scholarly journals Degradation mechanism and life prediction of tailings and waste rock aggregate geopolymer concrete under freeze-thaw corrosion

2022 ◽  
Author(s):  
Qi Sun ◽  
Botao Li ◽  
Hui Wang ◽  
Yiting Wang
Keyword(s):  
Life Prediction ◽  
Transmission Rate ◽  
Early Stage ◽  
Degradation Mechanism ◽  
Waste Rock ◽  
Geopolymer Concrete ◽  
Reaction Products ◽  
Natural Sand ◽  
Freeze Thaw ◽  
Rock Aggregate

Abstract To study the durability of tailings and waste rock aggregate geopolymer concrete (TWGPC), a large number of tailings and waste rock were used to replace natural sand and stone as aggregates, and a fly ash geopolymer was used to replace cement as cementing material to prepare TWGPC. The slow freezing method was used to carry out single freeze-thaw and freeze-thaw corrosion tests. Scanning electron microscopy and energy dispersive spectroscopy (SEM–EDS) were used to analyse the microstructure and reaction products of TWGPC. The degradation mechanism of TWGPC was studied, and the life of TWGPC was predicted. The results show that the higher the concentration of corrosion solution was, the more significant the change trend of the mechanical properties test results. In the early stage of the cycle, acinar gypsum and short columnar ettringite were generated to fill the pores and improve the compactness and frost resistance of TWGPC. In the late stage of the cycle: calcium-silicate-hydrate (C-S-H) was decomposed and gradually replaced by magnesium-silicate-hydrate (M-S-H). The cohesion between mortar and aggregate was reduced, and a large number of products were generated. Cl- inhibited the transmission rate of SO42- and reduced the erosion effect of SO42- on TWGPC. The single freezing-thawing life prediction model had high accuracy, and the life prediction conclusion based on reliability was consistent with the appearance damage analysis, mechanical property testing and microscopic morphology analysis.

scholarly journals A modified SEIR model to predict the behavior of the early stage in coronavirus and coronavirus-like outbreaks

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Wilfredo Angulo ◽  
José M. Ramírez ◽  
Dany De Cecchis ◽  
Juan Primera ◽  
Henry Pacheco ◽  
...  
Keyword(s):  
Molecular Structure ◽  
Risk Perceptions ◽  
Transmission Rate ◽  
Early Stage ◽  
Individual Risk ◽  
Seir Model ◽  
Proposed Model ◽  
Probable Site ◽  
Adjusted Model ◽  
The Impact

AbstractCOVID-19 is a highly infectious disease that emerged in China at the end of 2019. The COVID-19 pandemic is the first known pandemic caused by a coronavirus, namely, the new and emerging SARS-CoV-2 coronavirus. In the present work, we present simulations of the initial outbreak of this new coronavirus using a modified transmission rate SEIR model that takes into account the impact of government actions and the perception of risk by individuals in reaction to the proportion of fatal cases. The parameters related to these effects were fitted to the number of infected cases in the 33 provinces of China. The data for Hubei Province, the probable site of origin of the current pandemic, were considered as a particular case for the simulation and showed that the theoretical model reproduces the behavior of the data, thus indicating the importance of combining government actions and individual risk perceptions when the proportion of fatal cases is greater than $$4\%$$ 4 % . The results show that the adjusted model reproduces the behavior of the data quite well for some provinces, suggesting that the spread of the disease differs when different actions are evaluated. The proposed model could help to predict outbreaks of viruses with a biological and molecular structure similar to that of SARS-CoV-2.

scholarly journals Use of Coal Bottom Ash and CaO-CaCl2-Activated GGBFS Binder in the Manufacturing of Artificial Fine Aggregates through Cold-Bonded Pelletization

Materials ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 5598
Author(s):  
Dongho Jeon ◽  
Woo Sung Yum ◽  
Haemin Song ◽  
Seyoon Yoon ◽  
Younghoon Bae ◽  
...  
Keyword(s):  
Early Stage ◽  
Bottom Ash ◽  
Relative Weight ◽  
Main Reaction ◽  
Reaction Products ◽  
Coal Bottom Ash ◽  
Heavy Metal Leaching ◽  
Granulated Blast Furnace Slag ◽  
Fine Aggregates ◽  
Cementless Binder

This study investigated the use of coal bottom ash (bottom ash) and CaO-CaCl2-activated ground granulated blast furnace slag (GGBFS) binder in the manufacturing of artificial fine aggregates using cold-bonded pelletization. Mixture samples were prepared with varying added contents of bottom ash of varying added contents of bottom ash relative to the weight of the cementless binder (= GGBFS + quicklime (CaO) + calcium chloride (CaCl2)). In the system, the added bottom ash was not simply an inert filler but was dissolved at an early stage. As the ionic concentrations of Ca and Si increased due to dissolved bottom ash, calcium silicate hydrate (C-S-H) formed both earlier and at higher levels, which increased the strength of the earlier stages. However, the added bottom ash did not affect the total quantities of main reaction products, C-S-H and hydrocalumite, in later phases (e.g., 28 days), but simply accelerated the binder reaction until it had occurred for 14 days. After considering both the mechanical strength and the pelletizing formability of all the mixtures, the proportion with 40 relative weight of bottom ash was selected for the manufacturing of pilot samples of aggregates. The produced fine aggregates had a water absorption rate of 9.83% and demonstrated a much smaller amount of heavy metal leaching than the raw bottom ash.

