15 March 2001
If a mineral filler is used in the slurry, a portland cement or hydrated lime should be used. The
filler tends to improve the stability of the mixture. If stability or segregation problems occur,
mineral filler at 0.4 to 0.5 percent of the total mixture should be used. Only potable water shall be
used. Water is the primary control for workability of the mixture.
6.3. Procedural Steps. The following are steps for placement of a slurry seal.
6.3.1. Prepare the surface. All loose material (including any loose or flaking paint), dirt, and
vegetation shall be removed from the surface. Cracks greater than 1/8 inch (3 millimeters) wide
shall be sealed. During sealing, the sealant should be placed 1/8 to 1/4 inch (3 to 6 millimeters)
below the surface. After sealing all cracks and cleaning the surface, a very light tack coat should
be sprayed at a rate of 0.05 to 0.10 gallons per square yard (0.23 to 0.45 liters per square meter)
and allowed to fully cure.
6.3.2. Apply the slurry. Immediately before applying the slurry, a fog spray of water should be
applied to the surface with the spray bar on the slurry machine. There should be no standing
water after the spray. The spray should be adjusted to compensate for temperature, surface
texture, humidity, and dryness of the surface. The slurry shall be applied with a slurry machine
(Figure 6.1.). The slurry machine is a self-propelled, continuous-flow mixing unit. It should be
capable of delivering the proper amount of aggregate, water, mineral filler, and emulsion to the
mixing unit (Figure 6.2.). The mixing unit is either a single or double pugmill mixer. The mixing
unit discharges the material into the spreader box that is equipped with flexible squeegees and
width adjustment. Other parts of the machine include the spray bar for wetting the pavement and
an aggregate prewetting device. Most of the time, a burlap drag is located behind the spreader
box to improve the joints and overall appearance of the mixture. The slurry is applied from
1/8 inch (3 millimeters) and is usually no more than 1/4 inch (6 millimeters) thick in one pass. If