Waste to Wealth Strategy: Preparation and Properties of Lightweight Al2O3-SiO2-Rich Castables Using Aluminum Dross Waste

Aluminum dross is a well-known industrial waste generated in the aluminium industry, and its recycling and reuse is still a worldwide issue. Herein, aluminum dross waste (ADW) was recycled to progressively replace the aggregate fraction of clay at 70, 75, 80, 85, and 90 wt% for the fabrication of Al2O3-SiO2-rich porous castable refractories. Their physical properties and mechanical behavior were assessed by the measurement of linear shrinkage rate, bulk density, apparent porosity, cold crushing strength, and thermal conductivity. The microstructure and phase evolutions were analyzed via scanning electron microscopy (SEM) and X-ray diffraction (XRD). The incorporation of 85 wt% of ADW allowed the development of a waste-containing conventional refractory castable with improved properties as compared to those of the other samples. The sustainable refractory castable exhibited decent thermal conductivity and physical and mechanical characteristics, and is suitable for application as reheating furnace lining. It is a “green” practice to partially replace the traditional raw materials with industrial waste in the manufacture of conventional refractory castables and provides environmental and economic benefits.

Effect of percent air voids content on the deformation properties of the asphalt mixture

Asphalt mixture is a building material with many advantages. Therefore, it is most used in road construction. If the asphalt mixture is laid with the prescribed technology, it can withstand load effects to long-term. It is necessary to take samples that will be subjected to laboratory measurements. There are several laboratory test, for example measurement thickness of the asphalt mixture layers, the aggregate fraction, quantity of binder in the mixture, determination of air void in asphalt mixture layers. Samples taken directly from the construction site are subjected to laboratory tests. This article focuses on one of the laboratory tests and it is determination of air void in asphalt mixture layers. The determination of air void in asphalt mixture layers is test in detail, because this effect has influence on the deformation properties of asphalt mixture layers. Therefore, it was necessary to model of air void in asphalt mixture layers with different degrees air void. On this purpose was use program Abaqus. The results were plotted. This graphs showed that increasing the air void in asphalt mixture layers has effect on the expansion of deformations. This can lead to faster pavement degradation.

Litter Quality and Microbes Explain Aggregation Differences in a Tropical Sandy Soil

Soil aggregates store most soil organic carbon (SOC), but how does litter quality influence their formation? We hypothesized varying litter quality to facilitate differences in aggregate formation by altering the seasonal development of microbial biomass (MB) C and N, with MB driving aggregate development in a tropical sandy soil in Thailand. Aggregate development was studied in a long-term fallow experiment, receiving 10 Mg ha−1 annual applications of rice (Oryza sativa) straw (low N and polyphenols (PP)), groundnut (Arachis hypogaea) stover (high N, low PP), tamarind (Tamarindus indica) litter (medium N and PP), or dipterocarp (Dipterocarpus tuberculatus) leaf litter (low N, high PP) compared to a control. N-rich litter from groundnut and tamarind led to significantly higher MB, bulk soil C and aggregate C than dipterocarp, rice straw, and the control. Bulk soil C and small macroaggregates C of N-rich litter treatments increased about 7% in 30 weeks. Increasing MB N explained increasing small macroaggregate C and both, MB C or N were important covariates explaining temporal variations of C stored in the microaggregates, in silt and clay. MB also explained temporal variations of aggregate fraction weights. With time, SMA C only increased in the N-rich groundnut and tamarind treatments, but decreased in other treatments. Connections of MB to aggregate C and weight substantiated the importance of microbial activity for aggregate formation and carbon sequestration. By promoting MB for longest time spans, medium-quality tamarind could best facilitate aggregate formation, and increase silt and clay C.

Surface treatments of recycled brick aggregate and their influence on selected properties of concrete

The paper is devoted to surface treatment of recycled brick aggregate with various impregnating substances in order to reduce its absorbency and verify the use of such treated recycled material as a partial replacement of natural aggregate (fraction 4/8) in concrete. Selected properties of the tested samples were monitored after 28 and 60 days of curing. The results show that the treatment of recycled bricks with water glass appears to be a less suitable alternative compared to the use of a hydrophobic solution of silanes and siloxanes.

