New Experiences in Dike Construction with Soil-Ash Composites and Fine-Grained Dredged Materials

The supporting structure inside a coastal dike is often made of dredged non-uniform sand with good compaction properties. Due to the shortage of natural construction material for both coastal and river dikes and the surplus of different processed materials, new experiments were made with sand-ash mixtures and fine-grained dredged materials to replace both dike core and dike cover materials resulting in economical, environmentally friendly and sustainable dikes. Ash from EC Gdańsk and dredged sand from the Vistula river were mixed to form an engineering material used for dike construction. The optimum sand-ash composites were applied at a field test site to build a large-scale research dike. Fine-grained dredged materials from Germany were chosen to be applied in a second full-scale research dike in Rostock. All materials were investigated according to the standards for soil mechanical analysis. This includes basic soil properties, mechanical characteristics, such as grain-size distribution, compaction parameters, compressibility, shear strength, and water permeability. In the field, the infiltration of water into the dike body as well as the erosion resistance of the cover material against overflowing water was determined. Results of both laboratory and field testing are discussed in this paper. In conclusion, the mixing of bottom ash with mineral soil, such as relatively uniform dredged sand, fairly improves the geotechnical parameters of the composite, compared to the constituents. Depending on the composite, the materials may be suitable to build a dike core or an erosion-resistant dike cover

Effect of the alkaline reactivity process of aggregates on concrete and reinforced concrete engineering structures

Najczęściej stosowanym kruszywem do betonów używanych w konstrukcjach inżynierskich jest kruszywo pochodzenia magmowego: granitowe i bazaltowe oraz kruszywo naturalne (żwiry i piaski). Jednak coraz częściej, m.in. ze względów ekonomicznych i logistycznych stosuje się inne rodzaje kruszyw, m.in. pochodzenia metamorficznego (amfibolitowe), węglanowego (dolomitowe i wapienne) oraz kruszywa sztuczne. Jednym z kryteriów klasyfikujących kruszywo do zastosowania do betonu jest zawartość minerałów potencjalnie reaktywnych, do których należą m.in. chalcedon, opal, trydymit, mikrokrystaliczny/kryptokrystaliczny kwarc oraz kwarc w stanie naprężeń, tzw. highly-strained quartz. W artykule przedstawiono metody badawcze stosowane do oznaczenia potencjalnej reaktywności alkalicznej kruszyw w Polsce oraz efekty badań reaktywności alkalicznej żwirów czwartorzędowych, które poddano starannej analizie w mikroskopie skaningowym, zwracając szczególną uwagę na procesy zachodzące pomiędzy reaktywnymi minerałami (chalcedon, opal, trydymit, mikrokrystaliczny/kryptokrystaliczny kwarc oraz kwarc w stanie naprężeń, tzw. highly-strained quartz) a alkaliami występującymi w cemencie.The most commonly used aggregate in concrete construction and paving has natural aggregates (gravel and sand) and the aggregate magmatic origin: granite and basalt. However, more often, such as due to logistical and economical use different types of aggregates, eg, metamorphic origin (amphibolite), carbonate (dolomite and limestone) and artificial aggregates. One of the criteria for classifying the aggregates for use in concrete is potentially reactive mineral content, which include inter alia chalcedony, opal, tridymite, microcrystalline /cryptocrystalline Quartz and highly-strained quartz. The article presents the research methods used to determine the potential alkaline reactivity of aggregates in Poland and the results of the alkaline reactivity tests of quaternary gravels, which were carefully analyzed in a scanning microscope, paying particular attention to the processes taking place between reactive minerals (chalcedony, opal, trydymite, microcrystalline/cryptocrystalline quartz and highly-strained quartz) and alkali present in the cement