scholarly journals Volume change behaviour and microstructure of stabilized loess under cyclic freeze–thaw conditions

2016 ◽  
Vol 43 (10) ◽  
pp. 865-874 ◽  
Author(s):  
Sheng-lin Wang ◽  
Qing-feng Lv ◽  
Hassan Baaj ◽  
Xiao-yuan Li ◽  
Yan-xu Zhao
Keyword(s):  
Fly Ash ◽  
Volume Change ◽  
Cement Content ◽  
Frost Heave ◽  
Equivalent Diameter ◽  
Surface Porosity ◽  
Change Rate ◽  
Freeze Thaw ◽  
Significant Damage ◽  
The Impact

Freeze–thaw action is considered to be one of the most destructive actions that can induce significant damage in stabilized subgrades in seasonally frozen loess areas. Laboratory tests including frost heave – thaw shrinkage and microstructure change during freeze–thaw cycles were conducted to evaluate the volume change rate of loess stabilized with cement, lime, and fly ash under the impact of cyclic freeze–thaw conditions. The loess specimens collapsed after eight freeze–thaw cycles (192 h), but most stabilized loess specimens had no visible damage after all freeze–thaw cycles were completed. All of the stabilized loess samples underwent a much smaller volume change than the loess alone after the freeze–thaw cycles. Although surface porosity and equivalent diameter of stabilized loess samples increased, the stabilized loess can retain its microstructure during freeze–thaw cycles when the cement content was less than 6%. To ensure freeze–thaw resistance of stabilized loess subgrades, the mix proportions of the three additives was recommended to be 4 to 5% cement, 6% lime, and 10% fly ash.

scholarly journals A Study of the Strength Performance of Peat Soil: A Modified Cement-Based Stabilization Agent Using Fly Ash and Polypropylene Fiber

Polymers ◽  
2021 ◽  
Vol 13 (23) ◽  
pp. 4059
Author(s):  
Mohammed K. H. Radwan ◽  
Foo Wei Lee ◽  
Yoke Bee Woon ◽  
Ming Kun Yew ◽  
Kim Hung Mo ◽  
...  
Keyword(s):  
Fly Ash ◽  
Soil Stabilization ◽  
Cement Content ◽  
Peat Soil ◽  
Polypropylene Fiber ◽  
Soil Treatment ◽  
Engineering Properties ◽  
Test Results ◽  
Stabilizing Agent ◽  
The Impact

The use of cement as a soil stabilization agent is one of the common solutions to enhancing the engineering properties of soil. However, the impact and cost of using cement have raised environmental concerns, generating much interest in the search for alternative materials to reduce the use of cement as a stabilizing agent in soil treatment. This study looked into limiting cement content in peat soil stabilization by using fly ash waste and polypropylene fiber (PPF). It focused on soil mechanical mediation for stabilization of peat with fly ash cement and PPF cement by comparing the mechanical properties, using unconfined compressive strength (UCS) and California bearing ratio (CBR) tests. The control (untreated) peat specimen and specimens with either fly ash (10%, 20% and 30%) and PPF (0.1%, 0.15% and 0.2%) were studied. Test results showed that 30% of fly ash and cement content displays the highest UCS and CBR values and gives the most reliable compressibility properties. On the other hand, UCS and CBR test results indicate optimum values of PPF–cement stabilizing agent content in the specimen of 0.15% PPF and 30% cement. Selected specimens were analyzed using scanning electron microscopy (SEM), and PPF threads were found to be well surrounded by cement-stabilized peat matrices. It was also observed that the specimen with 30% fly ash generated more hydration products when compared to the specimen with 100% cement content. It is concluded that the use of fly ash cement and PPF cement as stabilizing agents to limit the cement usage in peat soil treatment is potentially viable.

