The upgrade of the ALICE TPC with GEMs and continuous readout

The upgrade of the ALICE TPC will allow the experiment to cope with the high interaction rates foreseen for the forthcoming Run 3 and Run 4 at the CERN LHC. In this article, we describe the design of new readout chambers and front-end electronics, which are driven by the goals of the experiment. Gas Electron Multiplier (GEM) detectors arranged in stacks containing four GEMs each, and continuous readout electronics based on the SAMPA chip, an ALICE development, are replacing the previous elements. The construction of these new elements, together with their associated quality control procedures, is explained in detail. Finally, the readout chamber and front-end electronics cards replacement, together with the commissioning of the detector prior to installation in the experimental cavern, are presented. After a nine-year period of R&D, construction, and assembly, the upgrade of the TPC was completed in 2020.publishedVersio

Corrosion performance of mild steel and epoxy coated rebar in concrete under simulated harsh environment

Purpose The purpose of this paper is to present the results of a two-year long study carried out in order to evaluate the corrosion performance of mild steel bare bars (BB) and epoxy-coated rebar (ECR) in concrete under a simulated harsh environment of chlorides. Design/methodology/approach The blocks are subjected to Southern Exposure testing. The electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) and Tafel plot are performed to measure the polarization resistance and corrosion current densities of these rebars. Knife-peel test was performed to assess the adhesion between epoxy and underlying steel after two years of exposure. Findings Mild steel BB showed a high corrosion current density of 1.24 µA/ cm2 in Tafel plots and a very low polarization resistance of 4.5 kΩ cm2 in LPR technique, whereas very high charge transfer resistance of 1672 and 1675 kΩ cm2 is observed on ECR and ECR with controlled damage (ECRCD), through EIS technique, respectively. EIS is observed to be a suitable tool to detect the defects in epoxy coatings. After two years of immersion in 3.89 percent NaCl− solution, the mild steel BB were severely corroded and a considerable weight loss was observed, whereas under heavy chloride attack, ECR showed no deterioration of epoxy coating and neither any corrosion of underlying steel. Results of this study show that the durability of reinforced concrete (RC) structures with respect to corrosion could be enhanced by using ECR, especially in harsh climatic conditions. Originality/value The corrosion performance of mild steel and ECR in concrete under a simulating splash zone environment is evaluated. EIS was used to evaluate the health of epoxy and corrosion state of underneath steel rebars. EIS was able to detect the defects in epoxy. The durability of RC structures could be enhanced in harsh climate regions by using ECR.The funding for this research was provided by the National Priorities Research Program of the Qatar National Research Fund (a member of Qatar Foundation) under the award no. NPRP 7-410-2-169. Authors would also like to thank Qatar Metals Coating Company (Q-Coat), Qatar Steel for providing the materials and support. The statements made herein are solely the responsibility of the authors and do not necessarily reflect the opinions of the Sponsor.Scopu

Influence of pH on chloride binding isotherms for cement paste and its components

In this paper, chloride (Cl−) binding isotherms are developed for cement hydration compounds, specifically, calcium-silicate-hydrates (CSH) and AFm phases including mono-sulfate aluminate, hydroxy-AFm, monocarbonate-AFm, and hemicarbonate-AFm, in simulated concrete pore solutions to account for the effect of pH and the presence of other ions. pH and the presence of other ions have a strong influence on the Cl− binding capacity of cement compounds, which have not been taken into consideration in previous research. A novel experimental technique is developed to characterize the binding capacity from very low (1 mM) to very high concentrations (5 M). To overcome the existing challenges of measuring both low and high Cl− concentrations without significant dilution and in the presence of SO42− and OH− ions, a potentiometric method was used. The amorphous CSH in the hydrated cement paste; thus, the heterogeneity of the hydrated components of the cement paste was also quantified and accounted for in this study.The funding for this research was provided partly by the National Priorities Research Program of the Qatar National Research Fund (a member of the Qatar Foundation) under the award no. NPRP 7-410-2-169 and the United States National Science Foundation under the award no. 1642488 . The authors thank Professor Melot, Professor Marinescu, their students: Nicholas H. Bashian and Eric Johnson, and Mohit Dave at the University of Southern California for providing access to their laboratory facilities to perform some of the experiments described in this paper. Authors are also grateful to Lafarge, U.S. for donating the cement used in the experimental work.Scopu

