Durability of particulate grouts: For isolation of low level radioactive wastes
Abstract
Over the years particulate grouts have been used for isolating low-level radioactive wastes in shallow burial trenches, however there are concerns that over time and following exposure to adverse environmental conditions (e.g. wet/dry and freeze/thaw), durability of the grouts may become grossly affected and contamination of groundwater system may result. To address some of these problems, a detailed laboratory study was conducted to characterize the fabric and performance of particulate grouts. Before and after exposure to several wet-dry and freeze-thaw cycles, pore size distribution measurements via mercury intrusion porosimetry, unconfined compressive strength, permeability and pulse velocity tests were performed on the studied grouts. Prediction equations were developed for assessing grout durability. Formulation factors: water/solid ratio; mix composition, and interaction between these were found to have significant statistical (P $<$ 0.05) effect on both wet-dry and freeze-thaw durability of the studied grouts. Fly ash in excess of 30 percent by weight of total solids present, was found to lower durability considerably. Addition of 7 grams of fiber to the high fly ash grout mix improved durability. Silica fume caused considerable reduction in pore sizes and initial grain in strength, but appear to lower durability particularly under wet-dry conditions. Latex, showed a potential for use as an additive for formulating durable grout mixes. The effects of wet-dry and freeze-thaw processes on grout durability were found to be nonlinear. The early wet-dry and freeze-thaw cycles produced more damage than the later cycles. However, significant correlation was found to exist between cycle-to-failure and grout durability as measured by pulse velocity. This constitutes a basis for using pulse velocity to monitor the state of a grout barrier in situ. Statistically based design procedures were developed to aid the waste management practitioner to select a range of formulation factors that will assure a desired magnitude of behavior over a specified service period.
Degree
Ph.D.
Advisors
Altschaeffl, Purdue University.
Subject Area
Civil engineering
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