Many municipalities and private owners have faced increased pavement maintenance and replacement costs when lime modified clay subgrades prematurely fail. Preliminary laboratory test results determined that the typical lime treatment (7% by dry weight) used by the City of Garland, TX was approximately one-half the amount of lime necessary to permanently stabilize a high P.I. (39) clay. Further laboratory and a field testing program was then undertaken to determine if an economical alternative to 14% lime could be used to extend the durability of street subgrades. Four test sections were constructed using various combinations of lime to pre-treat the clays before stabilizing with cement. The testing program revealed that using combinations of lime and cement increased the typical subgrade durability based upon 4.8 to 5.7 times greater strengths after one year of exposure to in-place conditions. In addition, 28 day moist cured then saturated samples had 3.7 times greater compressive strength and 3.5 times better strength following 12 cycles of wetting and drying after 4 months of moist curing.
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