This study investigated the effects of relative humidity (Rh) or total suction condition during curing on small-strain shear modulus (G0) of a cement-treated silty sand using free-free resonant frequency tests (FFR). The moduli were determined on samples cured at different suctions corresponding to three Rh values of 7%, 75%, and 100%, in both unsoaked and soaked conditions. Soil–water retention curves (SWRCs), and unconfined compression strength (UCS) were also determined along with x-ray diffraction (XRD) analysis. The cement-treated SWRCs showed a much flatter slope than the non-treated ones, and the air-entry suction increased with cement content. The values of G0 increased with cement content and curing time. The highest modulus was achieved in 75%Rh curing condition. The 7%Rh condition resulted in a significant drop in modulus, even close to the non-treated G0 for the 2% cement case. At the same UCS value, the soaked cement-treated samples had higher modulus than the non-treated ones in the unsoaked condition, indicating that the effect of suction on modulus was smaller than the effect of cementation. XRD analysis revealed a greater availability of C3S in 7%Rh curing condition at 7-day curing period suggesting that the hydration process was still not complete, which explained the decrease in G0 in this curing condition.
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