Abstract: This paper presents the findings of an
experimental investigation to study the effect of alkali content
in geopolymer mortar specimens exposed to sulphuric acid.
Geopolymer mortar specimens were manufactured from Class F fly
ash by activation with a mixture of sodium hydroxide and sodium
silicate solution containing 5% to 8% Na2O. Durability of specimens
were assessed by immersing them in 10% sulphuric acid solution and
periodically monitoring surface deterioration and depth of
dealkalization, changes in weight and residual compressive strength
over a period of 24 weeks. Microstructural changes in the specimens
were studied with Scanning electron microscopy (SEM) and EDAX.
Alkali content in the activator solution significantly affects the
durability of fly ash based geopolymer mortars in sulphuric acid.
Specimens manufactured with higher alkali content performed better
than those manufactured with lower alkali content. After 24 weeks in
sulphuric acid, specimen with 8% alkali still recorded a residual
strength as high as 55%.
Abstract: Batch adsorption of recalcitrant melanoidin using the abundantly available coal fly ash was carried out. It had low specific surface area (SBET) of 1.7287 m2/g and pore volume of 0.002245 cm3/g while qualitative evaluation of the predominant phases in it was done by XRD analysis. Colour removal efficiency was found to be dependent on various factors studied. Maximum colour removal was achieved around pH 6, whereas increasing sorbent mass from 10g/L to 200 g/L enhanced colour reduction from 25% to 86% at 298 K. Spontaneity of the process was suggested by negative Gibbs free energy while positive values for enthalpy change showed endothermic nature of the process. Non-linear optimization of error functions resulted in Freundlich and Redlich-Peterson isotherms describing sorption equilibrium data best. The coal fly ash had maximum sorption capacity of 53 mg/g and could thus be used as a low cost adsorbent in melanoidin removal.
Abstract: The research investigates the effects of super plasticizer and molarity of sodium hydroxide alkaline solution on the workability, microstructure and compressive strength of self compacting geopolymer concrete (SCGC). SCGC is an improved way of concreting execution that does not require compaction and is made by complete elimination of ordinary Portland cement content. The parameters studied were superplasticizer (SP) dosage and molarity of NaOH solution. SCGC were synthesized from low calcium fly ash, activated by combinations of sodium hydroxide and sodium silicate solutions, and by incorporation of superplasticizer for self compactability. The workability properties such as filling ability, passing ability and resistance to segregation were assessed using slump flow, T-50, V-funnel, L-Box and J-ring test methods. It was found that the essential workability requirements for self compactability according to EFNARC were satisfied. Results showed that the workability and compressive strength improved with the increase in superplasticizer dosage. An increase in strength and a decrease in workability of these concrete samples were observed with the increase in molarity of NaOH solution from 8M to 14M. Improvement of interfacial transition zone (ITZ) and micro structure with the increase of SP and increase of concentration from 8M to 12M were also identified.
Abstract: Natural pozzolan (NP) is one of the potential
prehistoric alternative binders in the construction industry. It has
been investigated as cement replacement in ordinary concrete by
several researchers for many purposes. Various supplementary
cementitious materials (SCMs) such as fly ash, limestone dust and
silica fume are widely used in the production of SCC; however,
limited studies to address the effect of NP on the properties of SCC
are documented. The current research is composed of different SCC
paste and concrete mixtures containing different replacement levels
of local NP as an alternative SCM. The effect of volume of paste
containing different amounts of local NP related to W/B ratio and
cement content on SCC fresh properties was assessed. The variations
in the fresh properties of SCC paste and concrete represented by
slump flow (flowability) and the flow rate were determined and
discussed. The results indicated that the flow properties of SCC paste
and concrete mixtures, at their optimized superplasticizer dosages,
were affected by the binder content of local NP and the total volume
fraction of SCC paste.
Abstract: Coal fly ash (CFA) generated by coal-based thermal
power plants is mainly composed of quartz, mullite, and unburned
carbon. In this study, the effect of unburned carbon on CFA toward
its adsorption capacity was investigated. CFA with various carbon
content was obtained by refluxing it with sulfuric acid having various
concentration at various temperature and reflux time, by heating at
400-800°C, and by sieving into 100-mesh in particle size. To
evaluate the effect of unburned carbon on CFA toward its adsorption
capacity, adsorption of methyl violet solution with treated CFA was
carried out. The research shows that unburned carbon leads to
adsorption capacity decrease. The highest adsorption capacity of
treated CFA was found 5.73 x 10-4mol.g-1.
