Branislava Lekić

Pervious concrete pavements have received increasing research attention because of their potential to improve stormwater runoff management in urban environments. Since they are usually exposed to low temperatures during the winter period, it is important to test their durability in a cold climate. Existing protocols for testing of the frost resistance of ordinary concrete are not completely suitable for this type of material, particularly for prefabricated pervious concrete pavers. The frost resistance of pervious concrete pavers designed with partial replacement of cement with fly ash (10 and 20%) was tested with and without the presence of de-icing salts. Two exposure conditions were used: specimens were either sealed in plastic foil to prevent drainage during cycling or were allowed to drain. Each freeze–thaw cycle lasted 24 h. After every seven cycles, specimen mass and ultrasonic pulse velocity were measured; the specimens were then rewetted and testing continued. At the end of the test, the specimens were dried and their flexural and compressive strengths were determined. The results indicate that ultrasonic pulse velocity is sensitive to changes in the properties of pervious concrete. The proposed method therefore shows promise for further development and application.

Urban areas are increasingly challenged by pluvial flooding, driven by climate change and the expansion of impervious surfaces. Conventional sewer systems often lack the capacity to manage increased volumes of stormwater, resulting in water spills in the lowest floors of buildings, retention of water on the ground and potential contamination. Implementing nature-based solutions, such as porous concrete pavements, supports controlled infiltration and retention of stormwater, thereby reducing peak flows, lowering runoff volumes, and improving infrastructure durability. The integration of nature-inspired solutions and gray infrastructure leads to an increased use of recycled materials for the sustainability and resilience of urban environments to flooding.

The paper presents challenges that urban drainage has to solve under altering hydrological regime due to urbanization. The need for reducing the negative impacts of urbanization on the quantity and quality of urban runoff is emphasized. Innovative methods of urban drainage have been presented, together with general recommendations for their application. The requirements from the proposal of the new EU Directive on urban wastewater related to the integrated management of urban wastewater, including rainwater, are presented in more detail.

Urban areas face increasing challenges from pluvial flooding due to climate change and increased urbanization rate. Sustainable construction practices involving circular economy principles offer a promising solution to enhance urban flood resilience. This paper investigates the utilization of waste materials in porous concrete pavers for mitigating urban flooding. The study examines the performance of porous concrete pavers incorporating waste materials such as solidified WWTP sludge in terms of permeability, durability, and flood resilience. Results demonstrate that the incorporation of waste materials influences paver’s mechanical properties but has no significant effect on the permeability of porous concrete.

Urban areas face increasing challenges from pluvial flooding due to climate change and increased urbanization rate. Sustainable construction practices involving circular economy principles offer a promising solution to enhance urban flood resilience. This paper investigates the utilization of waste materials in porous concrete pavers for mitigating urban flooding. The study examines the performance of porous concrete pavers incorporating waste materials such as solidified WWTP sludge in terms of permeability, durability, and flood resilience. Laboratory experiments and numerical simulations are conducted to assess the hydraulic properties and flood mitigation capabilities of these sustainable pavers. Results demonstrate that the incorporation of waste materials infuences paver’s mechanical properties but no significant effect are observed on the permeability of porous concrete. However, the use of waste materials contributes to the circular economy by repurposing industrial by-products and reducing environmental impact. This research provides valuable insights into sustainable construction practices for enhancing urban flood resilience while promoting the efficient utilization of waste materials

Two conventional experimental procedures for determination of the water permeability of saturated porous medium are the constant and the falling head permeability tests. The first one is more applicable on more permeable materials where the outflow from the sample is measured at variety of constant water heads, while the second one is more convenient for low permeable materials, utilizing the continuous measurements of the water head falling due to filtration through the saturated sample. However, neither of the two is useful for materials of high permeability and large cross‐sectional area. The constant head permeability test faces technical issues since a significant and continuous water discharge is required, while the falling head permeability test has limitations due to neglection of the Forchheimer's high‐velocity flow through the sample, but also the influence of inertia on the fluid mass. Here we proposed an approach for determination of the water permeability of saturated porous medium based on the agreement between the measured water level change in two connected reservoirs containing a porous sample and the new semi‐analytical expression describing that change by accounting for the mentioned theoretical deficiencies. This efficient approach has been tested on four pervious paver samples, and results showed satisfactory agreement with the constant head permeability data. It has been also confirmed the proposed semi‐analytical solution is more accurate than the falling head permeability approach in case of highly pervious materials, while for low permeable materials it reduces to the conventional approach.

Waste and recycled materials have recently been used in the construction industry to comply with the principles of circular economy and sustainable development. The aim of this paper is to examine the potentials of solidified wastewater treatment sludge (SWWTS) as a supplementary cementitious material (SCM) in the production of lightweight pervious concrete pavers (LWPCP) suitable for pedestrian trails and rooftops (green) that comply with EU standards. Detailed characterization of SWWTS was performed, in order to understand its properties related to application as SCM, which led to the conclusion that it may be applied only as a filler, having 89.5% of Ca(OH)₂. After thorough characterization, LWPCP samples were prepared and testing of physical and mechanical properties was conducted. The research showed that partial replacement of cement with SWWTS led to the decrease of all mechanical properties, ranging between 3.91 and 5.81 MPa for compressive strength and 0.97 to 1.23 MPa for flexural strength. However, all of the investigated mixtures showed a value higher than 3.5 MPa, which was defined as the lowest compressive strength in the range of pervious concrete properties. The addition of SWWTS led to a slight decrease in bulk density of the mixtures and an increase in water absorption. This could be explained by the reduction in hydration products that would fill in the micropores of the matrix, since SWWTS showed no pozzolanic reactivity. Pore sizes that prevail in the tested binder matrices are in accordance with the results measured on ordinary pervious concrete (the largest fraction of pores had a diameter between 0.02 and 0.2 μm). Low thermal conductivity nominates produced pavers as potential rooftop elements.

This paper presents the results of the investigation of pollutant build-up on impervious surfaces of a parking lot in Belgrade, Serbia during the summer months. Contaminant build-up was found to be greater on asphalt surfaces directly exposed to vehicular traffic than on concrete walkways. The difference in the amounts of accumulated pollutants between asphalt and concrete were significant: for total solids (TS), total suspended solids (TSS), chemical oxygen demand (COD), heavy metals and total phosphorus (TP) accumulations were two to three times higher, while only 30% higher for total nitrogen (TN) and anions. Build-up of most of the measured parameters was best described by power functions. The highest surface loads were found for solids, COD, iron and zinc. A strong correlation was found between turbidity, TS, TSS, COD, heavy metals and phosphorus, while conductivity, nitrates and nitrites were weakly correlated to other parameters.

Numerous regression approaches to isotherm parameters estimation appear in the literature. The real insight into the proper modeling pattern can be achieved only by testing methods on a very big number of cases. Experimentally, it cannot be done in a reasonable time, so the Monte Carlo simulation method was applied. The objective of this paper is to introduce and compare numerical approaches that involve different levels of knowledge about the noise structure of the analytical method used for initial and equilibrium concentration determination. Six levels of homoscedastic noise and five types of heteroscedastic noise precision models were considered. Performance of the methods was statistically evaluated based on median percentage error and mean absolute relative error in parameter estimates. The present study showed a clear distinction between two cases. When equilibrium experiments are performed only once, for the homoscedastic case, the winning error function is ordinary least squares, while for the case of heteroscedastic noise the use of orthogonal distance regression or Margart’s percent standard deviation is suggested. It was found that in case when experiments are repeated three times the simple method of weighted least squares performed as well as more complicated orthogonal distance regression method.