Abstract: Silver-exchanged zeolites and clays are used in
polymer composites to confer broad-spectrum antimicrobial
properties on a range of functional materials. Tobermorite is a layer
lattice mineral whose potential as a carrier for Ag+ ions in
antibacterial composites has not yet been investigated. Accordingly,
in this study, synthetic tobermorite was ion-exchanged with 10 wt%
silver ions and the resulting material was incorporated into a
composite film with chitosan. Chitosan is a biocompatible,
biodegradable derivative of chitin, a polysaccharide obtained from
the shells of crustaceans. The solvent-cast Ag+-exchanged
tobermorite-chitosan films were found to exhibit antimicrobial action
against Staphylococcus aureus, Escherichia coli and Pseudomonas
aeruginosa.
Abstract: In the forming of ceramic materials the plasticity
concept is commonly used. This term is related to a particular
mechanical behavior when clay is mixed with water. A plastic
ceramic material shows a permanent strain without rupture
when a compressive load produces a shear stress that exceeds
the material-s yield strength. For a plastic ceramic body it
observes a measurable elastic behavior before the yield
strength and when the applied load is removed. In this work, a
mathematical model was developed from applied concepts of
the plasticity theory by using the stress/strain diagram under
compression.
Abstract: The acidity of different raw Jordanian clays
containing zeolite, bentonite, red and white kaolinite and diatomite
was characterized by means of temperature programmed desorption
(TPD) of ammonia, conversion of 2-methyl-3-butyn-2-ol (MBOH),
FTIR and BET-measurements. FTIR spectra proved presence of
silanol and bridged hydroxyls on the clay surface. The number of
acidic sites was calculated from experimental TPD-profiles. We
observed the decrease of surface acidity correlates with the decrease
of Si/Al ratio except for diatomite. On the TPD-plot for zeolite two
maxima were registered due to different strength of surface acidic
sites. Values of MBOH conversion, product yields and selectivity
were calculated for the catalysis on Jordanian clays. We obtained that
all clay samples are able to convert MBOH into a major product
which is 3-methyl-3-buten-1-yne (MBYNE) catalyzed by acid
surface sites with the selectivity close to 70%. There was found a
correlation between MBOH conversion and acidity of clays
determined by TPD-NH3, i.e. the higher the acidity the higher the
conversion of MBOH. However, diatomite provided the lowest
conversion of MBOH as result of poor polarization of silanol groups.
Comparison of surface areas and conversions revealed the highest
density of active sites for red kaolinite and the lowest for zeolite and
diatomite.
Abstract: This paper studies the application of a variety of
sawdust materials in the production of lightweight insulating bricks.
First, the mineralogical and chemical composition of clays was determined. Next, ceramic bricks were fabricated with different
quantities of materials (3–6 and 9 wt. % for sawdust, 65 wt. % for grey clay, 24–27 and 30 wt. % for yellow clay and 2 wt% of tuff).
These bricks were fired at 800 and 950 °C. The effect of adding this sawdust on the technological behaviour of the brick was assessed by
drying and firing shrinkage, water absorption, porosity, bulk density
and compressive strength. The results have shown that the optimum
sintering temperature is 950 °C. Below this temperature, at 950 °C,
increased open porosity was observed, which decreased the compressive strength of the bricks. Based on the results obtained, the
optimum amounts of waste were 9 wt. % sawdust of eucalyptus, 24 wt. % shaping moisture and 1.6 particle size diameter. These percentages produced bricks whose mechanical properties were
suitable for use as secondary raw materials in ceramic brick
production.
Abstract: Soft clays are defined as cohesive soil whose water
content is higher than its liquid limits. Thus, soil-cement mixing is
adopted to improve the ground conditions by enhancing the strength
and deformation characteristics of the soft clays. For the above
mentioned reasons, a series of laboratory tests were carried out to
study some fundamental mechanical properties of cement stabilized
soft clay. The test specimens were prepared by varying the portion of
ordinary Portland cement to the soft clay sample retrieved from the
test site of RECESS (Research Centre for Soft Soil). Comparisons
were made for both homogeneous and columnar system specimens
by relating the effects of cement stabilized clay of for 0, 5 and 10 %
cement and curing for 3, 28 and 56 days. The mechanical properties
examined included one-dimensional compressibility and undrained
shear strength. For the mechanical properties, both homogeneous and
columnar system specimens were prepared to examine the effect of
different cement contents and curing periods on the stabilized soil.
