High Fly Research Articles

Flexible canvas produced from uncured-natural rubber composites filled with high calcium oxide fly ash/cement hybrid filler

Concrete canvas (CC) is an attractive composite based on a combination of textile and cement, applying for the slope protection and ditch lining. However, there is no binder between both the materials and its high thickness causes a strong detachment of cement particles, and the complex designing of CC shapes is limited. Therefore, the possibility of incorporating natural rubber (NR) as a binder for extending the applications of cement-based composites has been considered. In the present work, NR composites with fly ash (FA) and cement (CM) are prepared through an internal mixer and a two-roll mill with a total filler concentration of 1000 phr. It can be found that, FA/CM hybrid filler is successfully adhered together through the NR matrix, and it promotes the flexible canvas composites with controlled thickness and provides complex shapes. The existing calcium oxide (CaO) present in the filler reacts with water molecules, and the NR composites become hardened and restrict the deformation and decomposition. The optimum ratio of FA/CM hybrid filler has been fixed at 300/700 phr, which has recognized as the product-like concrete canvas. Tensile properties, dynamic properties and thermal stability are improved upon the incorporation of hybrid fillers and its flexibility is found to be sustained on soaking with water. The structural changes are confirmed from the infrared spectrum which clearly explains the transformation of CaO to the CSH network structure in the NR composites. Un-crosslinked composites exhibited similar mechanical properties compared to the chemically crosslinked NR with sulfur curing system. Thus the composites can be used as the flexible canvas, although it has not been vulcanized. To clarify this statement, tensile properties, abrasion resistance and bending propagation of NR composites, NR vulcanizates and commercial concrete canvas are compared. The composites exhibited comparable properties with superior flexibility performance. Along with the waste utilization, the uses of FA, provides an opportunity of using FA/CM as the flexible canvas.

Validation of numerical models for prediction of pressure drop in high capacity long distance lignite fly ash pneumatic conveying

This paper will validate two basic concepts of numerical models for prediction of pressure change along the transport pipeline in the case of long distance and high capacity lignite ash pneumatic conveying. Application of various friction factor correlations and variation of given parameter, led to the total of fourteen different numerical models and program codes in FORTRAN. The input data for numerical models are based on comprehensive experimental research of high capacity and long distance Kolubara lignite fly ash pneumatic conveying system within 620 MWe thermal power plant unit under operating conditions. Numerical simulation results are validated against experimental data and subjected to statistical analysis methods. The functional dependence obtained by the least squares method was evaluated using mean squared deviation and correlation ratio. The predicted pressure changes show the best agreement, with the measured decrease of pressure amplitudes along the transport pipelines, for the model based on the momentum balance of air-ash mixture flow and friction factor cor-relation given by Dogin and Lebedev for the parameter A = 1.4?10-6. This model achieved the best correlation ratio of 93.99% for Pipeline 1 and 91.33% for Pipeline 2, as well as the best mean squared deviation of 9.58% for Pipeline 1 and 13.66% for Pipeline 2. Also, the fanning friction factor values are fully consistent with previously examined cases available in the literature. Numerical simulation model can be used for prediction of the ash pneumatic conveying capacity and pressure drop for the specified transport pipeline.

Effect of Job Security on Employee Performance in Berger Construction Company in Nigeria

Securing and retaining a job is the desire of most, if not every employee, especially in the face of high rates of unemployment occasioned by several factors globalisation, harsh economic conditions, high mobility of labour and so on. On the demand side, organisations also seek to attract high flyers to ensure peak performance in order to attain set objectives. Between these two sides, several determinants are key to the realization of these objectives, chief amongst which is Job Security. One could say it is the major bridge linking the two. The study examined the effect of Job Security on employees performance at Berger Construction Company in Nigeria. The study adopted the survey research design. The population of the study consists of 518 employees of Berger Construction Company in Nigeria which was also used as the sample size. The method of data collection was a questionnaire which was administered to the respondents. The statistical tools adopted for this study were correlation and simple regression models. The findings revealed that there is a positive and significant effect of job security on employees performance in Berger Construction Company in Nigeria. The study recommended that Berger Construction Company should continue to ensure the effective promotion of their employees to higher statuses and higher positions and also ensure they improve their salary system.

