Types Of Fly Ash Research Articles

Mechanical properties of alkali activated geopolymer paste using different Romanian fly ash sources – experimental results

As concrete demand is constantly increasing in recent years and also considering that cement production is both a consumer of natural resources and a source of carbon dioxide release into the atmosphere, there have been worldwide investigations into green alternatives for making concrete environmentally friendlier and simultaneously to satisfy the development of infrastructure facilities. The use of fly ash as a component of cementitious binders is not new but when considering the specific case of alkaline activation and fly ash representing the only source for the binder formation, it necessitates a more complete understanding of its specific reactions during the alkaline activation process. Since the fly ash varies dramatically, not only from one source to another, but also from one batch to another even when provided by the same power plant, its chemistry in obtaining alkali-activated materials during the geopolymerisation process and the final mechanical properties are considered crucial for the performance of geopolymer concrete. This paper will provide a review of the experimental results concerning the physical and mechanical evaluation of the alkali-activated fly ash-based geopolymer materials, developed with different types of fly ash, for a better understanding of geopolymer concrete production control.

Primena otpadnih materijala u imobilizaciji teških metala i radionuklida sorpcijom

UTILIZATION of WASTE MATERIALS in HEAVY METALS and RADIONUCLIDES IMOBILIZATION by SORPTION the researching trend of sorption characteristics of various natural materials, i.e. easily accessible raw materials, by-products or waste from various types of industry in recent years has become more pronounced. Waste materials utilization reduces the exploitation of natural non-renewable resources and/or exploitation of various forms of energy for synthesis or modification of natural raw materials and artificial materials. Also, the utilization of waste materials as sorbents is extremely acceptable from the aspect of environmental protection since it affects the amount reduction of such waste types, costs of their disposal and reduction of the hazards risks that some of these wastes can potentially cause in the environment. This paper presents an overview of the contemporary research of waste materials in heavy metals and radionuclides immobilization. Studies have shown that the usage of waste materials in the sorption process, i.e. conditioning of liquid radioactive waste and wastewater treatment can be very efficient and economically viable alternatives for standardly used methods, i.e. sorbents. Recent research on application of different waste materials and undemanding techniques for their modification due to sorption process improving include a wide range of waste materials, such as the various types of sludge, slag, fly ash, biomass, food waste, construction and demolition waste, etc.

Early strength of various fly ash based concrete in peat environment

Fly ash is a by-product of coal combustion in a power station and usually used as additive or cement replacement material to improve properties of concrete in aggressive environments such as acid, chloride, and sulphate. Peatland is one of acidic environment that is common in Riau province with high organic content and low pH that is damaging for concrete, especially when exposed to concrete at an early age. This paper aims to study the early compressive and tensile strength of the various type of fly ash based concrete subjected to peat water. Seven fly ash-based concrete mixtures investigate were, i.e., geopolymer hybrid using 15% of Ordinary Portland Cement (OPC) as an additive, high volume fly ash using 25%, 50% and 75% of fly ash as cement replacement material, and blended OPC with fly ash with different grade of 15, 21 and 29 MPa. The OPC concrete with a target strength of 20 MPa was a control mix. The OPC based-specimens were cast and cured in water for 28 days before placed in peat water for another 28 days before the testing date. Compressive strength and tensile strength values of the concrete at 7 and 28 days were taken. Results show the type of concrete, fly ash content, and concrete grade significantly influence the early strength properties and resistance of the concrete to the acid attack. Four concrete mixtures with decreasing vulnerability to the attack were distinguished: OPC, high volume fly ash, geopolymer hybrid and blended cement concrete.

APPEARANCE FEATURES OF CLAYEY MIXTURES HAVING FLY ASHES

The use of wastes has become very significant and widespread in terms of sustainable production of clayey mixtures, since the wastes provide many advantages. In this study, the effects of two different types of fly ash, which were wastes of Seyitomer and Cayirhan thermal power plants, on the color change of brick samples with various amount of fly ash ranging between 0 to 60% at different sintering temperatures were investigated. As a result, traditional red colored bricks could be produced with fly ash without using a separate raw material to meet the color requirements. It was found that desired colors for special architectural applications could also be achieved by using fly ash.

