Comparison of different techniques to study the nanostructure and the microstructure of cementitious materials with and without superabsorbent polymers

It is difficult to study the microstructural porosity in time without destroying the samples and stopping hydration. Current techniques mainly involve mercury intrusion porosimetry and microscopic analysis. These destructive techniques are able to give information on the microstructure, but the nanostructure is affected due to sample preparation. Dynamic vapour sorption is a technique which is not often used to study the nanostructure of cementitious materials and requires the application of different models. Furthermore, nuclear magnetic resonance can be applied to non-destructive study not only the total water content but also the pore size distribution by comparing the T2 relaxation times, and can be combined with cryoporometry. In this paper, these different measuring techniques are compared and linked to each other. The obtained nano- and microstructures are compared to different models found in literature. Pore sizes in the range of 1.5–2 nm and of 8–12 nm are found, reflecting the gel pores. In addition, some bigger capillary pores are found. The measuring techniques are complementary to each other as they study different pore size ranges and are based on different phenomena.</p

Applying a biodeposition layer to increase the bond of a repair mortar on a mortar substrate

One of the major concerns in infrastructure repair is a sufficient bond between the substrate and the repair material, especially for the long-term performance and durability of the repaired structure. In this study, the bond of the repair material on the mortar substrate is promoted via the biodeposition of a calcium carbonate layer by a ureolytic bacterium. X-ray diffraction and scanning electron microscopy were used to examine the interfaces between the repair material and the substrate, as well as the polymorph of the deposited calcium carbonate. The approximately 50 mu m thick biodeposition film on the mortar surface mostly consisted of calcite and vaterite. Both the repair material and the substrate tended to show a good adherence to that layer. The bond, as assessed by slant shear specimen testing, was improved by the presence of the biodeposition layer. A further increase was found when engineering the substrate surface using a structured pattern layer of biodeposition. (C) 2017 Elsevier Ltd. All rights reserved

Experimental application of sum rules for electron energy loss magnetic chiral dichroism

We present a derivation of the orbital and spin sum rules for magnetic circular dichroic spectra measured by electron energy loss spectroscopy in a transmission electron microscope. These sum rules are obtained from the differential cross section calculated for symmetric positions in the diffraction pattern. Orbital and spin magnetic moments are expressed explicitly in terms of experimental spectra and dynamical diffraction coefficients. We estimate the ratio of spin to orbital magnetic moments and discuss first experimental results for the Fe L_{2,3} edge.Comment: 11 pages, 2 figure

Testing superabsorbent polymer (SAP) sorption properties prior to implementation in concrete: results of a RILEM Round-Robin Test

This article presents the results of a round-robin test performed by 13 international research groups in the framework of the activities of the RILEM Technical Committee 260 RSC "Recommendations for use of superabsorbent polymers in concrete construction''. Two commercially available superabsorbent polymers (SAP) with different chemical compositions and gradings were tested in terms of their kinetics of absorption in different media; demineralized water, cement filtrate solution with a particular cement distributed to every participant and a local cement chosen by the participant. Two absorption test methods were considered; the tea-bag method and the filtration method. The absorption capacity was evaluated as a function of time. The results showed correspondence in behaviour of the SAPs among all participants, but also between the two test methods, even though high scatter was observed at early minutes of testing after immersion. The tea-bag method proved to be more practical in terms of time dependent study, whereby the filtration method showed less variation in the absorption capacity after 24 h. However, absorption followed by intrinsic, ionmediated desorption of a specific SAP sample in the course of time was not detected by the filtration method. This SAP-specific characteristic was only displayed by the tea-bag method. This demonstrates the practical applicability of both test methods, each one having their own strengths and weaknesses at distinct testing times

Sr analyses from only known Scandinavian cremation cemetery in Britain illuminate early Viking journey with horse and dog across the North Sea

The barrow cemetery at Heath Wood, Derbyshire, is the only known Viking cremation cemetery in the British Isles. It dates to the late ninth century and is associated with the over-wintering of the Viking Great Army at nearby Repton in AD 873–4. Only the cremated remains of three humans and of a few animals are still available for research. Using strontium content and isotope ratios of these three people and three animals–a horse, a dog and a possible pig–this paper investigates the individuals’ residential origins. The results demonstrate that strontium isotope ratios of one of the adults and the non-adult are compatible with a local origin, while the other adult and all three animals are not. In conjunction with the archaeological context, the strontium isotope ratios indicate that these individuals most likely originated from the area of the Baltic Shield–and that they died soon after arrival in Britain. This discovery constitutes the first solid scientific evidence that Scandinavians crossed the North Sea with horses, dogs and other animals as early as the ninth century AD

Recommendations of RILEM TC 260-RSC for using superabsorbent polymers (SAP) for improving freeze–thaw resistance of cement-based materials

This recommendation is focused on application of superabsorbent polymers (SAP) for the improvement of the resistance of cement-based materials to freeze—thaw attack with or without deicing salts. A simple approach to the determination of the amount and properties of SAP as well as methods to verify SAP effectiveness for frost resistance protection are presented

Autonomous regeneration of concrete structures by incorporation of self-healing mechanisms

info:eu-repo/semantics/publishe

A multi-targeted drug candidate with dual anti-HIV and anti-HSV activity

Human immunodeficiency virus (HIV) infection is often accompanied by infection with other pathogens, in particular herpes simplex virus type 2 (HSV-2). The resulting coinfection is involved in a vicious circle of mutual facilitations. Therefore, an important task is to develop a compound that is highly potent against both viruses to suppress their transmission and replication. Here, we report on the discovery of such a compound, designated PMEO-DAPym. We compared its properties with those of the structurally related and clinically used acyclic nucleoside phosphonates (ANPs) tenofovir and adefovir. We demonstrated the potent anti-HIV and -HSV activity of this drug in a diverse set of clinically relevant in vitro, ex vivo, and in vivo systems including (i) CD4⁺ T-lymphocyte (CEM) cell cultures, (ii) embryonic lung (HEL) cell cultures, (iii) organotypic epithelial raft cultures of primary human keratinocytes (PHKs), (iv) primary human monocyte/macrophage (M/M) cell cultures, (v) human ex vivo lymphoid tissue, and (vi) athymic nude mice. Upon conversion to its diphosphate metabolite, PMEO-DAPym markedly inhibits both HIV-1 reverse transcriptase (RT) and HSV DNA polymerase. However, in striking contrast to tenofovir and adefovir, it also acts as an efficient immunomodulator, inducing β-chemokines in PBMC cultures, in particular the CCR5 agonists MIP-1β, MIP-1α and RANTES but not the CXCR4 agonist SDF-1, without the need to be intracellularly metabolized. Such specific β-chemokine upregulation required new mRNA synthesis. The upregulation of β-chemokines was shown to be associated with a pronounced downmodulation of the HIV-1 coreceptor CCR5 which may result in prevention of HIV entry. PMEO-DAPym belongs conceptually to a new class of efficient multitargeted antivirals for concomitant dual-viral (HSV/HIV) infection therapy through inhibition of virus-specific pathways (i.e. the viral polymerases) and HIV transmission prevention through interference with host pathways (i.e. CCR5 receptor down regulation)