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1

Growth and Development of Rhizophora spp. Seedlings on Different Substrates and Insertion Level in the Wouri Estuary Mangrove (Douala, Cameroon)

Boubakary Boubakary, Léopold Essomè-Koum Guillaume, Flavien Kottè-Mapoko Ernest, Maxemilie Ngo-Massou Vanessa, Laurant Nyamsi-Moussian, Alphonse Konango-Samè, Michel Emanè Jean, Din Ndongo

Journal of Ecological Engineering

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2024

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Vol. 25, nr 4

96--110

EN

Mangroves are threatened with extinction worldwide. Many mangrove reforestation projects have been developed, but very few have achieved their restoration objectives. With the ambitions to contribute for rehabilitation of mangrove ecosystems, the aim of this study was to assess the effects of substrate composition and level of insertion on the growth and development of Rhizophora seedlings in nurseries. The experiment was conducted in a semilighted nursery set up in situ. Rhizophora propagules were reared on three types of mangrove substrates (type 1:75% of mud and 25% of sand; type 2:50% of mud and 50% of sand, and type 3:25% of mud and 75% of sand) with different levels of insertion (at ¼; ½ and ¾). Seedling heights and diameters were recorded, as well as the time of appearance of the first leaves and the variation of number of leaves. The greatest average height (40.2±7.48 cm) and the highest mean diameter (1.2±0.01 cm) were obtained for the substrate composed of 75% mud and 25% sand. The best growth and development of seedlings were recorded on the substrate type 1 with an insertion at ¼. Seedling production at ¼ insertion of substrate type 1 appeared the most effective combination. The production of Rhizophora seedlings on the substrate combining 25% Sand and 75% Mud with an insertion level at 1/4 seems to be the best method for the complete restoration and rehabilitation of the mangrove ecosystem of the Wouri estuary.

2

Rheological and mechanical behavior study of eco-friendly cement mortar made with marble powder

Chahour Kahina, Mechakra Hamza, Safi Brahim, Dehbi Nacera-Melissa, Chaibet Cylia

International Journal of Applied Mechanics and Engineering

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2024

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Vol. 29, no. 1

19--35

EN

The work aim is to investigate the rheological and mechanical behavior of eco-friendly mortar made with marble powder. Marble have used as sand by total substitution of natural sand and as additional materials by partial substitution of cement. Firstly, rheological tests were carried out on the cement pastes in order to studying the effect of cement substitution by marble powder on the rheological behavior. Secondly, our study is devoted to evaluate the mechanical performances (flexural strength, compressive strength, mechanical behavior and ultrasonic pulse velocity) of a fluid mortar such as the case of the self-compacting mortars elaborated with the marble powder as addition materials and as a sand. The mechanical test results show that a significantly improved of compressive strength and mechanical behavior of an ecological cement mortar made with marble waste as a natural sand. However, marble-based mortars with 100% of marble sand have given a mechanical strength similar to that obtained by control cement mortar (100% natural sand). It was also noted that it can be obtained an ecological cement mortar made with 30% of marble powder as an addition supplementary materials. This leads to a reduction in cement consumption cad a reduction in CO2 gas emissions caused by cement production.

3

Bearing Capacity Evaluation of Shallow Foundations on Stabilized Layered Soil using ABAQUS

Bhardwaj Avinash, Sharma Ravi Kumar

Studia Geotechnica et Mechanica

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2023

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Vol. 45, nr 1

55--71

EN

In this paper, the finite element method (FEM) is applied to calculate the bearing capacity of two footings having the aspect ratio L/B (where L and B are the length and width of the footing, respectively) equal to 1, 2 resting on one-layer and two-layer soil. Soil profile contains two soil types including sand and clay. The soil strip is 500mm × 500mm × 350mm; however, only a quarter of the model (250mm × 250mm × 350mm) is examined in the study. Two primary situations are investigated in this study. In the first situation, the one-layer system is supposed to be sandy soil with footing overlays on medium-dense sand. The soft clay/stabilized clayey layer is supposed to be on top of the sandy soil in the second condition, with the footing resting on top of the soft clay/stabilized clay. The influence of layer thickness, aspect ratio, and material property on the bearing capacity value and footing failure mechanism is studied for eight different combinations of layered soil. The bearing capacity for a one-layer case is also estimated, and it agrees well with Vesic (1973), Hansen (1970), and Terzaghi's (1943) equations. The bearing capacity of footings is observed to decline when the height of unstabilized clayey soil increases, and it increases when clayey soil is stabilized with molasses, waste foundry sand, and lime alone and in combination with each other.