Sustainable self compacting hybrid fiber reinforced concrete using waste materials

The current study investigates the behavior of hybrid fiber reinforced self compacting concrete (HyFRSCC) with crimped steel fibers (CSF) and polypropylene fibers (PPF) along with class F type fly ash (FA) and colloidal nano silica (CNS). To ascertain the fresh properties of self compacting concrete, the maximum volume of fiber content is restricted. The L16 orthogonal array of Taguchi method is followed to avoid the huge amount of experiments. In comparison to the control mix, mechanical properties of concrete are increased due to the combined effect of FA, CNS, CSF, and PPF. Rapid chloride penetration test is conducted to study the durability aspect of hardened concrete. Non‐destructive tests like ultrasonic pulse velocity and rebound hammer tests are conducted for the characterization of the properties of concrete. Based on the present study, a combination of FA, CNS, CSF, and PPF is proposed for an optimal recommendation in producing a ready‐mix type of HyFRSCC.

Characterization of coal bio ash from wood pellets and low-alkali coal fly ash and use as partial cement replacement in mortar

Coal is increasingly replaced by biomass at the power plants. This results in new types of fly ashes, e.g. coal bio ash (CBA), where low-alkali coal fly ash (CFA) is injected to the boiler furnace during incineration of wood pellets to hinder corrosion and maintain the necessary thermal efficiency of the fuel. An assessment of the properties of this new type of ash is important for the utilization of this resource. This study reports an investigation of the filler behaviour and pozzolanic activity of CBA, when used as a partial cement replacement. Traditional CFA was used for comparison and CBA was shown to be a more favourable substitute compared to CFA. This study has shown, that by injecting CFA into the boiler furnace, wood fly ash is transformed from being a waste by-product, into a usable resource in concrete production.

Mechanical Properties of Fly Ash Polymer Concrete with Different Fibers

The experimental results obtained by studying the influence of different types of fibers on the mechanical properties of fly ash polymer concrete are presented in the paper. The general demand of using wastes found applicability in building material industry because some of them are beneficial in improving concrete properties. The waste additions type fly ash and fibers were incorporated in polymer concrete. The study focused on fibers type glass, polyester, metallic and cellulose. The mechanical properties such as compressive strength, flexural strength and split tensile strength were investigated having in view the type, dosage and length of fibers. The results show that fibers improved mechanical properties in comparison with that of polymer concrete without fibers, the test results being differently influenced by the factors which were considered.

On the interaction of Class C fly ash with Portland cement–calcium sulfoaluminate cement binder

Shrinkage cracking in concrete is a widespread problem, especially in concrete structures with high surface-to-volume ratio such as bridge decks. Expansive cements based on calcium sulfoaluminate phase were developed to mitigate the shrinkage cracking of concrete. The compressive stress induced due to restrained expansion of concrete has been shown to counteract the tensile stress generated during drying shrinkage. This research attempts to address the differential behavior of fly ash type (i.e., Class C vs. Class F) on early-age expansion and hydration characteristics of ordinary Portland cement (OPC)–calcium sulfoaluminate (CSA) cement blend. It was observed earlier that the presence of Class C fly ash (CFA), unlike Class F fly ash, shortened the expansion duration of OPC–CSA cement blend, which was hypothesized to be correlated to early depletion of gypsum. This paper presents a detailed verification of the hypothesis. Addition of external gypsum to OPC–CSA–CFA blend led to simultaneous increase in expansion and disappearance of a shoulder peak in the calorimetric curve. Thermodynamic calculations using a geochemical modeling program (GEMS-PSI) revealed higher saturation levels of ettringite in presence of external gypsum, which led to higher crystallization stress, and thereby increased expansion.

