Recycled Materials in Civil Engineering Application.

In recent years, the construction sector has shown great interest in the use of various by-products and industrial waste, as well as the consumer products used [...].

The Use of Biosilica to Increase the Compressive Strength of Cement Mortar: The Effect of the Mixing Method.

In this work, the effect of biosilica concentration and two different mixing methods with Portland cement on the compressive strength of cement-based mortars were investigated. The following values of the biosilica concentration of cement weight were investigated։ 2.5, 5, 7.5, and 10 wt.%. The mortar was prepared using the following two biosilica mixing methods: First, biosilica was mixed with cement and appropriate samples were prepared. For the other mixing method, samples were prepared by dissolving biosilica in water using a magnetic stirrer. Compressive tests were carried out on an automatic compression machine with a loading rate of 2.4 kN/s at the age of 7 and 28 days. It is shown that, for all cases, the compressive strength has the maximum value of 10% biosilica concentration. In particular, in the case of the first mixing method, the compressive strength of the specimen over 7 days of curing increased by 30.5%, and by 36.5% for a curing period of 28 days. In the case of the second mixing method, the compressive strength of the specimen over 7 days of curing increased by 23.4%, and by 47.3% for a curing period of 28 days. Additionally, using the first and second mixing methods, the water absorption parameters were reduced by 22% and 34%, respectively. Finally, it is worth noting that the obtained results were intend to provide valuable insights into optimizing biosilica incorporation in cement mortar. With the aim of contributing to the advancement of construction materials, this research delves into the intriguing application of biosilica in cement mortar, emphasizing the significant impact of mixing techniques on the resultant compressive strength.

Modification of Concrete Composition Doped by Sewage Sludge Fly Ash and Its Effect on Compressive Strength.

The sustainable development of construction materials is an essential aspect of current worldwide trends. Reusing post-production waste in the building industry has numerous positive effects on the environment. Since concrete is one of the materials that people manufacture and use the most, it will continue to be an integral element of the surrounding reality. In this study, the relationship between the individual components and parameters of concrete and its compressive strength properties was assessed. In the experimental works, concrete mixes with different contents of sand, gravel, Portland cement CEM II/B-S 42.5 N, water, superplasticizer, air-entraining admixture, and fly ash from the thermal conversion of municipal sewage sludge (SSFA) were designed. According to legal requirements in the European Union, SSFA waste from the sewage sludge incineration process in a fluidized bed furnace should not be stored in landfills but processed in various ways. Unfortunately, its generated amounts are too large, so new management technologies should be sought. During the experimental work, the compressive strength of concrete samples of various classes, namely, C8/10, C12/15, C16/20, C20/25, C25/30, C30/37, and C35/45, were measured. The higher-class concrete samples that were used, the greater the compressive strength obtained, ranging from 13.7 to 55.2 MPa. A correlation analysis was carried out between the mechanical strength of waste-modified concretes and the composition of concrete mixes (the amount of sand and gravel, cement, and FA), as well as the water-to-cement ratio and the sand point. No negative effect of the addition of SSFA on the strength of concrete samples was demonstrated, which translates into economic and environmental benefits.

Influence of Post-Consumer Waste Thermoplastic Elastomers Obtained from Used Car Floor Mats on Concrete Properties.

In this paper, the influence of post-consumer thermoplastic elastomer (TPE) additive derived from used car floor mats on the physical and mechanical properties of concrete is presented. Waste elastomer (fractions 0-2 and 2-8 mm) was used as a substitute for sand or fine aggregate in the amount of 2.5, 5.0, 7.5, and 10.0% by weight of cement. For all series, the physical and mechanical properties of concrete (for example, compressive strength, flexural tensile strength, water absorption, density, and frost resistance), as well as its microstructure, were tested. It has been shown that post-consumer elastomer waste from used car floor mats in the amount of 2.5% of cement weight can replace sand and gravel aggregate in concrete without reducing their mechanical strength and without changing their microstructure. The compressive strength (after 28 days) of concretes in which the waste was introduced as a substitute for sand and aggregate was 57.0 and 57.2 MPa, respectively (the strength of the control sample was 57.0 MPa). The use of post-consumer waste in concrete allows for a reduction in the consumption of natural aggregate (the addition of 2.5% of waste material saves natural aggregate approximately 20 kg/m3), which reduces the cost of concrete production and also has a positive impact on the environment (i.e., it saves cost and space in landfills, where currently used car floor mat are deposited).

Assessment of the Possibility of Using Fly Ash from Biomass Combustion for Concrete.

