Sieve Test Research Articles

Relationships between recycled concrete aggregates characteristics and recycled aggregates concretes properties

This research aims to analyze the quality and suitability of recycled concrete aggregates (RCA) produced by crushing concrete blocks provided from building demolition waste by comparison to natural ones in providing concretes for building structures. For each granular type, sieving, water absorption, porosity, Los Angeles and Micro-Deval tests were conducted before and after their exposure to freezing/thawing. Results show that the rules of mixtures (Voigt’s model) can be used to predict all the studied properties of granular mixes (natural gravels+recycled gravels) except for the prediction of Micro-Deval index. Relationships are established between physical and mechanical characteristics of aggregates. The analysis of the frost resistance performance show that recycled concrete gravels are less resistant to freeze/thaw than natural one but their degradation, estimated through water absorption, porosity and Micro-Deval index, is not significant. Furthermore, the influence of RCA on mechanical properties of recycled aggregates concretes (RAC) is investigated. It appears that porosity and young’s modulus of RAC are significantly affected by the porosity of the granular mixture and consequently of RCA. The compressive strength of RAC is dependent on the Los Angeles coefficient of gravels while tensile splitting strength depends on the porosity of concretes related to that of the granular mixture.

DEVELOPMENT OF ASPHALT EMULSIONS INCORPORATING WASTE LUBRICATING OIL

The aim of this study is to develop asphalt emulsions incorporating used lubricating oil (OLUC), as a modifier agent, to produce stable emulsions and resulting in cost-effective and environmentally friendly product suitable for paving applications. A central composite design (CCD) is proposed to reduce the experiment’s number. The asphalt emulsions were characterized by Saybolt Furol viscosity, residue by evaporation, settlement and storage stability, sieve test, ductility, and penetration over residue. The results showed that asphalt emulsions, in accordance with all technical specifications, can be produced at 80°C, using 5 minutes as emulsification time and low amounts of surfactant. Moreover, the experiment incorporated OLUC in the composition of asphalt emulsions to obtain new low-cost products for use in paving operations.

A Calibration Equation for Combining Dry-Sieving and Laser-Diffraction Techniques for Assessing Grain-Size Distributions of Beach Sands

ABSTRACT Ramsdale, T.M. and Fairweather, P.G., 2016. A calibration equation for combining dry-sieving and laser-diffraction techniques for assessing grain-size distributions of beach sands. Using laser diffraction to determine sediment grain-size distributions is faster than sieving methods; however, the results of these analytical methods can often differ. Samples are generally only analysed using one method, so the need to convert results, such as for comparison with published values or earlier data collected using different analytical techniques, may arise. To determine a calibration equation for comparing results obtained by laser diffraction to those from test sieves, natural beach-sand samples were processed by both methods and results for mean grain size, sorting, skewness, and kurtosis were compared. There was a strong, linear relationship between methods for mean grain-size values, and calibration between the two methods thus was found to be possible by using the equation: mean grain size (laser ...

Lime stabilization of expansive soil from Sergipe - Brazil

Expansive soils are characterized by volumetric changes caused by variations in moisture. They can cause several damages to civil constructions, especially to lightweight structures, including cracks and fissures. Chemical stabilization through addition of lime is one of the most effective techniques used to treat this type of soil. Due to cationic exchanges, lime can significantly reduce swell potential. This research studied a disturbed sample of expansive soil collected in Nossa Senhora do Socorro – Sergipe, Brazil, through the following laboratory tests: sieve and hydrometer tests, Atterberg Limits, compaction, free swell and swell pressure. All direct and indirect methods mentioned in this paper indicated that the natural soil presented high to very high degree of expansion, which reached approximately 20% of free swell and nearly 200 kPa of swell pressure. In order to evaluate the effect of lime, the same tests were conducted in soil-lime mixtures, using lime contents of 3%, 6% and 9%. The results confirmed the efficiency of lime stabilization. It was noted that, as lime content increased, there was reduction of clay fraction and increment of silt fraction; plasticity index decreased to nearly its half; compaction curve was displaced; and free swell and swell pressure reduced significantly.

