15 May 2001
SUMMARY OF DESIGN METHOD FOR SLURRY SEALS
a. The design method for determining the emulsion requirement consists of determining the
surface area of the job aggregate and calculating the amount of asphalt required to coat the surface
area with a film thickness of 8 microns. The absorption characteristics of the aggregate are determined
using the CKE test. The total asphalt is the asphalt required for coating the aggregate plus the asphalt
required to satisfy the aggregate absorption.
b. The water required for a given mixture is determined by a cone test as described in
ASTM D 3910. Water is added to a slurry mixture until a flow of 25.4 millimeters (1 inch) is obtained on
a reference plate. The consistency of the mixture when the 25.4 millimeter (1-inch) flow is obtained
must be such that there is no segregation in the mixture. Portland cement or hydrated lime can be
added to aid in overcoming the segregation; the cone test can serve as an aid for determining the
amount of portland cement or hydrated lime required in the mixture.
C-2. SURFACE AREA DESIGN METHOD. The surface area design method includes three
considerations: the calculation of the amount of asphalt required to coat the surface area of the job
aggregate, the absorption characteristics of the aggregate, and the total asphalt content.
a. Surface area asphalt calculation.
(1) The surface area of the job aggregate is determined by multiplying the percent of aggregate
passing a given sieve by a surface area factor based on the sieve size. The surface area of the
aggregate is determined for each particle size (group) and then summed to obtain the total surface area.
The surface area units are given in square meters per kilogram (feet per pound) of aggregate. The
surface area factors are shown in table C-1. The total surface area (SA) is then corrected to obtain a
corrected surface area (CSA); CSA = SA x 2.65/ASG, where ASG is the apparent specific gravity of the
aggregate. When the surface area and the desired bitumen film thickness are known, the volume of
asphalt required can be obtained. From these parameters the asphalt required to coat the surface area
is calculated. The equation for calculation of the surface area asphalt, SAA, is as follows:
Metric: CSA t 0.99941 SGA
U.S. Customary: CSA t 0.02047 SGA
SAA = surface area asphalt, percent of dry aggregate weight
CSA = corrected surface area, square meters per kilogram (feet per pound) of
t = asphalt film thickness, microns
SGA = specific gravity of the asphalt
0.99941 (0.02047) = conversion coefficient for the units of the equation