Development of structural-heat-insulating lightweight concrete composition using production of aerated concrete waste as a porous aggregate

Annually enterprises in the field of manufacturing of products from aerated concrete generate from 5000 to 10000 m3 of solid production waste. One of the perspective and under-investigated direction is the practical application of solid waste using a porous aggregate in structural-heat-insulating lightweight concrete in the production of construction materials. The aim of this study was to evaluate the possibility of using crushed aerated concrete as a large aggregate in lightweight concrete for structural and thermal insulation purposes and to establish optimal conditions for obtaining products with the best characteristics. There were defined the qualitative indicators of crushed aerated concrete, analyzed factors influencing on the preservation of the properties of concrete in time, selected the composition of concrete aggregates from crushed concrete, studied the structure and properties of the obtained samples in the research. It has been found that to obtain effective constructive insulating lightweight concrete using waste production of aerated concrete as an aggregate is possible due to the fractionated pre-treatment of the aggregate with water dispersion of deep-penetration acrylic copolymers, insertion excess sealing water to concrete mixture, including optimization of the rheological properties of the concrete mix due to insertion of polycarboxylate hyperplasticizer.

Performance and Sustainability of Halal Food Smes

This study investigates the performance and sustainability of halal food SMEs in the FinTech era. The large aggregate contribution of SMEs does not yet reflect good performance in domestic and foreign market competition due to lack of financial literacy. FinTech can support financial literacy so performance and sustainability SMEs will increase. Consequently, testing the effect of fintech and literacy on the performance and sustainability of MSMEs. A total of one hundred respondents are selected using the quantitative method as sources of data collection. The questionnaires are distributed using a purposive sampling method in Surakarta, Indonesia. The software used for analysis is SEM-PLS. The results of this study state that the performance and sustainability of SMEs are influenced by FinTech and financial literacy

Experimental Studies of Fiber-Reinforced Concrete under Axial Tension

The design of a stand for testing concrete and fiber-reinforced concrete specimens-"eight" in tension, which provides axial load application and minimizes the effect of stress concentration at the ends of the specimen. The design of the stand is such that the distance between the axis of load application and the central hinge is 108 cm, and between this hinge and the axis of the test specimen is 21 cm, as a result of which the load transferred to the specimen is 5.143 times greater than the applied one. At the first stage of testing, it was found that the optimal characteristics of the fiber-concrete mixture is a matrix with a large aggregate ≤ 10 mm with 1.0% fiber reinforcement. At the second stage, the ultimate strength of fiber-reinforced concrete for axial tension was determined - 1.28 MPa when reinforced with wave fiber and 1.37 MPa when reinforced with anchor fiber, which amounted to 4.1% and 4.4% of compressive strength, respectively. It was also found that concrete reinforced with anchor fiber has higher deformation properties than concrete reinforced with wave fiber.

COMPARATIVE TESTS OF LOCAL AND TRANSPORTED LARGE AGGREGATE FOR COMPRESSION STRENGTH IN CONCRETE OF DIFFERENT CLASSES

Результаты сравнительных испытаний местного и привозного крупного заполнителя на прочность при сжатии в бетонах разных классов. Проанализирован характер разрушения бетона. Представлены некоторые пути решения проблемы обогащения крупного заполнителя.Работа выполнена при финансовой поддержке РФФИ в рамках научного проекта № 18-48-200001. Results of comparative tests of local and imported coarse aggregate for compressive strength in concretes of different classes. The nature of concrete destruction is analyzed. Some ways of solving the problem of coarse aggregate enrichment are presented.This work was carried out with the financial support of the Russian Foundation for Basic Research in scientific project No. 18-48-200001.