Pragmática de la desinformación. Un estudio del leak de Prism a través de las reacciones de los gobiernos de Estados Unidos, Alemania y Venezuela

En este trabajo se exponen las técnicas de desinformación más comunes que se evidencian en el leak sobre el proyecto Prism de la NSA y sus inmediatas reacciones por parte de los gobiernos de Estados Unidos, Alemania y Venezuela. Para lograr este objetivo, se ha realizado un análisis cualitativo de base interpretativa al discurso de los mandatarios de los tres países, a través de las informaciones recogidas en medios digitales, mediante la localización, criba especializada, métodos de criterio de fuentes y selección aleatoria por metodología de semana construida. Los resultados evidencian el uso de al menos 11 estratagemas de desinformación.

Suitability of Chitosan as an emulsifier for cationic bitumen emulsions and its behaviour as an additive to bitumen emulsion

Chitosan contains amine and amino groups which have the ability to generate cationic type surfactants when combined with H+ ions. It has a high potential for use as a cationic emulsifier for negatively charged siliceous aggregates for paving of roads in Sri Lanka. Water soluble Chitosan was tested for suitability as an emulsifier in the production of cationic bituminous emulsions. The amine emulsifier currently in use was fractionally replaced with Chitosan and tested for emulsion properties; emulsion viscosity, storage stability, settlement, sieve test and breaking of emulsion. The viscosity of the emulsion was found to increase significantly from 16 SFS to 50 SFS and from 20 SFS to 72 SFS for Cationic Rapid Setting type (CRS1) emulsion and Cationic Slow Setting type (CSS1) emulsions respectively. For both types of emulsions, an exponential growth in viscosity was found to occur at a critical Chitosan to bitumen ratio of 0.0028. Results of storage stability indicated a tendency for floating, while in the presence of Chitosan, within the first 24h of preparation. However, a settling tendency developed for both types of emulsion when in longer storage as indicated by a 5day settlement test. A new model based on the interaction between reactive groups of Chitosan and bitumen emulsion droplets was proposed to describe the effect of Chitosan on bitumen emulsion.

Cause analysis on permanent deformation for asphalt pavements using field cores

Mechanical tests for asphalt mixtures generally use laboratory-produced specimens, which cannot truly represent material properties and construction conditions as they exist in the field. Therefore, field core samples have been increasingly selected for pavement performance testing. In this study, the field sampling and performance survey were firstly conducted on a highway with different pavement structures. Then, a three-dimensional finite element method (FEM) simulation was performed to compare the critical pavement responses related to permanent deformation (shear stress and pavement surface deflection) for different pavement structures. The advanced repeated load permanent deformation (ARLPD) and conventional repeated load permanent deformation (RLPD) tests were respectively employed to evaluate the rutting resistance on selected field cores. After mechanical tests, these specimens were further checked by the extraction and sieving tests. It is found from theoretical analysis that the maximum shear stress occurs at different locations (sublayers) for asphalt layers with different thicknesses. Consistent conclusions can be made from the ARLPD and RLPD tests results. Flow number index Fi shows the best ability to identify the field rutting resistance of asphalt pavements. A fair relationship is found between Fi measured from the ARLPD and RLPD tests. Compared with the control section with dense graded mixtures, heavy-duty long lasting pavement, porous permeable asphalt pavement, and asphalt rubber concrete pavement show superior rutting resistance while thin layer asphalt concrete pavement shows very poor anti-rutting performance at high temperatures. Finally, rutting causes and main factors for different pavement sections were respectively investigated. All these findings in this study are beneficial to accordingly improve the anti-rutting design for various pavement structures in future. The optimized pavement materials, structures, and techniques also have promising applicability prospects.

