Abstract: The recycling of concrete, bricks and masonry rubble
as concrete aggregates is an important way to contribute to a
sustainable material flow. However, there are still various
uncertainties limiting the widespread use of Recycled Concrete
Aggregates (RCA). The fluctuations in the composition of grade
recycled aggregates and their influence on the properties of fresh and
hardened concrete are of particular concern regarding the use of
RCA. Most of problems occurring while using recycled concrete
aggregates as aggregates are due to higher porosity and hence higher
water absorption, lower mechanical strengths, residual impurities on
the surface of the RCA forming weaker bond between cement paste
and aggregate. So, the reuse of RCA is still limited. Efficient
polymer based treatment is proposed in order to reuse RCA easier.
The silicon-based polymer treatments of RCA were carried out and
were compared. This kind of treatment can improve the properties of
RCA such as the rate of water absorption on treated RCA is
significantly reduced.
Abstract: In the present work homogeneous silica film on
silicon was fabricated by colloidal silica sol. The silica sol precursor
with uniformly granular particle was derived by the alkaline
hydrolysis of tetraethoxyorthosilicate (TEOS) in presence of glycerol
template. The film was prepared by dip coating process. The
templated hetero-structured silica film was annealed at elevated
temperatures to generate nano- and meso porosity in the film. The
film was subsequently annealed at different temperatures to make it
defect free and abrasion resistant. The sol and the film were
characterized by the measurement of particle size distribution,
scanning electron microscopy, XRD, FTIR spectroscopy,
transmission electron microscopy, atomic force microscopy,
measurement of the refractive index, thermal conductivity and
abrasion resistance. The porosity of the films decreased whereas
refractive index and dielectric constant of it `increased with the
increase in the annealing temperature. The thermal conductivity of
the films increased with the increase in the film thickness. The
developed porous silica film holds strong potential for use in
different areas.
Abstract: The storage of chemical fertilizers in concrete building often leads to durability problems due to chemical attack. The damage of concrete is mostly caused by certain ammonium salts. The main purpose of the research is to investigate the durability properties of concrete being exposed to ammonium nitrate solution. In this investigation, experiments are conducted on concrete type G50 and G60. The leaching process is achieved by the use of 20% concentration solution of ammonium nitrate. The durability properties investigated are water absorption, volume of permeable voids, and sorptivity. Compressive strength, pH value, and degradation depth are measured after a certain period of leaching. A decrease in compressive strength and an increase in porosity are found through the conducted experiments. Apart from that, the experimental data shows that pH value decreases with increased leaching time while the degradation depth of concrete increases with leaching time. By comparing concrete type G50 and G60, concrete type G60 is more resistant to ammonium nitrate attack.
Abstract: Effect of high temperature exposure on properties of cement mortar containing municipal solid waste incineration (MSWI) bottom ash as partial natural aggregate replacement is analyzed in the paper. The measurements of mechanical properties, bulk density, matrix density, total open porosity, sorption and desorption isotherms are done on samples exposed to the temperatures of 20°C to 1000°C. TGA analysis is performed as well. Finally, the studied samples are analyzed by IR spectroscopy in order to evaluate TGA data.
Abstract: The Yazd-Ardakan basin in Central Iran has two separated aquifers. The shallow unconfined aquifer is supplies 40 Qanats. The deep saturated confined aquifer is the main water storage. Due to over-withdrawal, water table has been decreasing during last 25 years. Recent study shows that the shortage of the aquifer is about 16 meters and land subsidence is 0.5 - 1.2 meters. Long deep cracks are found just above the aquifer and devour the irrigation water and floods. Although the most cracks direction is NW-SE and could be compared to the main direction of YA basin, there is no direct evidence for relation between land subsidence and the huge cracks. Large-scale water pumping has been decreased the water pressure in aquifer. The pressure decline disturbed the balance and increased the pressure of overlying sediments. So porosity decreased and compaction started. Then, sediments compaction developed and made land subsidence and some huge cracks slowly.
Abstract: The soil moisture content is an important property of
the soil. The results of mean weekly gravimetric soil moisture
content, measured for the three soil layers within the A horizon,
showed that it was higher for the top 5 cm over the whole period of
monitoring (15/7/2004 up to 10/11/05) with the variation becoming
greater during winter time. This reflects the pattern of rainfall in
Ireland which is spread over the whole year and shows that light
rainfall events during summer time were compensated by loss
through evapotranspiration, but only in the top 5 cm of soil. This
layer had the highest porosity and highest moisture holding capacity
due to the high content of organic matter. The gravimetric soil
moisture contents of the top 5 cm and the underlying 5-15 and 15-25
cm layers show that bottom site of the Hill Field had higher soil
moisture content than the middle and top sites during the whole
period of monitoring.
