Fly Ash Glass Research Articles

Rheology, Setting, Heat of Reaction, and Compressive Strength of a Geopolymer Radioactive Waste Form

This work contributes to our understanding of the properties of geopolymers as waste forms made of three pozzolans, to be used, e.g., to immobilize liquid low-activity radioactive waste. A binary blast furnace slag and metakaolin geopolymer composition was tailored to achieve flexible rheological properties and workability for in-can mixing or mixing/pumping applications by adding fly ash, a third pozzolan. We investigated quantitatively the early stages of geopolymerization (before and after setting) of alkali-activated slag–metakaolin–fly ash pozzolans. The effect of fly ash glass particle size on material properties was studied as well. Measurements include heat of reaction, compressive strength, yield stress, plastic viscosity, rheological setting, as well as initial and final setting following the Vicat method. A rheological time of initial setting is suggested for geopolymers, in analogy to Portland cement. The results of Vicat needle and rheological measurements are compared and quantitatively related to heat and set time data. Maximum heat flow and compressive strength are linearly correlated.

Effects of sulfur on variations in the chemical speciation of heavy metals from fly ash glass

Effects of sulfur on variations in the chemical speciation of heavy metals from fly ash glass

Characterization of Alkali Activated Materials Prepared from Continuous Attrition and Ball Milled Fly Ashes

Mechanical activation is known to greatly influence the reactivity of fly ashes. In this paper, we report a comparative study of the properties of alkali-activated geopolymer materials prepared using both ball-milled and attrition-milled fly ashes. Ball milling was carried out for 30 min and 60 min while attrition milling was carried out continuously in a high-speed attritor. The surface area of the raw fly ash decreased from 4017 cm2/g to 3999 cm2/g and 3912 cm2/g after ball milling for 30 min and 60 min, respectively. By contrast, the surface area of the continuously attrition-milled fly ash increased to 5545 cm2/g. Fly ash processed by continuous attrition milling showed a 50% particle size reduction to 25–38 μm, whereas fly ash ball-milled for 30 and 60 min was reduced in size by 33.4 and 42.9%. The milled fly ash samples were activated with 8 M NaOH solution and cured at 40 °C for 68 h. After curing, the samples were maintained at room temperature, and their 7-, 14-, and 28-day compressive strengths were measured. The compressive strength of the attrition-milled 28-day geopolymer paste was 24.6 MPa; that of the geopolymers ball-milled for 30 and 60 min was 23.37 MPa and 17.58 MPa, respectively; and that of the unmilled control geopolymer fly-ash-based paste was 17 MPa. The improvement in the mechanical properties is attributed to the increased gel formation resulting from the increased surface area (decreased particle size) in the fly ash glass starting material.

Dissolution and geopolymerization of synthetic fly ash glass

Dissolution and geopolymerization of synthetic fly ash glass

The effect of sulfur on the leaching of Cr3+, Cr6+, Pb2+ and Zn2+ from fly ash glass

This work assessed the capture and subsequent release of potentially harmful Cr(VI), Cr(III), Pb(II) and Zn(II) ions in and from dechlorinated fly ash glass. Differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy – energy dispersive spectroscopy and inductively coupled plasma spectrometry along with other analytical techniques were used to explore the mechanism by which sulfur affected the immobilization and long-term leaching behavior of heavy metals in fly ash glass. Working with a CaO–MgO–Al2O3–SiO2–SO3 system, increasing the sulfur content was found to promote the leaching of Cr but had only a minimal effect on the loss of Pb and Zn. The concentrations of Pb and Zn in the leachate were found to remain at essentially nil over time while the Cr level increased up to 64 h and then decreased. The presence of Sulfur ions degraded the glass network and this promoted the leaching of S2−, Cr3+/Cr6+, Pb2+ and Zn2+. In addition, the S2− ions reacted with Pb2+ and Zn2+ to form needle-shaped and flocculent sulfide precipitates, thus trapping the Pb2+ and Zn2+. Si4+, Ca2+, Al3+ and Fe3+ were also found to migrate into the leaching solution where they combined to form a dendritic flocculent that adsorbed and encapsulated Cr. This phenomenon greatly reduced the concentration of Cr in the leachate. Thus, sulfur prevented the leaching of Cr, Pb and Zn via different mechanisms.