Fresh Properties of Self-Compacting Concrete Integrating Coal Bottom Ash as a Replacement of Fine Aggregates

The influence of coal bottom ash on fresh properties of self-compacting concrete (SCC) were presented in this paper. Self-compacting concrete mixtures were produced by 0.40 water/powder ratio and coal bottom ash as a replacement of fine aggregates in varying percentages of 0%, 10%, 15%, 20%, 25% and 30%. The fresh concretes were tested for the key workability belongings of self-compacting concrete such as passing and filling abilities and segregation resistance. The fresh properties were investigated by slump flow; T500 spread time, sieve segregation and L-box test. It was found that the slump flow decreased whereas the T500 spread time increased with higher coal bottom ash content. The L-box blocking ratios changed from 0.92 to 0.65 and were mostly showed satisfactory blocking ratio. The presence of coal bottom ash improved the stability of SCC mixture and the segregation index obtained from sieve test reduced with greater bottom ash content. It can be concluding that the filling and passing ability of SCC decreased when the amount of coal bottom ash content increased. In addition, the segregation resistance index decreased with higher coal bottom ash content.

농경유역 중소하천에서 유량과 총유사량의 관계식 유도방법

본 연구는 농경유역 중소하천의 주요 지점에서 실측된 현장자료를 사용하여 유량과 총유사량 관계곡선과 이들 간의 관계식을 유도한다. 실측치 총유사량 자료는 수심평균농도와 하상에서 각각의 부유사와 소류사 채취기(DH-48, D-74 및 BLH-84, BL-84)에 의해 채집된 시료를 건조 또는 여과법, 체분석에 의한 입도분포곡선을 통해 얻은 부유사량에 소류사량을 합하여 얻었다. 이들 현장자료는 농경유역 논산수계 내 4개 대상하천의 국가-지방하천 수로구간 7개 측점에서 2012년 8월부터 2014년 9월까지 측정되었다. 그 결과, 유량과 총유사량에 대한 관계곡선과 관계식은 현장측정 자료군의 분포특성을 분석함으로써 멱함수형으로 유도하였으며, 이들 관계식은 수공 유사공학의 이론적 연구뿐만 아니라 실무적 응용에 있어 세굴, 퇴적 및 이송을 해석하는데 유용한 도구로 사용될 수 있을 것이다. This study aims to derivate of the relationship and rating curve for the flow discharge-total sediment using the measured field data from the main points of small-medium stream reaches in agrarian basin. The total sediment of measured data are obtained by bed load added to suspended load which analyzed using the particle size distribution curve of sieve test and the dry or the filtration method from the collected samples by samplers (DH-48, D-74 and BLH-84, BL-84) at the stream bed and the depth-averaged concentration, respectively. These field data had been collected from August 2012 to September 2014 at the seven measuring stations of the national-local channel reaches of the four study streams in the Nonsan river systems of agrarian basin. As a result, the relationships and the rating curve for the flow discharge-total sediment are derived as a function pattern of power law by analyzing on a distribution characteristic of the database set and it will be used as a useful tool to analyze erosion, deposition, and transportation in theoretical research as well as in practical application of the hydraulic sedimentation engineering.

Strength, fragmentation and fractal properties of mixed flaws

Experiments on Portland cement samples containing mixed flaws are conducted to investigate the strength, fragmentation and fractal properties. Flaw geometry is a new combination of two edge-notched flaws and an imbedded flaw, which is different from those in the previous studies, where parallel or coplanar flaws are used. The physical implications of the shear-box test applied to result to rock slopes are studied. The physical and analytical fragmentation characteristics of preflawed samples are analyzed through the sieve test and fractal theory, respectively. Three different patterns of tensile cracks and shear cracks are observed. A sliding crack model is presented to elucidate the brittle failure flaws. In all of the cases of the shear-box tests, the coalescence is produced by the linkage of shear cracks, and two types of coalescence (Type C1 and Type C2) have been classified, which tend to confirm the observations from the numerical model and field of jointed rock slopes. The shear strength is a function of the flaw geometry and the shear–normal stress ratio. The result of sieve tests indicates that the fragment size distribution of fragments has the fractal property, providing a physical understanding of the fragmentation mechanism. The fragments under the shear-box test have fractal dimensions between 2.2 and 2.6, which are larger than those under the compression test but similar to those in the fault cores. The fragmentation in the case of Type C2 has a smaller fractal dimension, corresponding to a larger shear strength.