Long-Term Behavior of Concrete Containing Wood Biomass Fly Ash

Wood biomass is widely used in the European Union as a fuel for the production of heat and electrical energy, generating a considerable amount of ash. The disposal of ash, especially its finest fraction, requires proper engineering solutions, since these particles contain heavy metals and caneasily pollute soil, groundwater, or air. In this work, wood fly ash with a high amount of pozzolanic oxides and one with a high CaO content were used in concrete as a 15% and 30% cement replacement. Incorporation of wood ash in concrete reduced the 28-day compressive strength of concrete by up to 37%, which was attributed to the low stiffness of the wood ash particles, while the 2-year compressive strength indicated very low pozzolanic reactivity. The capillary absorption of concrete increased with the increase in the ash content, but almost no influence on the gas permeability was observed. Wood fly ash with high CaO content reduced the drying shrinkage of concrete by up to 65% after 1 year. In a mix with 30% of high CaO fly ash, swelling occurred in the first days of hydration, which was attributed to the volume expansion due to the formation of portlandite and brucite, but did not lead to cracking or a decrease in long-term compressive strength.

Study on the Performance of Foam Concrete Prepared from Decarburized Fly Ash

Although the energy structure has been gradually enriched in recent years, China, as the world’s largest producer and consumer of coal, still accounts for more than 50% of resources. Therefore, in this paper, the high carbon fly ash raw ash (HCFARA) was mechanically activated, and the flotation was treated to obtain decarburized fly ash (DFA) with a loss on ignition of 1.18%, water demand ratio of 101% and strength activity coefficient of 74.5%. With the exception of for water demand ratio, the rest meet the national requirements for the use of Class I fly ash. The foam concrete was prepared by partially replacing cement with decarburized fly ash in different proportions and at different water-to-cement ratios (0.3, 0.4 and 0.5) in order to study its dry density, porosity, compressive strength and thermal conductivity. The results show that the porosity of foam concrete grows with the increase in water-to-cement ratio and fly ash replacement rate. In addition, the dry density and thermal conductivity of the prepared foam concrete can meet the requirements of A05 grade foam concrete (Density less than 500 kg/m3, thermal conductivity less than 0.12 W/(m·k)). The compressive strength can meet the requirements of C0.3 grade foam concrete (Minimum use standard).

Skjönsberg, Max. The Persistence of Party: Ideas of Harmonious Discord in Eighteenth-Century Britain

Skjönsberg, Max. <i>The Persistence of Party: Ideas of Harmonious Discord in Eighteenth-Century Britain</i>

Properties and mechanism of mullite whisker toughened ceramics

High-strength ceramics were prepared from high alumina fly ash (HAFA) and activated alumina as raw materials with magnesia as a sintering additive. The growth kinetics and influence mechanism of secondary mullite whiskers were investigated. Meanwhile, the effects of the Al2O3/SiO2 mass ratio (A/S) and the amount of magnesia on the content and morphology of mullite in the green body were investigated, so as to emphasize the effect of the liquid phase in the sintering process on the growth of secondary mullite whiskers. The results showed that the aspect ratio of secondary mullite whiskers increased significantly after adding activated alumina to increase the A/S ratio of raw materials. When 30 wt% activated alumina was added, the mullite content increased by 5.39%, and the whisker length increased from 1.36 μm to 4.18 μm. The addition of magnesia improved the liquid phase formed during the sintering process and the K value method was used to determine the sintering liquid phase content under various conditions. It was observed that increasing the magnesia level by 1 wt% could raise the liquid phase content by 5–7%. When the total liquid content of the system was 30–40%, the growth activation energy in the diameter direction of the whisker reduced significantly, promoting the growth of secondary mullite whiskers along the C axis. The morphology of mullite gradually developed from fibrous to long columnar crystal, making it combine more densely with the green body matrix. Furthermore, the staggered long columnar mullite crystal structure changes the fracture mode of ceramics from intergranular to transgranular fracture, which fully uses the high mechanical strength of mullite. As a result, the fracture energy and strength of ceramics are significantly improved.

