Using Hydrated Lime to Control Erosion of Dispersive Clays

Laboratory testing and actual field observations over the past 15 years have shown that 1 to 4% of hydrated lime has been successful in controlling erosion of highly dispersive clays. The modified pinhole test procedure has been used to determine the amount of hydrated lime needed. Dispersive clays are highly erosive because they contain a higher percentage of dissolved sodium in their pore water than ordinary clays. The colloids go into suspension in practically still water. Dispersive clays behave as individual particles instead of aggregates or as a mass. They are not easily detectable by the usual tests performed in a geotechnical laboratory. The pinhole test has proven to be a valuable aid in identifying dispersive clay soils. In the pinhole test, dispersive clays are classified as D-1 or D-2. Nondispersive clays are classified as ND-1 or ND-2. ND-3 and ND-4 classes are borderline. Field sampling, specimen preparation, test procedures, construction methods, field performance, and monitoring are discussed.