Evaluation of chemical and mechanical resistance of virgin and recycled poly (ethylene terephthalate) and poly(methylene oxide) when applied as gravel pack in petroleum wells

Nowadays more and more unexpected uses for common materials have been observed, especially when recycled polymers are concerned. In this work, the viability for application of virgin and recycled poly(ethylene terephthalate) (PETvir and PETrec, respectively) and also poly(methylene oxide) (PMO) as granular materials (gravel) for gravel packing in sand control systems for unconsolidated sandstone reservoirs was studied. Polymer samples were tested in conditions similar to those observed in Campos Basin sandstone formations, in Brazilian Southwest (70 °C and 24.1 MPa). Samples were individually confined in roller cells with chemicals used in formation treatment: hydrochloric acid, pentapotassic DTPA salt (chelant Trilon CK) and in a mixture of diesel, xylene and butyl glycol. Mass loss was measured and the changes in molecular mass verified by size exclusion chromatography (SEC). Physical shape and grain size distribution were verified by scanning electron microscopy (SEM) and sieving tests. The effects over the polymeric gravel pack confinement resistance and permeability were evaluated using an API permeability cell. PMO proved to have a limited use, whereas PETrec and PETvir samples were not significantly affected, suggesting the viability of applying that recycled polymer in gravel packing for sand control in petroleum wells.

Effects of Elevated Temperature on Compressive Strength Of Concrete: A Case Study of Grade 40 Concrete

This study presents the results of investigation of the effects of elevated temperatures on the compressive strength of Grade 40 concrete. A total of thirty cube specimens were cast, cured in water at ambient temperature in the laboratory and subjected to various temperature regimes before testing. A concrete mix of 1:1:3 (cement: fine aggregates: coarse aggregates) with water content ratio of 0.44, fine aggregates lying in zone 2 of sieve tests as well as granite of maximum size 12.5mmwas designed for these investigations using the Department of Environment Method. Specimens cured for 7 and 28 days were subjected to uniaxial compressive loading tests at room and elevated temperature of 24, 100, 150, 200, 250 and 300 degree Celsius at one hour duration. The result indicated 14.49%, 25%, 51%, 35.51% and 43.88% decrease in compressive strength at the earlier quoted temperatures respectively. At an elevated temperature of 300 degrees Celsius a peak decrease of 53.47% in compressive strength was observed. http://dx.doi.org/10.4314/njt.v34i3.7

Choice of aggregates for permeable pavements based on laboratory tests and DEM simulations

Permeable pavement plays an important role in the sustainable urban drainage system as they have the potential to reduce splash and spray. While the pavements need to be permeable for the water to drain into the ground, it must also be able to carry the traffic load without altering the permeability characteristics. This paper aims to investigate the permeability performance and serviceability of pavements constructed with aggregates having a range of crushing strength (crushability) and grading (particle size distribution). Laboratory tests consist of modelling a pavement and carrying out permeability and sieving tests before and after the application of the loading. Experimental investigations showed that particles having higher crushing strength will lead a lower reduction in permeability of the pavement without compromising the performance. Furthermore, it was observed that reduction of permeability depends on the particle breakage pattern. Numerical study was conducted using discrete element modelling to understand the underlying mechanism of this phenomenon, and it was found that a wide particle size range could distribute the load uniformly and reduce the particle breakages. It is suggested that all these factors may be considered while choosing the aggregate for permeable pavement.

Random-fractal-method-based generation of meso-model for concrete aggregates

Concrete is widely applied in various industries as a composite material, and the relationship between the structure and properties of concrete has been a topic of common interest. An understanding of the composite mechanical behavior of concrete is useful for concrete mix design and damage prediction. This prompted the proposal of an analysis based on the mesoscopic approach for modeling the behavior of concrete. The quality of the finite element analysis that is used to analyze the concrete meso-model depends on the shape, spatial distribution, and orientation of the simulated aggregates. This paper describes a versatile method for simulating the meso-model of concrete aggregates with the result of the sieving test affirmed, based on the formulation of three principal hypotheses. As the aggregates in concrete resemble those generated by random fractal iteration, the particular model is assumed to be random convex quadrilateral in 2D space, and random convex hexahedral in 3D space, and several parameters influencing the modeling result are defined and devised. Prior to generating the meso-model, an idealized model is mathematically defined, with reference to the fractal method, in which several property parameters of the mix conditions of the graded aggregates are explicitly described by mathematical expressions. Based on a comparison between the numerical and experimental tests performed on the concrete under uniaxial compression, it is validated that the random fractal method could basically be used to generate the meso-model of concrete aggregates. Several modifications and prospects expected from future work are discussed.