Greenhouse gas emissions of different fly ash based geopolymer concretes in building construction

Replacing virgin materials with recycled or sustainable materials to reduce energy consumptions and emissions is the focus of contemporary research to reduce building related emissions. Geopolymer concrete produced using 100% fly ash is a similar sustainable construction material capable of replacing Portland Cement (PC) concrete. As a replacement for PC, fly ash seems to be a sustainable solution, however the benefits from the production process of fly ash geopolymer (FAGP) concrete is the subject of considerable debate. In addition, factors such as local availability and transportation issues could potentially increase the emission profile of FAGP concrete. Thus, this study aims to evaluate the emission profiles for different types of fly ash in Australia considering availability and transportation. A case study and a scenario analysis are also presented to demonstrate the factors that affect the Green House Gas (GHG) emission profile of FAGP manufacture. The results indicate that to the GHG emission profile for FAGP concrete changes considerably based on the material availability, transportation and mix design. Alkali activators and elevated heat curing processes also significantly contribute the total GHG emissions of FAGP concrete production. The results further signify that the case study location could influence the employment of FAGP concrete in terms of GHG emissions. Further studies are encouraged on optimising the cost, GHG emissions, availability and strength characteristics to strike a balance between in sustainability for selecting the best FAGP type for construction. The results also provide the initial factors to be considered in developing a guideline for employing sustainable materials in the building industry.

Deformation Analysis of Reinforced Retaining Wall Using Separate Finite Element

In order to reveal the main factors affecting the deformation of reinforced soil retaining wall and the influence of various factors on the deformation, the constitutive relation is discretized into four aspects of soil, geogrid, wall panel, and contact surface, and discrete element matrices are, respectively, constructed, with the method of separate finite element. Based on the finite element geotechnical analysis technology platform, the deformation analysis model of reinforced soil retaining wall is established. Taking the modulus of foundation soil as the influencing factor of the foundation soil, taking the geogrid stiffness, length, and spacing as the influencing factors of geogrids, and taking the filling type of limestone, fly ash, and silty clay as the influencing factors of backfill in the wall, the horizontal and vertical deformations of reinforced retaining wall under different factors using the methods of controlling a single variable analysis are calculated. The results show that the increase of elastic modulus of foundation soil will reduce the vertical deformation of the wall but increase the horizontal deformation. The silty clay is not suitable as filler, and lime soil is slightly better than fly ash. The spacing between geogrids is 20 cm ~ 60 cm, which has less effect on wall deformation, but the horizontal deformation rapidly increases after the spacing increases to 80 cm, and other grid performance influencing factors also have the characteristic, where there exists a threshold. The wall will have a greater deformation when the threshold is not reached; a higher indicator of the grid to reduce the deformation of the retaining wall is not obvious after reaching the threshold.

Effect of mineralogical and physical characteristic of pozzolanic binders on enhancing strength in soil improvement work

Various binders such as pozzolanic binder already known for its ability on enhancing the physical characteristic on concrete or soil stabilization. Pozzolanic reaction requires several primary factors to provide maximum improvement on physical characteristic. This research is aimed to identify the effect of the origin characteristics (physical and mineralogical) of pozzolanic binder on increasing the strength on engineering properties in soil improvement work. Two type of fly ashes are utilized in this study with different types of physical and mineralogical characteristic. Laser Granulometric test, and mineralogical test are realized to identify the characteristics of each fly ash utilized. To determine the effect of the binder addition (with different characteristics), several tests are performed such as unconfined compressive test, tensile strength test are realized to identify the effect of fly ash addition. The results show that binder with higher SiO2, Fe2O3 and Al2O3 content produces higher strength.

