the roads you drive on are engineered to endure the harsh weather and make winter driving safer. no matter how accustomed we are to driving in winter, the ice and snow will always pose a threat. that’s why roads are designed to implement some of the following treatments and techniques.
protecting pavement from the elements
air entrainment – it’s not uncommon to experience several freeze-thaw cycles during the winter season. when subjected to freezing temperatures, moisture within a portland cement concrete (pcc) pavement freezes and expands. to prevent damage to the pavement from expanding moisture, pcc pavements are designed to include a specified amount of entrained air. tiny bubbles are produced and incorporated throughout the concrete mixture. when the pavement hardens, the bubbles allow room for moisture to freeze and expand without damage to the concrete.
tiny bubbles in concrete mixtures allow room for moisture to freeze and expand, without damage to the concrete.
supplementary cementitious materials (scms) – scms, such as fly ash and slag cement, are materials that have similar properties as cement. they are used to replace a portion of cement in pcc mixtures and improve its long-term strength and durability. scms improve the density of the pavement’s pore structure making it more difficult for fluids to pass through. de-icing salts that can penetrate the pore structure can lead to the development of a distress-causing material called calcium oxychloride. when a scm is used in the mixture, it chemically reacts with a byproduct from the concrete hardening process. with the removal of the bi-product, calcium oxychloride is not able to be formed, and future distress is mitigated.
hot mix asphalt (hma) – hma pavements are now engineered with special binders that help them withstand extreme temperatures. binders are sticky, black adhesives that hold asphalt concrete together. this substance is engineered to provide thermal crack resistance during cold temperatures and rut resistance during warmer temperatures. mixes are also selected based on the amount of force or “traffic loading” anticipated while the road is in use.
improving skid resistance
high friction surface treatment (hfst) – both pcc and hma pavements can be treated with a high friction surface treatment (hfst) to improve skid resistance and surface traction. hfst is composed of hard angular aggregate and thermosetting epoxy. it is typically only applied in designated problem areas where excessive speeds on curves can lead to accidents.
high friction surface treatment (hfst) helps to improve skid resistance and surface traction.
angular aggregate – special, hard angular aggregate can be used on hma pavement to improve surface friction. this aggregate is typically used on interstate pavement. the higher cost means it’s not a common solution for city roads.
diamond grinding – surface friction properties for pcc pavements can also be improved by diamond grinding, diamond grooving — or a combination of the two. diamond grinding is a technique that corrects irregularities by grinding long, parallel grooves into the surface of the concrete pavement. this process adds more surface area to the pavement to improve surface drainage and increase contact area with vehicle tires.
geometric design – to improve winter driving, the road must be designed for efficient drainage and effective plowing. in some areas, flat stretches of pavement can lead to water ponding, which ultimately can create ice patches. cross-slope transitions with tilted surfaces minimize the effectiveness of snow and ice removal. in addition, the layout of some roadways makes them more likely to accumulate drifting snow. comprehensive engineering design foresees and addresses these risks.
diamond grinding is achieved by grinding long, parallel grooves into the surface of the concrete pavement.
a transportation engineer may foresee that s-curves will require high-friction surface treatment. they may anticipate that an area is more susceptible to pooling water and implement a drainage system with diamond grinding on the road. although it’s not apparent, our roads are designed to be durable and prevent weather conditions from effecting our travel. transportation engineering works daily to keep us safe and get us where we need to go.
