Heat-induced phase transitions in mining tailings to create alternative supplementary cementitious materials

The present study investigated the mineralogical changes in five different mining tailings (i.e., bauxite, gold, copper, and lead) with varying heating conditions (i.e., non-heating, 600 °C, and 900 °C) to explore the feasibility of using thermally treated tailings as supplementary cementitious materials. In particular, among the used heating conditions, bauxite tailings heated to 600 °C showed the best reactivity as supplementary cementitious material and thus rigorously studied the fundamentals of the increased reactivity. Well-balanced Al and Si dissolutions from the thermal decompositions of gibbsite, boehmite, and kaolinite seem to be the result of the best reactivity at the bauxite tailings heated at 600 °C among used heating conditions. It is also noted that, although tailings originated from the same types of ore or contained high Al2O3 and SiO2 contents, their supplementary cementitious reactivity differed depending on the contents of highly (i) soluble, (ii) thermally decomposable, and (iii) Al or Si-bearing minerals such as boehmite, gibbsite, kaolinite, and chamosite

Gypsum-Dependent Effect of NaCl on Strength Enhancement of CaO-Activated Slag Binders

This study explores the combined effect of NaCl and gypsum on the strength of the CaO-activated ground-granulated blast furnace slag (GGBFS) binder system. In the CaO-activated GGBFS system, the incorporation of NaCl without gypsum did not improve the strength of the system. However, with the presence of gypsum, the use of NaCl yielded significantly greater strength than the use of either gypsum or NaCl alone. The presence of NaCl largely increases the solubility of gypsum in a solution, leading to a higher concentration of sulfate ions, which is essential for generating more and faster formations of ettringite in a fresh mixture of paste. The significant strength enhancement of gypsum was likely due to the accelerated and increased formation of ettringite, accompanied by more efficient filling of pores in the system

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

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

The role of S100A4 for bone metastasis in prostate cancer cells

Background Prostate cancers frequently metastasize to bone, where the best microenvironment for distant colonization is provided. Since osteotropic metastasis of prostate cancer is a critical determinant of patients survival, searches for preventive measures are ongoing in the field. Therefore, it is important to dissect the mechanisms of each step of bone metastasis, including the epithelial-mesenchymal transition (EMT) and cross-talk between metastatic niches and cancer cells. Methods In this study, we established a highly bone-metastatic subline of human prostate cancer cells by selecting bone-homing population of PC3 cells after cardiac injection of eight-week-old male BALB/c-nude mice. Then we assessed the proliferation, EMT characteristics, and migration properties of the subline (mtPC3) cells in comparison with the parental PC3 cells. To investigate the role of S100A4, we performed gene knock-down by lentiviral transduction, or treated cells with recombinant S100A4 protein or a S100A4-neutralizing antibody. The effect of cancer cells on osteoclastogenesis was evaluated after treatment of pre-osteoclasts with conditioned medium (CM) from cancer cells. Results The mtPC3 cells secreted a markedly high level of S100A4 protein and showed elevated cell proliferation and mesenchymal properties. The increased proliferation and EMT traits of mtPC3 cells was inhibited by S100A4 knock-down, but was not affected by exogenous S100A4. Furthermore, S100A4 released from mtPC3 cells stimulated osteoclast development via the cell surface receptor RAGE. Down-regulation or neutralization of S100A4 in the CM of mtPC3 cells attenuated cancer-induced osteoclastogenesis. Conclusion Altogether, our results suggest that intracellular S100A4 promotes cell proliferation and EMT characteristics in tumor cells, and that secreted S100A4 activates osteoclastogenesis, contributing to osteolytic bone metastasis. Thus, S100A4 upregulation in cancer cells highly metastatic to bone might be a key element in regulating bone metastasis.This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government MSIT (NRF-2020R1A2C2010082 and NRF-2018R1A5A2024418) to H.-H. Kim and by the National Research Foundation of Korea grant (NRF-2019R1A2C4070083) to H.J. Kim. The funding body has no role in the design of the study; collection, analysis, and interpretation of data; and in writing the manuscript

Integrated Thermal Analysis for Development and Numerical Model of Concrete containing Phase Change Materials