Intermediate Products Analysis of Phenol Degradation in Aqueous Solution Caused by Pulsed Discharge

2012 ◽  
Vol 518-523 ◽  
pp. 3146-3149
Author(s):  
Sheng Lan ◽  
Zhen Xing Zhang ◽  
Yong Bin Yuan ◽  
Abdus Samee
Keyword(s):  
Aqueous Solution ◽  
Degradation Mechanism ◽  
Pulse Discharge ◽  
Phenol Degradation ◽  
Reaction Products ◽  
Pulsed Discharge ◽  
Dc Voltage ◽  
Intermediate Products ◽  
Phenethyl Alcohol ◽  
Products Analysis

Abstract. In this paper we have presented the degradation of Phenol in aqueous solution which is caused by pulse discharge. The reaction products in the wastewater dissolved phenol under pulsed discharge were tested using GC-MS. Based on the experimental results intermediate products include 2,4hydroxyphnel, polyhydroxy phenethyl alcohol and so on. The final products are carbon dioxide and water. In addition, the theoretical analysis has been conducted These results will be helpful for further studying degradation mechanism of wastewater dissolved phenol under pulsed discharge, using either AC or DC voltage.

The Properties of Fine Recycled Aggregate Concrete Containing Recycled Bricks from Construction and Demolition Waste

2018 ◽  
Vol 760 ◽  
pp. 193-198 ◽  
Author(s):  
Kristina Fořtová ◽  
Tereza Pavlů
Keyword(s):  
Recycled Aggregate Concrete ◽  
Construction And Demolition Waste ◽  
Recycled Aggregate ◽  
Partial Replacement ◽  
Fine Aggregate ◽  
Demolition Waste ◽  
Natural Sand ◽  
Aggregate Concrete ◽  
Freeze Thaw ◽  
Recycled Fine Aggregate

This paper presents research results of recycled fine aggregate concrete testing. The main aim of this contribution is verification of properties of fine aggregate concrete with partial replacement of fine natural aggregate by recycled masonry aggregate originated from construction and demolition waste. The influence of partial replacement of natural sand to mechanical properties and freeze-thaw resistance is described. The compressive strength and flexural strength were tested at the age of 28 and 60 days and after 25, 50, 75 and 100 freeze-thaw cycles. Partial replacement of natural sand was 0, 25 and 50 % for all these tests. Prismatic specimens were examined.

Freeze-thaw resistance of Class F fly ash-based geopolymer concrete

2019 ◽  
Vol 222 ◽  
pp. 474-483 ◽  
Author(s):  
Renda Zhao ◽  
Yuan Yuan ◽  
Zhengqing Cheng ◽  
Tian Wen ◽  
Jian Li ◽  
...  
Keyword(s):  
Fly Ash ◽  
Geopolymer Concrete ◽  
Freeze Thaw ◽  
Class F Fly Ash ◽  
Class F

scholarly journals Improving water storage of reclamation soil covers by fractionation of coarse-textured soil

2014 ◽  
Vol 94 (4) ◽  
pp. 489-501
Author(s):  
Yekaterina V. Dobrovolskaya ◽  
Henry Wai Chau ◽  
Bing Chen Si
Keyword(s):  
Preferential Flow ◽  
Soil Cover ◽  
Water Storage ◽  
Waste Rock ◽  
Wetting Front ◽  
Mining Operations ◽  
Natural Sand ◽  
Soil System ◽  
Soil Covers ◽  
Number Of Layers

Dobrovolskaya, Y. V., Chau, H. W. and Si, B. C. 2014. Improving water storage of reclamation soil covers by fractionation of coarse-textured soil. Can. J. Soil Sci. 94: 489–501. Mining operations cause considerable land disturbance as well as the accumulation of large amounts of waste rock. Capping waste rock with a soil cover has proven to be a reliable, long-term reclamation technique. This study examines the question of whether it is possible to attain a considerable increase in water storage capacity (WSC) by separating coarse-textured soil into particle size fractions and layering them into a soil cover. Additionally, this study investigated whether preferential flow can be mitigated by increasing the number of layers and extending the interlayer transitions in fine-over-coarse-textured soil systems. Intermittent and constant infiltration experiments were conducted on homogeneous covers composed of natural sand, two-layered covers with abrupt and gradual interlayer transitions as well as on a four-layered cover under initially air-dry and field capacity (FC) conditions. Water storage capacities were determined from a sampling of soil covers’ water content at FC. Infiltration experiments showed that all tested covers under all initial and boundary conditions had limited susceptibility to preferential flow. Increasing the number of layers and extending the interlayer transitions had a stabilizing effect on the wetting front. Water storage capacities and residence time increased with the increased number of layers. Overall, it has been shown that it is possible to improve the WSC of coarse-textured soil by fractionation and layering of it into a relatively fine-over-coarse soil system.

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