Reinforced Concrete Degradation in the Harsh Climates of the Arabian Gulf: Field Study on 30-to-50-Year-Old Structures

This paper presents the results of a field study carried out on three reinforced concrete (RC) structures built in the 1960s, 1970s, and 1980s to determine the main load (environmental) and the resistance (for example, the concrete quality and clear cover) factors affecting the durability of the infrastructure in the harsh environmental conditions of the Arabian Gulf region. The effects of degradation, such as the carbonation depths and chloride concentration profiles, in the columns, beams and slabs were determined from concrete core samples. To determine the durability factors, the concrete resistivity to electrical charge, the rapid chloride permeability, and the sorpitivity were measured. Digital image processing was performed to estimate the cement contents and the proportions of other ingredients used in the concrete samples. In most of the structural members, the chloride threshold for steel depassivation had been surpassed and the carbonation had reached the steel surface. The spalling of the concrete cover was observed with severe corrosion damage to the reinforcing bars. It is expected that this study will help understand the degradation phenomena in RC structures in the Gulf region and similar hot, humid, and saline environments. The results will help to establish the input parameters for the chloride diffusion and carbonation models in aggressive environmental conditions. Because the concrete quality directly impacts the initiation of many deterioration processes such as corrosion of the steel reinforcement and carbonation, the results could be used to predict the remaining service life of existing RC structures with similar concrete properties.The funding for this research was provided by the National Priorities Research Program of the Qatar National Research Fund (a member of the Qatar Foundation) under the award NPRP 7-410-2-169

Advancements in concrete mix designs: High-performance and ultrahigh-performance concretes from 1970 to 2016

This paper reviews the methods adopted to produce high-performance concrete (HPC) and ultrahigh-performance concrete (UHPC). The chronological development of these concretes in terms of their constituents, mixture proportions, mixing protocols, and particle packing models from selected literature are presented. The paper highlights the earliest techniques that were used to obtain cementitious materials with high strength and durability, including pressure mixing and heat curing. The paper also covers the work done on HPC and UHPC since the late 1990s and summarizes the current state of the art. Numerous mixture proportions to attain target compressive strengths between 100 and 200 MPa are presented. Higher compressive strengths are achieved with denser mixtures (with practically achievable maximum particle packing densities, i.e., interparticle pores are minimized). In other words, particle packing density is a major attribute in the achievement of low porosity, flowability, durability, and reduced defects in concrete. Therefore, models, theories, and trial methods to achieve a higher packing density in concrete are presented. - 2017 American Society of Civil Engineers.Scopu

Implementation of GSM Module based Smart Aquarium Monitoring and Controlling System

The aquarist feeds the fish in the aquarium tanks which demands a proper setup for maintenance. The challenges faced are alterations in water quality, fish care, temperature regulation, light control, and difficulty in manually monitoring the aquarium’s conditions. Consequently, close monitoring of the physical parameters and improvement of water conditions become essential. As a result, this system utilizes a Global System for Mobile (GSM) module for aquarium observation and control, described real-time sensor capabilities. It conducts temperature checks, detects water pH levels, manages the aeration system, and handles water renewal operations. Based fish aquarium is a fully automated and remotely monitored aquarium, fully capable of operating without human intervention or interaction. The mechanical feed design, web-based fish feeding, and remote monitoring of all parameters are the crucial components of the project. Feed level, water temperature, pH, and water level are some of the parameters. These can be accessible through a phone app or through a website on a computer. This method’s objective is to reduce errors and effort required by humans to manage an aquarium containing aquatic animals. As a result, this system achieves optimal results in terms of accuracy and efficiency

The upgrade of the ALICE TPC with GEMs and continuous readout

The upgrade of the ALICE TPC will allow the experiment to cope with the high interaction rates foreseen for the forthcoming Run 3 and Run 4 at the CERN LHC. In this article, we describe the design of new readout chambers and front-end electronics, which are driven by the goals of the experiment. Gas Electron Multiplier (GEM) detectors arranged in stacks containing four GEMs each, and continuous readout electronics based on the SAMPA chip, an ALICE development, are replacing the previous elements. The construction of these new elements, together with their associated quality control procedures, is explained in detail. Finally, the readout chamber and front-end electronics cards replacement, together with the commissioning of the detector prior to installation in the experimental cavern, are presented. After a nine-year period of R&D, construction, and assembly, the upgrade of the TPC was completed in 2020