Production and Evaluation of Synthetic Lightweight Aggregates Based on Mixture of Fluidized Bed Fly Ash and Post-Mining Residues

This paper presents an attempt to obtain technically valuable lightweight aggregate produced from a mixture of fluidized bed fly ash and post-mining residues. The motivation to take up this study is a problem with the reasonable utilization of huge amounts of ashes produced by power plants in Poland. The ashes still produced and those stored in heaps amount to a tonnage of millions, and new ways to utilize them are desired. A real lack of mineral aggregates (non-renewable resources) demands the search for alternative materials. Using the industrial ashes as aggregates is a possible solution to the two above-mentioned problems. The aim of the study was to produce the lightweight aggregate components and to assess them in terms of their physical and mechanical properties. The components were prepared by mixing, granulation, and sintering at the temperature of over 1170 °C. Evaluation of physical parameters was based on parameters such as bulk density and water absorption. The study of mechanical properties was carried out on the basis of aggregates’ resistance to crushing. The obtained results revealed that using a mixture of the combustion and post-mining residues in the production of a lightweight aggregate is beneficial and results in the formation of a porous and durable structure. The measured resistance to the crushing of the produced aggregates varied from 5.9 MPa to 7.5 MPa. They also showed a high freeze-thaw resistance and good resistance to aggressive environments (bases, acids, salt). The registered properties indicate that the aggregates meet the basic requirements for materials used in construction and road-building. This study has a scientific and didactic value in that it describes the step-by-step process of planning and implementing the production of synthetic mineral aggregates.

Variation and Genetic Control of the Heartwood, Sapwood, Bark, Wood Color Parameter, and Physical and Mechanical Properties of Dipteryx panamensis in Costa Rica

The Dipteryx genus has a natural distribution throughout several tropical countries in Latin America. This taxon has several tree species, all recognized for their high-density wood. The objective of this research was to study the variation and genetic control of several wood properties, including bark, sapwood, heartwood, green density (GD), specific gravity (SG), moisture content in green condition (MC-G), and mechanical properties, in a Dipteryx panamensis provenance/progeny test at 8 years old. The results showed that bark varied little among families and provenances, but heartwood (diameter and percentage) showed high genetic variation. SG and MC-G showed significant variation between provenances and families, while GD showed little variation. Among the mechanical properties evaluated, the greatest genetic variation was observed in the MOR in bending and shear stress. Families from the Coope San Juan provenance registered the highest values in all wood properties investigated, and families from Puerto Viejo obtained the lowest. Family heritability and the coefficient of genetic variation exhibited high values in heartwood/sapwood and the MOR in bending (h2 > 0.9 and CV > 20%) and lower values in SG, MC-G, compression stress, and shear stress. D. panamensis wood properties have a high potential to be improved through breeding programs.

The Influence of Cement Grain Structure on Physical and Mechanical Properties of Cement

The paper presents the study of morphological characteristics of cement particles and reveals the influence of the structure of the cement grain composition on the physical and mechanical properties of cement. The following portland cements produced by “Hrazdan Cement Corporation” LLC, which have 52,5 MPa and 42,5 MPa compressive strength limit and hydraulic additives up to 20% and over 20% have been used for the experiment: CEM II/ A-P 42,5N, CEM II/ B-P 42,5N, CEM II/A-Q 42,5N, CEM II/B-Q, CEM II/A-L 42,5N, CEM II/B-L 42,5N, CEM II/A-M 42,5N, CEM II/B-M, CEM III/A-S 42,5N and CEM III/B-S 42,5N. Grain distribution in all the samples has been studied using a CILAS laser analyzer. Microscopic analysis of all the fractions has been carried out with the help of James Swift optical microscope. The given grain compositions have undergone chemical analysis in compliance with the requirements of interstate ISO 5382-2019 and ASTM C114-18 standards. Experimental studies and analyses show that the cements with microsilica have the highest value of water-cement ratio-W/C = 0.7, the highest by volume compression are the cements with volcanic slag-4 mm, the beginning of the bonding period is the longest in case of limestone cements - t = 140 minutes, followed by microsilica cements, and in third place there are artificial slag cements, the results of which are as follows: 130; 124 minutes. The summarized data show that microsilica cements have the highest compressive strength limit among the cements having the same percentage of additives-48.87 MPa.