4

Determination of the Degradation Degree of Pasture Lands in the West Kazakhstan Region Based on Monitoring Using Geoinformation Technologies

Yesmagulova Bayan Zhumabaevna, Assetova Assem Yurievna, Tassanova Zhadyra Baizhanovna, Zhildikbaeva Aizhan Naskenovna, Molzhigitova Dinara Kumarbekovna

Journal of Ecological Engineering

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2023

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Vol. 24, nr 1

179--187

EN

Land degradation, including pasture lands is one of the global problems. Currently, one of the most urgent problems of the West Kazakhstan region is the preservation and restoration of the vegetation cover of pasture lands. To date, large areas of the region have been occupied by agricultural land. Several main reasons negatively affect agriculture, one of which is land degradation associated with anthropogenic impact in terms of the irrationality of land use. Thus, to preserve the biodiversity of the pastures of the West Kazakhstan region, it is necessary to fully study the projective cover of the vegetation, determine the dominant plant species, and also monitor the condition of pastures to prevent land degradation on time by conducting land and forest improvement activities. The study aimed to carry out a phyto-ecological assessment of degraded pastures of the Karatobinsky district of the West Kazakhstan region using geoinformation technologies and field study results. The paper presents the results of desktop decoding of high-resolution satellite images and ecological profiling of the studied territories. Decoding features of landscape types allowed making a preliminary map of landscape contours. The use of this technique makes it possible to monitor the condition of degraded pasture lands in a short time and justify the organization of pastures with a regulated grazing system in the study area.

5

Testing and Evaluation of Physical and Chemical Properties of Waste from Desanding

Czop Monika, Petryk Agnieszka, Balcerzak Luzia, Jamry Agata, Kopiec Weronika, Nowak Katarzyna, Piwowarczyk Marta, Zackiewicz Weronika

Inżynieria Mineralna

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2023

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no. 2, vol. 2

129--134

EN

The study concerns evaluating the physical and chemical properties of sand from sand separators of wastewater treatment plants in terms of requirements for construction aggregates. Thus, an analysis of the physical properties of sand was carried out, i.e. its moisture content, bulk density, and grain density, as well as an analysis of the chemical composition of sand. The intention of the research is to find an alternative to the dwindling supply of this type of raw material, which is essential for the construction sector. It is currently estimated that within 20 years there will be a shortage of sand of suitable quality for use in construction. The article presents the results of physicochemical tests and leachability of selected harmful substances (P, F, N-NH4 +, Cl, SO4 2-) and heavy metals (Ba, Zn, Cu, Pb, Cd, Cr, Co, Fe, Ni) from waste from desanding

PL

W artykule dokonano oceny właściwości fizykochemicznych piasku z piaskowników oczyszczalni ścieków pod kątem wymagań stawianych kruszywom budowlanym. W związku z tym przeprowadzono analizę właściwości fizycznych piasku: wilgotność, gęstość nasypową, a także analizę składu chemicznego piasku i poziom wymywalności substancji szkodliwych oraz metali ciężkich. Celem badań było znalezienie alternatywy dla malejącej zasobów tego cennego surowca, niezbędnego dla sektora budowlanego. Obecnie szacuje się, że w ciągu 20 lat zabraknie piasku odpowiedniej jakości do wykorzystania w budownictwie. W artykule przedstawiono wyniki badań fizykochemicznych oraz wymywalności wybranych substancji szkodliwych (P, F, N-NH4 +, Cl, SO4 2-) i metali ciężkich (Ba, Zn, Cu, Pb, Cd, Cr, Co, Fe, Ni) z zawartości piaskownika.

