The objective of this study is to provide an experimental performance assessment of cement borehole plugs subjected to dynamic loadings. This includes the study of dried-out plugs as well as of plugs that have remained wet throughout the testing period. Literature review indicates lack of quantitative data on plug performance under dynamic loading. Nevertheless, it shows that deep underground structures in competent rocks are safer than surface structures, openings at shallow depth, and openings in fractured rocks, when subjected to earthquakes and subsurface blasts. Flow test results indicate that wet cement seals are less permeable than Charcoal granite. Sealing performance is severely degraded when cement seals are allowed to dry. Dye injection tests show that the flow penetrates uniformly through the wet plugs, but occurs only along the plug/rock interface of the dried-out plugs. The permeability of wet and dried-out cement seals does not change significantly after the application of dynamic loads.

The present study deals with the physical characterization of macrodefect free cements produced by ICI. These materials are made through a specialized mixing technique which incorporates an organic polymer into the cement/water system. The high mechanical strength and low porosity of this class of hardened cement paste had been well documented, however, a detailed characterization of the physical nature of the microstructure had not previously been attempted. Two classes of macrodefect free material were studied, based on Ordinary Portland cement and High Alumina cement, respectively. The porosities of these two materials were determined in their original state and after various forms of heat treatment and conditioning. Samples based on Ordinary Portland cement had a well defined narrow pore size distribution, even after heat treatment, while the High Alumina cement samples displayed a very low total pore volume in their original state, but subsequent heat treatment led to the developement of porosity over a wide range of pore sizes. These fundamental differences in the pore size distributions had significant effects on the homogeneity and reproducibility of the microstructures of the samples. The porosity generated by heat treatment was found to be unstable in the presence of water. In general, reductions in the porosities and permeabilities were observed. This was due to the formation of fresh cement hydrate gel within the pore structure, which caused a shift in the pore size distributions towards smaller pores.