ALKALI SILICA REACTION OF RECYCLED GLASS AGGREGATE MORTAR USING FLY ASH UNDER STEAM CURING

Utilization of recycled glass as fine and coarse aggregates in concrete materials can give significant economical and environmental benefits, especially in the case of developing countries. However, alkali-silica reaction (ASR) will be a serious problem when the recycled glass is used as concrete aggregates. This paper shows an investigation of the alkali-silica reaction of glass sand mortar under steam curing. The test for ASR expansion follows ASTM C1567. Type F fly ash (FA) is used together with Ordinary Portland cement (OPC) mixing with mixed color glass sand. FA contents are of 20%, 30%, 40% and 50% as OPC replacement. Steam curing accelerating FA reaction is used to contribute to the mitigation of ASR by strength improvement of the mortar. Under steam curing, the results show that the recommended contents of FA to use are of 20% to 30% to ensure expansion lower than the threshold of ASTM. Moreover, steam curing increases the expansion of the glass sand mortar in compared to the moist curing, and expansion crack appears at the interface between glass sand and cementitious matrix, not in the glass sand. In comparison with glass sand mortar under moist curing, expansion of glass sand mortar using fly ash under steam curing is contributed primarily by: (1) delayed ettringite formation, (2) reducing ion transportation, (3) increasing tensile strength of fly ash glass sand mortar and (4) reducing glass sand dissolution rate in rich alkalinity solution.

Conversion of coal fly ash glass into glass-ceramics by controlled thermal treatment

Glass-ceramics were fabricated by controlled crystallization of glass vitrified without any additives from coal fly ash. The glass transition temperature (Tg) and peak temperature (Tp) of the parent glass were 580 ºC and 1020 ºC, respectively. The crystallization tendency of the parent glass was estimated by the Hruby-coefficient (KH = 2.3). The ratio of the crystalline and amorphous phases in the glass-ceramics sintered at 1100 ºC/60 min was 68/32. The major crystalline phases were calcium aluminum silicate (anorthite) and hematite. The density, bending strength, and E-modulus of the glass-ceramics were 2.20 g/cm3, 78 MPa, and 32 GPa, respectively. The glass-ceramics can potentially be used as a construction material.

Experimental Analysis of Partial Replacement of Glass Powder and Fly Ash with Different-Different Percentages of Cement to Improve the Compressive and Flexural Strength of Concrete

Abstract: The ordinary material for construction is concrete in India and its production causes some environmental effects during the production. There are many countries seeing deficiency of human dumping wastes or it’s becoming very serious day by day for each nation. In order to deal with atmospheric impact related with cement manufacturing and so there is a requirement to produce an alternative binding material for preparing concrete. The development of concrete could reducing the utilization of naturally occurring sources or lesser the load of pollutants on atmosphere. In current scenario, no. of researchers have recognized the uses of additional cementing materials like silica fumes, fly ash, glass powder, rice husk ash, blast furnace slag etc. It could also change the different properties of hardened and freshen state of concrete, and also contributing the financial system in constructional cost. Efforts put on the concrete construction to mix fly ash and waste glass powder as half substitute with cement .Now a days Glass used in different way in day-to-day life. As glass is non-biodegradable, landfills don’t provided an environmental eco-friendly resolution for dumping. Fly ash containing large amount of silica in comparison to cement. In current scenerio lots of industries producing more quantity of fly ash or its sold out very cheapest price in market. Glass is an inert material which could be recycled and used several times without altering its chemical property. Glass is an amorphous material which having high % of silica content. This property makes it probable pozzolanic property when its particles sizes is less than 75 mm. An important anxiety related to the uses of glass powder in concrete mix is that is chemical reaction happen among the alkali in pore solution and silica rich glass particle, which is called Alkali-Silicate. Reactions could be more harmful for the stability parameters of concrete, for this proper safety measure should be taken to reduce its effects. The addition of fly ash in glass concrete reducing the alkalies, silica reaction and improves the workability and durability of concrete. Unwanted glass powder is using for preparing concrete which leads environmental ecofriendly. The main purpose of this study is to find out effectiveness on durability of unwanted glass powder and fly ash based concrete. For analysis it was proposed that the uses of unwanted glass powder and fly ash as half substitution with cement in following proportion (10%, 20%, 30%, 40%) in concrete mix. Compressive strengthening of cubes and flexural strengthening of beams at the interval of 7th, 28th days were considered and compared with the conventional concrete. The results showing the probability of using unwanted glass powder and fly ash as half substitution with cement in concrete. Keywords: Silica fumes, Blast furnace, Rice husk, Glass powder, Fly ash, Compressive strengthening, Flexure strengthening