Abstract: Work is focused to the study of unburned carbon in
ash from coal (and wastes) combustion in 8 combustion tests at 3
fluidised-bed power station, at co-combustion of coal and wastes
(also at fluidized bed) and at bench-scale unit simulating coal
combustion in small domestic furnaces. The attention is paid to
unburned carbon contents in bottom ashes and fly ashes at these 8
combustion tests and to morphology of unburned carbons. Specific
surface area of coals, unburned carbons and ashes and the relation of
specific surface area of unburned carbon and the content of volatile
combustibles in coal were studied as well.
Abstract: Fly ash is a significant waste that is released of
thermal power plants and defined as very fine particles that are drifted upward with up taken by the flue gases due to the burning of
used coal [1]. The fly-ash is capable of removing organic
contaminants in consequence of high carbon content, a large surface area per unit volume and contained heavy metals. Therefore, fly ash
is used as an effective coagulant and adsorbent by pelletization [2, 3].
In this study, the possibility of use of fly ash taken from Turkey like low-cost adsorbent for adsorption of zinc ions found in waste
water was investigated. The fly ash taken from Turkey was pelletized with bentonite and molass to evaluate the adsorption capaticity. For
this purpose; analyses such as sieve analysis, XRD, XRF, FTIR and SEM were performed. As a result, it was seen that pellets prepared
from fly ash, bentonite and molass would be used for zinc adsorption.
Abstract: Day by day technology increases and problems
associated with this technology also increase. Several researches
were carried out to investigate the deployment of such material safely
in geotechnical engineering in particular and civil engineering in
general. However, different types of waste material have such as
cement duct, fly ash and slag been proven to be suitable in several
applications. In this research cement dust mixed with different
percentages of sand will be used in some civil engineering
application as will be explained later in this paper throughout filed
and laboratory test. The used mixer (waste material with sand) prove
high performance, durability to environmental condition, low cost
and high benefits. At higher cement dust ratio, small cement ratio is
valuable for compressive strength and permeability. Also at small
cement dust ratio higher cement ratio is valuable for compressive
strength.
Abstract: Soil stabilization has been widely used to improve
soil strength and durability or to prevent erosion and dust generation.
Generally to reduce problems of clayey soils in engineering work and
to stabilize these soils additional materials are used. The most
common materials are lime, fly ash and cement. Using this materials,
although improve soil property , but in some cases due to financial
problems and the need to use special equipment are limited .One of
the best methods for stabilization clayey soils is neutralization the
clay particles. For this purpose we can use ion exchange materials.
Ion exchange solution like CBR plus can be used for soil
stabilization. One of the most important things in using CBR plus is
determination the amount of this solution for various soils with
different properties. In this study a laboratory experiment is conduct
to evaluate the ion exchange capacity of three soils with various
plasticity index (PI) to determine amount or required CBR plus
solution for soil stabilization.
Abstract: Typically thermal power plants are located near to
surface coal mines that produce huge amount of fly ash as a waste
byproduct. Disposal of fly ash causes significant economic and
environmental problems. Now-a-days, research is going on for bulk
utilization of fly ash. In order to increase its percentage utilization, an
investigation was carried out to evaluate its potential for haul road
construction. This paper presents the laboratory California bearing
ratio (CBR) tests and evaluates the effect of lime on CBR behavior of
fly ash - mine overburden mixes. Tests were performed with different
percentages of lime (2%, 3%, 6%, and 9%). The results show that the
increase in bearing ratio of fly ash-overburden mixes was achieved
by lime treatment. Scanning electron microscopy (SEM) analyses
were conducted on 28 days cured specimens. The SEM study showed
that the bearing ratio development is related to the microstructural
development.
Abstract: The article presents findings from the study and
analysis of the results of an experimental programme focused on the
production of concrete and fibre reinforced concrete in which natural
aggregate has been substituted with brick or concrete recyclate. The
research results are analyzed to monitor the effect of mechanicalphysical
characteristics on the durability properties of tested
cementitious composites. The key parts of the fibre reinforced
concrete mix are the basic components: aggregates – recyclate,
cement, fly ash, water and fibres. Their specific ratios and the
properties of individual components principally affect the resulting
behaviour of fresh fibre reinforced concrete and the characteristics of
the final product. The article builds on the sources dealing with the
use of recycled aggregates from construction and demolition waste in
the production of fibre reinforced concrete. The implemented
procedure of testing the composite contributes to the building
sustainability in environmental engineering.