Enhancement the Performance of Asphalt Pavement Using Fly Ash Wastes in Saudi Arabia

Saudi Arabia is the largest Arab country and is one of the most prolific producers of oil and energy consumption. The Kingdom uses heavy oil and diesel to generate electricity and desalinate seawater. This produces large amounts of ash, a toxic substance that is disposed of by landfill and may cause many environmental problems and contribute to pollution of groundwater, which is one of the most important sources of drinking water. This paper presents the possibility of using fly ash by-product waste from electric power generation plants to improve the properties of asphalt mixtures. This study investigates the use of two types of fly ash namely; class C and class F was used as a filler in two types of bitumen and asphalt material known as AC 40/50 and AC 60/70. The rheological performance of asphalt with different percentages of fly ash filler ranging from 0% to 10% with an increment of 2% was tested. The rheological properties of both asphalts modified using both types of ash were determined. The rutting factors of the modified asphalt with fly ash content were calculated using the rheological properties. The result indicates that rutting resistance of asphalt could be improved by both types of fly ash which can be lead to reduces the costs of repairing and rehabilitation of asphalt pavement and reduce environmental impacts of a significant amount of toxic waste fly ash. Class F fly ash shows higher rutting factor than class C. Also AC 60/70 asphalt possess higher rutting factor than AC 40/50 asphalt at both low and high temperature.

Investigating the two-dimensional diffusion-reaction behaviour of sulphate ions in cement-based systems

This paper describes experimental approaches to evaluate two-dimensional sulphate attack behaviour inside cement-based systems. First, the sulphate content at various depths was measured using titration. This was followed by mechanical evaluation on cylindrical samples to establish the associated stress-strain response. Three types of binder namely, Portland cement conforming to CSA Types GU and HS and, a 30:70 blend of fly ash and Portland cement Type GU, were employed. The specimens were immersed in a sulphate rich solution for up to 12 weeks. The results show that all specimens suffered more from two-dimensional sulphate attack as compared to that seen with exposure in one dimension. Also, the positive role played by an embedded aggregate emerged in that it was seen to impede the transport of sulphate ions inside the cement-based system. As well, self-healing under prolonged exposure was observed, which was more significant with both binders that contained Portland cement Type GU.

Life Cycle Assessment of Alternative Processes to Treat Fly Ash from Waste Incineration

Unsustainable consumption and production patterns, together with industrialization and population growth, have increased the generation of municipal solid waste (MSW), causing several environmental problems. The European Waste Framework Directive (WFD) sets waste prevention, preparation for reuse and recycling as priority strategies. Nevertheless, still a great amount of MSW ends up in landfills and waste-to-energy (WtE) plants. WtE plants reduces waste volume and allows efficient recovery of energy, however, incineration results in various types of solid wastes, bottom, boiler and fly ashes (FA). Due to the concentration of dangerous substances, FA are treated by means of stabilisation/solidification (S/S), thermal treatments or combined treatments, to reduce their toxicity and to avoid negative impacts on the environment and human health. Among S/S alternatives, stabilisation with cement and carbonation are one of the most popular. To determine the environmental performance of these processes this paper conducted a life cycle assessment (LCA). The study evaluated FA stabilisation with cement and water and FA carbonation for 55 % and 100 % excess of CO2 in the flue gas at the outlet of the reactor, and pressures of 1, 5, 10, 15 and 20 bar. The results showed that the range of pressure between 3 and 4 bar, and 55 % excess of CO2 in the flue gas have an efficient performance. The comparison of FA carbonation and stabilization displayed that the latter has higher impacts than the alternative carbonation due mainly to the cement production and the reduction of lixiviation and CO2 capture in the ash.

Utilization of Fly Ash Contaminated by SNCR Flue Gas Denitrification into Polymer Epoxy Anchor

The paper deals with the possibility of using two different types of fly ash contaminated by flue gas denitrification (Selective Non-Catalytic Reduction (SNCR)) as a filler into the polymer anchor based on epoxy resin. Due to the problematic use of contaminated fly ash in silicate materials, the use of such fly ash in polymer materials seems to be effective because by mixing with polymers such as polyester and epoxy resins, toxic gas ammonia (NH3) does not release. Determination of optimal percentage of filling by the fly ash was performed in order to achieve the best possible physical and mechanical properties of the epoxy anchor material. It was found out that the 45% addition of both used of contaminated fly ashes seems to be the most appropriate, when the polymer anchor material exhibited better tensile properties than reference anchors containing quartz sand Dorsilit. Furthermore, it was found that the optimal addition of contaminated fly ash also positively influenced the maximum anchoring force found in the tug test. Detailed connection of anchor material with anchored bar and concrete was observed on tomography images.