The Impact of Insect Infestation on Stored Purpled Cocoa Beans

2018 ◽  
Vol 1 (3) ◽  
pp. 176-181 ◽  
Author(s):  
E. Tettey
Keyword(s):  
Weight Loss ◽  
Insect Population ◽  
Insect Infestation ◽  
Percentage Weight Loss ◽  
Cocoa Beans ◽  
Significant Damage ◽  
Percentage Weight ◽  
Fermentation Period ◽  
The Impact

Under-fermentation of cocoa beans produces purple beans. The fermentation period is 6 to 7 days but some cocoa farmersunder-ferment their cocoa beans leading to the development of purple cocoa beans. This study determined the impact of insectinfestation on stored purple cocoa beans. Wet cocoa beans were fermented for 1, 2, 3, 4 and 5 days to produce the purple beans.Ephestia cautella and Tribolium castaneum, both singly and in combination, were introduced into the cocoa beans and storedfor different (30, 60, 90 and 120 days) period. Insect population, percentage weight loss and the contaminants produced bythese insects were determined. Cocoa beans infested with E. cautella alone had the highest population of 297.0 ± 22.7. Beansfermented for 3 days had the lowest insect population both singly and in combination after 120 days of storage. The highestpercentage weight loss was recorded in cocoa beans fermented for one day (10.1 ± 1.87%) and 4 days (10.1 ± 8.74%). T.castaneum did not cause much damage to the cocoa beans but E. cautella alone caused significant damage to stored cocoabeans. Insect infestation and poor fermentation contribute significantly to the reduction in quality of cocoa beans.

scholarly journals Freeze–Thaw Resistance and Air-Void Analysis of Concrete with Recycled Glass–Pozzolan Using X-ray Micro-Tomography

Materials ◽  
2020 ◽  
Vol 14 (1) ◽  
pp. 154
Author(s):  
Marija Krstic ◽  
Julio F. Davalos ◽  
Emanuele Rossi ◽  
Stefan C. Figueiredo ◽  
Oguzhan Copuroglu
Keyword(s):  
Fly Ash ◽  
Pore Structure ◽  
The United States ◽  
Adsorption Method ◽  
X Ray ◽  
Freeze Thaw ◽  
Void System ◽  
Spatial Parameters ◽  
Micro Tomography ◽  
Air Void

Recent studies have shown promising potential for using Glass Pozzolan (GP) as an alternative supplementary cementitious material (SCM) due to the scarcity of fly ash and slag in the United States. However, comprehensive studies on the freeze–thaw (FT) resistance and air void system of mixtures containing GP are lacking. Therefore, this study aimed to evaluate GP’s effect on FT resistance and characterize mixtures with different GP contents, both macro- and microscopically. In this study, six concrete mixes were considered: Three mixes with 20%, 30% and 40% GP as cement replacements and two other comparable mixes with 30% fly ash and 40% slag, as well as a mix with 100% Ordinary Portland cement (OPC) as a reference. Concrete samples were prepared, cured and tested according to the ASTM standards for accelerated FT resistance for 1000 cycles and corresponding dynamic modulus of elasticity (Ed). All the samples showed minimal deterioration and scaling and high F/T resistance with a durability factor of over 90%. The relationships among FT resistance parameters, air-pressured method measurements of fresh concretes and air void analysis parameters of hardened concretes were examined in this study. X-ray micro-tomography (micro-CT scan) was used to evaluate micro-cracks development after 1000 freeze–thaw cycles and to determine spatial parameters of air voids in the concretes. Pore structure properties obtained from mercury intrusion porosimetry (MIP) and N2 adsorption method showed refined pore structure for higher cement replacement with GP, indicating more gel formation (C-S-H) which was verified by thermogravimetric analysis (TGA).

The Effect on Cement Mortar and Concrete by Admixture of Spray Drying Absorption Products

1989 ◽  
Vol 178 ◽  
Author(s):  
Kirsten G. Jeppesen
Keyword(s):  
Grain Size ◽  
Fly Ash ◽  
Cement Mortar ◽  
Setting Time ◽  
Mineralogical Composition ◽  
Cement Clinker ◽  
Strength Development ◽  
Fall Meeting ◽  
Freeze Thaw ◽  
Spray Dried

