Water sensitivity of cement‐based materials Zhou, Chunsheng; Zhang, Xiaoyu; Wang, Zhendi ...
Journal of the American Ceramic Society,
September 2021, Letnik:
104, Številka:
9
Journal Article
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Cement‐based materials are the most widely used construction materials on the planet. Cement‐based materials play a fundamental role in modern civilization and will for the foreseeable future. ...Although great efforts have been devoted to discovering the behaviors and optimizing their performances, several long‐standing controversies persist for the fundamental water‐related properties of cement‐based materials, which hinder theoretical researches and mislead technological developments. Inspired by the decreasing water permeability of clay‐bearing rocks, the term “water sensitivity” in geophysics is borrowed and proposed for cement‐based materials. The lamellar structure of negatively charged nanoparticles is responsible for swelling in clay‐based reservoir rocks. Amorphous calcium silicate hydrate gels in cement‐based materials have similar micro‐structural characteristics. They probably swell upon wetting and contract upon drying, making the pore structure of cement‐based materials dependent on water content. More importantly, several unexplained behaviors of cement‐based materials can be rationalized using water sensitivity. Thorough exploration of both the micro‐structural characteristics and performances validate the use of water sensitivity for cement‐based materials. Because water participates in or regulates almost all physical and chemical processes of cement‐based materials, water sensitivity can be a part of the interpretations of almost all of their properties and performances.
In the sol–gel science, the influence of chemical aging on the fundamental water permeability remains open regarding to the durability performance of cement-based material. To reveal the pure effect ...of chemical aging, the water permeability and related micro-structural characteristics are measured on water-saturated mature mortars, whose aging is accelerated through heat treatment under water. It is found that, the chemical aging increases the volumetric porosity and coarsens the pore structure to a notable extent, which enlarge water permeability by 2.6–4.9 times. Based on the pore structure obtained through the low-field proton NMR technique, the water permeability is predicted by the Katz–Thompson theory with satisfactory accuracy, quantitatively confirming the direct effects of chemical aging on water permeability. Physically, because of the polymerization and rearrangement of C–S–H gel, cement mortars undergo substantial changes with enlarging radii for both interlayer and gel pores, slightly decreasing interlayer space but remarkably enlarging gel pore space.
Accumulating evidences suggest that circular RNAs play vital roles in human cancers. Previously, we found that circHIPK3 suppressed invasion of bladder cancer cells via sponging miR-558 and ...downregulating heparanase expression. In this study, we discovered that a circular RNA derived from NR3C1 (circNR3C1) was downregulated in bladder cancer tissues and cell lines according to RNA-Seq data and qRT-PCR analysis. Functionally, we found that overexpression of circNR3C1 could significantly inhibit cell cycle progression and proliferation of bladder cancer cells in vitro, as well as suppress tumor growth in vivo. Mechanistically, we demonstrated that circNR3C1 possessed four targeting sites of miR-27a-3p and could effectively sponge miR-27a-3p to suppress the expression of cyclin D1. Furthermore, we revealed that miR-27a-3p functioned as an oncogene through interacting with 5′UTR of cyclin D1 to enhance its expression, which led to promote cell cycle progression and proliferation in bladder cancer cells. Conclusively, our findings further confirm the hypothesis that circRNAs function as “microRNA sponges”, and our data suggest that circNR3C1 and miR-27a-3p would be potential therapeutic targets for bladder cancer treatment.
•CircNR3C1 is down-regulated in bladder cancer.•CircNR3C1 could inhibit cell cycle and cell proliferation in bladder cancer cells.•CircNR3C1 could directly sponge miR-27a-3p in bladder cancer.•miR-27a-3p could promote cell proliferation and cycle progression.•miR-27a-3p could interact with cyclinD1 5′UTR to enhance cyclinD1 expression.
Factors affecting oxidation stability for several commercially available biodiesels were primarily investigated by acid value (AV) and induction period (IP) evaluations in this study. It was found ...that the measured IP at different storage time points were somewhat dependent on the saturated degree of fatty acid methyl esters (FAMEs), the corresponding measured AV scattered randomly. Generally, AV increased and IP decreased after one year of storing in a dark cold room in an air‐tight tank. Solvents (methanol, acetone and water) did not show a contribution to altering IP. Metals (copper and lead) showed the strongest detrimental effects to oxidative stability although somewhat depending on the particle size and oxide coating thickness, however, aluminum alloy and steel were not the case. Among the antioxidants, pyrogallol (PY) was the best in enhancing IP with a concentration of less than 3000ppm, however, tert-butylhydroquinone (TBHQ) was the best after 3000ppm, followed by propyl gallate (PG), butylated hydroxyanisole (BHA), 3,5-di-tert-butyl-4-hydroxyltoluene (BHT), and α-tocopherol. The appropriate dosage of PY was also evaluated to achieve the specified IP regulated by EN-14112 for samples with copper or lead contamination.
