Durability of cement-stabilized Singapore clay subjected to freezing and thawing cycles

Abstract

Cement stabilization is widely used to treat soft clay in Singapore for various applications. In Singapore, the clay stabilization is mainly employed through deep mixing technology, an in-situ ground improvement method to deliver cement slurry or powder into the soft ground. Previous studies has only focused on the performance of cement-stabilized clay under ambient temperature. This FYP project is based on an industry-funded research project, which attempts to use cement stabilization to improve the Singapore clay for liquefied natural gas (LNG) storage underground. For this application, the cement-stabilized clay may work under low temperature, e.g. lower than 0◦C. Hence, this FYP project investigated the durability of cement-stabilized Singapore clay with and without the addition of fiber subjected to freezing and thawing cycles through laboratory testing. Samples preparation were conducted with different cement contents and fiber contents. All soil samples underwent 13 cycles of freeze-thaw as well as various laboratory tests to measure physical (volumetric strain, weight, and bulk density) and mechanical (unconfined compressive strength) properties. These tests were conducted on these soil-cement samples upon completion of the freeze-thaw cycles. In general, samples with 30% cement content stabilized resulted in smaller changes in volumetric strain (-1 to 1%) , weight (max -3%) and bulk density (max -3.8%) after freeze-thaw cycles, as compared with samples with 20% cement content stabilized with greater changes in volumetric strain (-2.5% to -0.75%), weight (max -7%), and bulk density (max -5.8%). Moreover, the addition of fibers further reduced changes in these properties, hence mitigating the detrimental impacts of freeze-thaw cycles on soil-cement samples. The addition of fiber improved the UCS of soil-cement samples for approximately 29% from 1700kPa to 2200kPa of the samples with 30% cement content stabilized clay, and 18% increase from 1400kPa to 1650kPa in UCS value of the samples with 20% cement content stabilized clay after 13 cycles of freeze-thaw.