scholarly journals Long-Term Strength Evolution in Ambient-Cured Solid-Activator Geopolymer Compositions

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 143
Author(s):  
Vincent Wong ◽  
William Jervis ◽  
Benjamin Fishburn ◽  
Takafumi Numata ◽  
William Joe ◽  
...  
Keyword(s):  
Early Stage ◽  
Sodium Metasilicate ◽  
High Energy ◽  
Strength Development ◽  
Gel Formation ◽  
Factors Affecting ◽  
Setting Times ◽  
Binder Ratio ◽  
Alkaline Activator ◽  
Aluminium Silicate

The major downsides of cement manufacturing are the high CO2 emissions and high energy usage. Geopolymers, which are fabricated by activation of blends of fly ash (FA) and ground granulated blast furnace slag (GGBFS) using an alkaline activator, offer a promising solution to this issue. However, to enhance the replacement of cement in construction applications, geopolymer compositions have to be designed such that they can be activated on site by just adding water, similar to how cements are used. Therefore, the present work uses solid sodium metasilicate (MS, Na2SiO3) as the alkaline activator in order to design an add-water-style FA/GGBFS-based geopolymer composition. These compositions were designed by optimising the binder (FA/GGBFS) ratio, Na2SiO3/binder ratio, and water/binder ratio individually to assess the effects of these parameters on the setting times and mechanical (flexural and compressive) strengths over extended curing times (three months). The major factors affecting the strength development and setting times (initial and final) were the amounts of GGBFS and Na2SiO3, with the former demonstrating the more dominant effect. The consistent strength development with curing time was attributed to calcium aluminium silicate hydrate (CASH) gel formation in the early curing times which was affected by the slag addition levels, and sodium aluminium silicate hydrate (NASH) gel formation at later curing times which was influenced by the metasilicate addition levels. The metasilicate amounts were observed to impact on CASH gel formation in early stage curing. Geopolymer compositions with FA/GGBFS ratio of 35/65 and MS/water ratios of 0.2 showed high compressive strengths of ~70 MPa at 28 days, which are superior to values seen in conventional ordinary Portland cement (OPC) mixes for the same curing times.

scholarly journals Slurry Preparation Effects on the Cemented Phosphogypsum Backfill through an Orthogonal Experiment

Minerals ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 31 ◽  
Author(s):  
Xibing Li ◽  
Yanan Zhou ◽  
Quanqi Zhu ◽  
Shitong Zhou ◽  
Chendi Min ◽  
...  
Keyword(s):  
Orthogonal Experiment ◽  
Dominant Role ◽  
Solid Content ◽  
Strength Development ◽  
Range Analysis ◽  
Setting Times ◽  
Stirring Time ◽  
Binder Ratio ◽  
Four Levels ◽  
Slurry Preparation

The cemented phosphogypsum (PG) backfill technique provides a new method for massive consumption of PG, and therefore alleviating the environmental pollution of PG. This study considered the effects of slurry preparation on the performance of cemented PG backfill. A L16(44) orthogonal experiment was designed to analyze four factors, namely the solid content, phosphogypsum-to-binder ratio (PG/B ratio), stirring time and stirring speed, with each factor having four levels. According to the range analysis, the solid content played the dominant role in controlling the bleeding rate, while the setting times strongly depended on the PG/B ratio. In terms of strength development of the backfill, the PG/B ratio was shown to be the most significant factor determining the unconfined compressive strength (UCS), followed by the solid content, stirring time and stirring speed. Furthermore, the results showed that the slurry preparation affected the environmental behavior of impurities that originated in PG. By analyzing the concentrations of impurities in the bleeding water of the slurry as well as the leachates of the tank leaching test, the results showed that the release of F− and SO42− was aggravated clearly with the increase in the PG/B ratio, while the release of PO43− always remained at relatively low levels.

scholarly journals From Exploratory Tunnel to Base Tunnel: Hard Rock TBM Performance Prediction by Means of a Stochastic Approach

