A novel flame retardant, silicone elastomeric nanoparticle (S-ENP) with
T
g of −120
°C and particle size of ∼100
nm has been developed and used as a modifier for polyamide 6 (nylon-6). It has been ...found that S-ENP can not only increase the toughness and improve the flame retardancy of nylon-6 but also helps unmodified clay exfoliate in nylon-6 matrix. It has been also found that the S-ENP and exfoliated clay platelet in nylon-6 have a synergistic flame retardant effect on nylon-6. A novel flame retardant nanocomposite of nylon-6/unmodified clay/S-ENP with high toughness, high heat resistance, high stiffness and good flowability has been prepared and a mechanism of synergistic flame retardancy has also been proposed.
•The properties of calcined PG is different from that of FGD, causing concern in application.•PG plaster sets slow and has a much lower strength in alkaline condition.•Alkali has magnitude effect on ...the hydration process of PG plaster and gypsum morphology.•The impurities in PG perform as retarder and microstructure modifiers in alkaline range.
Phosphogypsum (PG) which is a waste byproduct of fertilizer production is the promising source of the gypsum industry. In order to explore the application of hemihydrate PG (HPG) as a substitute of hemihydrate gypsum, the setting and hardening characters of HPG plaster at different pH after neutralization were examined and contrasted with hemihydrate flue gas desulfurization gypsum (HFGD) plaster. Results showed that HPG plaster sets slow with a fall in strength and this effect was more pronounced after retarders were added when pH increased from 5.85 to 11.08. By contrast, HFGD plaster sets fast and without strength variation in the similar alkaline range. Microscopic studies including chemically combined water and temperature evolution curves of HPG plaster revealed that with the increase of the pH, the hydration reaction mechanism of hemihydrate and the gypsum crystal morphology were radically changed due to the fact of interaction between impurities and alkali. Consequently, HPG plaster is very different from HFGD plaster and its application in thealkaline condition was restricted.
Apoptosis of virus infected cells can restrict or dampen full blown virus propagation and this can serve as a protective mechanism against virus infection. Consequently, viruses can also delay ...programmed cell death by enhancing the expression of anti-apoptotic proteins. Human Bcl-2 is expressed on the surface of the mitochondrial membrane and functions as the regulator of the delicate balance between cell survival and apoptosis. In this report, we showed that the replication and transcription activator (RTA) encoded by KSHV ORF 50, a key regulator for KSHV reactivation from latent to lytic infection, upregulates the mRNA and protein levels of Bcl-2 in 293 cells, and TPA-induced KSHV-infected cells. Further analysis revealed that upregulation of the cellular Bcl-2 promoter by RTA is dose-dependent and acts through targeting of the CCN(9)GG motifs within the Bcl-2 promoter. The Bcl-2 P2 but not the P1 promoter is primarily responsive to RTA. The results of ChIP confirmed the direct interaction of RTA protein with the CCN(9)GG motifs. Knockdown of cellular Bcl-2 by lentivirus-delivered small hairpin RNA (shRNA) resulted in increased cell apoptosis and decreased virion production in KSHV-infected cells. These findings provide an insight into another mechanism by which KSHV utilizes the intrinsic apoptosis signaling pathways for prolonging the survival of lytically infected host cells to allow for maximum production of virus progeny.
•The hydration mechanism of hemihydrate was proved to be dissolution and precipitation via in-situ ESEM observation.•The detailed dissolution process of hemihydrates were revealed: surface ...dissolution and particle fragmentation.•Gypsum precipitates at the beginning, crystallizes rapidly after 20 min hydration and tends to be stable after 2 h hydration.•The hydration reaction of hemihydrate is a process of particle size reduction.
Although the dissolution/precipitation mechanism for hemihydrate hydration is widely recognized, this study gives more detailed information for the hydration of hemihydrate by in-situ observation using environmental scanning electron microscope (ESEM). The hydration process was also monitored through numerous parameters, including phase, hydration degree, ion concentration, particle size, and morphology evolution with hydration time. The results indicated that the hemihydrate particles are porous containing numerous nanopores. It dissolves from the surface available to water, forming a transient flocculent intermediate with widen pores. Afterwards, large particles break to small particles due to crack connection and then continue to dissolve, leaving a few stubborn spots last to disappear. At the same time, gypsum precipitates in the first few minutes and evolves to the final crystal structure through three main stages. This work not only provides the most direct evidence for the hydration mechanism, but also gives new insights to enrich it further. It is helpful to adjust the hydration process of gypsum plaster and provide a significant reference for modeling.
•Use of RBP has good environmental and economic benefits.•RBP has nucleation and filling effects.•RBP has unique physical features and chemical properties.•RBP can adjust the workability of cement ...paste.
Recycled brick powder (RBP) are reused in cementitious materials by partially replacing cement in this study, the role of which was investigated in terms of workability of fresh cement paste and microstructure of the hardened cement paste. The results shows that the replacement ratio of RBP is inversely proportional to the hydration heat. The particle size of RBP plays an important role in hydration process of cement. The incorporation of RBP reduces the consistence and increases the yield stress and viscosity. Besides, it would reduce the increasing rate of hydration products of the system, causing a delay in setting.
Influences of polymer-based grinding aid（PGA） on the damage process of concrete exposed to sulfate attack under dry-wet cycles were investigated. The mass loss, dynamic modulus of elasticity（Erd）, ...and S and Ca element contents of concrete specimens were measured. Scanning electron microscopy（SEM）, mercury intrusion porosimetry（MIP）, and X-ray diffractometry（XRD） were used to investigate the changing of microstructure of interior concrete. The results indicated that PGA was capable of reducing the mass loss and improving the sulfate attack resistance of concrete. X-ray fluorescence（XRF） analysis revealed that PGA delayed the transport process of sulfate ions and Ca ions. In addition, MIP analysis disclosed that the micropores of concrete with PGA increased in the fraction of 20-100 nm and decreased in the residues of 200 nm. Compared with the blank sample, concrete with PGA had more slender and well-organized hydration products, and no changes in hydration products ratio or type were observed.