Hierarchical Virtual Bitmaps for Spread Estimation in Traffic Measurement

This paper introduces a hierarchical traffic model for spread measurement of network traffic flows. The hierarchical model, which aggregates lower level flows into higher-level flows in a hierarchical structure, will allow us to measure network traffic at different granularities at once to support diverse traffic analysis from a grand view to fine-grained details. The spread of a flow is the number of distinct elements (under measurement) in the flow, where the flow label (that identifies packets belonging to the flow) and the elements (which are defined based on application need) can be found in packet headers or payload. Traditional flow spread estimators are designed without hierarchical traffic modeling in mind, and incur high overhead when they are applied to each level of the traffic hierarchy. In this paper, we propose a new Hierarchical Virtual bitmap Estimator (HVE) that performs simultaneous multi-level traffic measurement, at the same cost of a traditional estimator, without degrading measurement accuracy. We implement the proposed solution and perform experiments based on real traffic traces. The experimental results demonstrate that HVE improves measurement throughput by 43% to 155%, thanks to the reduction of perpacket processing overhead. For small to medium flows, its measurement accuracy is largely similar to traditional estimators that work at one level at a time. For large aggregate and base flows, its accuracy is better, with up to 97% smaller error in our experiments.

Bacterial Communities in Concrete Reflect Its Composite Nature and Change with Weathering

ABSTRACT Concrete is an extreme but common environment and is home to microbial communities adapted to alkaline, saline, and oligotrophic conditions. Microbes inside the concrete that makes up buildings or roads have received little attention despite their ubiquity and capacity to interact with the concrete. Because concrete is a composite of materials which have their own microbial communities, we hypothesized that the microbial communities of concrete reflect those of the concrete components and that these communities change as the concrete ages. Here, we used a 16S amplicon study to show how microbial communities change over 2 years of outdoor weathering in two sets of concrete cylinders, one prone to the concrete-degrading alkali-silica reaction (ASR) and the other having the risk of the ASR mitigated. After identifying and removing taxa that were likely laboratory or reagent contaminants, we found that precursor materials, particularly the large aggregate (gravel), were the probable source of ∼50 to 60% of the bacteria observed in the first cylinders from each series. Overall, community diversity decreased over 2 years, with temporarily increased diversity in warmer summer months. We found that most of the concrete microbiome was composed of Proteobacteria, Firmicutes, and Actinobacteria, although community composition changed seasonally and over multiyear time scales and was likely influenced by environmental deposition. Although the community composition between the two series was not significantly different overall, several taxa, including Arcobacter, Modestobacter, Salinicoccus, Rheinheimera, Lawsonella, and Bryobacter, appear to be associated with ASR. IMPORTANCE Concrete is the most-used building material in the world and a biologically extreme environment, with a microbiome composed of bacteria that likely come from concrete precursor materials, aerosols, and environmental deposition. These microbes, though seeded from a variety of materials, are all subject to desiccation, heating, starvation, high salinity, and very high pH. Microbes that survive and even thrive under these conditions can potentially either degrade concrete or contribute to its repair. Thus, understanding which microbes survive in concrete, under what conditions, and for how long has potential implications for biorepair of concrete. Further, methodological pipelines for analyzing concrete microbial communities can be applied to concrete from a variety of structures or with different types of damage to identify bioindicator species that can be used for structural health monitoring and service life prediction.

Experimental Study on Short Steel Tube Columns Filled with Recycled Large Aggregate-Self Compacting Concrete Subjected to Compression

The mechanical characteristics of recycled large aggregate concrete show poorer performance than that of Portland-cement concrete due to the internal defects of recycled large aggregate (RLA). To improve the mechanical characteristics of recycled large particle size aggregate concrete, the recycled large aggregate Self-Compacting Concrete filled steel tube (RLA-SCCFST) is proposed. The external steel tube can not only keep the core recycled large aggregate concrete in the three-dimensional state of stress, but also prevent the crack expansion of the core recycled large aggregate concrete. RLA-SCCFST subjected to compression is studied experimentally. The compression failure tests use 20 specimens of circular section short column with different steel content rate, particle size of RLA, strength of RLA, strength of SCC, and eccentricity of the load. The influence of different factors on mechanical characteristics of RLA-SCCFST short cylindrical components subjected to compression is analyzed. The results indicate that the load-bearing performance of RLA-SCCFST short columns increases following with the augmentation of RLA particle size, strength of RLA particle size, strength of SCC and steel content rate. The load-bearing performance of RLA-SCCFST short columns reduced with the augmentation of the load eccentricity. And the experimental results are in high coincidence with those calculated by different formulas.