AbstractSpray dried absorption products (SDA) having special characteristics are used as substitutes for cement in the preparation of mortars; the qualities of the resulting mixed mortars are described. Conditions are described for mortar mixes, data for which were presented at the MRS Fall Meeting 1987.The influence of the composition of the SDA on water requirement and setting time has been studied. A full scale project involving 3 precast, reinforced concrete front-elements containing 20 and 30 wt.% SDA is described. Strength development, mineralogical composition and corrosion were monitored for two years.A non-standard freeze-thaw experiment was performed which compares mortars containing SDA and fly ash (FA) and also shows the effect of superplasticizer.The possibility of improving the SDA by grinding has been tested and a limited improvement has been found. The strength of the mixed mortars seems slightly influenced by the grain size of SDAGypsum (CaSO4·2H2O), synthetic calcium-sulphite (CaSO3·½H2O) and 2 SDAs have been used as retarders for cement clinker. Mortar test prisms have been cast and comparative strengths after curing for 3 years are reported

Geological and geomorphological problems caused by transportation and industry

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Lorant David ◽  
Zoltan Ilyes ◽  
Zoltan Baros
Keyword(s):  
Fly Ash ◽  
Industrial Development ◽  
Transport Infrastructure ◽  
Narrow Strip ◽  
Complex Processes ◽  
Shopping Centres ◽  
Industrial Parks ◽  
Surface Sealing ◽  
Steep Slopes ◽  
The Impact

AbstractAlterations in topography due to the construction of transport infrastructure and industrial development are the results of rather complex processes. The impact of transport constructions upsetting (topographic) equilibrium is manifested in a relatively narrow strip, and, mostly, through producing abnormally steep slopes, in reducing relief stability. The earthworks for transport routes are themselves also landscape-forming factors whereas in the case of industrial developments, planation is usually mentioned. Topographic changes related to the construction of transport infrastructure and industrial development are discussed historically in this chapter. Among the direct impacts of the first are those related to the construction of Roman and Medieval roads, hollow roads in loess, public roads, motorways, railways, canals, tunnels and airports; while of the second are those of early mining and metallurgy, cellars, sludge reservoirs, slag cones and fly-ash reservoirs, cooling ponds, industrial parks, shopping centres and waste disposal sites. Of the indirect ones, an introduction is given to impacts of surface sealing, changes in runoff, the ‘waterfall effect,’ as well as to environmental impacts under permafrost conditions.

Cleaner Environment Approach by the Utilization of Low Calcium Wood Ash in Geopolymer Concrete

2021 ◽  
Author(s):  
Kadarkarai Arunkumar ◽  
Muthiah Muthukannan ◽  
Arunachalam Suresh Kumar ◽  
Arunasankar Chithambar Ganesh ◽  
Rangaswamy Kanniga Devi
Keyword(s):  
Fly Ash ◽  
Microstructural Characterization ◽  
Wood Ash ◽  
Geopolymer Concrete ◽  
X Ray Diffraction ◽  
High Potassium ◽  
Waste Wood ◽  
Research Findings ◽  
Research Gap ◽  
The Impact

The waste disposal issues were the most severe problems that could cause global warming, which depletes the environment. The research hypothesis was to find the suitability and sustainability of utilizing the waste by-products in the invention of green geopolymer concrete to eliminate the tremendous effects caused by the wastes. Due to the increased demand for fly ash in recent years, the requirement of high alkaline activators, and elevated temperature for curing, there was a research gap to find an alternative binder. The novelty of this research was to utilize the waste wood ash, which is available plenty in nearby hotels and has an inbuilt composition of high potassium that can act as a self alkaline activator. Waste wood ash procured from the local hotels was replaced with fly ash by 0 to 100% at 10% intervals. The setting and mechanical characteristics were found on the prolonged ages to understand the influence of waste wood ash. Microstructural characterization was found using Scanning Electron Microscope and X-Ray Diffraction Analysis to define the impact of waste wood ash in the microstructure. The research findings showed that replacing 30% waste wood ash with fly ash attained better performance in setting properties and all mechanical parameters. The obtained optimum mix could provide the best alternative for fly ash in geopolymer to eliminate the economic thrust by the requirement of alkaline activators and deploy the environmental impact caused by the waste wood ash.