This article analyses the possibility of using fly ash from the combustion of wood-sunflower biomass in a fluidized bed boiler as an additive to concrete. The research shows that fly ash applied in an amount of 10-30% can be added as a sand substitute for the production of concrete, without reducing quality (compression strength and low-temperature resistance) compared to control concrete. The 28-day compressive strength of concrete with fly ash increases with the amount of ash added (up to 30%), giving a strength 28% higher than the control concrete sample. The addition of fly ash reduces the extent to which the compression strength of concrete is lowered after low-temperature resistance tests by 22-82%. The addition of fly ash in the range of 10-30% causes a slight increase in the water absorption of concrete. Concretes containing the addition of fly ash from biomass combustion do not have a negative environmental impact with respect to the leaching of heavy metal ions into the environment.

Polymer Membranes in Separation Process.

Among the many known physicochemical methods for the separation of organic compounds and metal ions from aqueous solutions, liquid-liquid extraction and membrane techniques hold a special position, enabling their recovery from dilute aqueous solutions [...].

Recycled Materials for Concrete and Other Composites.

In recent years, industry, including the construction sector, has been focused on effectively reducing the consumption of natural resources, in compliance with the idea of sustainable development [...].

Properties and Structure of Concretes Doped with Production Waste of Thermoplastic Elastomers from the Production of Car Floor Mats.

This article presents physical and mechanical properties of concrete composites that include waste thermoplastic elastomer (TPE) from the production process of car floor mats. Waste elastomer (2-8 mm fraction) was used as a substitute for fine aggregate in quantities of 2.5, 5.0, 7.5, and 10% of the cement weight. For all series of concrete, the following tests were carried out: compression strength, bending tensile strength, splitting tensile strength, absorbability, density, resistance to water penetration under pressure, frost resistance, and abrasion resistance, according to applicable standards. Moreover, SEM/EDS analysis was carried out on the surface microstructure of synthesized concrete composites. It was proven that the use of production waste from the production process of car floor mats in the quantity of 2.5% does not influence the change of the concrete microstructure and it does not result in the decrease of the mechanical parameters of concrete modified with waste. All concrete modified with the addition of waste meet standards requirements after carrying out 15 cycles of freezing and thawing, and the average decrease in compression strength did not exceed 20%. Adding waste in the quantity of 2.5% allows for limiting the use of aggregate by about 5%, which is beneficial for the natural environment.

Application of Hydrophobic Alkylimidazoles in the Separation of Non-Ferrous Metal Ions across Plasticised Membranes-A Review.

Currently, a lot of attention is paid to polymer inclusion membranes (PIMs). Their particular advantages include effective support fixation, easy preparation, versatility, stability, good mechanical properties and good chemical resistance. The paper presents a review of the literature related to the applications of polymer inclusion membranes containing alkylimidazole derivatives as carriers in the processes of transporting ions of heavy and toxic metals, such as Zn(II), Cu(II), Cd(II), Co(II), Ni(II), and Mn(II). It has been proven that alkylimidazoles exhibit varying complex-forming properties towards metal ions, and that their properties (hydrophobic and alkaline) can be modified easily by changing the size of the alkyl group and its position in the imidazole ring, which allows obtaining efficiently working metal ion carriers. The stability of an imidazole derivative-metal ion complex determines the speed and selectivity of the process of transporting metal ions across polymer inclusion membranes. Also, the morphological structure of polymer inclusion membranes impacts the efficiency of the process involving the release and separation of metal ions.

Application of Polymer Inclusion Membranes Doped with Alkylimidazole to Separation of Silver and Zinc Ions from Model Solutions and after Battery Leaching.

New materials, such as polymer inclusion membranes, can be used for water and wastewater treatment. In this paper, the selective transport of silver(I) and zinc(II) ions from nitrate solutions through the polymer inclusion membranes (PIMs), which consist of cellulose triacetate as a polymeric support, o-nitrophenyl pentyl ether as a plasticizer, and either 1-hexylimidazole (1) or 1-hexyl-2-methylimidazole (2) as an ion carrier, is studied. Both Zn(II) and Ag(I) model solutions (CM = 0.001 M, pH = 6.5), as well as the solutions after the leaching of a spent battery with a silver-zinc cell (silver-oxide battery), are tested. The results show that Zn(II) ions are effectively transported through PIMs containing either carrier, whereas Ag(I) is more easily transported through PIMs doped with (1). In the case of the leaching solution after 24 h transport, the recovery coefficients of Ag(I) and Zn(II) for PIMs doped with (1) are 86% and 90%, respectively, and for PIMs doped with (2), 47% and 94%, respectively. The influence of basicity and structure of carrier molecules on transport kinetics is discussed as well. PIMs are characterized by using an atomic force microscopy (AFM) technique.