2020 ◽  
Vol 53 (12) ◽  
pp. 5473-5487 ◽  
Author(s):  
Andrea Rispoli ◽  
Anna Maria Ferrero ◽  
Marilena Cardu
Keyword(s):  
Performance Prediction ◽  
Early Stage ◽  
Tunnel Boring Machine ◽  
Stochastic Approach ◽  
Critical Issue ◽  
Utilization Factor ◽  
Tbm Performance ◽  
Factors Affecting ◽  
Tunnel Section ◽  
Input Variables

AbstractTunnel boring machine (TBM) performance prediction is often a critical issue in the early stage of a tunnelling project, mainly due to the unpredictable nature of some important factors affecting the machine performance. In this regard, deterministic approaches are normally employed, providing results in terms of average values expected for the TBM performance. Stochastic approaches would offer improvement over deterministic methods, taking into account the parameter variability; however, their use is limited, since the level of information required is often not available. In this study, the data provided by the excavation of the Maddalena exploratory tunnel were used to predict the net and overall TBM performance for a 2.96 km section of the Mont Cenis base tunnel by using a stochastic approach. The preliminary design of the TBM cutterhead was carried out. A prediction model based on field penetration index, machine operating level and utilization factor was adopted. The variability of the parameters involved was analysed. A procedure to take into account the correlation between the input variables was described. The probability of occurrence of the outcomes was evaluated, and the total excavation time expected for the tunnel section analysed was calculated.

scholarly journals Control of the setting reaction and strength development of slag-blended volcanic ash-based phosphate geopolymer with the addition of boric acid

2021 ◽  
Author(s):  
Jean Noël Yankwa Djobo ◽  
Dietmar Stephan
Keyword(s):  
Blast Furnace ◽  
Boric Acid ◽  
Blast Furnace Slag ◽  
Volcanic Ash ◽  
Strength Development ◽  
Main Process ◽  
Reaction Products ◽  
Setting Times ◽  
Granulated Blast Furnace Slag ◽  
Furnace Slag

AbstractThis work aimed to evaluate the role of the addition of blast furnace slag for the formation of reaction products and the strength development of volcanic ash-based phosphate geopolymer. Volcanic ash was replaced by 4 and 6 wt% of ground granulated blast furnace slag to accelerate the reaction kinetics. Then, the influence of boric acid for controlling the setting and kinetics reactions was also evaluated. The results demonstrated that the competition between the dissolution of boric acid and volcanic ash-slag particles is the main process controlling the setting and kinetics reaction. The addition of slag has significantly accelerated the initial and final setting times, whereas the addition of boric acid was beneficial for delaying the setting times. Consequently, it also enhanced the flowability of the paste. The compressive strength increased significantly with the addition of slag, and the optimum replaced rate was 4 wt% which resulted in 28 d strength of 27 MPa. Beyond that percentage, the strength was reduced because of the flash setting of the binder which does not allow a subsequent dissolution of the particles and their precipitation. The binders formed with the addition of slag and/or boric acid are beneficial for the improvement of the water stability of the volcanic ash-based phosphate geopolymer.

scholarly journals Interactive effects between travel behaviour and COVID-19: a questionnaire study

2021 ◽  
Author(s):  
Jinbao Zhang ◽  
Jaeyoung Lee
Keyword(s):  
Early Stage ◽  
Travel Behaviour ◽  
Interactive Effects ◽  
Factors Affecting ◽  
Individual Level ◽  
Passenger Volume ◽  
Spatial Autoregressive ◽  
Railway Passenger ◽  
The Individual ◽  
And Control

Abstract This study has two main objectives: (i) to analyse the effect of travel characteristics on the spreading of disease, and (ii) to determine the effect of COVID-19 on travel behaviour at the individual level. First, the study analyses the effect of passenger volume and the proportions of different modes of travel on the spread of COVID-19 in the early stage. The developed spatial autoregressive model shows that total passenger volume and proportions of air and railway passenger volumes are positively associated with the cumulative confirmed cases. Second, a questionnaire is analysed to determine changes in travel behaviour after COVID-19. The results indicate that the number of total trips considerably decreased. Public transport usage decreased by 20.5%, while private car usage increased by 6.4%. Then the factors affecting the changes in travel behaviour are analysed by logit models. The findings reveal significant factors, including gender, occupation and travel restriction. It is expected that the findings from this study would be helpful for management and control of traffic during a pandemic.

