TRANSPORTA T/ON RESEARCH RECORD 1295 45 Improved Characteristics in Sulfate Soils Treated with Barium Compounds Before Lime Stabilization G. A. FERRIS, J. L. EADES, R. E. GRAVES, AND G. H. McCLELLAN
[email protected]&ssabili1aQi;witaflaltti11rmbi dt&lliil Tua~s.odiWllisuliat<t:andi<0iliwm-suLfate.~msum.), ha.1,1~dif.- - - - islfleul,l.il i::ll:nl snlidD"'Jti:w 1llD el Slllllar.s to resuft from reactions of sofubfe suffates, calcium hydroxide, in a soil plays an active role in the degree to which ettringite and free aluminum in the soil or groundwater, or both, to will form. Gypsum is approximately 100 times less soluble form ettringite (3 CaO·Al20 3·3CaS04·32H20), a highly water expansive mineral. Laboratory testing, using the California bear than other sulfate minerals normally found in soils (5) . Cal ing ratio (CBR) method, has indicated increased bearing strength cium and sodium sulfate commonly form evaporite minerals values and decreased swell when barium hydroxide or barium in arid to semiarid regions, because of little or no leaching, chloride was added to sulfate-rich soils before lime application. crystallizing when their concentrations exceed their solubility A California soil containing sodium sulfate had increased strength limits. Gypsum is the most common sulfate mineral found in values when either barium compound was used with lime as com soils because of its relatively low solubility. pared with specimens with lime only. A barium hydroxide treat ment followed by lime application to a Texas soil containing The percentage and type of clay minerals present in a soil sodium sulfate was successful, showing increased CBR values and generally dictate the amount of lime required for stabilization.