The asymmetric gender effects of high flyers

Using longitudinal information on a representative sample of U.S. students, we study the effects of exposure to female and male high flyers in high school. We identify a causal effect by exploiting quasi-random variation to peers with highly-educated parents across grades within a school. Greater exposure to male high flyers decreases the likelihood that women obtain a bachelor’s degree, lowers their math and science grades, decreases their LFP and increases fertility. They show lower levels of self-confidence/aspirations. The effects are found for girls with below median ability and for those with at least one college-educated parent. There are no effects of high flyers of either gender on boys.

Utilization of high and low calcium oxide fly ashes as the alternative fillers for natural rubber composites: A waste to wealth approach

Recently, fillers from renewable resources or agricultural wastes have been considered as the alternative fillers to reduce the environmental problems. Therefore, utilization of the fly ashes (FA) collected from the electric power plants as the reinforcing filler in natural rubber (NR) composites was carried out and compared these high (HCaO) and low (LCaO) calcium oxides with carbon black (CB). The FA concentration was varied up to an optimum loading of 1000 parts per hundred rubber (phr) by using melt mixing technique. Particle size and chemical composition of HCaO and LCaO were reported and the properties of NR composites in terms of cure characteristics, Payne effect, mechanical and dynamical properties together with morphologies were examined. It was found that the addition of HCaO significantly reduced the vulcanization time of the NR composites, while the one with LCaO provided higher degree of reinforcement efficiency to the NR matrix. It clearly supports the relation of storage modulus as a function of strain sweep and their morphologies, which are the major requirements in case of composites. Upon increasing of FA loading, NR has changed its role from rubber matrix to an adhesive binder and therefore the Young’s modulus was found to be strongly changed. FA can be used to replace CB in NR composites with the composition ratios starting from 1:2–1:6 phr. Although, CB exhibited a slightly better reinforcing effect than FA, based on the lowered glass transition temperature (Tg), Tan delta (Tan δ) exhibited the same elasticity and CB can be replaced in case of several CB-based composites, particularly, the artificial wood, car stopper and tire industries to produce rubber belt and bead.

Thrombin as a Potential Proxy to Select for Horn Fly Abundance in Beef Cattle.

Horn flies are a major nuisance to cattle and induce significant economic losses. Fly abundance varies within and across breeds and genetic analyses have shown sufficient genetic variation to permit selection. A major bottleneck for selecting against horn fly abundance is the complexity of measuring fly attraction phenotypes. Easy-to-measure proxy phenotypes could be an attractive option to indirectly estimate fly abundance. In the current study, thrombin was investigated as a potential proxy to assess fly abundance. Fly counts and blood samples were collected on 355 cows. Pearson correlation between subjective fly count and thrombin was -0.13, indicating a decrease in fly abundance with the increase in thrombin concentration. When thrombin was discretized into three classes, there was a 22% difference in fly count between the top and bottom classes. Heritability estimates of thrombin were 0.38 and 0.39 using linear and threshold models, respectively. The correlation between estimated thrombin breeding values and fly count was around -0.18. There was a noticeably lower density of high fly counts among animals with high breeding values for thrombin. These results indicate that thrombin could be used in combination with other biological factors to estimate fly abundance and as a proxy for selection against fly abundance.

Four-point bending tests of ECC: Mechanical response and toughness evaluation

This work investigated the mechanical response of engineered cementitious composites (ECC) with high content fly ash by four-point bending tests, and a suitable method was recommended for the flexural toughness evaluation of ECC. The test variables were fiber volume fraction (for polyvinyl alcohol (PVA) fiber), fiber type (PVA and polyethylene (PE)), curing age (56d, 28d and 7d), water-to-binder ratio, sand-to-binder ratio and fly ash content. The results of the tests showed that the crack pattern, deflection-hardening behavior and energy dissipation capacity of ECC were mainly affected by fiber volume fraction, fiber type and curing age. The larger the proportion of fiber pulling out during crack bridging was, the higher the deflection and energy dissipation of ECC exhibited. The commonly used JSCE-SF4 method, ASTM C1609 method and post crack strength (PCS) method for evaluating the flexural toughness of fiber reinforced concrete were not applicable to evaluate the toughness of ECC, because the significant deflection-hardening behavior of ECC could not be considered. An improved method was proposed for flexural toughness evaluation of ECC materials, which included two modified indexes (equivalent initial flexural and post-peak flexural toughness index) and a new index (initial energy factor). The large deformation of ECC was taken into account and the determining the first crack point was eliminated in this new method.

