Abstract
Lime treatment is widely applied to improve the workability and long-term durability of soils. In this study, the curing time effect on the mineralogy and microstructure of lime-treated soil was investigated. The soil samples were prepared with 2 % lime and statically compacted at dry (w = 17 %) and wet (w = 20%) sides of optimum. X-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) were performed on lime-treated soil at various curing times. The presence of XRD peaks attributed to portlandite even after 150 days curing time indicated that it was not totally converted in cementitious compounds after reaction with silica and alumina from clay minerals. By contrast, no obvious XRD reflections of well-crystallized cementitious compounds were identified. Furthermore, all samples compacted at dry and wet side of optimum exhibited bi-modal pore size distribution, with a decrease of macro-pore frequency with increasing water content. The microstructure changes with increasing curing time did not follow monotonic tendency. On the whole, the quantities of pores less than 0.006 μm and micro-pores increased and the quantity of macro-pores decreased with increasing curing time due to the possible creation of poorly crystallized or amorphous cementitious compounds.
Highlights
Lime stabilization is a widespread technique applied in recent years to soils with poor physical and mechanical characteristics
For the lime-treated Impersol soil which contained 86 % clay minerals (48 % bentonite and 38 % kaolinite), the products from pozzolanic reaction were observed in the form of calcium aluminate hydrate (C-A-H) after 1 day and in the form of calcium silicate hydrate (C-S-H) after 7 days of curing [5]
Calcium hydroxide provided an alkaline environment in soil, inducing the dissolution of the silica and alumina present in the clay minerals
Summary
Lime stabilization is a widespread technique applied in recent years to soils with poor physical and mechanical characteristics. The cementitious compounds produced in pozzolanic reaction play a major role in improving soil hydromechanical behaviour [3,4]. The production of cementitious compounds is strongly dependent on curing time and mineral composition of soils. For the lime-treated Impersol soil which contained 86 % clay minerals (48 % bentonite and 38 % kaolinite), the products from pozzolanic reaction were observed in the form of calcium aluminate hydrate (C-A-H) after 1 day and in the form of calcium silicate hydrate (C-S-H) after 7 days of curing [5]. The cementitious compounds were produced from the reactions of lime and alumino-silicate such as clay minerals and from the reactions of lime and silicate such as fine quartz (or feldspars). The presence of a low amount of amorphous silica mixed with quartz and characterized by higher
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