Coupled reliability model of biodeterioration, chloride ingress and cracking for reinforced concrete structures

Maintaining and operating civil infrastructure systems has been recognized as a critical issue worldwide. Among all possible causes of safety reduction during the structural lifetime, deterioration is particularly important. Structural deterioration is usually a slow time-dependent process controlled by safety and operation threshold specifications. This paper presents a model of RC deterioration by coupling biodeterioration (i.e., chemical, physical and mechanical action of live organisms), steel corrosion, and concrete cracking. The final purpose of the model is to compute the reduction of the concrete section and the area of steel reinforcement in order to assess the change of structural capacity with time. Given the uncertainties in both the parameters and the model, the probabilistic nature of loads, the material properties and the diffusion process are taken into account to evaluate structural reliability. The model is illustrated with an example where the inelastic behavior of a pile subject to random loading is considered. The results of the analysis have shown that the effect of biodeterioration on the structural performance is significant and can cause an important reduction of its lifetime. On the whole, the paper states that modeling the effects of biodeterioration in RC structures should be included as part of infrastructure planning and design, especially, when they are located in aggressive environments.     

Using the Physically Based Constitutive Model and Processing Maps to Understand the Hot Deformation Behavior of 2304 Lean Duplex Stainless Steel

Metallurgical and Materials Transactions A - The hot deformation behavior of 2304 lean duplex stainless steel was investigated by means of processing maps and physically based constitutive modeling...     

Characterization and in vitro evaluation of electrospun aligned-fiber membranes of poly(L-co-D,L-lactic acid)

poly(L-co-D,L-lactic acid) (PLDLA) is a bioresorbable and biocompatible copolymer obtained from the combination of L -lactic and D , L -lactic monomers. PLDLA membranes formed by aligned fibers were prepared by AC/DC electrospinning. Solutions of 8 and 10 wt % of PLDLA were used and membranes were collected by a rotating cylindrical collector. The results showed a slight increase in the fiber diameter with the increase in the polymer concentration. Fourier transform infrared spectroscopy results showed no changes in the chemical structure. Dynamic mechanical analysis results showed an increase in the storage modulus and a decrease in glass-transition temperature for the 10 wt % samples, which was corroborated by differential scanning calorimetry. Thermogravimetric analysis showed a slight variation of the peak degradation temperature. Nevertheless, the samples did not present solvent residues. The membranes were tested in vitro using adipose-derived mesenchymal stem cells (ASCs). The ASCs proliferated after 1, 7, and 14 days of culture, maintaining a spindle-like morphology, which evidences their potential for tissue engineering applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47657.     

Distribution of vanadium(V) species between soil and plants in the vicinity of vanadium mine

The distribution of vanadium(V) species between soil and plants around the vanadium mine have been studied. The mine dam spilled water around this area after collapsing some time ago. V(V) species were determined by electrothermal atomic absorption spectrometry (ETAAS) after leaching of vanadium(V) compounds with 0.1M of Na2CO3, with a limit of detection 0.2 microg g(-1). The validity of V(V) determination had been confirmed by the spike recovery and of the total amount of vanadium by the analysis of CRM's with good correspondence of found to certified values. The concentration of V(V) species were found to be in the range of 620-1680 microg g(-1) in soil and 4-6 microg g(-1) in grass samples, respectively. The total amount of vanadium in soil varied from 1570 to 3600 microg g(-1) and from 8 to 13 microg g(-1) in grass. The results indicate that considerable amount of vanadium (about 50%) in soils and plants is present as V(V) species.     

The impact of the RGD peptide on osteoblast adhesion and spreading on zinc-substituted hydroxyapatite surface

The incorporation of zinc into the hydroxyapatite structure (ZnHA) has been proposed to stimulate osteoblast proliferation and differentiation. Another approach to improve cell adhesion and hydroxyapatite (HA) performance is coating HA with adhesive proteins or peptides such as RGD (arginine–glycine–aspartic acid). The present study investigated the adhesion of murine osteoblastic cells to non-sintered zinc-substituted HA disks before and after the adsorption of RGD. The incorporation of zinc into the HA structure simultaneously changed the topography of disk’s surface on the nanoscale and the disk’s surface chemistry. Fluorescence microscopy analyses using RGD conjugated to a fluorescein derivative demonstrated that ZnHA adsorbed higher amounts of RGD than non-substituted HA. Zinc incorporation into HA promoted cell adhesion and spreading, but no differences in the cell density, adhesion and spreading were detected when RGD was adsorbed onto ZnHA. The pre-treatment of disks with fetal bovine serum (FBS) greatly increased the cell density and cell surface area for all RGD-free groups, overcoming the positive contribution of zinc to cell adhesion. The presence of RGD on the ZnHA surface impaired the effects of FBS pre-treatment possibly due to competition between FBS proteins and RGD for surface binding sites.     

Prospective LCA of Waste Electrical and Electronic Equipment Thermo-Chemical Recycling by Pyrolysis

Waste electrical and electronic equipment (WEEE) is a particularly difficult waste to manage, characterized by hazardous and valuable chemicals. Emerging chemical recycling technologies are developed to unveil the possibility of sustainable treatment providing valuable resources from WEEE. This study develops a framework for prospective life cycle assessment (LCA) to explore a range of future scenarios in which the technology can be operated with low environmental impact. This is demonstrated in a case study focusing on plastics from WEEE, which are currently predominantly incinerated. The results reveal environmental benefits by WEEE treated via chemical recycling. In terms of climate change impacts, the best-case scenario of chemical recycling shows a reduction potential of 74 % compared to current treatment.