Abstract
Improvements of soft soils by mechanically mixing cementitious additives have been widely practised for construction of infrastructure. Mixing of additives improves strength and compressibility properties of soils through the development of soil structure. This study investigates the 1-D compression behaviour of alkali-activated slag treated acid sulphate soils (ASS) cured up to 365 days. The void ratio-logarithm of pressure (e-logσ′) behaviour of treated ASS, including the destructuration behaviour, with additive contents and curing time have been analysed. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses have been undertaken to explain the observed variations of the 1-D compression behaviour. This paper presents the results of these analyses in view of obtaining an insight into the 1-D compression behaviour of treated ASS with the help of mineralogical analysis.
Highlights
Improvements of soft soils by mechanically mixing cementitious additives have been practised over a long time for the construction of infrastructure
The 1-D compression behaviour of soil is represented by the change of void ratio with the logarithm of vertical effective stress (e-logσ1 ), and is represented by two distinctly different zones: (i) recompression line whose slope is defined by the recompression index (Cr ); and (ii) virgin compression line whose slope is defined by the compression index (Cc )
It can be seen from this figure that both the recompression and virgin compression behaviour of acid sulphate soils (ASS) have been affected by the slag content and curing time due to the formation of various quantities of cementitious reaction products
Summary
Improvements of soft soils by mechanically mixing cementitious additives (e.g., lime, cement) have been practised over a long time for the construction of infrastructure. Islam et al [7] reported a reduction of strength for lime-ground granulated blast furnace slag (GGBS) treated ASS resulting from the development of deleterious minerals (thaumasite-ettringite phase). This mineral has been found to be responsible for the degradation of cementitious bonds, which may have an adverse effect on the soil structure and 1-D compression behaviour of treated ASS. The changes of yield stress (σ1 y ), compression/recompression indices and the process of breaking of bonds with applied stresses, which is known as destructuration, of ASS treated with various proportions of additives and curing time have been discussed. Results of X-ray diffraction (XRD) analysis with quantitative mineral phases and scanning electron microscopy (SEM) including energy dispersive spectroscopy (EDS) have been incorporated to identify mineralogical changes that are affecting the 1-D compression behaviour of treated ASS
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