Abstract:
One method for stabilizing soft clay is to mix it with cement. Portland composite
cement (PCC) is a cement produced by grinding together portland slag and gypsum with one or
more inorganic materials that is suitable for stabilization of soft soils. The purpose of this study
was to mix soft clay from Bukit Rawi, Central Kalimantan with PCC, which was then tested for
unconfined compression strength (UCS) and the California Bearing Ratio (CBR) to see if it could
be used as a road subgrade. Soft soil from Bukit Rawi was mixed with PCC with percentages of
6%, 8%, 10%, and 12% on a dry weight basis. The mixture was tested by Proctor standard
compaction to obtain the optimum moisture content and maximum dry density. At these
optimum conditions, UCS and CBR tests were carried out. The findings reveal that adding PCC
to Bukit Rawi soil enhances UCS and CBR, which were previously 3.47% of CBR and
0.67kg/cm2 of UCS. The addition of PCC with a level of 2‒3% is planned for field application,
because it is considered capable of fulfilling the requirements as a subgrade layer with a CBR of
15%. Furthermore, 12 percent PCC is required in the combination as a foundation (minimum
20kg/cm2 of UCS)