6

Review of possibilities of using sandy waste obtained in wastewater treatment plants as an alternative raw material in construction

Kostrzewa Jacek, Popielski Paweł, Dąbska Agnieszka

Gospodarka Materiałowa i Logistyka

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2023

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nr 3

25--37

EN

Sand is a globally mined natural resource. It is applied, among others, in construction, because sand is one of the main components of concrete mixtures and a material used in earthworks. The aim of the manuscript is to organize the state of knowledge regarding the management of sandy waste generated in wastewater treatment plants and to indicate the possibilities of using this waste as an alternative raw material in construction applications. The main thesis is the claim that sand recovered in wastewater treatment plants, perceived as waste, can be an alternative for the global economy to obtain a significant amount of raw material for various uses in construction and to replace natural raw materials extracted for industry. The paper presents data on natural sand resources and its use, the effects of uncontrolled exploitation of the worlds sand resources and the potential of the Polish sand resource base. Particular attention was paid to the review of the possibilities of using sandy waste generated in wastewater treatment plants as an alternative raw material for natural sand resources. The practical applications of sand obtained in the processes used in wastewater treatment plants were also presented.

PL

Piasek jest globalnie wydobywanym zasobem naturalnym. Stosuje się go m.in. w budownictwie, ponieważ piasek jest jednym z głównych składników mieszanek betonowych oraz materiałem wykorzystywanym w robotach ziemnych. Celem artykułu jest uporządkowanie stanu wiedzy dotyczącego zagospodarowania odpadów piaszczystych powstających w oczyszczalniach ścieków i wskazanie możliwości wykorzystania tych odpadów jako surowca alternatywnego w zastosowaniach budowlanych. Główną tezę stanowi twierdzenie, że piasek odzyskiwany w oczyszczalniach ścieków, postrzegany jako odpad, może być alternatywą dla światowej gospodarki na pozyskanie znacznej ilości surowca do różnych zastosowań w budownictwie i zastąpienia nim surowców naturalnych wydobywanych dla przemysłu. W pracy przedstawiono dane dotyczące zasobów piasku naturalnego i jego wykorzystania, skutki niekontrolowanej eksploatacji światowych zasobów piasku oraz potencjał polskiej bazy zasobowej piasku. Szczególną uwagę poświęcono przeglądowi możliwości wykorzystania odpadów piaszczystych powstających w oczyszczalniach ścieków jako alternatywnego surowca dla piasku naturalnego. Przedstawiono również dotychczasowe, praktyczne zastosowania piasku uzyskanego w procesach stosowanych w oczyszczalniach ścieków.

7

Study the Effects of Using Different Water Types on the Mechanical Properties of Concrete

Fadil Sanad Aldeen, Al Kindi Ghayda Y., Tobeia Sameh B.

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 1

175--184

EN

The issue of water sustainability is a major topic due to the lack of water sources and the scarcity of drinking water, so the search for alternatives began. In this paper, the effect of using three water sources will be studied (the tap water (as control reference mix.), the Tigris River, and the Pepsi Company factory). To study the physical and chemical properties, and the effect of this water on the concrete mixture, and for each source the concrete mixture was placed in cube molds and cylinders. Put the concrete mixture in a water basin for curing. Compression and splitting tests are performed at intervals of (7-28-90) days to evaluate these mixtures. From the results it was found that the compressive and splitting strength of concrete for tap water, Tigris River and Pepsi factory, which was recorded at the age of 7 days, the compressive strength of cubes was an average of 18.5 MPa, 19 MPa and 13 and the splitting strength was an average of 1.5 MPa and 1.4 MPa and 0.5 MPa, respectively, at the age of 28 days, which were recorded at 32.1 MPa, 28 MPa, and 16.4 MPa, respectively, and the splitting strength was 3 MPa, and 2.7 MPa, and 1.5 MPa, respectively, and at 90 days they were 36 MPa, 32 MPa, and 18 MPa, respectively, and the splitting strength was 3.2 MPa, 3 MPa, and 1.7 MPa respectively also was observed a decrease in compressive strength and splitting by more than 40% for Pepsi Baghdad company factory wastewater samples. Finally, the drinking water and the water of the Tigris River was suitable for making concrete mixtures.

8

Environmental Assessment of a Unique Filtration Process for Treatment of Polluted Storm Water

Al-Khalaf Safaa K. Hashim, Al-Ridah Zaid Abed, Shlash Marwah Abdullah, Naje Ahmed Samir