Abstract: The aluminum bronze matrix alumina composites using hot press and resin infiltration were investigated to study their porosities, hardness, bending strengths, and microstructures. The experiment results show that the hardness of the sintered composites with the decrease of porosity increases. The composites without and with resin infiltration have about HRF 42-61 of about 34-40% of porosity and about HRF 62-83 of about 30-36% of porosity, respectively. Besides, the alumina composites contain a more amount of iron and nickel powders would cause a lower bending strength due to forming some weaker bonding among the iron, nickel, copper, aluminum under this hot pressing of shorter time.
Abstract: Methanol-to-olefins coupled with transformation of
coal or natural gas to methanol gives an interesting and promising way
to produce ethylene and propylene. To investigate solid concentration
in gas-solid fluidized bed for methanol-to-olefins process catalyzed by
SAPO-34, a cold model experiment system is established in this paper.
The system comprises a gas distributor in a 300mm internal diameter
and 5000mm height acrylic column, the fiber optic probe system and
series of cyclones. The experiments are carried out at ambient
conditions and under different superficial gas velocity ranging from
0.3930m/s to 0.7860m/s and different initial bed height ranging from
600mm to 1200mm. The effects of radial distance, axial distance,
superficial gas velocity, initial bed height on solid concentration in the
bed are discussed. The effects of distributor shape and porosity on
solid concentration are also discussed. The time-averaged solid
concentration profiles under different conditions are obtained.
Abstract: A CFD software was employed to analyze the
characteristics of the flat round porous aerostatic bearings. The effects
of gap between the bearing and the guide way and the porosity of the
porous material on the load capacity of the bearing were studied. The
adequacy of the simulation model and the approach was verified. From
the parametric study, it is found that the depth of the flow path does not
influence the load capacity of the bearing; the load capacity of the
bearing will decrease if the thickness of the porous material increases
or the porous material protrudes above the bearing housing; the
variation of the chamfer at the edge of the bearing does not affect the
bearing load capacity. For a bearing with an air gap of 5μm and a
porosity of 0.1, the average load capacity and the pressure distribution
of the bearing are nearly unchanged no matter the bearing moves at a
constant or a varying speed.
Abstract: There are few studies on eggshell of leatherback turtle
which is endangered species in Thailand. This study was focusing on
the ultrastructure and elemental composition of leatherback turtle
eggshells collected from Andaman Sea Shore, Thailand during the
nesting season using scanning electron microscope (SEM). Three
eggshell layers of leatherback turtle; the outer cuticle layer or
calcareous layer, the middle layer or middle multistrata layer and the
inner fibrous layer were recognized. The outer calcareous layer was
thick and porosity which consisted of loose nodular units of various
crystal shapes and sizes. The loose attachment between these units
resulted in numerous spaces and openings. The middle layer was
compact thick with several multistrata and contained numerous
openings connecting to both outer cuticle layer and inner fibrous
layer. The inner fibrous layer was compact and thin, and composed of
numerous reticular fibers. Energy dispersive X-ray microanalysis
detector revealed energy spectrum of X-rays character emitted from
all elements on each layer. The percentages of all elements were
found in the following order: carbon (C) > oxygen (O) > calcium
(Ca) > sulfur (S) > potassium (K) > aluminum (Al) > iodine (I) >
silicon (Si) > chlorine (Cl) > sodium (Na) > fluorine (F) >
phosphorus (P) > magnesium (Mg). Each layer consisted of high
percentage of CaCO3 (approximately 98%) implying that it was
essential for turtle embryonic development. A significant difference
was found in the percentages of Ca and Mo in the 3layers. Moreover,
transition metal, metal and toxic non-metal contaminations were
found in leatherback turtle eggshell samples. These were palladium
(Pd), molybdenum (Mo), copper (Cu), aluminum (Al), lead (Pb), and
bromine (Br). The contamination elements were seen in the outer
layers except for Mo. All elements were readily observed and
mapped using Smiling program. X-ray images which mapped the
location of all elements were showed. Calcium containing in the
eggshell appeared in high contents and was widely distributing in
clusters of the outer cuticle layer to form CaCO3 structure. Moreover,
the accumulation of Na and Cl was observed to form NaCl which was
widely distributing in 3 eggshell layers. The results from this study
would be valuable on assessing the emergent success in this
endangered species.
Abstract: This investigation examines the effect of the sintering
temperature curve in manufactured nickel powder capillary structure
(wick) for a loop heat pipe (LHP). The sintering temperature curve is
composed of a region of increasing temperature; a region of constant
temperature and a region of declining temperature. The most important
region is that in which the temperature increases, as an index in the
stage in which the temperature increases. The wick of nickel powder is
manufactured in the stage of fixed sintering temperature and the time
between the stage of constant temperature and the stage of falling
temperature. When the slope of the curve in the region of increasing
temperature is unity (equivalent to 10 °C/min), the structure of the
wick is complete and the heat transfer performance is optimal. The
result of experiment test demonstrates that the heat transfer
performance is optimal at 320W; the minimal total thermal resistance
is approximately 0.18°C/W, and the heat flux is 17W/cm2; the internal
parameters of the wick are an effective pore radius of 3.1 μm, a
permeability of 3.25×10-13m2 and a porosity of 71%.