scholarly journals Mathematical modeling and experimental study on solid–liquid suspension separation in ultrasonic standing wave field

2021 ◽  
pp. 146134842110229
Author(s):  
Yajing Wang ◽  
Liqun Wu ◽  
Yaxing Wang ◽  
Yafei Fan
Keyword(s):  
Standing Wave ◽  
Sound Pressure ◽  
Acoustic Radiation ◽  
Sound Field ◽  
Radiation Force ◽  
High Energy ◽  
Factors Affecting ◽  
Liquid Suspension ◽  
Ultrasonic Standing Wave ◽  
Solid Liquid

A new method of removing waste chips is proposed by focusing on the key factors affecting the processing quality and efficiency of high energy beams. Firstly, a mathematical model has been established to provide the theoretical basis for the separation of solid–liquid suspension under ultrasonic standing wave. Secondly, the distribution of sound field with and without droplet has been simulated. Thirdly, the deformation and movement of droplets are simulated and tested. It is found that the sound pressure around the droplet is greater than the sound pressure in the droplet, which can promote the separation of droplets and provide theoretical support for the ultrasonic suspension separation of droplet; under the interaction of acoustic radiation force, surface tension, adhesion, and static pressure, the droplet is deformed so that the gas fluid around the droplet is concentrated in the center to achieve droplet separation, and the droplet just as a flat ball with a central sag is stably suspended in the acoustic wave node.

scholarly journals Pots as alternative and sustainable fishing gears in the Mediterranean Sea: an overview

2021 ◽  
Author(s):  
Andrea Petetta ◽  
Massimo Virgili ◽  
Stefano Guicciardi ◽  
Alessandro Lucchetti
Keyword(s):  
Mediterranean Sea ◽  
Early Stage ◽  
Spiny Lobster ◽  
Mesh Size ◽  
Octopus Vulgaris ◽  
Target Species ◽  
Factors Affecting ◽  
Fishing Gears ◽  
Pros And Cons ◽  
The Mediterranean

AbstractStock overexploitation, bycatch, discards and gear impacts on the environment are outstanding issues for Mediterranean fisheries. The adoption of alternative fishing gears is an appealing solution to ensure a more sustainable exploitation of resources. We discuss the pros and cons of pots as alternative gears by reviewing their main designs, spatial distribution and target species in the Mediterranean basin. We assessed the technical factors affecting the catch efficiency of the different pot designs for four target species: spiny lobster, Palinurus elephas; Norway lobster, Nephrops norvegicus; common octopus, Octopus vulgaris and pandalid shrimps, Plesionika spp. We found that pot volume is important to catch Octopus; mesh size to catch Nephrops and Plesionika; entrance surface to catch Octopus, Nephrops and Plesionika; pot shape/colour and entrance shape/position to catch Octopus and Plesionika; and bait type to catch Octopus and Nephrops. The literature review shows that pot fisheries have several considerable advantages over conventional gears, especially in terms of discards, bycatch, seabed impacts (particularly compared with bottom trawls and passive set nets), size and species selectivity, gear depredation, catch quality and gear cost, besides saving time and labour. Disadvantages hampering their wider diffusion include ghost fishing, a low catch of finfish species, the narrow range of species targeted by each pot design and the current early stage of research. These data make a clear case for using pots as alternative gears to traditional ones in the Mediterranean Sea in some areas and seasons to catch certain target species.

scholarly journals Evaluation of Energy Absorption Capabilities of Polyethylene Foam under Impact Deformation

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3613
Author(s):  
Baohui Yang ◽  
Yangjie Zuo ◽  
Zhengping Chang
Keyword(s):  
Energy Absorption ◽  
Failure Modes ◽  
High Strain ◽  
Early Stage ◽  
High Energy ◽  
Test Method ◽  
Test Theory ◽  
Strain Rates ◽  
Impact Properties ◽  
The Impact