Ecological Engineering & Environmental Technology

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2023

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Vol. 24, iss. 1

116--124

EN

As a result of poor human activities, storm water is now contaminated, notably in the Middle East. The filtering process is a physical separation with no chemical reactions occurring throughout the operation. The goal of this research is to use three distinct types of filters to improve the quality of storm water: sand, sand with granular activated carbon (GAC), and sand with cotton. Before and after treatment, the pH, turbidity, electric conductivity, TDS, and temperature of storm water are all monitored. In addition, the water quality index (WQI) was computed. The parameters of treated storm water varied depending on the filter media used, such as sand (turbidity = 83 NTU, TDS = 585 mg/L, conductivity = 1190 S/cm, pH = 7.1 and temperature =17.8 °C), sand with GAC (turbidity = 12NTU, TDS = 540 mg/L, conductivity = 910 S/cm, pH = 7 and temperature =18 °C) and sand with cotton (turbidity = 6.4 NTU, TDS = 490 mg/L, conductivity = 1090 μS/cm, pH = 7.2 and temperature =17.6 °C). Sand has a treatment efficiency of 63.6 percent, sand with GAC has an efficiency of 84.9 percent, and sand with cotton has an efficiency of 84.2 percent at a flow rate of 0.66 L/min, when WQI is clean. With GAC, it is clear that the dual media filter is the finest special sand.

9

Graphite oxide coated sand composites for efficient removal of calcium ions from hard water: isotherm, kinetics, and adsorption mechanism

Perera W.P.R.T., Premasinghe Niroshan, Fernando W.S.K., Perera P.L.R.A., Sandaruwan Chanaka, Kumarasinghe A.R., Liyanage Janitha A.

Composites Theory and Practice

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2023

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R. 23, nr 4

209--219

EN

Even if granular media filtration effectively reduces the turbidity of water, its limited surface functionalities and physical properties may constrain its ability to effectively remove critical contaminants from water. In our research, we successfully synthesized a new type of porous material – multiple coated GO/sand (M-GO/S) by integrating ordinary river sand with graphite oxide (GO) for the adsorptive removal of calcium ions in terms of water softening. Prior investigations confirmed it could remove water turbidity and fluoride simultaneously. M-GO/S was characterized using microscopic and spectroscopic techniques. The results indicate the presence of an uneven coating of graphite oxide, and the nanocomposite contains oxygencontaining functional groups. Under given conditions, the M-GO/S nanocomposite demonstrated remarkable efficacy in removing 75% of calcium ions (a higher removal percentage than commercial coal powdered activated carbon) from simulated hard water: pH 8, 5.0 g dosage, 50 mg/L calcium ions, and 20 min contact time. The isotherm and kinetic data revealed that the adsorption mechanism primarily comprises multilayer adsorption by means of a chemical sorption process. The mechanism of the proposed M-GO/S nanocomposite for removing calcium ions from hard water is elucidated using (XPS) analysis. The presence of (-O-Ca-O-) chemical bonds on the surface of the nanocomposite after equilibration with calcium ions suggests the occurrence of chemical interactions between the calcium ions and oxygen-containing functional groups of the M-GO/S. Consequently, the synthesized M-GO/S nanocomposite can be identified as a promising candidate for hard water treatment.

10

Proposal of concept for structural modelling of hybrid beams

Kożuch Maciej, Skrętkowicz Łukasz

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 4

317--332

EN

Investigation on the behaviour of a hybrid beam is presented. Hybrid beam stands for an element with hybrid cross sections. This means sections that consist of steel and concrete parts, connected together with composite dowels, and both are considered for shear flow analysis. In practice, a more general solution may be used for bridges in the form of a beam in which the span sections are hybrid and the support sections are concrete. Recently such a solution has been introduced for bridge engineering in Poland and a new problem with performing a global analysis of hybrid beams was identified. The solution is new itself and requires also a new approach for internal forces determination. Discussion of this problem is made in the paper. Influences of (1) concrete cracking, (2) rheology of concrete and (3) methods of modelling on the redistribution of internal forces are highlighted. On an example of one of the real bridge girder (being currently under design) analysis is made to show how the abovementioned factors are affecting obtained results. Results are analysed and conclusions are presented. As a final step, a new concept of hybrid beam design is proposed. The proposed solution enables a quick and easy engineering approach to perform a static calculation of the considered structure.

