A patented machine that can apply liquid coatings to concrete floors in a fraction of the time it takes to apply coatings manually is now available. This self-propelled machine has two 10-foot-long applicator blades, one at the front and one at the rear, that quickly and evenly spread coatings onto prepared concrete or asphalt surfaces. Power is supplied by a 5-hp gasoline engine. The machine is as easy to operate as a riding lawn mower. As the machine travels forward, the driver simply steers it around any obstacles by pushing levers that control the drive wheels. On straight paths with no obstacles, the floor coater doesn't even need a driver. It automatically travels in a straight track and follows the contour of the base being coated.
A passivating oxide layer protects embedded steel reinforcement from corrosion. Over time, however, chloride and carbonation can cause the passivating oxide layer to deteriorate, leaving rebar open to corrosion. One way to rehabilitate concrete that has been corroded by carbonation is to remove the contaminated concrete and expose the corroded rebar so corrosion can be removed. Another newer option stops corrosion by drawing chloride ions out of contaminated concrete and restoring the high pH level. This process can restore concrete in 10 days to 10 weeks, according to its developer.
Diversified Concrete Cutting, Sparks, Nevada, found itself facing dust problems when it attempted to clean sawed joints along I-395, just north of Reno, using conventional abrasive blasting methods. Contract specifications originally called for sandblast cleaning of expansion joints before sealing. But workers soon found that it blew so much sand and dust into the air that it created a visibility hazard for motorists. So the contractor decided to try wet blasting. This method doesn't create dust because it uses a mixture of abrasive and water, which is then removed from the area by vacuum equipment. On this project, however, it was impossible to remove all water from the pavement surfaces and joint cuts without interfering with traffic. After water evaporated, cutting fines, abrasive, and dust that were suspended in the water remained in the cuts.
The manufacturer of a new imprinting tool described the tool's speed and ease of use by saying it was as easy as broom finishing and twice as fast as pattern stamping. The tool consists of a hollow aluminum cylinder, having either a brick- or cobblestone-patterned relief, and a detachable bracket that can receive any standard bull float handle. To roll the cylinder across the slab surface, simply push it using the float handle. Using several float handles attached end-to-end allows rolling the cylinder across a wide slab without having to walk on fresh concrete.
To reduce time caused by road rehabilitation, highway engineers are giving more attention to whitetopping - placing an unbonded concrete overlay over deteriorated asphalt - as an alternative to reconstructing roads or resurfacing them with asphalt. The Colorado Department of Highways (CDOH) is evaluating whitetopping as a possible solution to the state's road rehabilitation problems. On June 2, 1990, it participated in a test project involving the whitetopping of a section of Harmony Road in Fort Collins. Concrete overlay sections of 3.5 inches thick and 5 inches thick were placed. For the next few years, the CDOH will monitor the performance of the two overlays.
