Comparison of the effect of mixing methods (dry vs. wet) on mechanical and hydraulic properties of treated soil with cement or lime

• For cement treated samples wet mixing method gave higher strength.
• For lime treated samples dry mixing method gave higher strength.
• Samples using dry mixing method showed higher k value.
• The gain in strength for dry mixing method for cement is faster.

Where difficult foundation soils are encountered in civil engineering projects, deep soil mixing method is a choice as a solution to deal with the problem. In this soil improvement method, cement or lime in slurry form (wet method) or in dry powder (dry method) is mixed with the in situ soil. To the knowledge of the authors no comparison between cement and lime treated soil using wet or dry method has been made for saturated soils. In this research saturated bentonite-sand mixtures were treated with 2, 4, 6, 8 and 10% by dry mass of cement, lime and cement–lime using both wet and dry methods. Treated soil samples after curing periods of 7, 14 and 28-days were tested in unconfined compression strength and consolidation. The results of unconfined compression tests indicated that the strength of wet cement treated samples was higher than dry cement treated samples and this was opposite for lime treated samples. The results of consolidation tests in terms of the e–logσv′ relationship indicated that they were in general, function of the type and the amount of the admixture and the curing time. Compression index decreased with amount of additive in contrast with previous finding for cement treated samples of a low plastic clay soil. Lime treated samples showed higher elastic modulus than cement treated samples and dry treated samples in general showed higher elastic modulus than wet treated samples.