11

Behavior of Vertically Confined Square Footing on Reinforced Sand under Centric Inclined Loading

Kirtimayee B., Samadhiya Narendra Kumar

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 3

224--238

EN

This study presents the behavior of vertically confined square footing on geogrid-reinforced sand under centric inclined loading through a series of experimental tests. The load was applied at 5°, 10° and 20° angles of inclination with the vertical. The tests were conducted on surface footing, footing with confiner and footing with confiner and horizontal reinforcement configurations subjected to inclined loading. Parametric variations like depth of the confiner (d=1B, 1.5B, 2B), number of geogrid layers (N; varies with variation in depth of confiner), and spacing between horizontal reinforcements (Y=0.25B, 0.5B, 0.75B, 1B) have been investigated at the top surface dimension of confiner (D) as 1.0B, 1.5B and 2.0B (where B is the width of the model footing). Results show that combined effect of confiner and horizontal reinforcement increases the ultimate bearing capacity of footing significantly compared to only confiner for all angle of inclinations. It can also be observed that load bearing capacities decrease with increase in angles of inclination and record the minimum improvement at 20° angle of inclination. Improvement in bearing capacities and reduction in settlement of footing analyzed in terms of bearing capacity ratio (BCR) and settlement reduction factor (SRF) are compared for all footing configurations. To summarize, the test results showed that confiner along with reinforcement can be considered as an economic ground improvement technique for shallow foundations to counter against heavily inclined loading.

12

An analytical model to predict water retention curves for granular materials using the grain-size distribution curve

Bouacida Linda, Feia Sadok, Denine Sid Ali, Della Noureddine

Studia Geotechnica et Mechanica

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2022

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Vol. 44, nr 4

354--369

EN

The present work aims to propose a new analytical model intended to predict the water retention curves for granular materials based on data from tensiometric tests. Different analytical models have been used for the evaluation of soil water retention curves so far. It should be noted that the proposed model considers only one criterion in the selection of soils. This criterion is the physical property of particle distribution curve that can be used to determine the values of D50 and CU. In this study, the pore-access size distribution is investigated considering the effect of the coefficient of uniformity of sandy soils that were prepared with different density indexes (0.5, 0.7, and 0.9). Moreover, the proposed model equation is based on the physical properties of soil. This equation made it possible to describe the water retention curve and to estimate the pore-access size distribution without performing any experimental tests. The findings allowed asserting that the uniformity of the particle size curves corresponds to a good uniformity of the pore-access size distribution. In addition, it was revealed that the suction increased as the density index went up, which matches well with the experimental data. Moreover, it may clearly be noted that the distinctive retention properties of unsaturated soils can be observed on the above-mentioned curves. Further, it was found that the ratio of the grain size over the pore-access size increased as the uniformity coefficient augmented.

13

Potential alkaline reactivity of sands from domestic deposits

Jóźwiak-Niedźwiedzka Daria, Antolik Aneta, Dziedzic Kinga, Lisowski Paweł

Roads and Bridges - Drogi i Mosty

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2022

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Vol. 21, no. 3

253--271

EN

Sand used as fine aggregate in concrete may, under unfavorable environmental conditions, cause alkali-silica reaction and the consequent deterioration of durability and functional properties of concrete. The aim of this work is to compare alkali-silica reactivity of 18 natural sands of various origin. The potential reactivity of sands was tested according to the procedures PB/1/18 and PB/3/18 established in the Technical Guidelines issued by the General Directorate for National Roads and Motorways. Mineral composition of aggregate was analyzed in order to identify reactive minerals. Mortar bar expansion tests and microscopic analyses of the products of alkali-silica reaction were performed. The research indicated that 6 (33%) out of 18 tested aggregates should be classified as “moderately reactive” and 12 (67%) aggregates should be classified as “non-reactive”. It was demonstrated that the origin of sand affects its susceptibility to alkali-silica reaction.

PL

Piasek stosowany jako kruszywo drobne w betonie w niekorzystnych warunkach środowiska może spowodować reakcję alkaliczno-krzemionkową, a w konsekwencji – pogorszenie właściwości użytkowych i trwałości betonu. Celem pracy jest porównanie reaktywności alkaliczno-krzemionkowej 18 piasków naturalnych o różnym pochodzeniu. Wykonano badania potencjalnej reaktywności piasku zgodnie z procedurami PB/1/18 i PB/3/18 przedstawionymi w Wytycznych Technicznych GDDKiA. Przeprowadzono analizę składu mineralnego kruszywa pod kątem zawartości reaktywnych minerałów, badanie wydłużenia próbek zapraw oraz analizę mikroskopową produktów reakcji alkalia-krzemionka. W toku badań dowiedziono, że 6 kruszyw (33%) spośród 18 przebadanych należy zaklasyfikować do kategorii „umiarkowanie reaktywne”, natomiast 12 kruszyw (67%) należy przypisać do kategorii „niereaktywne”. Wykazano wpływ pochodzenia piasku na jego podatność na wystąpienie reakcji alkalicznej.

