Effect of a Fine Fraction on Dynamic Properties of Recycled Concrete Aggregate as a Special Anthropogenic Soil.

The literature confirms that fine recycled concrete aggregate (fRCA) can be used as a replacement for natural soil in new concrete, offering many advantages. Despite these advantages, there are also critical barriers to the development of fRCA in new mixes. Among these, the first challenge is the variability of fRCA properties, in both physical, chemical, and mechanical terms. Many individual studies have been carried out on different RCA or fRCA properties, but little investigative work has been performed to analyze their dynamic properties. Therefore, the influence of the non-cohesive fine fraction content of RCA on the dynamic properties of this waste material, when used as a specific anthropogenic soil, has been studied in laboratory conditions, employing a standard resonant column apparatus, as well as piezoelectric elements. In the present research, special emphasis has been placed on the dynamic shear modulus, dynamic damping ratio, small-strain shear modulus, and small-strain damping ratio, as well as shear modulus degradation G(γ)/Gmax, the damping ratio increase D(γ)/Dmin, and the threshold shear strain amplitudes γtl and γtv. Artificially prepared fRCAs with varying fine fraction contents (0% ≤ FF ≤ 30%, within increments of 5%) have been tested at different pressures (p' = 90, 180, and 270 kPa) and relative densities of Dr > 65%. This study also examined the effect of two tamping-based sample preparation methods, i.e., dry and wet tamping. The results presented herein indicate that the analyzed anthropogenic material, although derived from concrete and produced by human activities, behaves very similarly to natural aggregate when subjected to dynamic loading. The introduction of a fine fraction content to fRCA leads to changes in the dynamic properties of the tested mixture. Concrete material with lower stiffness but, at the same time, with stronger damping properties can be obtained. A fine fraction content of at least 30% is sufficient to cause a significant loss of stiffness and, at the same time, a significant increase in the damping properties of the mixture. This study can serve as a reference for designing fRCA mixtures in engineering applications.

Geotechnical and Environmental Assessment of Blast Furnace Slag for Engineering Applications.

The increasing demand for building materials in the road industry creates interest for a new source of high-quality aggregates. In order to conserve natural resources, more attention is focused on anthropogenic soils and industrial solid wastes. For the successful application of these types of soil, a series of geotechnical and environmental tests have to be conducted. A potential hazard in the reuse of wastes from thermal degradation in the construction industry, particularly in reinforced concrete (RC) construction, is the migration of heavy metals into the groundwater environment. In this article, a geotechnical assessment of blast furnace slag (BFS) properties is presented. We conducted a series of CBR, and oedometric tests to evaluate the feasibility of BFS application in earth construction. The oedometric test results show acceptable compression characteristics which are in the range of natural aggregates. The CBR shows that this material may be used as a pavement subbase. We also noticed the preconsolidation pressure phenomenon in both Proctor and vibro-compacted soil during the oedometric test. The compression index and recompression index value show that the compression characteristics are close to those of dense sand. Based on the results described in the article, blast furnace slag is a candidate for technological application and can become one of the elements of sustainable development by contributing to a reduction in the negative environmental impact of production and use of building materials.

Assessment of chemical and microbiological parameters on the Leite River Lithuania.

The most common source of pollution is wastewater that comes from the industrial, agricultural, and household sectors. The aim of this work is to evaluate the impact of a new innovative wastewater treatment technology on the water quality of the Leite River, Lithuania. The Leite River basin receives wastewater from the Leitgiriai agglomeration; it is then released into a channel, which is 73 m away from the river. During the implementation of the BSR Interreg project "Water emissions and their reduction in village communities in the Baltic Sea Region as pilots (VillageWater)," the ineffective Leitgiriai wastewater treatment plant (WWTP) was reconstructed in September and October of 2017. Water samples from Leite River were collected in 2010-2018 in three locations: near the Kulynai, Leitgiriai, and Sausgalviai villages in Lithuania. The results show that the wastewater treatment efficiency is statistically higher than that before the reconstruction of the WWTP. The treated wastewater (before and after reconstruction) is released from the Leitgiriai WWTP into the surface water (channel), which flows into the Leite River. The highest concentrations (according to all examined indicators) have been observed in the channel and in the Leite River 500 m after the release point before the reconstruction. All differences are statistically significant (p < 0.05). According to the 2018 values, the water quality of the Leite River did comply with the good ecological status/potential class indicators near the Leitgiriai village. After the Leitgiriai WWTP reconstruction, the wastewater treatment efficiency increased two times on average. Therefore, the Leite River water quality near Leitgiriai improved.

The impact of livestock farming activity on the quality of surface water.

The most dangerous pollution sources are intensive agricultural activity and livestock farming, whose production waste has a negative impact on soil and water quality. Livestock farming is separated into two systems: indoor (pigs and poultry) and pasture-based (livestock and sheep). Numerous studies aimed at elucidating how different systems affect the environment have been performed. In Lithuania, the biggest environmental problems are caused by 24 farms with more than 5000 pigs, 21 poultry farm with more than 1000 chickens, 2179 cow-cattle farms larger than 50 places, and about 200,000 sheep. We aimed to assess the quality of surface water in the Kaunas region next to the pig and livestock farms. In 2008-2017, seven livestock agricultural companies and seven larger farmers were regarded as potential sources of pollution in the Kaunas region. Half of these sources were pig farms, and the rest were livestock farms. Locations next to potential agricultural pollution sources were chosen to monitor the surface water. The results indicated that although the agricultural areas, number of livestock units, and nitrogen rate per 1 ha were similar between the pig and livestock farms, the activity on the pig farms affected the surface water quality more than that on livestock farms. As the number of livestock units (LU) increased on the farms, the pH decreased and the suspended materials, nitrates, and phosphates increased in the surface water. With increasing nitrogen kg/ha, the pH values decreased, thereby yielding more acidic water. The intensity of agricultural activity did not affect the water quality near the livestock farms, except for livestock units (LU), which affected the pH.