According to the Caltrans “Foundation Manual,” the “use of the slurry displacement method for constructing drilled shafts began in Texas in the years following World War II.” Mineral (bentonite clay-based) slurry was first used back then for the construction of foundation drilled shafts. It worked to stabilize the soil and prevent cave-ins, while facilitating the removal of material and without the need for casing from top to bottom.
Synthetic (polymer) slurry for the construction of foundation drilled shafts came into play during the 1980s. It offered many advantages over mineral slurry. Unfortunately, uses for synthetic slurry were limited in unconsolidated soil conditions, such as coarse sand, gravel and cobble. Contractors had to either utilize mineral slurry or oscillate casing, which led to higher construction costs.