Search Results (5)

The present work analyzes the effect of releasing physically bound water from hydrogel, cork, perlite, and ceramsite on materials exposed to microwave radiation and subsequently investigates possible changes in the physical properties of these materials (water absorption and thermal conductivity coefficient). The release of physically bound water from individual materials has potential practical applications in materials engineering, for example, in the internal curing of concrete, where individual aggregates could, under the influence of microwave radiation, release water into the structure of the concrete and thus further cure it. Experimental analysis was carried out with samples of the above-mentioned materials, which were first weighed and then immersed in water for 24 h. Then, they were weighed again and exposed to microwave radiation. After exposure, the samples were weighed again, left immersed in water for 24 h, and weighed again. The focus of the study was on the ability of the aggregates to release water due to microwave radiation and on the changes in the properties (water absorption, thermal conductivity coefficient) of these materials when exposed to microwave radiation. The samples were further monitored by digital microscopy for possible changes in the surface layer of the materials. The hydrogels show the highest water absorption (1000%) and the fastest water release (45 min to complete desiccation). After the release of water due to microwave radiation, their ability to absorb water is maintained. Of interest, however, is that in the case of almost complete removal of water from the soaked hydrogel, the original powdered state of the hydrogel is not obtained, but the outcome has rather a solid structure. In the case of cork, the water absorption depends on the fraction of the material. Full article

The development of novel materials made from waste is one of the main measures to achieve sustainable materials development. In this study, ash of mushroom and corn straw (MCA) and furnace slag (FS) were used as raw materials to prepare alkali-activated biomass ash-slag material (AABS) and sustainable ecological non-sintered ceramsite (SENC). In this paper, the effects of quicklime powder (QL), NaOH, and sodium silicate solution (SS) on AABS were analyzed using single factor and orthogonal tests, and the preferred ratio of the composite alkali activator configuration was established. SENC was prepared based on the composite alkali activator, and the microstructure and phase composition of SENC were explored using XRD and SEM–EDS. The results showed that 3 wt% QL enhanced the early age compressive strength of AABS. The composite alkali activator was best configured when the additions of QL, NaOH, and SS were 3%, 2%, and 15%, respectively. At this configuration, the 28 d compressive strength of AABS was 47.4 MPa, and most of the internal pores were less than 0.4 μm; the 28 d numerical tube pressure of the SENC reached 12.2 MPa with a softening coefficient of 0.96. According to the results of XRD and SEM–EDS, SENC contained various hydration products such as C-A-S-H, calcium hemicarboaluminate, hydrotalcite, portlandite, and vaterite. The largest proportion of hydration products was C-A-S-H, which contributed to the pore refinement and structural densification. SENC has the potential to be used as coarse aggregate in sustainable lightweight concrete. Full article

Nitrogen, phosphorus, and metals’ pollutants discharged from industrial sources eventually accumulate in lake sediment, hence increasing the difficulty of sediment treatment and disposal. In this work, the water storage ceramsite is prepared from dredged lake sediment and cyano-bacterial powder. The effects of pyrolysis temperature and cyanobacterial sediment on the porosity of ceramsite were investigated. The results showed that the pyrolysis of organic matter and the de-composition of compounds or salts can produce gas, causing a rich pore structure inside the ceramsite. When the temperature increased to 1150 °C, vitrification would collapse the pore structure inside the material. At the cyanobacterial-to-sediment ratio of 3:7, the porosity and water absorption of the material could reach 81.82% and 92.45% when the pyrolysis temperature was 500 and 1050 °C, respectively. The internal macropore structure of ceramsite improved the water absorption performance, and the mesoporous structure was responsible for its long water release time and stable water release structure. The ceramsite exhibited a superior metals’ retention effect. Under different pH and temperature conditions, the consolidation rates of Fe, Ni, Mn, Cr, and Pb in ceramsite were all more than 99%, suggesting the safety of the material in environmental applications. This study demonstrates the feasibility of the resourceful production of water storage ceramsite from lake sediment and cyanobacterial slurry, which helps to reduce the impact of solid waste on the environment. Thus, this work provides a practical basis for guiding water storage ceramsite in the construction of sponge cities. Full article

In this paper, the preparation method and reasonable mix ratio of non-calcination brick with rock powder, cement, lime and fly ash ceramsite (FAC) as the raw materials were experimentally evaluated. To better understand the effects of each component on the performance of non-calcination rock powder brick (NCRPB), an orthogonal experimental design was conducted with the water–cement ratio (W/C), rock powder–cement ratio (R/C), lime content (w_l) and FAC content (w_f) as the main factors, which involved four factors and three factor levels. According to the orthogonal experimental design, the compressive strength, water resistance and bulk density of nine groups of NCRPB specimens were tested. The results show that R/C was the most important factor affecting the compressive strength and water resistance, while the FAC content influenced the bulk density of NCRPB greatly. In this study, the reasonable mix of W/C, R/C, w_l, and w_f in weight was 0.6, 3.0, 30% and 21%, respectively. In addition, the microstructure and strength formation mechanism of NCRPB were analyzed by using SEM and XRD. The test results show that the rock powder having pozzolanic activity could react with the additional Ca(OH)₂ to produce hydration products, leading to the improvement of the performance of NCRPB. Full article

The effects of two powdered mineral materials (powdered ceramsite and powdered limestone) on aerobic granulation of sludge were evaluated. The experiment was conducted on a laboratory scale bioreactors treating wastewater for 89 days. Three granular sequencing batch reactors (GSBRs) were operated at the lowest optimal organic loading rate (OLR) of 2.55 g COD/(L∙d). In the control reactor (R1), the mean diameter (d) of the biomass ranged from 124.0 to 210.0 µm, and complete granulation was not achieved. However, complete granulation did occur in reactors to which either ceramsite (251.9 µm < d < 783.1 µm) or limestone (246.0 µm < d < 518.9 µm) was added. Both powdered materials served as a ballast for the sludge flocs making up the seed sludge. Ceramsite particles also acted as microcarriers of granule-forming biomass. The granules in the reactors with added powdered materials had nonfibrous and smoother surfaces. The reactor with ceramsite exhibited the highest average efficiencies for COD, total nitrogen, and total phosphorus removal (85.4 ± 5.4%, 56.6 ± 10.2%, and 56.8 ± 9.9%, respectively). By contrast, the average nitrification efficiency was 95.1 ± 12.8%. Full article