Sorption of Polycyclic Musks on Soil Components of Different Aggregate Sizes: The Effect of Organic-mineral Interactions

Polycyclic musks (PCMs) in soil environments have been of increasing concern because of their potential characteristic of persistence, bioaccumulation, and potential ecological risk. However, little is known about their fate process in soil environments. Here, we selected two PCMs as sorbates, namely galaxolide (HHCB) and tonalite (AHTN), to explore their sorption process in soils. Sorption batch experiments with six nature soils and their different aggregate fractions were carried out to elucidate the effect of organic–mineral interactions in different aggregate sizes on sorption of these two PCMs. The possible causes of variation in the organic carbon-normalized partition coefficient (Koc) for HHCB and AHTN have been investigated. The results indicated that the sorption contribution to different aggregate fractions to the overall sorption was dependent on both Koc and content of each aggregate fraction. The strong influence of organic–mineral interactions on Koc was evidenced by the large variation in Koc on HF-treatment for both bulk soils and their different aggregate fractions. This study verified the dual effect of organic–mineral interactions among selected soils. By comparing the measured and theoretical overlay ∆ Koc values, it was indicated that the interaction between particles of different size fractions will also affect Koc variation. This study represents a valuable contribution to the understanding of the fate processes and behaviors of PCMs in soil and its implication on the risk assessment.

Optimization of the Concrete Composition Mix at the Design Stage

The problem of the composition optimization of concrete mixes seems to be quite urgent as errors at the composition design stage can lead to problems of concrete at the stage of exploitation such as delamination, cracking etc. Reasonable selection of concrete mix components guarantees the required strength of concrete and reinforced concrete structures in the future. This paper investigates the influence of the concrete mix composition on the strength of concrete. Firstly, typical risks that can occur on the composition design stage have been identified through the experts' interviews. Secondly, this risks were associated with indicators and characteristics that can be tested experimentally. Running of several mathematical models has allowed to outline concrete mix parameters of highest importance and formulate an empirical equation for the dependence of the strength of the concrete mixture on the values of the coarse aggregate quality factor, the fine aggregate fraction and the consumption of the Portland cement has been proposed. As a result, a methodology for controlling the quality of concrete at the stage of the composition design has been formulated. Doi: 10.28991/cej-2021-03091732 Full Text: PDF

New Tillage System with Additional Renovation of Soil Properties in Tramlines

Fertilizing and spraying techniques are repeatedly driven in tramlines for crop care with products whose demand increases for higher yields. The soil in tramlines is so compacted by heavy crop care machinery what leads breakdown to lifelessness. Such damaged state of the soil continues all season and leads to dejected soil productivity. The aim of this study is to find an optimal process of soil renovation in tramlines on loam and clay loam soil and to determine the required fuel consumption. The soil renovation was investigated by specially made Tiller on the dependence of tine shape types (narrow and winged) and working speed 1.6, 2.2 and 3.6 m∙s−1 in loam and clay loam soil. The beneficial relationships of soil aggregate fraction ratio, which varied from 0.54 to 4.08 and fuel consumption, which varied from 1.04 to 1.82 L·km−1 independence on tine shape and soil type was established. Based on research results, the sufficient soil loosening to suitable proportion of soil aggregates fraction ratio on loam soil was accomplished at working speed 3.6 m∙s−1 with winged tine type and fuel consumption was 1.04 L·km−1. The suitable soil aggregate fraction ratio on clay loam was achieved at working speed 3.6 m∙s−1 with narrow tine shape type and fuel consumption was 1.31 L·km−1. The volume of loosed soil in tramlines was particularly influenced by variation of tines shapes but was not influenced by the working speed majorly. The aligning of soil surface was influenced by the working speed majorly and particularly by variation of tines shapes.

Combining Reclaimed Asphalt Pavement (RAP) and Recycled Concrete Aggregate (RCA) from Cuba to Obtain a Coarse Aggregate Fraction

In Cuba, tons of construction and demolition waste (CDW) are generated during urban construction and reconstruction activities every year. The use of CDW, such as recycled concrete aggregates (RCA) and reclaimed asphalt pavement (RAP), in pavement construction is a viable solution to preserve the consumption of natural aggregates (NA), and to minimize the impact of landfill. The main objective of this work is to obtain a 5–10 mm aggregate fraction of RCA and RAP, to obtain an appropriate recycled coarse aggregate for manufacturing hot mix asphalt (HMA). Each source of RCA, RAP and NA, and the combinations RCA/RAP (0/100, 25/75, 50/50, 75/25 and 100/0) were characterized (moisture, asphalt content of RAP, specific gravity, water absorption, and flakiness index) for determining a better combination. The results showed that the combination (RCA/RAP) that best meets the NA aggregates specifications used for hot mix asphalt were RCA/RAP: 25/75 and 50/50. The results show the possibility of combining both wastes to obtain a coarse aggregate fraction with a high environmental benefit, by reducing the use of natural resources.