Lightweight Concrete with Agglomerated Aggregate Based on Fly Ash

The production of lightweight concrete is mainly carried out in the traditional way using lightweight ceramic aggregates. The aim of the pilot research was to verify the possibility of producing lightweight concrete based on artificial aggregate in the form of agglomerated aggregate from high temperature fly ash. A representative of such aggregate is the artificial aggregate referred to as aploporite. This aggregate is characterised by comparable grain strength to ceramic aggregates but, on the other hand, has a relatively high absorption rate of up to 30 %. Concrete formulations with up to 50% replacement of natural aggregate by aploporite have been proposed in order to achieve the volumetric weights characteristic of lightweight concrete. The results obtained confirmed that it is possible to produce lightweight concrete with this aggregate and to achieve strengths comparable to those of ordinary concrete.

Synthesis of kaliophilite from high calcium fly ash: Effect of alkali concentration

In recent years, the synthesis of zeolite-like products (such as kaliophilite) has been a hot spot due to its high thermal stability, which is excellent inorganic insulating filler and is expected to be widely applied in the field of fireproof materials. Therein, high calcium fly ash is applied to synthesize kaliophilite by hydrothermal method. The microstructure evolution of kaliophilite was investigated, and the effect of alkali concentration on the kaliophilite formation mechanism was analyzed by XRD, SEM, TG-DSC, FT-IR and 29Si NMR. The results showed that the synthesized kaliophilite presented high thermal stability, and the mass loss was low by 8.83 % at 1000 °C. Hydrothermal promoted the formation of kaliophilite that Q4(0Al), Q4(1Al), Q4(2Al), Q4(3Al) and crystal silicon turned into Q4(4Al) after hydrothermal transformation. Furthermore, alkali concentration played a key role in the hydrothermal transforming process that low alkali concentration below 8 mol/L had little effect on the synthesis of kaliophilite, while high alkali concentration (≥ 8 mol/L) contributed to the formation of kaliophilite.

Towards greener one-part geopolymers through solid sodium activators modification

This paper investigates the influence of various solid activators and their mixing parameters on the physical, mechanical and microstructural characteristics of greener one-part geopolymers (OPG) based on high calcium fly ash. The high calcium fly ash that has rarely been explored was utilised to develop OPG in this study. The anhydrous sodium metasilicate (Na2SiO3) with negative environmental impact propelled the partial replacement of Na2SiO3 with sodium hydroxide (NaOH) and sodium carbonate (Na2CO3). Two sets of high calcium fly ash OPGs were developed: (1) the MH-OPG comprised Na2SiO3 and NaOH; (2) the MC-OPG comprised Na2SiO3 and Na2CO3. The optimal MH-OPG (73 MPa) and MC-OPG (75 MPa) exhibited superior compressive strength, higher than the minimal requirement (>28 MPa) of ASTM C150/C150M-18 for construction binder material. Various solid alkali activators triggered different reaction mechanisms, yielding distinctive reaction products that contributed to strength growth. The sodium calcium aluminosilicate hydrate ((N,C)-A-S-H) gel was developed in MH-OPG, whereas the sodium carbonate hydrate, sodium aluminosilicate hydrate (N-A-S-H) and calcium aluminosilicate hydrate (C-A-S-H) binding phases were developed in the MC-OPG. Although Na2CO3 reduced the water demand, improved the fluidity and setting time, the MC-OPG was more sensitive to the alteration of mixing compositions, suggesting a tougher performance control during field application than the MH-OPG. The total embodied carbon (EC) of MC-OPG was lowered by 15.4% compared to that of MH-OPG. The embodied carbon index (ECI) of MH-OPG and MC-OPG were 81.3% and 84.7% less than that of OPC products. This work suggests that substituting Na2SiO3 with NaOH or Na2CO3 effectively produced a greener construction material without compromising mechanical strength.

