LIME FIXATION IN CLAYEY SOILS

PREVIOUS WORK IN STABILIZATION OF CLAYEY SOILS WITH LIME HAS SHOWN THAT SMALL AMOUNTS OF LIME CONSIDERABLY IMPROVE WORKABILITY BUT CONTRIBUTE LITTLE TO STRENGTH, WHEREAS LARGER AMOUNTS OF LIME ALSO IMPROVE THE STRENGTH AND BEARING CAPACITIES OF THESE SOILS. THIS SUGGESTS THE POSSIBILITY THAT LIME ADDED TO SOIL MUST FIRST SATISFY AN AFFINITY OF THE SOIL FOR LIME, AN AFFINITY REFERRED TO AS LIME FIXATION. IN SOME CLAYEY SOILS THE ADDITION OF FLYASH WITH THE LIME CAUSED AN EVEN MORE SIGNIFICANT GAIN IN STRENGTH. THE RESEARCH DESCRIBED IN THIS PAPER WAS UNDERTAKEN TO DETERMINE WHETHER LIME FIXATION DOES OCCUR, AND IF SO, TO DETERMINE THE MECHANISMS INVOLVED AND THE AMOUNT OF LIME UTILIZED. SAMPLES OF SIX NATURAL CLAYEY SOILS WERE MIXED WITH VARYING AMOUNTS OF LIME (0 TO 12 PERCENT), CURED TWO DAYS AT 100 PERCENT HUMIDITY AND 70 F TEMPERATURE, AND SUBJECTED TO ATTERBERG LIMITS TESTS. SIMILAR MIXES WERE COMPACTED AT OPTIMUM MOISTURE CONTENT TO STANDARD PROCTOR DENSITY AND TESTED IN UNCONFINED COMPRESSION AFTER 7 AND 28 DAYS MOIST CURING. CURVES OF LIME CONTENT VS. ATTERBERG LIMITS AND LIME CONTENT VS. UNCONFINED COMPRESSIVE STRENGTH INDICATE THAT WHEN THE PLASTIC LIMIT INCREASES, WITH SMALL AMOUNTS OF LIME, THE STRENGTH REMAINS RELATIVELY CONSTANT, WHEREAS WITH LARGER AMOUNTS OF LIME THE PLASTIC LIMIT REMAINS CONSTANT AND STRENGTH INCREASES. THUS, THE PLASTIC LIMIT IS INDICATIVE OF THE AMOUNT OF LIME FIXATION IN CLAYEY SOILS. FURTHER CORRELATIONS SHOW THAT THE AMOUNT OF FIXATION IS PROPORTIONAL TO THE TYPE AND AMOUNT OF 2-MICRON CLAY PRESENT AND IS INDEPENDENT OF THE ADSORBED CATION PRESENT. AS A RESULT OF THE UNCONFINED COMPRESSIVE STRENGTHS, KAOLINITIC AND MONTMORILLONITIC CLAYEY SOILS WERE FOUND TO BE WELL STABILIZED WITH LIME ALONE, WHEREAS ILLITIC- CHLORITIC CLAYEY SOILS REQUIRE ADDITIONS OF FLYASH TO OBTAIN SIGNIFICANT GAINS IN STRENGTH. /AUTHOR/