Improvement of geotechnical properties of silty sand soils using natural pozzolan and lime

In this study the effect of different amounts of lime and natural pozzolan on geotechnical properties of a silty sand soil has been investigated. To do this, 20 treatments were prepared with adding five lime levels of 0, 1, 3, 5 and 7% (by weight) and four levels of pozzolan including; 0, 5, 10 and 15%. Compaction characteristics, compressive strength and bearing capacity of the treatments were determined using standard test procedures. For evaluation of compressive strength, cylindrical specimens (3.5 cm in diameter and 7 cm in length) were made and cured for three different ages including 7, 14 and 28 days in three replication. Result of compaction tests showed that adding of both lime and pozzolan alone and with together increase optimum moisture content and decrease the maximum dry density of treated soil samples. Statistical analysis using SPSS software showed that although adding of natural pozzolan and lime to the soil increases the compressive strength significantly, but adding of them with together is more effective. So that the compressive strength of a treatment having 3% lime and 15% pozzolan was found to be 16 times of untreated sample. Furthermore, the results of California Bearing Ratio, CBR test showed that the values of CBR in different treatment increased up to 12 times of untreated sample.