Use of the Methylene blue stain test to evaluate the efficiency of lime treatment on selected clayey soils.

The Methylene Blue (MB) stain test was used to determine the efficiency of lime modification of clay soils and to define the percentage of lime required to reach the stabilization field. Montmorillonite and kaolinite, mixed in variable proportions with quartz sand, were treated with differing percentages of lime, and the MB test was performed on both untreated and treated soils. Results show that the test can determine whether a soil is prone to efficient modification, follows the evolution of clay minerals in the lime modification field, and also determines the quantity of lime necessary to enter the stabilization field. X-ray powder diffraction, thermal analyses and electron microscopy observations of the montmorillonite-richer sample showed its crystal chemical evolution in the modification field. Mineralogical results match the outcome of the MB test, defining the same lime percentage for best modification (4%) and confirming that the test can be used for preliminary and ongoing analyses of lime treatment.