Within- and Between-Event Variabilities of Strong-Velocity Pulses of Moderate Earthquakes within Dense Seismic Arrays

2021 ◽  
Author(s):  
Ming-Hsuan Yen ◽  
Sebastian von Specht ◽  
Yen-Yu Lin ◽  
Fabrice Cotton ◽  
Kuo-Fong Ma
Keyword(s):  
Ground Motion ◽  
Structural Engineering ◽  
Strike Slip ◽  
Physical Factors ◽  
Velocity Amplitude ◽  
Seismic Arrays ◽  
Directivity Effect ◽  
Forward Directivity ◽  
Significant Damage ◽  
The Impact

ABSTRACT Ground motion with strong-velocity pulses can cause significant damage to buildings and structures at certain periods; hence, knowing the period and velocity amplitude of such pulses is critical for earthquake structural engineering. However, the physical factors relating the scaling of pulse periods with magnitude are poorly understood. In this study, we investigate moderate but damaging earthquakes (Mw 6–7) and characterize ground-motion pulses using the method of Shahi and Baker (2014) while considering the potential static-offset effects. We confirm that the within-event variability of the pulses is large. The identified pulses in this study are mostly from strike-slip-like earthquakes. We further perform simulations using the frequency–wavenumber algorithm to investigate the causes of the variability of the pulse periods within and between events for moderate strike-slip earthquakes. We test the effect of fault dips, and the impact of the asperity locations and sizes. The simulations reveal that the asperity properties have a high impact on the pulse periods and amplitudes at nearby stations. Our results emphasize the importance of asperity characteristics, in addition to earthquake magnitudes for the occurrence and properties of pulses produced by the forward directivity effect. We finally quantify and discuss within- and between-event variabilities of pulse properties at short distances.

Investigation of Droplet Impinging on a Heated Porous Surface Under Various Working Conditions; A Mathematical Modeling

2021 ◽  
pp. 2150015
Author(s):  
Mohammad Azadeh ◽  
Hamidreza Khakrah
Keyword(s):  
Droplet Diameter ◽  
High Surface ◽  
Adaptive Method ◽  
Porous Surface ◽  
Droplet Temperature ◽  
Surface Porosity ◽  
Two Phase ◽  
Air Interface ◽  
Accuracy Of Results ◽  
The Impact

This study numerically investigated the behavior of a Newtonian droplet impacting a heated porous surface. In this regard, a two-phase finite volume code was used for laminar flow. The time adaptive method was applied to enhance the accuracy of results and better convergence of the solving process. Also, the dynamic grid adaptation technique was adopted to predict the liquid-air interface precisely. The results were first validated against experimental data at different Weber numbers. Then the effect of variations in the droplet temperature was investigated on the spreading factor. The obtained results revealed that the rise in droplet temperature led to an increase in the maximum spreading diameter due to the reduction in the effects of viscosity, density, and surface tension. In the next step, the effects of droplet impact on the hydrophilic and superhydrophobic surfaces with the porosities of 20–80% were evaluated. The obtained results revealed that the increase in the surface porosity caused a decrease in the droplet diameter during the impact time. Also, at high surface porosity values, the decline in the contact angle influence on the droplet dynamic behavior was observed.

Impactul inundaţiilor pluviale din Republica Moldova și măsurile de diminuare a lui

2019 ◽  
Author(s):  
Galina Mindru ◽  
Keyword(s):  
Statistical Data ◽  
Negative Effects ◽  
Digital Map ◽  
Republic Of Moldova ◽  
Significant Damage ◽  
Annual Frequency ◽  
The Republic ◽  
Favorable Conditions ◽  
The Impact ◽  
Main Factor

In the Republic of Moldova, the main factor contributing to the floods is the torrential rains from the warm semester of the year, which create favorable conditions for triggering strong, sometimes catastrophic floods in the rivers of the republic, especially in the smaller ones. During the study period, 40 floods with significant damage were recorded in the country, with an annual frequency ranging from 0 to 12 cases. In the administrativeterritorial profile, the damages caused by the aforementioned floods varied greatly. Based on the statistical data, a digital map was developed reflecting the degree of exposure of the territory of the Republic of Moldova in the administrative-territorial aspect to the mentioned risk, expressed by the value of the damages caused. In order to reduce the impact caused by the flood floods, measures have been developed to prevent, reduce and combat the negative effects of that risk.

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