Department of Urban and Environmental Engineering (Urban Infrastructure Engineering)clos

Production of lightweight cementless binders using supplementary cementitious materials to replace autoclaved aerated concrete blocks

Recently, the application of sustainable cementitious materials to improve the efficiency of buildings has become of great importance as part of carbon neutrality. This study aims to develop lightweight cementitious binders made of supplementary cementitious materials and various additives to replace autoclaved aerated concrete blocks. To this end, the mechanical properties of 36 cementless binders using fly ash (FA), fly ash cenosphere (FAC), and ground granulated blast-furnace slag were assessed. The FA or FAC activated with Ca(OH)(2) and Na2CO3 binders, which showed a density of 637.6-1576.3 kg/m(3) and a compressive strength of 7.4-65.0 MPa, were selected as representative samples, and their microstructure and thermal performance were further characterized. The results showed that FAC acted as a filler and precursor, occupying space in the binder, and reacting partially with activators simultaneously. In particular, increasing FAC content increased the porosity of the hardened matrix, remarkably reducing the weight of the binders. In addition, the thermal conductivity of the binders was significantly reduced to 0.25-0.27 W/m center dot K, which increased their thermal efficiency. This light-weight, thermally efficient cementless binder is expected to be applied to commercially available blocks

Recycling of limestone fines using Ca(OH)2- and Ba(OH)2-activated slag systems for eco-friendly concrete brick production

This study explored the possibility of using limestone fines (LF) as a supplementary material in activated slag binder systems using two types of activators (i.e., 10 wt% of Ca(OH)2 or 10 wt% of Ba(OH)2) and investigated the interactions of the activators with LF in each binder system through strength testing, powder X-ray diffraction, thermogravimetry, and mercury intrusion porosimetry. Using these binders, concrete brick samples containing LF were also made and examined for possible industrial applications. Although the influences of the LF addition on the strength, dissolution degree of the slag, reaction products, and pore-size distribution depended on the type and dosage of the activator, the addition was generally advantageous for all these aspects in both types of activations. The concrete brick made of 20 wt% LF using the Ba(OH)2 activation fulfilled the Korean standard requirements of strength and water absorption for concrete bricks, and it also satisfied the criteria of the leaching test for possible toxic elements

The temperature-dependent action of sugar in the retardation and strength improvement of Ca(OH)2-Na2CO3-activated fly ash systems through calcium complexation

This study reports the temperature-dependent strength improvement and retardation in Ca(OH)2-Na2CO3-activated fly ash binders with sugar. Without sugar, the system exhibited rapid stiffening due to the calcite formation. The addition of sugar clearly removed the false set; however, at room temperature, it retarded strength development because the calcium complexation of sugar inhibits the dissolved calcium ions from participating in calcite and C-S-H formation. However, at 90 ??C, the use of sugar significantly improved the compressive strength by increasing the (1) degree of dissolution of fly ash and Ca(OH)2, (2) C-S-H formation, and (3) reduction of overall pore size and volume

A study of thermal decomposition of phases in cementitious systems using HT-XRD and TG

Significant variations have been reported on the temperature range of thermal decomposition of cementitious phases. Thus, this study identified temperature ranges on the phases in actual cementitious systems (portland cement (OPC) pastes, blended pastes of ground granulated blast furnace slag (GGBFS) with OPC, and Ca(OH)2-activated GGBFS) by simultaneously using thermogravimetry (TG) and high-temperature X-ray diffraction (HT-XRD) as follows: (1) 81??-91 ??C for dehydration of ettringite, (2) ???80??-240 ??C for major dehydration of C-S-H, (3) ???241??-244 ??C for hydrogarnet, (4) ???129??-138 ??C for Al2O3-Fe2O3-mono phase (AFm), (5) ???411??-427 ??C for Ca(OH)2, and (6) ???648??-691 ??C for CaCO3. The CaO layers and SiO2 chains of C-S-H likely started to decompose from 615??-630 ??C, and eventually transformed to new crystalline phases. This study also demonstrated that (a) the quantity of calcite could be overestimated due to additional carbonation when Ca(OH)2 is plentifully present in samples, and (b) the quantification of phases would be greatly affected by sample particle size when GGBFS is used in the system