Abstract: Zeolite A and MCM-41 have extensive applications in basic science, petrochemical science, energy conservation/storage, medicine, chemical sensor, air purification, environmentally benign composite structure and waste remediation. However, the use of zeolite A and MCM-41 in these areas, especially environmental remediation, are restricted due to prohibitive production cost. Efficient recycling of and resource recovery from coal fly ash has been a major topic of current international research interest, aimed at achieving sustainable development of human society from the viewpoints of energy, economy, and environmental strategy. This project reported an original, novel, green and fast methods to produce nano-porous zeolite A and MCM-41 materials from coal fly ash. For zeolite A, this novel production method allows a reduction by half of the total production time while maintaining a high degree of crystallinity of zeolite A which exists in a narrower particle size distribution. For MCM-41, this remarkably green approach, being an environmentally friendly process and reducing generation of toxic waste, can produce pure and long-range ordered MCM-41 materials from coal fly ash. This approach took 24 h at 25 oC to produce 9 g of MCM-41 materials from 30 g of the coal fly ash, which is the shortest time and lowest reaction temperature required to produce pure and ordered MCM-41 materials (having the largest internal surface area) compared to the values reported in the literature. Performance evaluation of the produced zeolite A and MCM-41 materials in wastewater treatment and air pollution control were reported. The residual fly ash was also converted to zeolite Na-P1 which showed good performance in removal of multi-metal ions in wastewater. In wastewater treatment, compared to commercial-grade zeolite A, adsorbents produced from coal fly ash were effective in removing multi heavy metal ions in water and could be an alternative material for treatment of wastewater. In methane emission abatement, the zeolite A (produced from coal fly ash) achieved similar methane removal efficiency compared to the zeolite A prepared from pure chemicals. This report provides the guidance for production of zeolite A and MCM-41 from coal fly ash by a cost-effective approach which opens potential applications of these materials in environmental industry. Finally, environmental and economic aspects of production of zeolite A and MCM-41 from coal fly ash were discussed.
Abstract: The paper presents the potential of fuzzy logic (FL-I)
and neural network techniques (ANN-I) for predicting the
compressive strength, for SCC mixtures. Six input parameters that is
contents of cement, sand, coarse aggregate, fly ash, superplasticizer
percentage and water-to-binder ratio and an output parameter i.e. 28-
day compressive strength for ANN-I and FL-I are used for modeling.
The fuzzy logic model showed better performance than neural
network model.
Abstract: Due to growing environmental concerns of the cement
industry, alternative cement technologies have become an area of
increasing interest. It is now believed that new binders are
indispensable for enhanced environmental and durability
performance. Self-compacting Geopolymer concrete is an innovative
method and improved way of concreting operation that does not
require vibration for placing it and is produced by complete
elimination of ordinary Portland cement.
This paper documents the assessment of the compressive strength
and workability characteristics of low-calcium fly ash based selfcompacting
geopolymer concrete. The essential workability
properties of the freshly prepared Self-compacting Geopolymer
concrete such as filling ability, passing ability and segregation
resistance were evaluated by using Slump flow, V-funnel, L-box and
J-ring test methods. The fundamental requirements of high
flowability and segregation resistance as specified by guidelines on
Self Compacting Concrete by EFNARC were satisfied. In addition,
compressive strength was determined and the test results are included
here. This paper also reports the effect of extra water, curing time and
curing temperature on the compressive strength of self-compacting
geopolymer concrete. The test results show that extra water in the
concrete mix plays a significant role. Also, longer curing time and
curing the concrete specimens at higher temperatures will result in
higher compressive strength.
Abstract: The present paper reports results of an experimental
program conducted to study performance of fly ash based
geopolymer pastes at elevated temperature. Three series of
geopolymer pastes differing in Na2O content (8.5%, 10% and 11.5%)
were manufactured by activating low calcium fly ash with a mixture
of sodium hydroxide and sodium silicate solution. The paste
specimens were subjected to temperatures as high as 900oC and the
behaviour at elevated temperatures were investigated on the basis of
physical appearance, weight losses, residual strength, shrinkage
measurements and sorptivity tests at different temperatures. Scanning
electron microscopy along with EDX and XRD tests were also
conducted to examine microstructure and mineralogical changes
during the thermal exposure. Specimens which were initially grey
turned reddish accompanied by appearance of small cracks as the
temperature increased to 900oC. Loss of weight was more in
specimens manufactured with highest Na2O content. Geopolymer
paste specimen containing minimum Na2O performed better than
those with higher Na2O content in terms of residual compressive
strength.
