https://etalpykla.vilniustech.lt/handle/123456789/157276 2026-04-04T22:04:17Z 2026-04-04T22:04:17Z Žvironaitė, Jadvyga Pranckevičienė, Jolanta https://etalpykla.vilniustech.lt/handle/123456789/157623 2025-05-16T07:20:46Z 2017-01-01T00:00:00Z

The investigation of alkali – silica reactivity (ASR) of Lithuanian aggregates Žvironaitė, Jadvyga; Pranckevičienė, Jolanta The potential alkali-silica reactivity (ASR) of Lithuanian aggregates from five quarries was investigated using national chemical method, accelerated mortar bar test method RILEM AAR-2 (specimens 40×40×160 mm) and storage of specimens at 60 °C and 100% RH conditions. It was found, that all aggregates are contaminated with reactive rocks (4.0% - 4.6% in sand and 1.5% - 2.4% in gravel). The most of aggregates can be assigned to Class II-S according AAR-0. “Pop-out” and ASR-gel were observed after 15 weeks in the mortar specimens stored at 60 °C and 100% RH.

2017-01-01T00:00:00Z Zieliński, Krzysztof Babiak, Michał Ratajczak, Maria Kosno, Jacek https://etalpykla.vilniustech.lt/handle/123456789/157622 2025-05-16T08:13:58Z 2017-01-01T00:00:00Z

Impact of chemical and physical modification on thermoplastic characteristics of bitumen Zieliński, Krzysztof; Babiak, Michał; Ratajczak, Maria; Kosno, Jacek In spite of strong competition of synthetic materials (including PVC, EPDM), bitumen remains the major component of most waterproofing materials. It makes up approx. 80% by weight of the final product. The characteristics of bitumen mix have a decisive impact on the quality of the final product. During storage, transport, manufacturing and installation of waterproofing materials, bitumen is subject to ageing. As a result of the ageing process the characteristics of bitumen waterproofing materials deteriorate, roofing membrane becomes more rigid and cracks. The damaged waterproofing layer ceases to perform its function; it does not protect the building envelopes against water penetration. The development of organic chemistry allowed the synthesis of a number of modifying substances used for chemical modification of bitumen. Among the most promising are heterocyclic organic compounds belonging to the group of imidazolines. The article presents the results of preliminary laboratory tests of bitumen modified jointly by SBS and imidazoline. The objective of the study was to find a new type of bitumen modifier (hybrid modifier) synergically combining the advantages of both types of presented modifications.

2017-01-01T00:00:00Z Zieliński, Krzysztof https://etalpykla.vilniustech.lt/handle/123456789/157621 2025-05-16T07:21:05Z 2017-01-01T00:00:00Z

Impact of recycled aggregates on selected physical and mechanical characteristics of cement concrete Zieliński, Krzysztof The issue of using construction rubble was recognized in Europe not earlier than in the nineties of the twentieth century. This was due to economic and ecological considerations. However, recycled aggregate is characterized by high volatility of physical and mechanical properties. The quantity and type of various kinds of impurities harmful to the durability of concrete is virtually unpredictable. For over twenty years various organizations in different countries have tried to sort out this problem and possibly unequivocally define the criteria for the suitability of different types of recycled aggregates to the production of concrete. The article presents and compares the most important guidelines, currently in force, regulating the scope of use of recycled aggregates (RILEM as well as Japanese, German and European standards). The article also contains the results and the analysis of comparative studies of selected physical and mechanical characteristics of concrete produced with the use of natural aggregate and concrete produced with the use of recycled aggregate obtained from milling of masonry.

2017-01-01T00:00:00Z Zdancevičius, Evaldas Kačianauskas, Rimantas Zabulionis, Darius https://etalpykla.vilniustech.lt/handle/123456789/157620 2025-05-16T08:10:28Z 2017-01-01T00:00:00Z

Improvement of viscoelastic damping for the Hertz contact of particles due to impact velocity Zdancevičius, Evaldas; Kačianauskas, Rimantas; Zabulionis, Darius One of the most important task in application of the Discrete Element Method (DEM) to simulation of geomaterials is the adequacy of description of contact between interacting mineral particles. In most of the cases the elastic force is expressed by using Hertz model, while description of viscoelastic damping force is still under discussion. Recently various damping models described by different values of overlap power factor are used in DEM calculations. The general form of viscoelastic damping constant was presented, where well-known damping models present particular cases of general relationships. It known no one already existing models can precisely represent experimental results in most of the cases. In this paper general damping model comprising several existing approaches is developed. Here displacement power factor is evaluated on the basis of experiment results. It was found that the proposed approach gives more accurate simulation results of coefficient of restitution in comparison to already existing damping models.

2017-01-01T00:00:00Z