There are several key factors, which are considered, when selecting methods and systems for concrete repair. Good bonding between repair material and concrete substrate is a crucial and simultaneously complex phenomenon. This paper shortly presents methods used for the bond strength evaluation with different ways of loading of bonded joints. A systems consisting of high performance concrete substrate and two types of repair materials are investigated. The main goal of the work is to compare a polymer-cement modified mortar (PCC) and a rapidly setting repair concrete (based on alumina cement). Technical characteristic of the materials as well as their bond strength to concrete substrate are presented. Surface of concrete substrate is prepared by using different roughening techniques commonly applicable on site. Bond strength is measured by standard pull-of test and by the wedge splitting test (WST). WST test adaptation for that purpose allows to extend the description of adhesion using fracture mechanics parameters such a work of adhesion and fracture energy
Alpha power attenuation during cognitive task performing has been suggested to reflect a process of release of inhibition, increase of excitability, and thereby benefit the improvement of performance. Here, we hypothesized that changes in individual alpha power during the execution of a complex language comprehension task may correlate with the individual performance in that task. We tested this using magnetoencephalography (MEG) recorded during comprehension of German sentences of different syntactic complexity.
Results showed that neither the frequency nor the power of the spontaneous oscillatory activity at rest were associated with the individual performance. However, during the execution of a sentences processing task, the individual alpha power attenuation did correlate with individual language comprehension performance. Source reconstruction localized effects in temporal-parietal regions of both hemispheres. While the effect of increased task difficulty is localized in the right hemisphere, the difference in power attenuation between tasks of different complexity exhibiting a correlation with performance was localized in left temporal-parietal brain regions known to be associated with language processing.
From our results, we conclude that in-task attenuation of individual alpha power is related to the essential mechanisms of the underlying cognitive processes, rather than merely to general phenomena like attention or vigilance.
Concrete-polymer composites (CPC) pose a major concern of construction industry in recent years. The use of polymer in concrete has long been proven successful due to its good compatibility and the improvement it makes to the concrete. This overview summarizes status of research and applications of CPC in China within the past 3 years, i.e. the influence of polymer on early hydration of cement, the interaction between polymer and cement, and the applications of CPC in waterproofing materials, pavement, repairing materials and so on.
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