Effect of cooking duration on the antioxidant and antihyperglycemic properties of Andrographis paniculata (king of bitters) leaves in high sucrose diet-fed fruit flies (Drosophila melanogaster)

Effect of cooking duration on the antioxidant and antihyperglycemic properties of Andrographis paniculata (king of bitters) leaves in high sucrose diet-fed fruit flies (Drosophila melanogaster)

Corrosion evaluation of steel bars in steam-cured concrete under chloride attack and alkali–silica reaction

One of the challenges to reinforced concrete slabs in bridges is deterioration due to rebar corrosion by deicing salts. In order to simulate a concrete slab subjected to deicing salt penetration from the top surface of the bridge slab during winter, high-strength steam-cured concrete with double-layer reinforcements was exposed to 10% sodium chloride solution to investigate rebar corrosion. Five concrete mix proportions were prepared, including high early strength concrete and concrete containing fly ash and blast furnace slag as supplementary cementitious materials (SCMs). For both the high early strength and fly ash concretes, alkali active andesite in the pessimum proportion was mixed with coarse aggregates to investigate the effect of alkali–silica reaction (ASR) on rebar corrosion. It was found that the combined effects of chloride attack and ASR adversely affected the corrosion resistance of high early strength concrete. Fly ash concrete had excellent performance as to corrosion resistance and ASR mitigation. Results also showed that a widely used electrochemical technique known as the half-cell potential test can satisfactorily diagnose corrosion of double-layer reinforced concrete. Concrete specimens containing SCMs with no ASR threat showed no signs of steel bar corrosion and significantly low chloride diffusion coefficients after 3 years.

Stabilization of Recycled Concrete Aggregate Using High Calcium Fly Ash Geopolymer as Pavement Base Material

This research investigated high calcium fly ash geopolymer stabilized recycled concrete aggregate (RCA-FAG) as pavement base material. The effect of recycled concrete aggregate (RCA):high calcium fly ash (FA) ratios, sodium silicate (Na2SiO3):sodium hydroxide (NaOH) ratio, and curing time on the unconfined compressive strength (UCS) and scanning electron microscope (SEM) properties of RCA-FAG samples were evaluated. The maximum dry unit weight of the RCA-FAG sample was 20.73 kN/m3 at RCA:FA ratio of 80:20 and Na2SiO3:NaOH ratio of 60:40. The 7-d UCS of RCA-FAG samples increased as the FA content and Na2SiO3:NaOH ratio increased. The 7-d UCS of the RCA-FAG sample was better than that of the RCA with no FA because FA particles filled in RCA particles, resulting in a dense matrix. The 7-d UCS of RCA-FAG samples passed the 7-d UCS requirement for the low-traffic road. All ingredients met the 7-d UCS requirement for the high-traffic road except the sample with RCA:FA of 100:0 and Na2SiO3:NaOH of 50:50 and 60:40. The 7-d SEM images indicated that spherical FA and RCA particles are bonded together, resulting in the dense matrix for all Na2SiO3:NaOH ratios. The proposed equation for predicting the UCS of RCA-FAG offered a good coefficient of correlation, which is useful in designing pavement base material from RCA-FAG material.