Связь ширины зерен шлифовальных порошков из карбида кремния черного с размерами ячеек контрольных сит

Связь ширины зерен шлифовальных порошков из карбида кремния черного с размерами ячеек контрольных сит

Assessment of radionuclides and heavy metals in marine sediments along the Upper Gulf of Thailand

Due to the Fukushima Daiichi nuclear disaster in 2011 and the development of nuclear power plant in neighboring countries such as Vietnam in the near future, radionuclide assessment in marine sediment during 2010 - 2011 may be useful as background levels for radiation protection in Thailand. Marine sediments (10 samples) were collected approximately 1 km away from the coastline along Chonburi to Pattaya, Chonburi Province. The sediments were ground and sieved through 2-mm test sieve after air drying. Radionuclides were measured with a gamma spectrometer equipped with a well-calibrated HPGe detector. The samples were prepared in the same geometry as the reference material. The optimal counting time was 60,000 - 80,000 s for statistical evaluation and uncertainties. No contamination of 137Cs as an artificial radionuclide was found. Naturally-occurring radionuclides including 238U, 232Th and 40K were found. The mean specific activities of 238U, 232Th and 40K were 44 ± 10, 59 ± 17 and 463 ± 94 Bq/kg in the rainy season (2010); 41 ± 6, 50 ± 9 and 484 ± 83 Bq/kg in the winter (2010), and 39 ± 6, 41 ± 7 and 472 ± 81 Bq/kg in the summer (2011), respectively. The mean specific activities were higher than the values in the UNSCEAR report of 35, 30 and 400 Bq/kg for 238U, 232Th and 40K, respectively. From the measured specific activities, the absorbed dose rate, radium equivalent activity, external hazard index and annual external effective dose rate were calculated in order to assess the health risk. No radiation hazards related to the radioactivity in the sediment were expected. The accumulation of radionuclides varied with the particle size and the organic matter content in the sediment. The accumulation of heavy metals showed similar results to that of the radionuclides in the sediment.

A comparison of chewing rate between overweight and normal BMI individuals

ObjectivePrevious attempts to identify an ‘obese eating style’ have led to conflicting findings. This observational study compared the chewing features of overweight or obese young adults with those of normal range BMI. We hypothesised that chewing features are individual-specific and differ between participants of a normal BMI and high BMI. MethodsFourteen overweight to obese participants (BMI≥25.0) were pairwise matched with 14 normal range BMI participants (18.5<BMI<25.0). Masticatory muscle activity was recorded using portable recorders during consumption of two rice meals in a laboratory setting and one pizza meal in the natural environment. A previously validated algorithm was used to assess time-frequency features of chewing episodes, including rate, duration, and power. Masticatory performance was assessed by a sieve test and was expressed as the percentage of particles ≤2mm after a standardised chewing test. ResultsRegardless of the meal, chewing rate was remarkably consistent among participants (ICC=0.89; 95% CI=0.79–0.94). Chewing rate did not differ between high and normal BMI participants (p>0.05), whereas chewing power was significantly higher in high BMI participants (p<0.05). No other differences in chewing characteristics were found between BMI groups. Participants chewed at similar rate in the natural environment (pizza) and in the laboratory (rice) setting (p>0.05). Masticatory performance did not differ significantly (p>0.05) between the high (55.9%) and normal (52.4%) BMI groups. ConclusionsWithin the limitations of the present study, chewing characteristics appear to be individual-specific with wide variability. Overweight participants chew at a similar rate to control participants, albeit slightly stronger. Our preliminary findings need to be replicated in larger samples.

