Mineral wool made from basalt fibers is frequently used as an insulating material in construction systems. In this study, both unused mineral wool and wool obtained from the softened roofing area were comprehensively analyzed in a laboratory using different characterization techniques. Firstly, the initial water content and compressive strength at 10% deformation were determined. Secondly, microstructure and surface chemical composition were analyzed by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectroscopy (EDX). To study heterogeneities near the fiber surface and to examine cross-sectional composition, a scanning transmission electron microscope (STEM) was used. Finally, to verify possible reasons for resin degradation, thermogravimetric analysis and differential scanning colometry (TGA-DSC) were simultaneously carried out. The results show that natural aging under high humidity and thermal fluctuations greatly affected the surface morphology and chemical composition of the fibrous composite. Phenol-formaldehyde and other hydrophobic compounds that protect fibers against moisture and give compressive resistance were found to be degraded.

Delayed ettringite formation (DEF) is a chemical reaction with proven damaging effects on the mechanical properties of hydrated cementitious composite (concrete). Ettringite crystals can cause cracks and the widening of cracks due to pressure on the crack walls caused by the positive volume difference in the reaction. In this paper, we investigated the potential to utilise the positive volume difference in DEF in order to improve the mechanical properties of hydrated fine grained aerated concrete. Fine dispersed crystallisation nuclei, achieved by adding air-entraining agent (AEA) and by short vibration of specimens, are presented as the main requirement for such improvements. Control tests of expansion and mechanical properties were performed on samples of concrete with and without AEA by inducing DEF. The microstructure of fine grained aerated concrete was examined with an optical microscope and scanning electron microscope. We found that the controlled DEF, which is guaranteed by adding AEA and with the formation of uniformly dispersed air bubbles, which are crystallisation sites for ettringite crystals, improves the mechanical properties. The specimens with induced DEF were measured and found to have a 6.8% increase of compressive strength.

Structure objects are exposed to different natural influences resulting in long-term and catastrophic outcomes. In order to avoid them, regular monitoring is needed. Various approaches to control condition of a structure can be considered, one of them is the measurement by means of monitoring which can be performed in different ways, depending on responses – static or dynamic, or both simultaneously. Specifically, technological development has enabled to monitor not only static but also dynamic responses by non-contact geodetic methods. Due to their simplicity and reliability of results, geodetic methods are more and more useful in this area. Moreover, state-of-art instruments and additional programme equipment allows up to 100 readings per second with an almost constant frequency of sampling, which is a condition for calculation of a dynamic response according to Fourier’s transformation. The article presents non-contact geodetic method of RTS on a bridging object.

Measurement of displacement and deformation of structures is a very demanding engineering task and is carried out on all existing and newly built bridges and other demanding structures. The results of the measured displacements are thus influenced by several atmospheric parameters, among which the temperature is exposed, since the measurements are usually carried out over the whole day at different seasons and conditions, where the temperature differences are significant. In this paper the influence of temperature on the geodetic measurements of the displacements of the steel structure in the unburdened state is presented. To this end, measurements of the steel bridge during the summer time were performed. The temperature and thermal imaging at various locations every half hour were investigated. To calculate the influence of the temperature on the position of the observed point some statistical methods were used. It is evident from the results that in this kind of geodetic measurements, temperature measurements are indispensable. By taking into account the temperature correction results that are very comparable with the predicted values of displacements which can be obtained. Not observing the temperature can result in misleading values of displacement which can lead to misinterpretation and consideration of the obtained value.

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Structural monitoring of objects is primarily executed to assess external and internal effects on the object, in order to ensure the safety of people, animals, and material assets. Such monitoring can be executed through various methods, depending on the object, conditions for execution, and purpose of the monitoring. In this case, the focus is on the execution of the monitoring of Maribor footbridge, where the dynamic effects of the object are monitored. For this purpose, geophone, accelerometer, and geodetic methods—using Global Navigation Satellite System (GNSS) and Robotic Total Station (RTS) equipment—are used, of which one is controlled by the additional programme GeoComZG. The emphasis of our experiment is on the application of non-contact geodetic methods, with which the measurements of dynamic response are typically performed, as they enable measurements up to 30 and 100 Hz with RTS and GNSS, respectively. In this article, the application of various procedures of non-contact data capture on the footbridge are detailed and a comparison and analysis of the obtained values for monitoring the dynamic response of the structure are presented.

This paper deals with the infl uence of admixtures -silica fume, superplasticizer and air entraining agent -on the improvement of the bond strength between bundled carbon fi laments and cement mortars. Pull-out tests were carried out to examine the bond between carbon-fi ber yarn and various cement matrices. An overall microstructural analysis was conducted and correlated with pull-out data. Experimental results showed that all the applied admixtures contributed to improved bonding. The air entraining agent was found to be the most effective in improving the bond strength of the studied carbon-fi ber reinforced cement mortar. Air bubbles formed inside the mortar mix as a result of added air entraining agent and the ones formed in the vicinity of the outer fi laments of the yarn may provide a mechanical barrier at the interface, leading to a signifi cant increase in interface friction.

In the present work, both unused plasticized poly(1-chloroethylene) membranes and membranes taken from a flat roof area were comprehensively analysed. First, tensile strength and elongation at breaking points were determined, followed by measurements of wettability. Secondly, morphological changes were analysed using scanning electron microscopy (SEM). To study chemical changes in aged membranes, Fourier transform infrared spectroscopy (FTIR) analysis in the attenuated total reflection mode (ATR) was used. Finally, thermogravimetric analysis and differential scanning calorimetry (TGA-DSC) were performed simultaneously to study thermal degradation. The results show obvious changes in the mechanical, physical and chemical properties of membranes caused by plasticizer loss. Surface microstructure becomes stiffer, which leads to contractions and the prevalence of voids. In cross-sectional area, average thickness values decrease. Due to the degradation of the plasticized waterproofing membranes, the roofing area had to be completely replaced.