3 - North Washinton Avenue Discussion

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_ Some manufacturers supply pigments in pure oxide form, while others offer pigments combined with set-controlling and water-reducing admixtures. Pigments are also available in liquid form and can be added at the ready mix plant or at the job site when the specifications permit. It is important to follow the manufacturer's recommendations, especially when mixing various colors. Powdered, dry shake colors have also been used to color concrete surfaces, particularly in combination with stamped textures to give the texture some definition and contrast. However, dry shake color alone is not recommended for vehicular pavements — to maintain consistent color, use integral color due to the potential for abrasion of the surface. Crosswalks Typically, the different colors and patterns of a stamped and colored crosswalk are placed in different stages to separate the colors and textures. Incorporating stamped and colored crosswalks into concrete pavements is not difficult, but in order to design and construct this area correctly, you need to follow a few simple steps. First, identify the need to have each pattern placed separately. Consider placing the crosswalk integrally with the rest of the concrete pavement, with blockouts to define the colored areas. Within a stretch of approximately 10 feet (3 m) of pavement (typical crosswalk widths are 6-10 feet [2-3 m]), there could possibly be up to four construction joints. If separate pours are required for the decorative design, decide in your jointing plan whether to tie or dowel the crosswalk to the surrounding pavement. If there is no separate border as in Figure 1, the jointing plan is made simpler. If a border section is required as in Figure 2, one successful method is to tie the border section to the crosswalk or to the pavement with tiebars, and then dowel the other side of the border into the adjacent pavement or crosswalk (Figures 3 through 5). Use the same dowel and tiebar sizing requirements as you would for standard pavement design. Do use tiebars on both sides of a border—this will restrain the movement of the joints and will likely cause cracking. The width of the border should be at least 16 in. (400 mm), or wide enough to accommodate the tiebars and/or dowel bars. The borders should have more joints along their length than in the surrounding pavement; try to keep the aspect ratio (length to width) of the panels in the border portion around 2.0 if possible. For regions of the country that receive snowfall, a key point when using stamped patterns in an area subject to vehicular traffic is choosing a pattern that is minimally impacted by snowplows. Use a non-aggressive pattern, i.e. one that protrudes only slightly, to avoid breaking or chipping of the stamped concrete surface by snowplow blades. Figure 1.Different color identifies the crosswalk Figure 2.Colored crosswalk with stamped brick boundary