Abstract: The efficiency of chitosan beads processed from 4
marine animal shells; white leg shrimp (Litopenaeus vannamei), mud
crab (Scylla sp.), horseshoe crab (Carcinoscorpius rotundicauda),
and cuttlefish bone (Sepia sp.), for the adsorption experiments of
ammonia and formaldehyde were investigated. The porosities of
chitosan from the shells looked like beads were distinctly examined
under SEM. The original pores of those shells on the surface areas
compose of evenly fine pores. The shell beads of cuttlefish bone and
horseshoe crab show the larger probably even porosity, while on
those white leg shrimp and mud crab contain various large and fine
pores. The best adsorption at pH 9 in 18 mg/l ammonia at 2 hours
yield on cuttlefish bone, horseshoe crab, mud crab and white leg
shrimp with the average percent of 59.12, 51.45, 45.66 and 43.52,
respectively. Within 30 minutes the formaldehyde absorbers (at pH 5
in 8 μg/ml) revealed 46.27, 26.56, and 18.04 percent capacities in
cuttlefish bone, mud crab and white leg shrimp beads; while 22.44
percent in the horseshoe crab at pH 7. The adsorption capacities and
the amounts of beads showed a positive correlation. The adsorption
capacity relationship between pH and the gas concentrations were
affected by these qualities of chitosan beads.
Abstract: Significant changes in oil and gas drilling have
emphasized the need to verify the integrity and reliability of drill
stem components. Defects are inevitable in cast components,
regardless of application; but if these defects go undetected, any
severe defect could cause down-hole failure.
One such defect is shrinkage porosity. Castings with lower level
shrinkage porosity (CB levels 1 and 2) have scattered pores and do
not occupy large volumes; so pressure testing and helium leak testing
(HLT) are sufficient for qualifying the castings. However, castings
with shrinkage porosity of CB level 3 and higher, behave erratically
under pressure testing and HLT making these techniques insufficient
for evaluating the castings- integrity.
This paper presents a case study to highlight how the radiography
technique is much more effective than pressure testing and HLT.
Abstract: The paper discusses a 3D numerical solution of the inverse boundary problem for a continuous casting process of alloy. The main goal of the analysis presented within the paper was to estimate heat fluxes along the external surface of the ingot. The verified information on these fluxes was crucial for a good design of a mould, effective cooling system and generally the whole caster. In the study an enthalpy-porosity technique implemented in Fluent package was used for modeling the solidification process. In this method, the phase change interface was determined on the basis of the liquid fraction approach. In inverse procedure the sensitivity analysis was applied for retrieving boundary conditions. A comparison of the measured and retrieved values showed a high accuracy of the computations. Additionally, the influence of the accuracy of measurements on the estimated heat fluxes was also investigated.
Abstract: Methanol-to-olefins (MTO) coupled with
transformation of coal or natural gas to methanol gives an interesting
and promising way to produce ethylene and propylene. To investigate
solid concentration in gas-solid fluidized bed for methanol-to-olefins
process catalyzed by SAPO-34, a cold model experiment system is
established in this paper. The system comprises a gas distributor in a
300mm internal diameter and 5000mm height acrylic column, the
fiber optic probe system and series of cyclones. The experiments are
carried out at ambient conditions and under different superficial gas
velocity ranging from 0.3930m/s to 0.7860m/s and different initial bed
height ranging from 600mm to 1200mm. The effects of radial
distance, axial distance, superficial gas velocity, initial bed height on
solid concentration in the bed are discussed. The effects of distributor
shape and porosity on solid concentration are also discussed. The
time-averaged solid concentration profiles under different conditions
are obtained.
Abstract: The combustion of liquid fuel in the porous burner
(PB) was experimented to investigate evaporation mechanism and
combustion behavior. The diesel oil was used as fuel and the pebbles
carefully chosen in the same size like the solid sphere homogeneously
was adopted as the porous media. Two structures of the liquid porous
burner, i.e. the PB without and with installation of porous emitter
(PE), were performed. PE was installed by lower than PB with
distance of 20 cm. The pebbles having porosity (φ) of 0.45 and 0.52
were, respectively, used in PB and PE. The fuel was supplied dropwise
from the top through the PB and the combustion was occurred between
PB and PE. Axial profiles of temperature along the burner length were
measured to clarify the evaporation and combustion phenomena. The
pollutant emission characteristics were monitored at the burner exit.
