Ultra-High Performance Fibre Reinforced Concrete (UHPFRC) is characterized by a unique combination of extremely low permeability, high strength and deformability. Extensive R&D works and applications over the last 10 years have demonstrated that cast on site UHPFRC is a fast, efficient and price competitive method for the repair/rehabilitation of existing structures. More recently, an original concept of ECO-UHPFRC with a high dosage of mineral addition, a low clinker content, and a majority of local components has been applied successfully for the rehabilitation of a bridge in Slovenia. The objective of the present study is to evaluate the global warming impact of bridge rehabilitations with different types of UHPFRC and to compare them to more standard solutions, both on the basis of the bridge rehabilitation performed in Slovenia. Life Cycle Assessment (LCA) methodology is used. The analysis shows that rehabilitations with UHPFRC, and even more ECO-UHPFRC, have a lower impact than traditional methods over the life cycle.
COBISS.SI-ID: 1991527
The paper presents a new method to determine the transition of different cementitious materials from liquid to solid state, usually defined as a setting period. The method is based on a ratio between maximum amplitudes of two dominant frequency ranges that appear in the frequency spectrum of ultrasonic (US) P-waves, called a TG parameter. Clear and unambiguous correlation between characteristic points in the evolution of TG parameter and penetration resistance in time is established on samples with different material composition during the early hydration process. The correlation indicates that TG parameter detects the development of rigid bonds between hydrating cement particles. The ability and accuracy of the method to determine setting period is unaffected by the material composition. Non-destructive nature and insensitivity of the method to aggregate size gives it an advantage over penetration methods and other US methods in determining the setting period of cement pastes, mortars, and concretes.
COBISS.SI-ID: 1967207
In the study characterization of steel corrosion in concrete at the macro- andmicro-level was performed. Physical (electrical-resistance probes) and electrochemical techniques (coupled multi-electrode arrays) were implemented in order to upgrade the general information that conventional electrochemical techniques can provide. Measurements were performed in mortar exposed to periodic wetting and drying. Steel corrosion damage was assessed by micro X-ray computer tomography (CT) and SEM. The results were compared and interpreted. By combined use of Micro-CT and electrochemical methods, new insights into the corrosion mechanisms of steel in concrete were obtained.
COBISS.SI-ID: 1966695
Nanocomposites consisting of PA12 and Mo6S3I6 nanowires at concentrations of 0.5, 1.0 and 2.0 wt.% were prepared by extrusion and characterised. Using electron microscopy it was confirmed that bundles of nanowires were present, whose size increases with increasing concentrations. Differential dynamic calorimetry showed that the nanowires act as a nucleating agent, increasing the crystallization rate and the overall degree of crystallinity, but at the same time the size of the crystals is decreased. As a result, Young’s modulus was increased by 15% with the addition of only 0.5 wt.% of Mo6S3I6. The improved mechanical properties are attributed to changes in the polymer morphology and crystallinity.
COBISS.SI-ID: 5311770
In case of foamed lightweight aggregates (LWA), porosity is introduced by the addition of a foaming agent to the glassy matrix, which degasses at an elevated temperature, so that the resulting gasses remain trapped inside the glassy structure. The efficiency of action of MnO2 as a foaming agent in wasteglass and waste glass / silica mud systems was studied. Samples were fired at different temperatures and with different dwelling times at a certaintemperature, and the development of porosity was investigated by means of X-ray micro-tomography. It was found that, with the prolongation in dwelling times, the number of pores decreased, while, on the other hand, the volume of these pores increased, and that the addition of silica mud increasesthe foaming temperature and slows down the foaming process.
COBISS.SI-ID: 1980007