Optimization of a Two-Species Microbial Consortium for Improved Mcl-PHA Production From Glucose–Xylose Mixtures

Polyhydroxyalkanoates (PHAs) have attracted much attention as a good substitute for petroleum-based plastics, especially mcl-PHA due to their superior physical and mechanical properties with broader applications. Artificial microbial consortia can solve the problems of low metabolic capacity of single engineered strains and low conversion efficiency of natural consortia while expanding the scope of substrate utilization. Therefore, the use of artificial microbial consortia is considered a promising method for the production of mcl-PHA. In this work, we designed and constructed a microbial consortium composed of engineered Escherichia coli MG1655 and Pseudomonas putida KT2440 based on the “nutrition supply–detoxification” concept, which improved mcl-PHA production from glucose-xylose mixtures. An engineered E. coli that preferentially uses xylose was engineered with an enhanced ability to secrete acetic acid and free fatty acids (FFAs), producing 6.44 g/L acetic acid and 2.51 g/L FFAs with 20 g/L xylose as substrate. The mcl-PHA producing strain of P. putida in the microbial consortium has been engineered to enhance its ability to convert acetic acid and FFAs into mcl-PHA, producing 0.75 g/L mcl-PHA with mixed substrates consisting of glucose, acetic acid, and octanoate, while also reducing the growth inhibition of E. coli by acetic acid. The further developed artificial microbial consortium finally produced 1.32 g/L of mcl-PHA from 20 g/L of a glucose–xylose mixture (1:1) after substrate competition control and process optimization. The substrate utilization and product synthesis functions were successfully divided into the two strains in the constructed artificial microbial consortium, and a mutually beneficial symbiosis of “nutrition supply–detoxification” with a relatively high mcl-PHA titer was achieved, enabling the efficient accumulation of mcl-PHA. The consortium developed in this study is a potential platform for mcl-PHA production from lignocellulosic biomass.

Innovative technology of the process of disinfection and inactivation of antinutrients in compound feeds using liquid components

Научный и практический интересы представляют процессы обеззараживания и инактивации антипитательных веществ в комбикормах. Известны разные технологии обеззараживания (например, нагрев, давление, растворы антимикробных препаратов и другие новые технологии) для повышения эффективности снижения риска заболеваний не только животных и птиц, но и людей. Процессы обеззараживания и инактивации антипитательных веществ может применяться к широкому набору пищевых продуктов и к сырью комбикормовой промышленности. Однако необходимо провести дальнейшие исследования, чтобы понять кинетику инактивации антипитательных веществ в комбикормах для достижения приемлемой технологии обеззараживания. Исследовано влияние гидротермической обработки на поверхностную и глубинную микрофлору зернового сырья. С увеличением времени обработки пшеница и ячмень, искусственно зараженные, а также зараженные естественным способом, были обеззаражены предлагаемым способом на 100 %. Получены химико-технологические характеристики кондиционированного зерна, результаты которых представлены для процессов пропаривания и охлаждения. Установлено, что с увеличением температуры влажность пропаренных и увлажненных зерен пшеницы возрастает с 15,2 до 21,7 %, для зерен ячменя - с 15,3 до 12,8 %. При этом исходная влажность пшеницы составила 10,8 %, а ячменя - 11,2 %. Определено, что при увеличении продолжительности пропаривания и увлажнения зерен пшеницы давление уменьшается с 0,15 до 0,19 МПа и уменьшается расход пара с 85 до 60 кг/т. Анализ физико-механических свойств для пшеницы и ячменя показал, что объемная масса исследуемых образцов возросла. Угол естественного откоса составил для пшеницы 45-48, для ячменя 43-50. Трехстадийную технологию гидротермической обработки комбикормов рекомендуется использовать в трехсекционном реакторе-кондиционере, в котором продукт равномерно кондиционируется с инактивацией антипитательных веществ, обеззараживается и частично желатинизируется. The processes of anti-nutrients disinfection and inactivation in compound feeds are of scientific and practical interest. Various disinfection technologies are known (for example, heating, pressure, solutions of antimicrobial preparations and other new technologies) to increase the effectiveness of diseases risk reducing not only for animals and birds, but for humans as well. The processes of anti-nutrients desinfection and inactivation can be applied to a wide variety of food products and feedstock raw materials. However, further research is necessary to understand the kinetics of anti-nutrients inactivation in compound feeds to achieve an acceptable disinfection technology. The influence of hydrothermal treatment on the surface and deep microflora of grain raw materials was investigated in the work. With an increase in the processing time, both artificially infected and naturally infected wheat and barley were 100 % disinfected with the method proposed. Chemical- and technological characteristics of conditioned grain were received. Their results are presented for the steaming and cooling processes. It was found out that with an increase in temperature, the humidity of steamed and moistened wheat grains increases from 15.2 to 21.7 %, and of barley grains from 15.3 to 12.8 %. At the same time, the initial moisture content of wheat was 10.8 %, and of barley - 11.2 %. It was determined that with an increase in the duration of steaming and moistening of wheat grains, the pressure decreases from 0.15 to 0.19 MPa, and the steam consumption decreases from 85 to 60 kg/t. Analysis of wheat and barley physical- and mechanical properties revealed that the bulk density of the samples studied increased. The repose angle was 45-48 for wheat and 43-50 for barley. It is recommended to use a three-stage technology of compound feed hydrothermal treatment in a three-section reactor-conditioner. The product is uniformly conditioned with anti-nutrients inactivation, disinfected and partially gelatinized in it.

