The entrance driveway to a new plant and headquarters office will include a bridge that crosses a small stream. The owner wants to avoid scaling of the bridge deck from road salts and, for the sake of appearance, also wants to avoid using any black membrane or other blacktop surface on it. We know that eventually even air-entrained concrete may suffer to some extent from road salts. Is there any way of getting a concrete bridge deck surface that will survive indefinitely without a coating or membrane and continue to look good?
A promising new method is to add 2 1/2 percent of wax beads to the concrete, which, in this case, should be non-air-entrained. The beads are a blend of 25 percent montan wax and 75 percent paraffin in sizes passing the Number 20 sieve but retained on the Number 80. After the concrete is cured and dried the slab surface is heated enough so that the temperature 3 inches below the surface is about 187°F. One method is to move radiant heat lamps slowly along the length of the slab. Pressurized steam blankets, hot air tents or gas-fired infrared heaters might also be used. The heat melts the wax and renders the concrete almost impermeable to the corrosive salts that might otherwise damage it. This suggestion is based on a report, "Internally Sealed Concrete," by G. H. Jenkins and J. M. Butler (Report PB 243011) available through the National Technical Information Service, Springfield, Virginia 22161 for $5.25. Most of the information needed for utilizing the method in the field is given in the 1-page article, "Wax Seals New Bridge Decks Internally," published in Concrete Construction,
September 1975, page 402.