One of the key challenges in implementing solid waste landfills is the high degree of control of the leachate produced in the system. The sealing of these systems is ensured by the combination of a low hydraulic conductivity compacted clay (CCL) subgrade, a geosynthetic clay coating and a geomembrane. In this context, the study of GCL performance is fundamental, as this layer acts as a hydraulic safety barrier. Currently, the main concern is the shrinkage behavior of this material, which occurs mainly during the construction phase, when exposed to the elements. Naturally, the risk of contamination of soil and water bodies increases significantly due to this problem. Recent studies have shown that the initial moisture content of GCL and the hydration and rehydration dynamics of this material by the subgrade are important factors in shrinkage behavior. Exposure to daily thermal cycles imposes a loss of moisture from the GCL to the foundation soil. However, there are certain moisture indices in which the subgrade may rehydrate this material, canceling or attenuating the significant moisture loss and consequently the shrinkage values found. Considering the tropical climatic and the field conditions to which GCL can be submitted in Brazil, the present work evaluated the shrinkage a calcium (Naadded) GCL samples submitted to 50% initial water content and with 100% initial water content, after 15 days of hydrationdrying cycles. The results showed influence of GCL initial water content and shrinkage behavior. Also, this GCL showed similar shrinkage to some data found in the literature for other GCLs.
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