Improvement of eco-efficient self-compacting concrete manufacture by recycling high quantity of waste materials

Recycling plastic waste to obtain new materials such as concrete or mortar seems to be one of the best solutions for disposing of plastic waste. Second, in the construction industry, due to the increasing costs of landfills and the lack of a natural large aggregate, the increased interest in crushed ceramics is significant. The third type of waste that is dealt with in this article is tea ash because tea is the second most consumed beverage in the world and large amounts of waste are generated. This article attempts to develop the appropriate characteristics of self-compacting concrete by adding the following waste materials: plastic waste, tea waste and collapsed ceramics. In this paper, Fresh and hardened properties of self-compacting concrete with waste materials were investigated. The diameter and time of sediment flow, segregation, L-box ratio, and density of freshly compacted concrete mixtures were measured. Moreover, both 7, 14, and 28-day bending strength and 7 and 28-day bending strength of hardened self-compacting concrete samples were measured. The results proved the possibility of using plastic waste, tea waste and collapsed ceramics in self-compacted concrete, because they do not significantly reduce the hardened and fresh properties of self-compacted concrete.

SPECIFIC FEATURES OF FILLERS FROM SAND-GRAVEL MIXTURE ON THE EXAMPLE OF THE VEDENSKOE DEPOSIT

Представлены основные результаты исследований особенностей заполнителей из песчано-гравийной смеси (ПГС) Веденского месторождения Чеченской Республики. Приведены минералогический и петрографический составы известных месторождений ПГС Северного Кавказа. Изучены физико-механические и другие свойства как самих ПГС, так и отдельных их мелких и крупных фракций заполнителей. Получена зависимость стоимости бетонов на основе ПГС от класса бетона по прочности на сжатие. Представлены сравнительные данные бетонов на основе ПГС с бетонами на искусственном заполнителе - щебне. Доказана эффективность применения ПГС в технологии бетона после их обогащения и фракционирования, способствующих улучшению контактной зоны такого заполнителя и цементного камня и, как следствие, повышению прочности бетона. Работа выполнена при поддержке Российского фонда фундаментальных исследований» (РФФИ) в рамках научного проекта № 18-48-200001. The main results of studies of the features of aggregates from a sand and gravel mixture (SGM) of the Vedensky deposit in the Chechen Republic are presented. The mineralogical and petrographic compositions of the known deposits of SGM in the North Caucasus are presented. The physicomechanical and other properties of both the SGM themselves and their individual small and large aggregate fractions have been studied. The dependence of the cost of concrete based on SGM on the class of concrete in terms of compressive strength is obtained. Comparative data of concretes based on SGM with concretes based on artificial aggregate - crushed stone are presented. The effectiveness of the use of SGM in concrete technology after their enrichment and fractionation has been proven, which helps to improve the contact zone of such a filler and cement stone and, as a result, to increase the strength of concrete.This work is supported by the Russian Foundation for Basic Research (RFBR) in the framework of the scientific project No. 18-48-200001.

Trade, Productivity and (Mis)allocation

We examine the gains from globalization in the presence of firm heterogeneity and potential resource misallocation. We show theoretically that without distortions, bilateral and export liberalizations increase aggregate welfare and productivity, while import liberalization has ambiguous effects. Resource misallocation can either amplify, dampen or reverse the gains from trade. Using model-consistent measures and unique new data on 14 European countries and 20 industries in 1998-2011, we empirically establish that exogenous shocks to export demand and import competition both generate large aggregate productivity gains. Guided by theory, we provide evidence consistent with these effects operating through reallocations across firms in the presence of distortions: (i) Both export and import expansion increase average firm productivity, but the former also shifts activity towards more productive firms, while the latter acts in reverse; (ii) Both export and import exposure raise the productivity threshold for survival, but this cut-off is not a sufficient statistic for aggregate productivity; (iii) Efficient institutions, factor and product markets amplify the gains from import competition but dampen those from export access.