HYPOXIA AWARENESS TRAINING AND HYPOXIA SIGNATURE: AN APPRAISAL

Hypoxia is an omnipresent threat in high altitude flying and considered the number one physiological problem in aviation. The Hypoxia incident is at its minimum in last one century since heavier than air flying began in 1903. This could be possible because of improved and robust oxygen system design over the last century and Hypoxia Awareness Training which an aviator receives throughout his career. Acute exposure to hypoxia leads to manifestation of various Psychomotor and Cognitive signs and symptoms which vary from person to person. However, this constellation of symptoms does not vary in the same individual on repeated exposure to acute hypoxia. This has been termed as Hypoxia Signature which forms the basis of Hypoxia Awareness Training among aircrew. Various studies have concluded that Hypoxia Awareness Training results in early identification of in-flight hypoxia leading to corrective action on time and prevention of catastrophic events in the air. Hypobaric Chamber Training has traditionally been the mainstay for hypoxia awareness training. However, various other modalities like Reduced Oxygen Breathing Device (ROBD) and Combined Altitude and Oxygen Depleted (CADO) paradigm are also being used to impart Hypoxia Awareness Training. In this article, author has reviewed need for Hypoxia Awareness Training (HAT), rationale behind such training along with various methods being employed currently in IAF and world over. The article also discusses objective evidence of effectiveness of HAT and its need to be extended to commercial and general aviation to prevent avoidable loss of lives, property and precious resources due to hypoxia.

Study on laboratory and engineering application of multi source solid waste based soft soil solidification materials

The study on multi source solid wastes solidified organic clay is limited, as well as engineering application in deep mixing pile. In this paper, steel slag powder (SS) and high calcium fly ash (HCFA) are used as raw materials, by-product sodium sulfate was recycled to develop a kind of multi-source solid waste based low carbon emission solidifying material. The solidification mechanism was analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), thermogravimetry (TG) and pH tests. Finally, the solidifying agent was applied to the deep mixing pile project, and the solidification effect was studied. The results reveal that the fluidity of preferred multi-source solid waste based solidifying agent slurry was 170 mm (50 °C, 1 h), which is 55% higher than that of cement. The optimum content of solidifying agent in organic clay was determined as 27%, and the unconfined compressive strength (28d) of the solidified soil was 5 MPa. Na2SO4 showed double effect of alkali activation and dense packing. The pH of solidifying agent slurry was maintained at 13.31 after the addition of 0.7% Na2SO4. More C-S-H and AFt generated under the effect of pH and SO42-. The application study reveals that the multi-source solid waste based solidifying agent deep mixing pile exhibited excellent pile integrity in organic clay. The compressive strength of deep mixing pile with the 40 kg/m solidifying agent at the curing of 14d and 28d is 0.95 MPa and 2.77 MPa, respectively. Solidifying agent deep mixing pile field strength prediction equation “y = 0.832x+ 0.1225, R2 = 0.936″ was proposed.

Utilisation of waste-to-energy fly ash in ceramic tiles

• Sustainable and effective utilisation of high calcium MSWI fly ash (FA) in unglazed ceramic tiles has been investigated. • The tiles containing 3–15 wt% high calcium FA achieved comparable or superior performances to the control sample fired at 1150 °C. • Flexural strength of 3% FA tiles enhanced from 15.88 to 24.41 MPa. • The 3% and 6% FA tiles have a lower water absorption (<6%) than the control tiles. • Heavy metal leaching levels are within the thresholds at pH 2.9 and 5.0. Municipal solid waste incineration fly ash (MSWI FA) derived from the waste to energy plants has growing attention due to its risk of land contamination upon mass disposals. Authorities seek ways and means of its safe disposal by spending high costs to manage these wastes. This paper investigates an efficient and novel use of high calcium MSWI FA to manufacture ceramic tiles which are in high demand to facilitate increased building construction. A number of experiments were conducted by adding 3 wt% − 15 wt% MSWI FA to tiles fired at 1150 °C to investigate the key properties, including firing shrinkage, water absorption, breaking strength, modulus of rupture, and heavy metal leachates. Detailed morphological analysis such as X-ray diffraction, scanning electron microscope imaging, and X-ray micro-computed tomography was also performed with the new fly ash matrix to understand the performance of MSWI FA incorporated ceramic tiles. Results indicate MSWI FA reduces density, but the addition of 3 wt% − 15 wt% MSWI FA can achieve comparable or superior technical performance to the control sample in addition to satisfying heavy metal leachate limits specified by national standards. Outcomes reveal that the novel use of MSWI FA to manufacture ceramic tiles has great potential for a sustainable tile manufacturing process and possible energy savings in the firing process while enabling an efficient way to manage MSWI wastes.