► Induction period (IP) not acid value (AV) depended on the saturated degree of FAME. ► AV increased but IP decreased after one year storage in -4°C in air tight tanks. ► Cu and Pb showed strong catalytic effects on deteriorate the quality of biodiesels. ► Solvents and metals (steel and aluminum) did not alter IP significantly. ► Selective antioxidants extended the IP of biodiesels with/without metal presence.
A scoping study was conducted to investigate the residues of nineteen pharmaceuticals and personal care products (PPCPs), including 4 natural and 3 synthetic steroid estrogens, 7 endocrine-disrupting ...phenols, and 5 acid pharmaceuticals in three urban streams and the Major Pearl River at Guangzhou, a megapolis in the Pearl River Delta, South China. Estrone was detected in >
60% water samples with a maximum concentration of 65 ng L
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1
. Endocrine-disrupting phenols (nonylphenol, bisphenol A, triclosan, 2-phenylphenol, methyparaben, and propylparaben) were found to be widely present at rather high concentrations in the urban riverine water of Guangzhou. Salicylic acid, clofibric acid and ibuprofen were detected in most water samples with maximum concentrations of 2098, 248 and 1417 ng L
−
1
respectively, whereas naproxen was less frequently detected and also at lower concentration. Both the detection frequencies and median concentrations of the PPCPs appeared higher during the low-flow season than during the high-flow season. The seasonal difference in PPCPs occurrence was probably attributed to the dilution effect caused by the rainfall. PPCPs in the urban riverine water of Guangzhou originated mainly from random discharge and/or leakage of municipal wastewater. PPCPs contamination in the Major Pearl River may be of a potential environmental issue, especially during the low-flow season.
Modified cement mortar was prepared by incorporating a superabsorbent polymer (SAP) with two kinds of dosing state, dry powdery SAP and swelled SAP (where the SAP has been pre-wetted in tap water), ...respectively. The mechanical properties, drying shrinkage and freeze-thaw resistance of the mortars were compared and analyzed with the variation of SAP content and entrained water-to-cement ratios. Additionally, the effect of SAP on the microstructure of mortar was characterized by scanning electron microscopy (SEM). The results indicate that agglomerative accumulation is formed in the voids of mortar after water desorption from SAP and there are abundant hydration products, most of which are C-S-H gels, around the SAP voids. The incorporation of the powdery SAP increases the 28 d compressive strength of the mortars by about 10% to 50%, while for the incorporation of swelled SAP, the 28 d compressive strength of the mortar can be increased by about -26% to 6%. At a dosage of 0.1% SAP and an entrained water-cement ratio of 0.06, the powdery SAP and the swelled SAP can reduce the mortar shrinkage rate by about 32.2% and 14.5%, respectively. Both the incorporation of powdery and swelled SAP has a positive effect on the freeze-thaw resistance of cement mortar. In particular, for powdery SAP with an entrained water-to-cement ratio of 0.06, the mass loss rate after 300 cycles is still lower than 5%.
Most concrete structures service under external loads and the studies of the external-loading effects on chloride diffusivity in these porous media remain insufficient. This paper reports a ...relationship between porosity variation and external load inspired by poroelastic theory. This porosity-load relationship, together with an empirical equation for chloride diffusivity versus porosity, provides an explicit diffusivity-load model for saturated porous media. Without the specific assumptions of geometries of the pores and the matrix phases, the present model shows flexible expressions. Comprehensive analyses are performed to demonstrate the effects of external load and initial porosity on the porosity variation, chloride diffusion coefficient, penetration depth and durable time of specific cement-based samples. Two models reported in the literature are employed for the purpose of comparison. Overall, initial porosity is a primarily dominative factor affecting the chloride diffusivity, penetration profile and durability of cement-based porous materials. Within the elastic regime, external loads only influence the outcomes in limited degrees.
Background. Tacrolimus has unpredictable pharmacokinetic (PK) characteristics, which are partially attributed to CYP3A5 polymorphism. The potential effects of clinical factors in the postoperative ...period of transplantation on tacrolimus PK and those of early tacrolimus PK variability on clinical outcomes are yet to be clarified. Methods. We examined the genetic and clinical factors affecting early tacrolimus PK variability in 256 kidney transplant recipients. The relationships among tacrolimus exposure, graft function delay (DGF), and acute rejection (AR) were further explored. Findings. The CYP3A5 genotype were strongly associated with tacrolimus concentration/dose ratio (C0/D). Additionally, ABCB1 (rs1045642 and rs2032582) and ABCC2 (rs3740066) were found to have potential independent effects on early tacrolimus C0/D in multivariate analysis. Red blood counts and albumin level were the most significant clinical factors associated with tacrolimus C0/D. Wuzhi capsule also exerted an effect on tacrolimus PK. A model combined with pharmacogenetic and clinical factors explained 43.4% tacrolimus PK variability compared with 16.3% on the basis of CYP3A5 genotype only. Notably, increasing tacrolimus concentrations in the early postoperative stage were associated with AR, but not DGF. Conclusions. Combined analysis of genotype and specific clinical factors is important for the formulation of precise tacrolimus dose regimens in the early stage after kidney transplantation.
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