Design of underground mine voids filling operations in difficult flow conditions of fly ash – water mixtures

Filling the underground voids created during mining extraction of minerals plays a crucial role in different phases of mining operations. A common practice in Polish coal mines is filling the cavings resulted from coal extraction in longwalls for various safety and technical purposes. Moreover, liquidation of redundant underground workings and decommissioning of mines also require filling of large volumes of voids. As the obsolete mining systems with hydraulic backfill have been entirely replaced by longwalls with caving, a need arose for flexible and easily available method for filing of voids. Nowadays, the most frequently applied are mixtures of fly ash and water, which are able to meet a wide range of requirements of specific applications. These objectives may be achieved by the selection of the type of fly ash and adjustment of concentration of solid in mixture in the respect to geometrical parameters of the transport pipeline. These correlations have been demonstrated on the example of measurements conducted on a laboratory pipeline loop for a wide range of fly ash – water mixtures and flow conditions. Measurement results revealed a complex relationship between rheological properties of mixtures and geometrical parameters of pipelines, which strongly influence the distance at which a mixture may be delivered.

Methods to Characterize Fly Ash Quality in the Field

Fly ash is applied widely in concrete. Therefore, the quality of fly ash plays a critical role in altering the compressive strength of concrete. As the fact, it is necessary to provide better insight on the characterization of fly ash based on their correlation index against the strength. This is regarded as the prior studies were merely focused on the relationship of fly ash percentage and compressive strength due to high demand and time-consuming. On the other hand, this paper offers more advanced analysis on the utilization of several methods to determine the effect of different fly ashes on the quality of mortar. In this study, 12 types of fly ash and six methods were involved. The differences between the methods consisted of how the samples were prepared and cured. In the mixture, 20% of fly ash and 80% of OPC (Ordinary Portland Cement) were used as a binder. The specimens were cured in two different methods (normal curing and steam curing). After 28-day of curing, specimens were tested under compression load to obtain the strength. The test results indicated that the method, where the fly ash was sieved in the preparation phase and was cured at a high temperature increased gradually, was found to be the fastest to analyze.

Testing of algae colonization growth risk on building materials

Due to biological colonization, properties of building materials change. Green algae represent one group of the entire complex of biodeteriogens that interact with each other. For the purpose of testing algae growth risk on concrete with varied composition, a growth resistance testing methodology was developed based on ČSN EN 15458 (672032) Paints and varnishes -Laboratory method for testing the efficacy of film preservatives in a coating against algae. The modified method was employed to test ten samples of concrete with different composition, i.e. two types of cement and two types of classical fly ash were incorporated in the samples. The green algae growth was influenced by both the type of cement and the type of fly ash used. The results show that any addition of classic fly ash increases the risk of green algae colonization on the surface of concrete.

Applicability of Fly Ash from Fluidized Bed Combustion of Peat, Wood, or Wastes to Concrete

The chemical and physical characteristics of five different fly ashes originating from fluidized bed combustion of peat, wood, or different wastes were investigated to determine whether they fulfilled the requirements for concrete set by the European EN 450-1 standard. Fly ash originating mostly from peat combustion fulfilled all the requirements of the EN 450-1 standard, without any treatments. Some chemical and physical characteristics (i.e., free calcium oxide, sulfate, chloride, and fineness) of the other types of fly ash exceeded the limits in standard, and the sum of the main components (SiO2, Al2O3, and Fe2O3) failed to comply with the standard. However, it should be noted that the requirements of the European standard are more restrictive than similar standards in the US; all applications are not needing standardized concrete, and the potential utility of the studied fly ash materials could be improved by mechanical treatments.

Preparation of a Ceramic Proppants for Hydraulic Fracturing Using F – Type Fly Ash

Preparation of a Ceramic Proppants for Hydraulic Fracturing Using F – Type Fly Ash