From the experiment, it was found that the temperature profiles of both
structures decreased with the three ways swirling air flows (QA)
increasing. On the other hand, the temperature profiles increased with
fuel heat input (QF). Obviously, the profile of the porous burner
installed with PE was higher than that of the porous burner without
PE
Abstract: Magnesium alloys have gained increased attention in recent years in automotive, electronics, and medical industry. This because of magnesium alloys have better properties than aluminum alloys and steels in respects of their low density and high strength to weight ratio. However, the main problems of magnesium alloy welding are the crack formation and the appearance of porosity during the solidification. This paper proposes a unique technique to weld two thin sheets of AZ31B magnesium alloy using a paste containing Ag nanoparticles. The paste containing Ag nanoparticles of 5 nm in average diameter and an organic solvent was used to coat the surface of AZ31B thin sheet. The coated sheet was heated at 100 °C for 60 s to evaporate the solvent. The dried sheet was set as a lower AZ31B sheet on the jig, and then lap fillet welding was carried out by using a pulsed Nd:YAG laser in a closed box filled with argon gas. The characteristics of the microstructure and the corrosion behavior of the joints were analyzed by opticalmicroscopy (OM), energy dispersive spectrometry (EDS), electron probe micro-analyzer (EPMA), scanning electron microscopy (SEM), and immersion corrosion test. The experimental results show that the wrought AZ31B magnesium alloy can be joined successfully using Ag nanoparticles. Ag nanoparticles insert promote grain refinement, narrower the HAZ width and wider bond width compared to weld without and insert. Corrosion rate of welded AZ31B with Ag nanoparticles reduced up to 44 % compared to base metal. The improvement of corrosion resistance of welded AZ31B with Ag nanoparticles due to finer grains and large grain boundaries area which consist of high Al content. β-phase Mg17Al12 could serve as effective barrier and suppressed further propagation of corrosion. Furthermore, Ag distribution in fusion zone provide much more finer grains and may stabilize the magnesium solid solution making it less soluble or less anodic in aqueous
Abstract: This paper presents the experiment results of investigating the effects of adding various types and proportions of fibre on mechanical strength and permeability characteristics of recycled aggregate concrete (RAC), which was produced with treated coarse recycled concrete aggregate (RCA). Two types of synthetic fibres (i.e., barchip and polypropylene fibre) with various volume fractions were added to the RAC, which was calculated by the weight of the cement. The hardened RAC properties such as compressive strength, flexural strength, ultrasonic pulse velocity, water absorption and total porosity at the curing ages of 7 and 28 days were evaluated and compared with the properties of the control specimens. Results indicate that the treated coarse RCA enhances the mechanical strength and permeability properties of RAC and adding barchip fibre further optimises the results. Adding 1.2% barchip fibre has the best effect on the mechanical strength performance of the RAC.
Abstract: Physical and mechanical properties of Russian olive
fruits were measured at moisture content of 14.43% w.b. The results
revealed that the mean length, width and thickness of Russian olive
fruits were 20.72, 15.73 and 14.69mm, respectively. Mean mass and
volume of Russian olive fruits were measured as 1.45 g and 2.55 cm3,
respectively. The sphericity, aspect ratio and surface area were
calculated as 0.81, 0.72 and 8.96 cm2, respectively, while arithmetic
mean diameter, geometric mean diameter and equivalent diameter of
Russian olive fruits were 17.05, 16.83 and 16.84 mm, respectively.
Whole fruit density, bulk density and porosity of jujube fruits were
measured and found to be 1.01 g/cm3, 0.29 g/cm3 and 69.5%,
respectively. The values of static coefficient of friction on three
surfaces of glass, galvanized iron and plywood were 0.35, 0.36 and
0.43, respectively. The skin color (L*, a*, b*) varied from 9.92 to
16.08; 2.04 to 3.91 and 1.12 to 3.83, respectively. The values of
rupture force, deformation, energy absorbed and hardness were found
to be between 12.14-16.85 N, 2.16-4.25 mm, 3.42-6.99 N mm and
17.1-23.85 N/mm.
Abstract: Brick is one of the most common masonry units used as building material. Due to the demand, different types of waste have been investigated to be incorporated into the bricks. Many types of sludge have been incorporated in fired clay brick for example marble sludge, stone sludge, water sludge, sewage sludge, and ceramic sludge. The utilization of these waste materials in fired clay bricks usually has positive effects on the properties such as lightweight bricks with improved shrinkage, porosity, and strength. This paper reviews on utilization of different types of sludge wastes into fired clay bricks. Previous investigations have demonstrated positive effects on the physical and mechanical properties as well as less impact towards the environment. Thus, the utilizations of sludge waste could produce a good quality of brick and could be one of alternative disposal methods for the sludge wastes.