14

Piasek – (nie)policzone złoto

Moszniński Sławomir

Kruszywa : produkcja - transport - zastosowanie

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2022

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Nr 2

28--30

PL

W artykule omówiono kwestie związane z piaskiem wykorzystywanym w budownictwie – jego występowanie, zapotrzebowanie, pozyskiwanie, koncesje, wykorzystanie i prognozy.

15

Predictive modelling of a rapid stratified bed filter for turbidity removal from surface water

Tejada-Tovar Candelaria N., Villabona-Ortíz Ángel, López-Barbosa David

Journal of Water and Land Development

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2022

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no. 53

192--202

EN

The objective of the present work was to evaluate the hydrodynamic behaviour of a stratified bed filtration column consisting of 4 cm of sand and 2 cm of limestone to remove turbidity and measuring the head loss through the filter in several runs. In this study, two types of sand were used as filtering bed material, one fine and one medium. Crushed limestone was also available. These materials were characterized to determine the average particle diameter, porosity, and permeability coefficient. These were respectively 1.7∙10-4 m, 336.96 and 0.68 m∙day-1 for fine sand, 3.3∙10-1 m, 654.24 and 2.59 m∙day-1 for the medium sand and 1.26∙10-3 m, 388.8 and 8.64 m∙day-1 for crushed limestone. Using these materials, hydrodynamic analyses were carried out using clean water under rapid filtration conditions. In these analyses, different filtration rates were determined to be used in each experiment. Once the filtration rates were determined, the filtration analysis was performed with synthetic turbid water prepared at 8 NTU using tap water and bentonite. From the results obtained, a predictive model was developed based on total head losses for the evaluated filter, maintaining the rapid filtration condition. As a result, a turbidity removal efficiency of 97.7% was obtained with a total head loss of 17.8 cm at a filtration rate of 153 m·day-1 . The developed model predicted head loss as a function of operating time, filtration rate, and filter depth to maximise turbidity removal. The model showed excellent prediction accuracy with R2 of 0.9999, which indicates that the model predictions are not biased. It was concluded that, due to the porosity of these materials, a stratified bed of sedimentary rocks has a great potential to be used in surface water filtration processes, which implies that it could be used at the rural community level as a form of water treatment, since the material is a readily available, maintenance is simple and low cost, and installation and operation are effortless.

16

Ability of Response Surface Methodology to Optimize Photocatalytic Degradation of Amoxicillin from Aqueous Solutions Using Immobilized TiO2/Sand

Sulaiman Fadia A., Alwared Abeer I.

Journal of Ecological Engineering

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2022

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Vol. 23, nr 5

293--304

EN

The response surface method was applied to optimize operational factors in the solar photocatalytic process on the removal of Amoxicillin (AMOX) residues from aqueous solution using TiO2 immobilized on the sand as a catalyst. The results reveal that the degradation percentage of AMOX is 93.12%, when optimal conditions of pH=5, 75 mg/l of TiO2, 400 mg/l of H2O2, and 10 mg/l of AMOX concentration at 150 min irradiation time were used. Furthermore, the model’s expected response results have reasonable similarity with the actual data (R2 = 93.58%), demonstrating the efficiency of this method in making an accurate prediction. A second-order polynomial multiple regression model was used to evaluate the responses, which confirms that was a satisfactory adjustment with the achieved data through analysis of variance (R2 = 93.58%, R2adj = 91.48% and R2pred =89.68%). In addition, it is observed that the removal of undesirable compounds follows a pseudo-2nd order kinetic model with R2 = 0.9862. In conclusion, with the ease of usage of immobilized TiO2 and good photocatalytic efficiency, the findings showed the potential application to the antibiotics from an aqueous solution.

17

Sustainable deployment of crushed concrete aggregates strengthened with cement and sand

Sharma V., Kumar A., Kaur A.

