The microstructural effects of exposure to a 15% magnesium sulphate, 15% sodium sulphate, and mixed solutions were observed in mortars with and without silica fume, using the non-destructive impedance spectroscopy technique. The non-destructive "Wenner" resistivity test and the classical mercury intrusion porosimetry were used as contrast techniques. The compressive strength of the mortars was also studied. In view of the results obtained, impedance spectroscopy was the most sensitive technique for detecting changes in the porous network of the studied mortars. The addition of silica fume results in a more refined microstructure and a higher compressive strength in mortars exposed to aggressive sulphate solutions.

Nowadays, the reuse of wastes is essential in order to reach a more sustainable environment. The cement production results in CO2 emissions which significantly contribute to anthropogenic greenhouse gas emissions. One way to reduce them is by partially replacing clinker by additions, such as silica fumes or other wastes. On the other hand, the pore structure of cementitious materials has a direct influence on their service properties. One of the most popular techniques for characterizing the microstructure of those materials is mercury intrusion porosimetry. In this work, this technique has been used for studying the evolution of the pore network of mortars with different percentages of silica fume (until 10%), which were exposed to aggressive sodium and magnesium sulfate solutions up to 90 days. Between the results of this technique, intrusion-extrusion curves and logarithms of differential intrusion volume versus pore size curves were studied. This characterization of the pore network of mortars has been complemented with the study of their compressive strength and their steady-state ionic diffusion coefficient obtained from samples’ resistivity. Generally, silica fume mortars showed different performance depending on the aggressive condition, although the greatest deleterious effects were observed in the medium with presence of both magnesium and sodium sulfates.

It has been proposed that creep of acrylic bone cement may contribute to loosening of cemented total joint replacements. If true, it is important that factors affecting creep of bone cement are identified. The objective of this study was to evaluate the effect of an operator-controlled variable, injection time, on the creep behavior of acrylic bone cement. Results from this investigation showed that injection time significantly (p < 0.0001) influenced creep behavior of bone cement. "Delayed" injection time of acrylic bone cement increased creep by approximately 5 times in 24 h compared to specimens prepared according to standard injection procedures.

The use of additions as clinker replacement has become very popular, due to the advantages that they provide, especially regarding the improvement of cement industry sustainability. The microstructure of cement-based materials has a direct influence on their service properties. In this research, mortars with different contents of silica fume (up to 10%) have been studied. These mortars were exposed to aggressive media with presence of sodium and magnesium sulphate along 90 days. On one hand, the evolution of their pore structure was characterised using different results provided by mercury intrusion porosimetry technique, such as intrusion-extrusion curves and logarithm of differential intrusion volume versus pore size curves. On the other hand, the compressive strength and the steady-state ionic diffusion coefficient obtained from resistivity of the samples, which was measured using impedance spectroscopy, were also studied. In general, silica fume mortars showed good performance, although the greatest deterioration of these mortars was observed in a mixed magnesium and sodium sulphate solution.