Fly Ash Mixtures Research Articles

Accelerated Weathering of Limestone Bicarbonate Induced CaCO3 Precipitation in A Mixture of Sand, Fly Ash and CaO

Excessive generation of CO2 and industrial wastes has sparked environmental concerns around the globe. In this research, Accelerated Weathering of Limestone (AWL) process uses calcium carbonate (CaCO3) to capture CO2 from ambient air. It achieved an absorption efficiency of 31.88 %. The calcium bicarbonate effluent produced via AWL is used to precipitate calcium carbonate in lime mortar (LM) mixture containing sand and calcium oxide (CaO) with fly ash, an industrial waste. This helps develop a novel utilization pathway for the respective wastes via production of a novel green construction material termed bicarbonate lime mortar infused with fly ash (BLMFA). The fly ash addition percentage in bicarbonate lime mortar (BLM) mix are 12.12, 17.15 and 21.63 wt.%. This project also studies the effect of curing time (7, 28 and 88 days) on development of BLMFA strength. Experimental results found that at 7 days, the strength of BLMFA (0.44 to 0.48 MPa) is lower than the conventional LM, which has a strength of 0.52 MPa. However, on 88 days, 17.15 wt.% BLMFA achieved a strength of 0.82 MPa, which is 0.060 MPa higher than the conventional LM sample. In addition, BLMFA also possesses high CaCO3 content of 36.7 to 44 wt.% out of the targeted 54.37 wt.% compared to conventional LM, which could only achieve 27.14 wt.% CaCO3. This indicates that infusion of fly ash can enhance the carbonation efficiency of calcium sources to CaCO3. All in all, AWL process and BLMFA precipitation possess the capability to diminish anthropogenic CO2 while beneficially utilizing industrial waste.

Compressibility of Fly Ash and Fly Ash-Bentonite Mixtures

Environmental protection, one of the most important issues nowadays, forces civil engineers to look for alternative solutions to the known ones. The use of substitute materials as an embankment fill or a ground material under the embankment instead of natural soil follows these trends. A great amount of fly ash is disposed of in landfills. It is a cost-effective material that can be used in construction instead of natural soil. The geotechnical properties of fly ash as a construction material in place of soil need to be examined. It includes laboratory tests to determine the chemical composition and geotechnical characteristics. In the present work, one-dimensional consolidation tests have been conducted to examine the compressibility behaviour of compacted fly ash and fly ash-bentonite mixtures used in the earth structures like road embankments. The analysis of the consolidation phenomenon is useful for predicting the magnitude and rate of settlement of the structure. Materials compacted at OMC to their MDD, according to Standard Proctor, were tested in Rowe-Barden type consolidometer on saturated and non-saturated samples. Coefficients of consolidation have been compared between values derived from log-time and square-root-of-time methods and direct hydraulic conductivity tests. Bentonite amount in fly ash-bentonite mixtures influences the vertical deformation of the sample.

Effect of high temperatures on the properties of lightweight geopolymer concrete based fly ash and glass powder mixtures

Given the large manufacturing and consumption of concrete globally, there has been widespread speculation that it is a significant source of greenhouse gas emissions. Consequently, scientists are looking for sustainable and beneficial solutions to the environment. The influence of adding expanded clays (Leca) and crushed recycled bricks clay lightweight aggregates (RBA) on the fly ash and glass powder-based geopolymer concrete were investigated at ambient and high temperatures. High temperature influences the significant characteristics of mortar and lightweight aggregate geopolymer concrete. Low calcium fly ash was utilized as a binder in the concrete paste with a 10% replacement rate of Glass Powder. The concrete specimens were heated to 200, 400, 550, and 800 °C at a 7 °C/min rate for 60 min. Lower coarse aggregate strength is a contributing factor to concrete compressive strength reductions. The influences of high temperatures on geopolymer concrete were studied in terms of mass loss, cracking, water absorption, and microstructure. The research outcomes show that the geopolymer concrete suffered damage and dehydration at a heating temperature of 550 °C and above. Acceptable correlation between the temperature degree and Ultrasonic Pulse Velocity UPV with the compressive strength of the lightweight concrete. The test results showed the residual compressive strength 110.2%, 92.9%, 71.9%, and 55.6% as well as 109.2%, 91.5%, 79.6%, and 52.6% in addition to the density reduced 0.17%, 2.56%, 7.29%, and 12.18%, and 0.74%, 3.97%, 6.31%, and 13.25% in 200,400,550, and 800 °C for Leca and RBA type respectively. The equations showed acceptable results with experimental data. The impact of replacing waste glass powder with fly ash on the development of microstructures and gels was also investigated.

Performance of Porous Asphalt Mixtures Containing Recycled Concrete Aggregate and Fly Ash.

This study investigates the effects of two waste materials from construction and industry, namely recycled concrete aggregate (RCA) and Type C fly ash, on the overall performance of a special type of pavement surface mixture, porous asphalt mixture. Mixtures of different combinations of RCA (for partial aggregate replacement) and fly ash (for filler replacement) were prepared in the laboratory and tested for a variety of pavement surface performance parameters, including air-void content, permeability, Marshall stability, indirect tensile strength, moisture susceptibility, Cantabro loss, macrotexture, and sound absorption. The analysis of the results showed that incorporating RCA or fly ash in a porous asphalt mixture slightly reduced the air-void content, permeability, and surface macrotexture of the mixture. A 10% replacement of granite aggregates with RCA in the porous asphalt mixtures led to a reduction in mixture stability, indirect tensile strength, resistance to raveling, and sound absorption. The further substitution of mineral filler with fly ash in the mixture, however, helped to offset the negative impact of RCA and brought the mechanical properties of the mixture with 10% RCA to levels comparable to those of the control mixture.