Separation of Zn(II), Cr(III), and Ni(II) Ions Using the Polymer Inclusion Membranes Containing Acetylacetone Derivative as the Carrier.

Polymer inclusion membranes (PIMs) doped with ethylenodiamino-bis-acetylacetone as fixed carrier was applied for the investigation of the facilitated transport of Zn(II), Cr(III), and Ni(II) ions from an aqueous nitrate feed phase (cM = 0.001 mol/dm3). The optimal membrane composition (amount of carrier and o-NPPE-plasticizer) was determined. For the optimal polymer inclusion membranes doped with ethylenodiamino-bis-acetylacetone, the following patterns of transport selectivity were found: Zn(II) > Cr(III) > Ni(II). The initial flux of Zn(II), Cr(III), and Ni(II) ions was 6.37 µmol/m2∙s, 5.53 µmol/m2∙s, and 0.40 µmol/m2∙s, respectively. The selectivity coefficients equal to 1.2 and 15.9 were found for Zn(II)/Cr(III) and Zn(II)/Ni(II), respectively. After 24-h transport, the recovery factor of Zn(II), Cr(III), and Ni(II) were 90%, 65%, and 6%, respectively. The polymer inclusion membranes doped with ethylenodiamino-bis-acetylacetone were characterized by scanning electron microscopy and non-contact atomic force microscopy. The influence of membrane morphology on transport process was discussed.

Polymer Inclusion Membranes (PIMs) Doped with Alkylimidazole and their Application in the Separation of Non-Ferrous Metal Ions.

The study involved the transport of zinc(II), cadmium(II), and nickel(II) ions from acidic aqueous solutions using polymer inclusion membranes (PIMs). PIMs consisted of cellulose triacetate (CTA) as a support; o-nitrophenyl pentyl ether (o-NPPE) as a plasticizer; and 1-octylimidazole (1), 1-octyl-2-methylimidazole (2), 1-octyl-4-methylimidazole (3), or 1-octyl-2,4-dimethylimidazole (4) as ion carriers. The membranes were characterized by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM). The results show that Zn(II) and Cd(II) are effectively transported across PIMs, while Ni(II) transport is not effective. The rate of transport of metal ions across PIMs is determined by the diffusion rate of the M(II)-carrier complex across the membrane. The best result achieved for Zn(II) removal after 24 h was 95.5% for the ternary Zn(II)-Cd(II)-Ni(II) solution for PIM doped (4). For this membrane, the separation coefficients for Zn(II)/Cd(II), Zn(II)/Ni(II), and Cd(II)/Ni(II) were 2.8, 104.5, and 23.5, respectively. Additionally, the influence of basicity and structure of carrier molecules on transport kinetics was discussed.

The Application of Polymer Inclusion Membranes Based on CTA with 1-alkylimidazole for the Separation of Zinc(II) and Manganese(II) Ions from Aqueous Solutions.

Polymer cellulose triacetate membranes doped with 1-alkylimidazole as fixed carriers were applied for the investigation of the facilitated transport of Zn(II) and Mn(II) ions from an aqueous sulphate feed phase (cM = 0.001 mol/dm³). For the polymer inclusion membranes (PIMs) doped with 1-alkylimidazole (alkyl ⁻ from hexyl up to decyl), the following patterns of transport selectivity were found: Zn(II) > Mn(II). The highest initial flux of Zn(II) ions (2.65 µmol/m²·s) was found for PIMs doped with 1-decyl-imidazole, whereas the best Zn(II)/Mn(II) selectivity coefficients equal to 19.7 were found for 1-hexyl-imidazole. Permeability coefficients for Zn(II) and Mn(II) ions transported across PIMs increase with an increase in the pKa values of 1-alkylimidazole. The polymer membranes of cellulose triacetate-o-NPPE with 1-alkylimidazole were characterised by scanning electron microscopy, non-contact atomic force microscopy and thermal analysis techniques. The influence of membrane morphology on the Zn(II) and Mn(II) transport process was discussed.

Ion flotation of cadmium(II) and zinc(II) in the presence of proton-ionizable lariat ethers.

Competitive flotation of Cd(II) and Zn(II) from very dilute aqueous solutions by proton-ionizable lariat ethers in the presence of nonylphenol nona(ethylene glycol) ether as a nonionic foaming agent is reported. Influences of structural variation within the collector (identity of the pendent acidic group and lipophilicity), concentration of the collector, and pH of the aqueous solution are assessed. A monoethyl lariat ether phosphonic acid collector is found to exhibit high Cd(II)/Zn(II) flotation selectivity under certain conditions.