CURING TIME EFFECTS ON CBR OF STABILIZED KAOLINE WITH FLY ASH, LIME AND CEMENT

Abstract

California Bearing Ratio (CBR) is used to determine bearing capacity of additives mixtured soils. The CBR test estimates behaviour of road sub-base and granular layers for flexible pavement. In the standard CBR test, samples are compacted after waiting 24 hours in air and 4 days in water for curing. But these times are not adequate for a pozzolanic stabilization. It is just enough for the first solidification of pozzolanic effect but is not sufficient for determination of total strength. Hence mixtures should be cured longer to obtain actual bearing capacity of soil. In this study 1, 7, 28 and 56 days cured effects were examined on the CBR percents of soils stabilized with class F fly-ash and cement. There are two main matrices in this study: The first matrice consists of kaolin and lime and the second matrice consists of kaolin, bentonite and lime. In samples, fly-ash (class-F) and cement were used as additives. Different mixtures were prepared with various combinations of these materials and the samples compacted under optimum water content. At the end of curing, the mechanical strength for wet CBR, triaxial un-consolidated and un-drained (UU) and unconfined pressure tests, the physical characteristic for hydrometer analysis, wet sieving were performed on the mixtures. From test results, mechanical characteristics as CBR percentages, strength parameters, physical characteristics as grain size distribution and specific gravity were calculated. At the end of tests, it was determined that CBR values of mixtures cured 28 days are higher than conventional CBR values by 4-160% for the mixtures cured with fly-ash. In same circumstances, it was determined that CBR values decreased by 50% by cement stabilization. According to these results, CBR test should be performed on 28 days cured samples, in terms of bearing capacity of stabilized soil.