Effect of Chemical Composition and Network of Fly Ash Glass on the Hydration Process and Properties of Portland-Fly Ash Cement

In the experiment, the aluminosilicate glasses with aluminum saturation index (ASI), defined as the Al2O3/(Na2O+K2O+2CaO), equal to 0.74, 1.72. 2.52, or 4.05 were synthesized. The spectroscopy tests (MIR and 27Al MAS-NMR) confirm that in glass with ASI < 1, the aluminum ions occur in the [AlO4]5- only. In glasses with ASI > 1, the aluminum ions create mainly [AlO4]5-, but part of them occurs in the form of [AlO6]9-. The content of [AlO6]9- octahedrons increases successively for ASI from 1.72 to 4.05. Glass with ASI equal to 4.05 demonstrates the highest content of pozzolanic active Al2O3. Model ashes were prepared by mixing 70 wt.% of glass, 20 wt.% of synthetic mullite and 10 wt.% of SiO2 as an equivalent of quartz. Then Portland cement CEM I 42.5R was milled together with 20 wt.% of each of model ashes to Blaine’s specific surface area of 4,200±50 cm2 g-1. It was found that the addition of ash with higher content of [AlO6]9- octahedrons in the structure of glass accelerates the hydration process of cement blend, which, in turn, positively affects its usable features (heat of hydration, initial setting time and compressive strength). According to the requirements of PN-EN 197-1:2012 standard, the introduction of ash with ASI coefficient equal to 4.05 gives cement blend of strength class of 52.5N. Cement blends with the ash of ASI value equal to 1.72 and 2.52 correspond to strength class of 32.5R, whereas the cement blend with the ash of ASI value equal to 0.74 does not achieve the minimum value of strength for any cement strength class. Results show that the change in chemical composition of fly ash glass and resulting from this diversified structure are essential from the point of view of hydration and properties of cement containing fly ashes in its composition.

Effectiveness of binary and ternary blended cements of class C fly ash and ground glass fibers in improving the durability of concrete

Class C fly ash (CFA) has been used extensively as supplementary cementitious material (SCM) to partially replace cement in concrete. However, to meet the concrete durability demand, such as to mitigate alkali-silica reaction (ASR) or sulfate attack, higher amounts of CFA are required, which results in a slower strength gain and longer setting time. Studies have shown that ground glass fiber (GGF) is quite an effective SCM if it is finely ground. This work explores the performance of binary and ternary blends of GGF and CFA with portland cement. Pozzolanicity of the combinations was first assessed by the Thermogravimetric analysis (TGA) and strength activity index (SAI). Then, drying shrinkage, resistance to sulfate attack, and alkali-silica reaction were evaluated. Results showed that GGF could significantly alleviate the shortcomings of CFA, both in terms of strength and durability, even when GGF is introduced in ternary blends at modest levels.

Unbaked materials from mixtures of waste sludge of a water purification plant, fly ash, and water glass

