An experimental study on fly ash with lime and gypsum for quality improvement in pavement subgrade materials

Abstract

Characteristics of pavement subgrade materials play a paramount role in determining the quality and longevity of a pavement. An experimental study has been undertaken to improve such subgrade material on addition of fly ash (percentage of addition 9.7–30%) as main additive. Two broad sets of samples have been mixed with varying proportions of moorum, silver sand, fly ash mix with stabilizer, i.e. lime and gypsum (percentage of addition from 2 to 3%) for one set, and another set of samples where it consists of moorum, silver sand and soil mix (percentage of addition 10–30%) without fly ash and stabilizer. For each set of sample, the main broad constituent materials have been taken as moorum and silver sand which have percentage of variations 47.53–70% and 20.37–30%, respectively, because they are the main constituents for pavement subgrade material. To investigate the effects of addition of these stabilizers to assess whether it improves the performance of pavement subgrade materials Proctor tests, CBR and UCS tests have been done on both types of soil samples. The test results have shown that lateritic soil like moorum with silver sand used with addition of stabilizer as a sub-base materials of pavement can be used as a better replacement of commonly used graded traditional coarse aggregate and fly ash used as fines has shown better replacement of local soil. A high correlation coefficient indicates that the CBR value can be well predicted from UCS test results.