The paper presents the results of exploratory research on the use of reclaimed cement concrete in cold-recycled mixes with foamed bitumen. Because reclaimed cement concrete, unlike natural aggregates, is expected to have a residue of the non-hydrated cement covering the aggregate grains, which may result in a secondary cementation process after its application in a road base, this avenue was explored by tracking the time evolution of the compressive strength of the final material. The tests were performed using two mixtures, i.e., a reference mixture and a mixture containing 25% reclaimed cement concrete. The mixtures containing reclaimed cement concrete were characterized by increased uniaxial compressive strengths after each curing period (3, 4, 7, 14 and 28 days)—by 11.5 kPa on average and e.g., 498 kPa vs. 506 kPa after 28 days. The obtained differences between the mixtures were not found to be statistically significant. The small effects of the incorporation of reclaimed cement concrete were attributed to the time passed typically between the demolition and new pavement construction and to the presence of a second binding material—bitumen.
The use of moist/wet aggregate fractions in the asphalt mixtures with reduced production and compaction temperatures (HWMA - Half Warm Mix Asphalt) with foamed bitumen is aimed at obtaining an additional foaming effect of the binder. The paper presents results of investigations on the possibility of producing the asphalt concrete for the upper layers of the road pavement at reduced technological temperatures utilizing fine wet aggregates and foamed asphalt in opposition to specific patented solutions. This modification of the production process was evaluated in the scope of moisture content in the 0/4 mm aggregates in terms of mixture compactibility using the gyratory compactor and the assessment of related physical and mechanical properties of the asphalt mixtures. The analysed moisture contents resulted in a final 1% and 3% water contents in the whole mineral mix. In order to assess the effect of the addition of wet aggregates on the properties of the mixture produced at the reduced temperature with foamed bitumen, three identical asphalt concrete AC 16 mixtures in terms of composition were used, hot-mix HMAREF and warm-mix WMAREF, with differences only in technological temperatures of the mix constituents during their preparation and mix compaction, the form of the binder (liquid in HMAREF mixture, foamed with water in WMAREF mixtures) and half-warm mix HWMA with foamed bitumen additionally utilizing a portion of fine wet aggregates in the blends. The conducted studies have shown that the presence of the wet aggregates in the mixtures with foamed bitumen had a significant impact on the air void contents in the samples formed in the gyratory compactor. In a mixture with foamed bitumen, produced and compacted at a reduced temperature (HWMA), an improvement in the compaction in relation to the reference mixture WMAREF was found. Based on the results of indirect tensile strength tests and analysis of the ITSR indices, it was found that the use of wet aggregates had major, significant effects on the mechanical properties of the samples subjected to water and frost susceptibility testing. The mixture produced with wet aggregates obtained indices for resistance to the moisture and frost damage which were unsatisfying for the upper bituminous pavement courses as for Polish climatic conditions (ITSR<70%). This result was attributed to inadequate the aggregate coating and reduced adhesion of the binder. It was stated that the mixtures resembling HWMA, produced with moist or wet aggregates at reduced technological temperatures can be utilized in Polish and similarly harsh climatic conditions in the lower pavement structural layers, mainly due to their reduced moisture and frost resistance. The application of the tested mixtures to the upper structural layer would require using special treatments, e.g. chemical additives, in order to improve the adhesion of asphalt to aggregate or raise the technological temperature (as for WMA blends) to increase the dynamics of water evaporation from the damp aggregates.
The twenty-fifth anniversary of self-government in Poland is a good occasion to reflect on the road we have travelled so far. While we still remember well the intentions of the creators of the system (members of the First Senate) we can now compare them with the current state of affairsand the status quo of government in Poland today. Two concepts have always been there since the beginning. Whereas the original solutions were to be inscribed in the tradition of Polish self-government, everything was done from the very start to draw as much as possible from the achievements of legal political thinking, later manifested in the provisions of the European Charter on Local Self-Government – a document which is the quintessence of the Western model of a local authority. Self-government is an institution characteristic of Western civilisation, practically unknown elsewhere, and it extends the principles of representation onto the local space inhabited by its citizens. Examples offered in the article illustrate how the initially planned model of government in Poland, rooted in the city fathers model has, in the course of subsequent reforms, been losing its original Western clarity in favour of the previous host model of local authority that characterised the past system.
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