In water purification plants, a large area of urban land is using to store waste sludge (WS). The waste sludge from water filtration plants is aluminosilicate, which can be form a geopolymer. However, the waste sludge has low alkaline activity, so it must be used in combination with fly ash (FA) to create geopolymer products. Fly ash is a solid waste containing amorphous silica so that has high alkaline activity, suitable for treatment by geopolymer method. The geopolymerization of waste sludge from water purification plants is a relatively new method. The geopolymer is a binder formed by the chemical reaction between aluminosilicate materials and alkaline activated solutions. The alkaline activated solution used in these experiments was water glass (WG). The water glass is solution of sodium silicate (Na2O.nSiO2) dissolved in water. The research results of geopolymer materials from the mixture of fly ash, the waste sludge of Thu Duc water purification plant, Ho Chi Minh City (Vietnam), and water glass (WG) were introduced in this study. The activated Al2O3 and SiO2 oxides in the fly ash and the waste sludge can be dissolved in the water glass and polymerized into a geopolymer material. The test samples had pressed at a high pressure of 225 MPa to form cylindrical ones weighing approximately 3 grams, height about 18 mm, and 10 mm in diameter. These samples were then cured at 110 ◦C for 24 hours and at room temperature (30 +/- 5 ◦C). The methods of Fourier infrared spectroscopy (FTIR) and scanning electron microscope (SEM) had used to detect the microscopic structure and geopolymer bond formation of the samples. The compressive strength of the tested samples at 28 days old was higher than 3.5 MPa, the pH was less than 12.5, meeting the Vietnamese National Standards for unbaked materials (TCVN 6477:2016) and National Technical Regulation on environmental impact (QCVN 50:2013 / BTNMT), respectively. The results show a new approach of solidifying the waste sludge for further applications such as the manufacture of geopolymer concretes or landfill materials.

Estimating reaction kinetics of cementitious pastes containing fly ash

This paper proposes an approach to estimate reaction kinetics for major fly ash glassy oxides in cementitious mixtures. The approach is compared to experimental results from multiple independent datasets. The kinetic model is based on the rate limiting step for various oxides and phases using the general form of a widely used model for ordinary portland cement (OPC)-based systems. The empirical parameters in the model were fit from dissolution studies for glass oxides in two fly ashes from literature using a nonlinear optimization algorithm. The outputs of the model provide the inputs needed to introduce reaction kinetics into thermodynamic simulations at non-equilibrium conditions. The model is used to determine the amount of each phase that can react by estimating the dissolved mass of each major cement phase and fly ash glass oxide at different ages. This approach enables accurate modeling predictions of solid hydration products (such as calcium hydroxide and ettringite), pore solution pH, and pore solution chemistry at any age for any OPC/fly ash system. Results from the model and thermodynamic calculations are compared to a modeling approach without kinetic constraints on the fly ash, assuming 100% reactivity. The prediction of reaction products made assuming 100% fly ash reactivity significantly differs from experimental values when a fly ash kinetic model is not used. Predictions are greatly improved when the model is used. The model can be used as a framework for future modeling efforts, and the empirical parameters be updated as additional dissolution studies and thermodynamic data become available.

Nano-Scale Rare Earth Distribution in Fly Ash Derived from the Combustion of the Fire Clay Coal, Kentucky

Fly ash from the combustion of eastern Kentucky Fire Clay coal in a southeastern United States pulverized-coal power plant was studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and selected area electron diffraction (SAED). TEM combined with elemental analysis via energy dispersive X-ray spectroscopy (EDS) showed that rare earth elements (REE; specifically, La, Ce, Nd, Pr, and Sm) were distributed within glassy particles. In certain cases, the REE were accompanied by phosphorous, suggesting a monazite or similar mineral form. However, the electron diffraction patterns of apparent phosphate minerals were not definitive, and P-lean regions of the glass consisted of amorphous phases. Therefore, the distribution of the REE in the fly ash seemed to be in the form of TEM-visible nano-scale crystalline minerals, with additional distributions corresponding to overlapping ultra-fine minerals and even true atomic dispersion within the fly ash glass.

An Experimental Investigation on the Properties of High Volume Flyash Glass Fibre Reinforced Self Compacting Concrete

Civil engineering is a professional engineering discipline that deals with the designing and construction. In construction one of the main resource is concrete in the world. The concrete is day-to-day have many changes like strength, durability, shrinkage. This project deals with the self-compaction concrete with use of fibre reinforcement. The self-compacting in concrete is achieved by adding super plasticizers and glass fibres are used as reinforcement. The influence of including fly ash on the properties of self-compacting concrete is investigated. Fly ash is introduced by 50% in the total weight of cement. The water to binder ratio was maintained at 0.38%. Properties included workability, compressive strength, split tensile test, modulus of elasticity and shrinkage. The results indicate the high volume FA can be used in SCC to produce the high strength and low shrinkage. Increasing the admixture content beyond the certain level leads to a reduction in strength and increasing in absorption. Making concrete structure without compaction has been done in the past. Like placement of concrete under water by the use of term without compaction. Inaccessible areas were concrete using such a techniques. The production of such mixes use expensive admixtures ad large amount of cement but such type of concrete is low strength. To eliminate such issues lead to the development of self-compacting concrete (SCC). Usage of fibres makes the mixing of concrete complex. Self-compacting concrete (SCC) is an innovative concrete that does not require vibration for placing and compaction.