•Nano-silica increase sulfate attack resistance of C3S through the modification of the C-S-H gel and CH.•The introduction of aluminum from FA/GGBS increase the risk of sulfate attack.•The C-S-H gel ...modified by NS has high resistance to sulfate erosion.
Tricalcium silicate (C3S), the most crucial component in Portland cement, determines the durability of cementitious materials. This research studied the effect of nano-silica (NS) on the sulfate attack resistance of the C3S hydration system. Results showed that NS retarded the sulfate attack process in the C3S system, by preventing the expansive transformation of calcium hydroxide (CH) to gypsum. Higher aluminum content in FA and GGBS cause more serious deterioration. The C-(A)-S-H gel in the systems with FA and GBBS was more easily decomposed in sulfate attack. C-S-H in the NS-modified samples had higher sulfate attack resistance than that in the SF/GGBS/FA modified ones.
•Chloride penetration into RAC subjected to wetting–drying cycles and flexural loading was investigated.•Chloride diffusion coefficient for RAC was determined by the error function solution to Fick’s ...second law.•Chloride binding capacity of RAC was analyzed.•Chloride ions transport progress in RAC were monitored by in situ X-ray computed tomography.
This paper presents the experimental results of chloride penetration into Recycled Aggregate Concrete (RAC) subjected to sodium chloride solution coupled with wetting–drying cycles and flexural loading. Detailed chloride profiles were tested by potentiometric titrimeter which show the variation of water-soluble (free) and acid-soluble (total) chloride contents in RAC. For purpose of studying the influence of coarse Recycled Concrete Aggregate (coarse RCA) on the chloride penetration, different replacement of coarse RCA were used by ranging from 0%, 30%, 50%,70% and 100% ratio by weight. Additionally, the effect of mineral admixtures and stress ratio on such penetration was studied. The chloride diffusion coefficient for RAC was calculated by the error function solution to Fick’s second law. The chloride binding capacity of RAC was also analyzed. Finally, X-ray computed tomography (X- CT) was used to estimate chloride transport progress in RAC for the first time. The results show that the chloride profiles in RAC is dependent on the mixtures and the flexural loading applied to the concrete. Coarse RCA induces considerable influence on chloride penetration in concrete. The addition of mineral admixtures makes concrete more compactness hinder chloride ions ingress into interior concrete. The increased magnitude of flexural loading results in higher chloride contents in RAC probably due to micro-cracks generated and extended. The influence of coarse RCA replacement and mineral admixtures on the chloride binding capacity is obvious, but the influence of stress ration is no regularity. The results of X-CT indicate that the solution does not transport through the old attached mortar in coarse RCA.
The large-scale recycling of concrete waste and its high-value utilization are key research topic in the field of sustainable building materials. This paper investigated the properties of fully ...recycled mortar made with thermoactivated recycled cement and recycled fine aggregate (RFA) up to 100%. The 600 °C thermoactivated recycled cement contained active compounds such as C2S and CaO. Substituting recycled cement for ordinary Portland cement reduced the hydration reaction and enlarged the pore structure of paste, but mixing active admixture could improve the micro-structure of recycled cement paste. Incorporating recycled cement and RFA decreased the mechanical strength of mortar, as well as elevated the drying shrinkage and transport properties. The detrimental impact of incorporating recycled cement on the performance degradation was more prominent than that of RFA incorporation. Nevertheless, the properties of fully recycled mortar with both 100% recycled cement and RFA still achieved a relatively satisfactory level. Besides, recycled mortar made with recycled cement derived from cement paste waste exhibited superior performance to that made with recycled cement from concrete waste. Substituting active admixture for 10% recycled cement could obviously improve the strength and permeability resistance of fully recycled mortar. Therefore, optimizing the replacement rate of recycled cement, RFA and active admixture is expected to prepare the fully recycled mortar with good performance. The maximal utilization of concrete waste could be achieved through preparing fully recycled mortar with the use of recycled cement and RFA completely instead of natural sand and ordinary Portland cement. This approach resulted in lower CO2 emissions and provided superior environmental benefits.
•Durability of concrete under sulfate-chloride, dry-wet cycle and flexural load was investigated.•Compared to long-term loading, short-term loading accelerated the damage of concrete slightly.•Load ...accelerated the damage of concrete in tensile region, while retarded it in compressive zone.
This paper presents an experimental study on the damage progress of concrete subject to combined sulfate-chloride attack under drying-wetting cycles and flexural loading. Two different loading regimes (long-term loading and short-term loading), which contain three different stress levels and both tensile and compressive regions, are applied in this test. The research results indicate that flexural loading accelerates the deterioration of concrete subject to sulfate and chloride attack under dry-wetting cycles. The damage of concrete was increased with the increasing stress level under both long-term loading and short-term loading. Compare to long-term loading, concrete under short-term loading shows slight damage. In the tensile region, loading accelerate the sulfate and chloride attack of the concrete, while in the compressive region, loading improve resistance of concrete against sulfate and chloride attack and this effect is more obvious with the increase of stress levels. It was also found that mineral admixtures, such as fly ash and ground granulated blast slag can improve the resistance of concrete under combined sulfate-chloride attack, with drying-wetting cycles and flexural loading.
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