Effect of Variable Conditions of Exposure on the Physical and Mechanical Properties of Blockboards

The growing demand for wood and the continued increase of the raw material price have resulted in companies using more efficient wood resources in wood-based products such as blockboard. These boards are used in the field of interior design, especially. The aim of this research was to evaluate the effect of variable environmental conditions on the physical and mechanical properties of blockboard (BK). Two types of commercial BK were exposed in variable environmental conditions (kitchen, bathroom and climatic chamber) for three months. The BK structures were composed of veneer (V) and high-density fibreboards (HDF) for the face sheets and glued, solid wood, resinous strips for the core. The temperature and relative humidity of the air (RH) ranged from 18 °C to 25 °C and from 25% to 90%, respectively. In the climatic chamber (CC), the dynamics of the parameter variations were different than in the other two exposure climates, being determined by the programmed cyclic changes in RH. The changes observed on physical and mechanical properties were more extreme for the blockboards tested in the CC than in the kitchen (K) and bathroom (Ba). After 3 months of exposure in the CC, the thickness and weight of the boards increased by 1.8 and 1.1 times, respectively, for veneered BK, and by 4.4 and 0.4 times, for BK with HDF faces, compared to values recorded in the kitchen. The panels exposed in the CC exhibited the highest increase in moisture content (MC): 41% for veneered BK and 82% for BK with HDF faces after three months of exposure, followed by those exposed in the bathroom and kitchen. Increases in MC determined decreases of flexural properties and soundness surfaces, more evident for HDF face structures compared to V ones.

Physical and Mechanical Properties of Tilapia Scale Hydroxyapatite-Filled High-Density Polyethylene Composites

The effects of filler loading and silane coupling agent on the properties of hydroxyapatite (HAp)-filled high density polyethylene (HDPE) composites have been studied. The (HAp) powder was successfully produced from tilapia scales using the spray drying process utilized to prepare the HDPE/HAp composites. The FTIR peaks for the untreated HDPE/30HAp composite corresponded to the functional groups of HDPE (C-CH3) and –CH2 and HAp (PO4−3 and O-H). The FTIR spectrum for the silane-treated composite showed that the C=O and silanol groups were eliminated, which strongly confirms the chemical interaction between the HAp fillers and the HDPE matrix. The developed composites demonstrated enhanced mechanical performance, and in particular the treated HDPE/30HAp-S composite exhibited superior tensile strength, Young’s modulus and flexural modulus of 28.26 MPa, 1272 MPa and 796 MPa, respectively. In vitro cytotoxicity analysis showed that the developed composites were non-toxic and have great potential to be used for biomedical application.