Key Engineering Materials Vol. 466

Abstract: Glass rovings undergo a loss in tensile strength when aged in highly alkaline concrete. Based on the hypothesis that this loss is due to hydrolysis of the silicate network, binary polymer/pozzolan and ternary polymer/pozzolan/cement coating formulations have been developed in order to provide both corrosion protection and improved fibre-matrix adhesion. While the ternary mixtures were found to do either or, the best overall result was obtained with the binary mixture poly(vinyl acetate)/silica 20:80, showing a 1.8-fold increase in the pull-out load and a 1.6-fold increase in the residual tensile strength when compared to the as-received glass.

Abstract: For concrete structures in chloride containing environments, hydrophobic surface treatments are often used as an additional protective measure for protecting the embedded steel against corrosion. In recent years, silane-based hydrophobic agents that can be used as concrete admixtures for making the whole concrete hydrophobic have also been introduced. In the present paper, the protective effectiveness of such an admixture against chloride penetration has been investigated. For comparison, some field investigations on the effectiveness of a traditional surface hydrophobation of two concrete harbor structures based on similar products are also briefly reported.

Abstract: The paper focuses on optimizing the elastic polymer-cement protection coating composition using material model. The material model consists of mathematical relations between composition and technical features demanded for protection, which are: flexibility, waterproofness and vapor permeability. The optimization that enabled obtaining the desirable values of features was proceeded by using statistical experimental design. Taking data from tests and choosing material variables, a material model based on quadratic functions was determined and in consequence three top rank compositions – each for a given feature – have been formulated. Evaluation of compositions was done using the desirability function approach. The individual desirability functions for the particular feature and the combined overall desirability function were treated as additional properties of the coating. Also, after defining the relation between desirability and composition, the overall desirability was enclosed in the material model as its generalization. High values of overall desirability confirmed the usefulness of compositions. The investigation proved that material models based on statistical methods are efficient tools for designing polymer-cement protective coatings.

Abstract: Nanofibers are very promising new type of material with a broad range of possible applications. The new NANOSPIDER technology opens a possibility to produce nanofabrics in an amount large enough for them to start being interesting as a construction material. There are many so-called passive applications of nanotextiles (including different types of filters and protective layers), and active applications, when the active chemical agent is incorporated in their structure. In the present paper, however, the new possible application of nanofabrics is proposed: as a base material on which technically interesting nanoclusters are heterogeneously nucleated. The basic thermodynamics of heterogeneous nucleation on nanofibers is considered. The extreme curvature of nanofibers manifests itself in an energetic barrier of nucleation, which is quite different from a case of nucleation on a flat surface. The expression for Gibbs energy of cluster formation is derived, taking into account the elastic strain resulting from a volume (or shape) changes during nucleation.

Abstract: Modern infrastructures such as viaducts, bullet train (Shinkansen) elevated tracks, and subway facilities in addition to houses and buildings were greatly damaged at the Hyogo-Ken Nanbu Earthquake that hit heavily populated urban cities in 1995. As a learning lesson from this earthquake, seismic countermeasures for civil infrastructures have been rapidly reviewed and implemented. In this study, damage of bridge structures due to this strong earthquake was reported and the current effective seismic retrofit of concrete columns and bridge-falling prevention systems by use of concrete polymer composites in Japan were introduced. Two main seismic countermeasure methods were introduced and discussed: Steel plate and fiber jacketing methods for existing reinforced concrete piers/columns, and unseating devices for bridge-falling prevention. Both these countermeasures use epoxy resin as essential component.

Abstract: Hardened concretes were studied by several spectroscopic techniques (FTIR, Raman and XPS) to determine the surface composition after demoulding and after coating. After demoulding, most of the paste was constituted of calcite but some areas were identified by µRaman as portlandite, ettringite, belite, alite and ferrite phases. The FTIR (in ATR mode) allowed detecting portlandite and C-S-H but it highlighted also organic residues from the demoulding oil. XPS allowed recording interesting atomic ratios to study the extreme surface and the presence of contamination. After post-treatments, the main organic units were determined by FTIR and XPS at the concrete’ surface. Raman was also interesting: no vibration modes of organic species were detected but mineral/hydrated phases were clearly characterized under a thick organic layer. Due to their own specificities, these complementary techniques allowed identifying the mineral/hydrated phases and organic residues/coating at the concrete surfaces.

Abstract: Three kinds of repair methods of cracked concrete floors are presented in the paper. One of them, based on coating using of polymer-cement composites, is discussed with presentation of the influence of different amount of styrene-butadiene co-polymer dispersion additive onto the shrinkage and strength. The next two correspond to injecting repair methods. There are also presented two different approaches in repair bonding of damaged floors. Following these ideas, results of testing of epoxy and polymer (PU) bonding of cracked specimens made of concrete and polymer-cement composites are discussed. Proposed new repair polymer flexible joints introduce energy dissipaters which allow protecting concrete pavements against large deformations. Presented comparisons of results indicate that the use of flexible polymers in repair process is efficient, what was confirmed by tests and observations of repair done at the KRK airport concrete pavement.