THE CALCIUM-MAGNESIUM RATIO IN SOIL-LIME STABILIZATION

PRELIMINARY STUDIES OF SOIL-LIME STABILIZATION WITH LOESS POINTED UP THE FACT THAT DIFFERENT LIMES GIVE WIDELY VARYING STRENGTH RESULTS, AND STRENGTHS SEEMED TO BE RELATED TO CA: MG RATIO AND TO THE USE OF QUICKLIME VS HYDRATED LIME. NOW ADDITIONAL DATA ARE AVAILABLE VERIFYING THIS FACT FOR LOESS, GLACIAL TILL, DUNE SAND, AND AN ALLUVIAL BACKSWAMP CLAY. MIXTURES OF PURE CHEMICALS WERE USED TO CERTIFY THE TRENDS, AND RESULTS GENERALLY SUPPORTED THOSE OBTAINED WITH COMMERCIAL LIMES. DOLOMITIC LIME USUALLY GIVES HIGHER STRENGTHS, PARTICULARLY WHEN ADDED IN AMOUNTS GREATER THAN 4 PERCENT BY WEIGHT OF THE SOIL. THE DIHYDRATE DOLOMITIC LIME (TYPE S) PREPARED BY AUTOCLAVE PROCESS IS NOT SO EFFECTIVE AS THE MONOHYDRATE (TYPE N) IN WHICH MG OCCURS AS THE OXIDE. THIS ALSO WAS REAFFIRMED USING PURE CHEMICALS. HIGHEST STRENGTHS WERE REALIZED WITH DOLOMITIC QUICKLIME, THE STRENGTH ADVANTAGE OVER OTHER LIMES BEING 50 TO 100 PERCENT OR MORE WITH 6 OR 8 PERCENT ADMIXTURE. THE DIFFERENCE WAS FOUND TO DEPEND ON THE KIND OF SOIL, BUT THE DIFFERENCE WAS SIGNIFICANT WITH ALL SOILS TESTED. PRACTICAL VALUE OF THE SOIL-LIME RESULTS IS EMPHASIZED BY THE CBR AND WET-DRY AND FREEZE-THAW DATA. CBR VALUES FOR LIME STABILIZED LOESS AND TILL WERE FREQUENTLY DOUBLED BY USE OF DOLOMITIC QUICKLIME, AND CBR'S WITH 4 TO 9 PERCENT DOLOMITIC LIME RAN FROM 100 TO OVER 200 AFTER 28 DAYS MOIST CURING. IN THESE AND OTHER TESTS ALL MOLDED SPECIMENS WERE WRAPPED TO PREVENT KILLING OF THE LIME BY CARBON DIOXIDE FROM THE ATMOSPHERE. USE OF DOLOMITIC LIME GIVES THE FIRST IMPORTANT INDICATION OF SOIL-LIME HAVING A SATISFACTORY RESISTANCE TO WEATHERING. STABILIZED LOESS AND TILL SPECIMENS CURED 1 TO 12 WEEKS WERE FOUND IN MANY CASES TO GAIN STRENGTH THROUGH 12 CYCLES OF WET-DRY. FREEZE-THAW SPECIMENS SHOWED ONLY SLIGHT DECREASE IN STRENGTH OR IN SOME CASES GAINED STRENGTH THROUGH 12 CYCLES. THE BEST RESULTS WERE AGAIN OBTAINED WITH DOLOMITIC QUICKLIME. FREEZE-THAW RESULTS WITH CALCITIC LIME WERE MUCH LESS FAVORABLE, AND MOST SPECIMENS LOST STRENGTH RAPIDLY AFTER THE FIRST FEW CYCLES. /AUTHOR/