Electrical resistivity and electrical impedance measurement in mortar and concrete elements: A systematic review

This paper aims at analyzing the state-of-the-art techniques to measure electrical impedance (and, consequently, electrical resistivity) of mortar/concrete elements. Despite the validity of the concept being widely proven in the literature, a clear standard for this measurement is still missing. Different methods are described and discussed, highlighting pros and cons with respect to their performance, reliability, and degree of maturity. Both monitoring and inspection approaches are possible by using electrical resistivity measurements; since electrical resistivity is an important indicator of the health status of mortar/concrete, as it changes whenever phenomena modifying the conductivity of mortar/concrete (e.g., degradation or attacks by external agents) occur, this review aims to serve as a guide for those interested in this type of measurements

GCMC Simulations in Zeolite MFI and Activated Carbon for Benzene Removal from Exhaust Gaseous Streams

ABSTRACT A set of GCMC molecular simulations has been performed over zeolite MFI and disordered, activated carbon structures, to determine adsorption isotherms and thermodynamic characteristics of a gaseous mixture adsorbed into porous structures, activated carbon, all-silica MFI and hydrophilic FAUNaY zeolites. Simulations have been carried out over a multicomponent mixture, in order to mimic a more realistic gaseous emission, when benzene has to be removed. Validation of the model has been obtained by comparison with available experimental data. Different conditions, as temperature and total pressure of the stream have been taken into account. Results give a ranking for the most appropriate process conditions, and for the best materials to be employed for the separation process. Data fitting with the Sips thermodynamic model has also been provided for benzene isotherms. Our procedure is simple and may be adapted to different temperature and pressure conditions, adsorbate or adsorbent characteristics, and gas composition

Hydrogen sulphide removal from biogas by zeolite adsorption: part I. GCMC molecular simulations

In this work Grand Canonical Monte Carlo (GCMC) simulations have been used to study hydrogen sulfide (H2S) removal from biogas streams by different zeolites such as FAU (Faujasite, NaX and NaY), LTA (zeolite A (Lynde division, Union Carbide)) and MFI (Zeolite Socony Mobil \u2013 five). Additionally, quantum mechanics (QM) molecular simulations have been performed to obtain structures and partial charges of some sorbates. The computational procedure adopted has been validated by comparison with experimental data available for H2S removal in atmospheric environment by zeolite NaY. In order to obtain a priority list in terms of both H2S isotherms and adsorption selectivity, adsorption simulations for pure H2S at low pressures and for a prototype biogas mixture (i.e., CO2, CH4, and H2S) have been performed and compared. The adsorption mechanisms and competition for accessible adsorption sites in terms of thermodynamic behavior have been also examined. Overall, the results obtained in this work could be routinely applied to different case studies, thus yielding deeper qualitative and quantitative insights into adsorption pollutant removal processes in environmental fields

Hydrogen sulphide removal from biogas by zeolite adsorption: part II. A MD simulation

Coupled Grand Canonical-Canonical Monte Carlo and molecular dynamics (MD) simulation techniques have been used to investigate in details the adsorption of low-pressure hydrogen sulfide (H2S) in zeolites, and the selective adsorption behavior towards carbon dioxide and methane, the main biogas constituents. Results from Monte Carlo (MC) simulations indicated, among many others, zeolite NaY as the best option for H2S removal. Afterwards, deterministic simulations have been performed to investigate hydrogen sulfide pathway inside NaY, with respect to other adsorbed molecules (methane and carbon dioxide), as a function of zeolite loading and H2S partial pressure (i.e., biogas composition). Thermodynamic evaluations for 2D molecular dynamic simulations in terms of binding energy evolution vs. time confirm and reinforce the results obtained from Monte Carlo simulations, testifying the greater affinity for H2S to NaY zeolite framework. Results give also new quantitative insights in terms of pathways, binding energies, and equilibration time inside zeolite pores for stabilization