Archives of Materials Science and Engineering

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2022

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Vol. 113, nr 1

19--34

EN

Purpose: Paper assessed the feasibility of crushed concrete aggregates (CCA), a subsidiary of construction and demolition (C&D) waste, blended with cement and sand to form a composite for civil engineering field applications. Design/methodology/approach: The compaction and strength characteristics of CCA were observed by conducting Proctor compaction and California Bearing Ratio (CBR) tests. Different proportions of CCA, sand and cement were used. Moreover, the effect of curing period (0, 4, 7, 14 and 28 days) was also studied. In addition, regression analyses were performed to develop empirical expressions to predict the compaction and strength characteristics of the CCA composite. Findings: Increasing the CCA content up to 50% increases the maximum dry unit weight (MDUW) and decreases the optimum moisture content (OMC). However, on further increasing its content the MDUW decreases and OMC increases. Percent increase in the CBR value can go up to 412% if the CCA content is increased up to 50%. However, the percent reduction in CBR of about 20% can take place if 100% CCA content is used. Moreover, multiple regression shows that the experimental results are in good agreement with the predicted values. Research limitations/implications: The results obtained are purely dependent on the type of material. However, they are in favour of the used material as a probable option for road sub-base layer, and also for reducing burden on available natural resources. Therefore, it is recommended to conduct some initial tests to confirm the feasibility of the material. Practical implications: The proposed study will guide the design Engineers to choose CCA as one of the potential materials for road construction. Originality/value: It was observed that there is a need to maximize the utilization of C&D waste without making any compromise with its mechanical properties. So keeping that in view, the present study was conducted.

18

Research on sand resistance performance of comprehensive protection facilities for desert hinterland highways under strong wind environment

Yin Wenhua, Wang Xu, Wu Yongxiang, Wang Fang

Archives of Civil Engineering

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2022

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Vol. 68, nr 4

683--698

EN

Based on the test and observation of the desert hinterland wind field, combined with the numerical simulation of Fluent wind-sand two-phase flow, the sand resistance performances of comprehensive protection in the desert hinterland under strong wind environment are researched. The transient wind speed and wind direction around the comprehensive protection facility are measured by two 3D ultrasonic anemometers on the highway in the desert hinterland, and the initial wind speed of the sand flow is provided for the numerical simulation boundary. The sedimentary sand particles around the comprehensive protection facility are collected for particle size analysis, and the particle size distributions of sedimentary sand particles at different locations are obtained. Numerical models of high vertical sand barriers, grass checkered sand barriers and roadbeds are established by Fluent, the wind-sand flow structures around the comprehensive protection facilities and desert hinterland highway under the strong wind environment are obtained, and the influence laws of the comprehensive protection facilities on the movement of wind-sand flow and sand deposition characteristics are obtained. The study found that the comprehensive protection facilities disturbed the wind and sand flow, and there are significant airflow partitions around the comprehensive protection facilities. The wind speed decreases rapidly after the wind-sand flows through the high vertical sand barrier; the wind-sand flow rises at the end of the high vertical sand barrier. When the wind-sand flow moves around the grass checkered sand barrier, the wind speed has dropped to the range of 0-3 m/s, and the wind speed near the ground by the grass checkered sand barrier is further reduced. Due to the existence of the concave surface of the grass grid, there are small vortices inside the grass grid sand barrier. Large sand particles are mainly deposited on the windward side and inside of high vertical sand barriers. The grass checkered sand barrier forms a stable concave surface to generate backflow, which can ensure that the sand surface does not sand itself in a strong wind environment, and can also make a small amount of sand carried in the airflow accumulate around the groove of the grass checkered sand barrier. The numerical simulation results are consistent with the measured results, and the comprehensive protection measures have achieved good sand control effects.

19

Z piaskiem po drodze

Skoneczny Andrzej

Surowce i Maszyny Budowlane

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2020

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nr 1

12--14

PL

Surowce mineralne, których nie można zastąpić żadnym substytutem, a wśród nich piaski i żwiry, są jednym z podstawowych dóbr, które decydują o egzystencji człowieka.

20

Piasek na wagę złota

Moszniński Sławomir

Surowce i Maszyny Budowlane

|

2020

|

nr 1

10--11

PL

Czy alarmowany przez ekologów brak piasku i jego wpływ na rujnowanie środowiska naturalnego to kolejny rozdmuchany, sztuczny problem, czy rzeczywiście coś jest na rzeczy? Czy grozi nam niedobór materiału, który stanowi podstawę branży budownictwa i jest odpowiedzialny za rozwój infrastruktury i urbanistyki? Wg naukowców piasek jest najbardziej zapomnianym surowcem naturalnym na świecie...