THE APPLICABILITY OF DISINTEGRATION TESTS FOR COHESIVE ORGANIC SOILS

The use of ripened fine-grained organic dredged materials as construction materials, e.g. as top soil on slopes such as landfills or dikes, is an important contribution to environmental engineering science. The materials are legally considered a waste and need to be beneficially re-used. Therefore, not only standard geotechnical parameter shave to be determined but also their erosion resistance which is a particularly critical environmental parameter. There is a variety of different tests to determine the flow dependent erosion resistance of soils, such as the erosion function apparatus (Briaud et al. 2001). In this study, however, the focus lays on the aggregate stability as an indicator for the erosion resistance under static loading, which can be determined using wet sieving and disintegration tests. The disintegration tests after Weißmann (2003) and Endell (RPW 2006) have a similar setup; however, the specific boundary conditions for the tests as well as the evaluation procedures are different. Weißmann proposed his test to determine the erosion stability of dike cover materials while the Endell test should be used for mineral sealing liners in navigation channels. In this study both tests have been used to evaluate the aggregate stability of fine-grained organic dredged materials that have been installed in large-scale research dike facilities and in the recultivation layers of different landfills. The materials showed good visual performance with respect to rainfall induced erosion so far; however, problems in determining erosion and aggregate stability indices limit the value of the studies: both disintegration tests investigated have major limitations with respect to the organic soils tested. Particularly the evaluation methods are not suitable for the soils but also some boundary conditions are critical and are discussed in this paper. The gained knowledge is a valuable basis for the development of standard characterisation methods for dredged materials in environmental and geotechnical applications.

Assessment of swallowing and masticatory performance in obturator wearers: a clinical study.

PURPOSETo assess function by identifying changes in swallowing and masticatory performance in maxillary obturator prosthesis wearers.MATERIALS AND METHODSSixty subjects were recruited for the study, of which 20 were obturator wearers, 20 were completely dentulous and 20 had removable partial/complete dentures with similar Eichner's Index. Swallowing ability was evaluated with and without obturator using the "Water Drinking Test"; Masticatory performance was evaluated with the Sieve test; and maximum occlusal force was recorded with the help of a digital bite sensor. The data was analyzed using the Statistical Package for Social Science version 15.0 with a confidence level at 95%.RESULTSProfile, behavior of drinking and time taken to drink were significantly improved (P<.001) in subjects after wearing obturator. Masticatory performance was not significantly different (P=.252) in obturator wearer when compared with dentulous or removable partial/complete denture wearer, but significantly (P<.001) high inter group difference in maximum occlusal force existed. Correlation between masticatory performance and maximum occlusal force was not significant (P=.124).CONCLUSIONSwallowing ability was significantly improved after wearing obturator but masticatory performance was not significantly different from those having similar occlusal support zone in their dentition.

Investigation of Using Free-Standing Thick-Film Piezoelectric Energy Harvesters to Develop Wideband Devices

This paper is concerned with the wideband behavior of single-frequency and multi-frequency free-standing thick-film piezoelectric energy harvesters. The energy harvesting devices have been fabricated and brief fabrication information is provided. The individual harvesters have been combined with either symmetric or asymmetric tip masses, with some being connected together to form a harvester array. Testing has been undertaken using harmonic vibrations with a wide range of frequencies and accelerations, and also using a random machinery vibration, and data have been recorded in terms of un-rectified and rectified open-circuit voltage, output power with matched resistive loads, peak-to-peak tip displacement, and even charging rates of capacitors. As a general result, the individual harvesters with asymmetric tip masses have vibrated nonlinearly below and in the vicinity of the resonant frequencies. An individual harvester vibrating at the resonant frequency with 0.5 g acceleration has been able to charge a 1000 μF capacitor to 1 V within 12 min and to 1.5 V within 30 min. Also, the harvester array has exhibited a wideband response, where an open-circuit voltage of above 0.8 V has been provided within a certain range of frequencies. Finally, the harvester array has successfully charged a capacitor on a vibrating test sieve shaker, proving the feasibility of the proposed device in real applications.