Foams are widely used in protective applications requiring high energy absorption under impact, and evaluating impact properties of foams is vital. Therefore, a novel test method based on a shock tube was developed to investigate the impact properties of closed-cell polyethylene (PE) foams at strain rates over 6000 s−1, and the test theory is presented. Based on the test method, the failure progress and final failure modes of PE foams are discussed. Moreover, energy absorption capabilities of PE foams were assessed under both quasi-static and high strain rate loading conditions. The results showed that the foam exhibited a nonuniform deformation along the specimen length under high strain rates. The energy absorption rate of PE foam increased with the increasing of strain rates. The specimen energy absorption varied linearly in the early stage and then increased rapidly, corresponding to a uniform compression process. However, in the shock wave deformation process, the energy absorption capacity of the foam maintained a good stability and exhibited the best energy absorption state when the speed was higher than 26 m/s. This stable energy absorption state disappeared until the speed was lower than 1.3 m/s. The loading speed exhibited an obvious influence on energy density.

scholarly journals Geotechnical Approach to Early-Stage Site Characterisation of Shallow Wave Energy Sites

2021 ◽  
Vol 9 (6) ◽  
pp. 605
Author(s):  
Craig Heatherington ◽  
Alistair Grinham ◽  
Irene Penesis ◽  
Scott Hunter ◽  
Remo Cossu
Keyword(s):  
Wave Energy ◽  
Early Stage ◽  
Breaking Waves ◽  
Time Frame ◽  
High Energy ◽  
Specific Information ◽  
Terrain Analysis ◽  
Site Suitability ◽  
Site Characterisation ◽  
A Site

Marine renewable energy is still in its infancy and poses serious challenges due to the harsh marine conditions encountered for wave or tidal installations and the survivability of devices. Geophysical and hydrodynamic initial site surveys need to be able to provide repeatable, reliable, and economical solutions. An oscillating water column wave energy converter is to be installed on the west coast of King Island, Tasmania. The location is in a high-energy nearshore environment to take advantage of sustained shoaling non-breaking waves of the Southern Ocean and required site-specific information for the deployment. We provide insight into scalable geophysical site surveys capable of capturing large amounts of data within a short time frame. This data was incorporated into a site suitability model, utilising seabed slope, sediment depth, and water depth to provide the terrain analysis needed to match deployment-specific characteristics. In addition, short-term hydrology and geotechnical work found a highly energetic seabed (near seafloor water velocities <1 m/s) with sufficient bearing capacity (6 MPa). In a highly energetic environment, care was taken to collect the relevant data needed for an assessment of critical information to an emerging technology companies primary project. This is in addition to the malleable methodology for a site suitability model that can incorporate various weighted parameters to prioritise the location for shallow wave energy sites in general.

Quality of life in breast cancer sufferers

2016 ◽  
Vol 29 (7) ◽  
pp. 721-732 ◽  
Author(s):  
Ahmed Essmat Shouman ◽  
Nahla Fawzy Abou El Ezz ◽  
Nivine Gado ◽  
Amal Mahmoud Ibrahim Goda
Keyword(s):  
Breast Cancer ◽  
Quality Of Life ◽  
Family Income ◽  
Early Stage ◽  
Functional Domain ◽  
Related Factors ◽  
Specific Patient ◽  
Content Type ◽  
Factors Affecting

Purpose – The purpose of this paper is to measure health-related quality of life (QOL) among patients with early stage cancer breast under curative treatment at department of oncology and nuclear medicine at Ain Shams University Hospitals. Identify factors affecting QOL among these patients. Design/methodology/approach – A cross-sectional study measured QOL among early stage female breast cancer (BC) patients and determined the main factors affecting their QOL. Three interviewer administered questionnaires were used. Findings – The physical domain mostly affected in BC patients and the functional domain least. Socio-demographic factors that significantly affected BC patients QOL scores were patient age, education, having children and family income. Specific patient characteristics include caregiver presence – a factor that affected different QOL scores. Age at diagnosis, affection in the side of the predominant hand, post-operative chemotherapy and difficulty in obtaining the medication were the disease-related factors that affected QOL scores. Originality/value – The final model predicting QOL for early stage female BC patients included age, education and difficulty in obtaining the medication as determinants for total QOL score. Carer presence was the specific patient characteristic that affected different QOL scores.

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