez.

“While the initial cost of concrete is slightly higher than asphalt’s, its durability translates to less repair and maintenance, rendering it a much wiser investment. In the end, the builder saves more by using concrete. On a national level, this means large savings for the government,” Ordoñez adds.

A 1998 report prepared by United States-based, internationally recognized pavement engineering firm ERES Consultants, Inc. pointed out that, based on their experience, concrete pavements can last up to 34 years, as compared to asphalt’s 17-year life span. Further, that asphalt roads require maintenance repairs every three to five years, with major rehabilitation becoming more frequent after the 17th year overlay. Concrete averages 12 years before needing only minor repairs on correctly constructed roads.

Other international studies also confirm that concrete pavements effect significant savings in energy costs. A study conducted by the National Research Council of Canada has found that heavy vehicles traveling on concrete roads save as much as 11 percent in fuel costs, as compared to those plying asphalt roads. Concrete’s rigid surfaces, the NRC states, create less deflection than asphalt, resulting in reduced fuel requirements in heavy vehicles.

Furthermore, since concrete roads are less slippery than asphalt roads, there is more safety for motorists. For night driving, the better visibility of concrete over asphalt is another safety advantage. Naturally lighter in color, concrete reflects far more light than asphalt does, making roadways more driver-friendly.

(Click image to enlarge)

While highway accidents kill millions annually, concrete-paved roads contribute significantly to driver and passenger safety. With value for money, safety and other reasons mentioned earlier, the concrete choice is obvious.

WHY CONCRETE IS A WISER INVESTMENT — A rigid concrete pavement (left) spreads the load over a wide area, thus reducing the stress on the sub-base. This makes the pavement more durable and less susceptible to potholes. On the other hand, asphalt (right) is flexible and transfers heavy loads directly into the sub-base. Potholes form when the weakened sub-base is undermined by water.

Although concrete is a slightly more expensive paving material than asphalt, it lasts longer and requires very little annual maintenance. Since concrete is more cost-effective, the Department of Public Works and Highways builds twice more concrete roads than asphalt roads in the Philippines.

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