Physical and optical properties of bismuth borosilicate glasses from subbituminous fly ash

This paper is report on the physical and optical properties of development bismuth-borate-subbituminous fly ash (BiBSFA) glass system. The glasses containing Bi2O3 in xBi2O3:(60-x)B2O3:20Na2O:20SFA (where x = 5, 10, 15, 20, 25 and 30 wt.%) have been prepared by melt quenching technique. The physical properties of this glass are shown from density data. The optical properties were investigated from refractive index and transmission by using Abbe-refractometer and UV-visible spectrometer respectively.

Heavy metal borate glasses: Potential use for radiation shielding

Heavy metal oxide borate (HMOB) glasses were studied for gamma, fast neutron and charged particle interaction using mass attenuation coefficients (MAC), effective atomic numbers (Zeff), buildup factors, fast neutron removal cross sections and ranges. The experimental values of MACs were verified by MCNP simulation at 662 keV. Also, HMOB glasses were compared to concretes and lead glass. HMOB glass systems were found to have better shielding properties than ordinary and hematite-serpentine concretes. Fly ash glass showed superior shielding than lead glasses in specific energy regions. The bismuth borate glass was found to have better shielding properties than the steel-magnetite concrete in different energy regions and showed superior shielding than lead glass in the entire energy region. Also, bismuth borate glass showed better fast neutron shielding than concretes and glasses while fly ash glass has almost the same fast neutron shielding properties with ordinary and hematite-serpentine concretes. The energy loss and radiation damage simulation showed that more replacement collisions, thus radiation damage would occur in ordinary and steel-magnetite concretes. It can be concluded that the lead free HMOB glasses have the potential for use as alternative shielding materials not only for gamma and fast neutrons but also for heavy ions.

Partial Replacement of Cement by Flyash Glass Fibre in Light Weight Fibre Reinforced Concrete

Partial Replacement of Cement by Flyash Glass Fibre in Light Weight Fibre Reinforced Concrete

Effects of Wood Ash and Waste Glass Powder on Properties of Concrete in Terms of Workability and Compressive Strength in Jaresh City

The potential for using fly ash as a supplementary cementing material in concrete has been known almost since the beginning of the previous century. Fly ash was used as a supplementary cementing material (SCM) in the production of Portland cement concrete. A supplementary cementing material, when used in conjunction with Portland cement, contributes to the properties of the hardened concrete through hydraulic or pozzolanic activity, or both. In this study, the fly ash and waste glass powder were used in concrete blocks to study the improvement of concrete in terms of workability and strength. Therefore, an experimental study will be conducted to measure the engineering properties of cured concrete. In this research, local raw material from Jaresh area was used.

The influence of chemical composition and network of fly ash glass on the cement properties

The influence of chemical composition and network of fly ash glass on the cement properties

Rare Earth Element Distribution in Fly Ash Derived from the Fire Clay Coal, Kentucky

Fly ash was collected from individual mechanical and electrostatic precipitator (ESP) hoppers at a 130-MW pulverized-coal utility unit burning a southeastern Kentucky moderate- to high-S Pennsylvanian Fire Clay coal. The fly ash particle size is generally similar within each row of the mechanical and ESP hoppers, with the mean particle diameter decreasing from \>36 µm in the mechanical hoppers to 6 µm in the last ESP row. Rare earth element (REE)-bearing phases occur within fine minerals and, possibly, as part of the fly ash glass phase. Transmission electron microscopy was used to identify Y-Ce-Nd-La-bearing regions within a glassy matrix. Y- and U-bearing zircons were also found in the fly ash. Total REE plus yttrium (REY) occupies a narrow range from 719 to 775 ppm, showing an overall lack of partitioning of the REY elements with respect to particle size and temperature in ash collection systems. The heavy REE increase and the light REE/heavy REE ratio decreases from the mechanical hoppers through ESP rows.