Effects of aggregate size on water retention capacity and microstructure of lime-treated silty soil

Abstract

International audienceLime treatment is a common technique of improving the workability and geotechnical properties of soils. In this study, the aggregate size effects on the water retention capacity and microstructure of lime-treated soil were investigated. Two soil powders with different maximum aggregate sizes (D max = 0·4 and 5 mm) were prepared and stabilised by 2% lime (by weight of dry soil). Soil samples were prepared by compaction at dry side of optimum water content (w = 17%) with a dry density of 1·65 Mg/m 3. Suction and pore size distribution were determined after different curing periods. The results obtained show that: (a) the treated soil with smaller D max presents relatively smaller modal sizes and lower frequency of macropores (10–330 μm); (b) lime addition effectively improves the soil water retention capacity and decreases both the modal sizes of macro-and micropores gradually over time. Moreover, a higher air entry value and larger water retention capacity were also observed for a smaller D max value, in agreement with the pore size distributions

Effects of aggregate size on the compressibility and air permeability of lime-treated fine-grained soil

“…It is observed that the air permeability of the samples prepared with large aggregates (Dmax = 5 mm) is generally one order of magnitude higher than that of the samples prepared with smaller aggregates (Dmax = 0.4 mm). This can be ascribed to the larger macro-pores of samples S5 (Wang et al, 2015). Even though the samples prepared with different sizes of aggregates present the same air-filled porosity (Va/V), they have different pore size distributions and different shapes: in the case of S5, the large macro-pores form a better pore continuity leading to a higher air permeability, while in the case of S04, the smaller macro-pores form a more complex arrangement and lower continuity, resulting in a much lower air permeability.…”

“…After compaction, they were covered by wax and cured in a chamber at a temperature of 20±2 °C for 7, 28, 60 and 90 days, respectively. More details about the geotechnical properties of this silt and the detailed procedure of samples' preparation can be found in Wang et al (2015;.…”

“…Tang et al (2011a) and Dong (2013) studied the aggregate size effect on the stiffness of lime-treated soils during curing and concluded that the treated soils with larger aggregates exhibit a lower small-strain shear modulus and lower resistance to wetting/drying cycles. Wang et al (2015) reported a relatively higher water retention capacity for the treated soil with smaller aggregates.…”

Aggregate size effect on the water retention properties of a lime-treated compacted silt during curing

“…Romero et al [13] explained that low water content range is related to intra and inter-cluster water, and the corresponding linear relationship between the logarithm suction and water content is controlled by the soil intra-aggregate microstructure. Wang et al [12] indicated that the aggregate size mainly affect the macro-pores (interaggregate pores) rather than the micro-pores (intraaggregate pores). In fact, different aggregate sizes form different contacts among soil aggregates and different size of inter-aggregate pores, which govern the lower suction range and air entry value.…”

“…Its main minerals are quartz (55%), kaolinite (12%), feldspars (11%), illite (10%), goethite (6.5%), montmorillonite (4%), chlorite (1%) and rutile (0.5%) [11]. More details about the geotechnical properties of this silt are indicated by Wang et al [12]. Nature soil was first air-dried, ground and passed through four target sieves in order to get four kinds of powders with different maximum aggregate sizes, namely S5, S2, S1 and S0.4 (as shown in Figure 1).…”