Abstract: Coal will continue to be the predominant source of
global energy for coming several decades. The huge generation of fly
ash (FA) from combustion of coal in thermal power plants (TPPs) is
apprehended to pose the concerns of its disposal and utilization. FA
application based on its typical characteristics as soil ameliorant for
agriculture and forestry is the potential area, and hence the global
attempt. The inferences drawn suffer from the variations of ash
characteristics, soil types, and agro-climatic conditions; thereby
correlating the effects of ash between various plant species and soil
types is difficult. Indian FAs have low bulk density, high water
holding capacity and porosity, rich silt-sized particles, alkaline
nature, negligible solubility, and reasonable plant nutrients. Findings
of the demonstrations trials for more than two decades from lab/pot
to field scale long-term experiments are developed as FA soil
amendment technology (FASAT) by Central Institute of Mining and
Fuel Research (CIMFR), Dhanbad. Performance of different crops
and plant species in cultivable and problematic soils, are
encouraging, eco-friendly, and being adopted by the farmers. FA
application includes ash alone and in combination with
inorganic/organic amendments; combination treatments including
bio-solids perform better than FA alone. Optimum dose being up to
100 t/ha for cultivable land and up to/ or above 200 t/ha of FA for
waste/degraded land/mine refuse, depending on the characteristics of
ash and soil. The elemental toxicity in Indian FA is usually not of
much concern owing to alkaline ashes, oxide forms of elements, and
elemental concentration within the threshold limits for soil
application. Combating toxicity, if any, is possible through
combination treatments with organic materials and phytoremediation.
Government initiatives through extension programme
involving farmers and ash generating organizations need to be
accelerated
Abstract: In present study, two kinds of thermal power plant ashes; one the fly ash and the other waste ash are mixed with adhesive tragacanth and cement to produce new composite materials. 48 new samples are produced by varying the percentages of the fly ash, waste ash, cement and tragacanth. The new samples are subjected to some tests to find out their properties such as thermal conductivity, compressive strength, tensile strength and sucking capability of water. It is found that; the thermal conductivity decreases with increasing amount of tragacanth in the mixture. The compressive, tensile strength increases when the rate of tragacanth is up to 1%, whilst as the amount of tragacanth increases up to 1.5%, the compressive, tensile strength decreases slightly. The rate of water absorption of samples was more than 30%. From this result, it is concluded that these materials can not be used as external plaster or internal plaster material that faces to water. They can be used in internal plaster unless touching water and they can be used as cover plaster under roof and riprap material in sandwich panels. It is also found that, these materials can be cut with saw, drilled with screw and painted with any kind of paint.
Abstract: Considering toxicity of heavy metals and their
accumulation in domestic wastes, immobilization of lead and
cadmium is envisaged inside glass-ceramics. We particularly
focused this work on calcium-rich phases embedded in a
glassy matrix.
Glass-ceramics were synthesized from glasses doped with
12 wt% and 16 wt% of PbO or CdO. They were observed and
analyzed by Electron MicroProbe Analysis (EMPA) and
Analytical Scanning Electron Microscopy (ASEM). Structural
characterization of the samples was performed by powder XRay
Diffraction.
Diopside crystals of CaMgSi2O6 composition are shown to
incorporate significant amounts of cadmium (up to 9 wt% of
CdO). Two new crystalline phases are observed with very
high Cd or Pb contents: about 40 wt% CdO for the cadmiumrich
phase and near 60 wt% PbO for the lead-rich phase. We
present complete chemical and structural characterization of
these phases. They represent a promising way for the
immobilization of toxic elements like Cd or Pb since glass
ceramics are known to propose a “double barrier" protection
(metal-rich crystals embedded in a glass matrix) against metal
release in the environment.
Abstract: Use of fly ash as a supplementary cementing material
in large volumes can bring both technological and economic benefits
for concrete industry. In this investigation mix proportions for high
volume fly ash concrete were determined at cement replacement
levels of 50%, 55%, 60% and 65% with low calcium fly ash. Flexural
and compressive strengths of different mixes were measured at ages
of 7, 28 and 90 days. Flexural strength of composite section prepared
from pavement quality and lean high volume fly ash concrete was
determined at the age of 28 days. High volume fly ash concrete mixes
exhibited higher rate of strength gain and age factors than
corresponding reference concrete mixes. The optimum cement
replacement level for pavement quality concrete was found to be
60%. The consideration of bond between pavement quality and lean
of high volume fly ash concrete will be beneficial in design of rigid
pavements.
Abstract: The paper presents a comparative performance of the
models developed to predict 28 days compressive strengths using
neural network techniques for data taken from literature (ANN-I) and
data developed experimentally for SCC containing bottom ash as
partial replacement of fine aggregates (ANN-II). The data used in the
models are arranged in the format of six and eight input parameters
that cover the contents of cement, sand, coarse aggregate, fly ash as
partial replacement of cement, bottom ash as partial replacement of
sand, water and water/powder ratio, superplasticizer dosage and an
output parameter that is 28-days compressive strength and
compressive strengths at 7 days, 28 days, 90 days and 365 days,
respectively for ANN-I and ANN-II. The importance of different
input parameters is also given for predicting the strengths at various
ages using neural network. The model developed from literature data
could be easily extended to the experimental data, with bottom ash as
partial replacement of sand with some modifications.