The one-dimensional compressibility test was conducted using an
oedometer, while a direct shear box was used for measuring the
undrained shear strength. The higher the value of cement content, the
greater is the enhancement of the yield stress and the decrease of
compression index. The value of cement content in a specimen is a
more active parameter than the curing period.
Abstract: CTMA-bentonite and BTEA-Bentonite prepared by Na-bentonite cation exchanged with cetyltrimethylammonium(CTMA) and benzyltriethylammonium (BTEA). Products were characterized by XRD and IR techniques.The d001 spacing value of CTMA-bentonite and BTEA-bentonite are 7.54Å and 3.50Å larger than that of Na-bentonite at 100% cation exchange capacity, respectively. The IR spectrum showed that the intensities of OH stretching and bending vibrations of the two organoclays decreased greatly comparing to untreated Na-bentonite. Batch experiments were carried out at 303 K, 318 K and 333 K to obtain the sorption isotherms of Crystal violet onto the two organoclays. The results show that the sorption isothermal data could be well described by Freundlich model. The dynamical data for the two organoclays fit well with pseudo-second-order kinetic model. The adsorption capacity of CTMA-bentonite was found higher than that of BTEA-Bentonite. Thermodynamic parameters such as changes in the free energy (ΔG°), the enthalpy (ΔH°) and the entropy (ΔS°) were also evaluated. The overall adsorption process of Crystal violet onto the two organoclays were spontaneous, endothermic physisorption. The CTMA-bentonite and BTEA-Bentonite could be employed as low-cost alternatives to activated carbon in wastewater treatment for the removal of color which comes from textile dyes.
Abstract: This paper is concerned with the study of mineralogy
and engineering characteristics of soil materials derived from the
eastern part of Nile Delta. The clay minerals of the studied soil by
using X- ray diffraction are mainly illite (average 72.6 %) and
kaolinite (average 2.6 %), expandable portion in illite-smectite mixed
layer (average 7 %). Smectite is more abundant in fluviatile clays,
whereas kaolinite is more abundant in lagoonal clays. On the other
hand, illite and illite-smectite are more abundant in marine clays. The
geotechnical results show that the soil under study consists mainly of
about 0.3 % gravel, 5 % sand, 51.5 % silt and 42.2 % clay in average.
The average shrinkage limit attains 11 % whereas the average value
of the plasticity index is 23.4 %. The free swelling ranges from 40 %
to 75 % and has a value of 55 % giving an indication about the
inadequacy of such soil under foundations.
From a construction point of view, the soil under investigation
poses many problems even under light foundations due to the
swelling and shrinkage. Such swelling and shrinkage is due to the
high content of soil materials in the expandable clay minerals of illite
and smectite. Based on the results of the present and earlier studies,
trial application of soil stabilisation is recommended.
Abstract: Compacted clay liners (CCLs) are the main materials
used in waste disposal landfills due to their low permeability. In this
study, the effect on the shear resistant of clays with inorganic salt
solutions as permeate fluid was experimentally investigated. For this
purpose, NaCl inorganic salt solution at concentrations of 2, 5, 10%
and deionized water were used. Laboratory direct shear and Vane
shear tests were conducted on three compacted clays with low,
medium and high plasticity. Results indicated that the solutions type
and its concentration affect the shear properties of the mixture. In the
light of this study, the influence magnitude of these inorganic salts in
varies concentrations in different clays were determined and more
suitable compacted clay with the compare of plasticity were found.
Abstract: The present work deals with the stabilisation of
organic clay using hydrated lime. Artificial organic clays were
prepared by adding kaolin and different humic acid contents. Results
given by physical testing show that the presence of humic acid has a
drawback effect on the untreated organic clay. The decrease in
specific gravity value was accompanied by a decrease in dry density
and plasticity of clay at higher humic acid contents. Significant
increase in shear strength at 7 days of curing period is observed in the
lime-treated samples up to 5% lime content. However shear strength
of lime-treated organic clay decreases at longer curing periods. The
results given by laboratory testing is further verified by
microstructure analysis. Based on the results obtained in this study, it
can be concluded that the presence of more than 1.5% humic acid
reduces significantly the efficiency of lime stabilization in organic
clays.