Thermal analysis and performance testing of heavy load truck composite brake linings

Abstract One of the most important variables that determine the braking performance of heavy-duty trucks is the high temperature increases in the brake components. In this study, the effects of high temperatures in brake lining compositions were investigated using thermogravimetric analysis (TGA). Furthermore, dynamometer tests and SEM analysis were performed. Three different compositions, which are called standard, fly ash and sisal fiber mixture, were compared with existing commercial heavy-duty truck brake lining. The thermal behavior of samples analyzed in TGA machine compared to the weight losses with increasing temperatures until 900 °C. Dynamometer tests which simulated the real part production and vehicle tests were realized in brake lining supplier. Finally, with the SEM analysis, both normal and worn surfaces were analyzed and reasons for wear surfaces were investigated. The findings suggest that there is a high potential in fly ash mixture to apply in commercial trucks applications which occurs at very high temperatures and is very suitable for environment and cost reduction points.

Assessment and characterization of waste material used as backfilling in an abandoned mine

ABSTRACT Overburden is the earth material removed during opencast mining, which is typically not contaminated with toxic materials. After mining operations, overburdens are dumped on exhausted mining sites. However, some opencast mines are not properly backfilled, and this causes harmful environmental effects, such as leaching of acid mine drainage. The flyash produced from thermal power plants is also a major waste that must be disposed of environmentally friendly. This study focuses on filling the voids of an abandoned mine with a mixture of 70% overburden + 30% flyash. A considerable improvement in acid mine drainage characteristics was found after either adding overburden or an overburden and flyash mixture. Sustainable management of coal mines should include the careful restoration of exhausted mines, which can be made possible by repurposing relevant industrial waste.

Utilization of Natural Zeolites and Fly Ash (Coal) Mixture Physically Activated Using Furnace As A Pellet - shaped Air Filter To Increase Engine Torque, Tecumseh TD110. 4-Stroke Petrol Motor

An air filter made from a mixture of natural zeolite and coal fly ash can be used to remove nitrogen (N2) and moisture (H2O) in the air. This filter can produce oxygen-rich air (O2) flowing into the combustion chamber to increase the quality of the combustion process so that complete combustion occurs and improve engine torque. In this research the filter was made from a physically activated mixture of natural zeolite and fly ash through heating in a furnace for 1 hour with temperature variations (200oC, 250oC, 300oC, 350oC), mass variations (50%, 75%, 100%) and variations in the composition of Z100%:F0%, Z75%:F25%, Z50%:F50%, Z25%:F75%, Z0%:F100%. Tests were carried out using a 4-stroke gasoline engine of Tecumseh TD110 located in the Motor Bakar and Propulsion Laboratory of the Mechanical Engineering Department, University of Lampung. Test results show that the biggest improvement in torque occurs in using a filter composition of Z50%:F50%, namely by 28.41%. The followed filter of the composition of Z75%:F25% is as big as 28.31%. The activation temperature of 350oC can improve the torque by 35.08%.

Potential application of over-burnt brick and fly ash for sustainable inverted pavement structure

• The potential application of overburnt brick has been shown for inverted pavement. • Fly ash can be used in the subbase of inverted pavement using cement stabilization. • Response spectrum method has been utilized for pavement thickness optimization. The scarcity of natural aggregate required for infrastructural development (including road construction) is a global problem. Therefore, researchers have constantly been exploring the possibility of different kinds of non-conventional aggregate for sustainable road construction. In this context, over-burnt brick is one among the most common wastes from the construction industry in India, which can be utilized as non-conventional aggregates in the granular layer of pavement structure with the help of a stabilization technique. Pavement structure containing stabilized/cementitious underlying base/sub-base layer is termed as inverted pavement (asphalt layer supported by a relatively stiffer stabilized layer). Attempts have been made in the past to utilize over-burnt brick as an alternative aggregate in different types of pavement structures. However, whether such over-burnt aggregate can be utilized in the stabilized layer of the inverted pavement structure is still unknown. Therefore, this research aimed to explore the potential application of over-burnt brick with the help of stabilization using a cement-fly ash mixture for the base layer of inverted pavement. Likewise, the mixture of fly ash and cement mixture was investigated for their potential application in the subbase layer of the inverted pavement structure. The optimal quantity of cement in both layers for stabilization was initially determined based on strength and durability criteria. Finally, the inverted pavement was analyzed based on the design of experiment approach using the response surface methodology. The analysis of strength and durability components indicated that cement content equal to 6% for brick-fly ash mixture is suitable for the base layer of the inverted pavement. Likewise, cement content equal to 7% with fly ash was found to be suitable for its application in the sub-base layer. It is expected that this research work will help improve the sustainability quotient associated with an inverted pavement structure.

Experimental Study on the Road Performance of High Content of Phosphogypsum in the Lime–Fly Ash Mixture

Phosphogypsum (PG), as a by-product of the production of phosphoric acid, faces the problems of large annual output and difficult treatment. There is a large demand for fillers in the process of road paving, which may be an effective method for the utilization of PG resources. In this study, three proportions of phosphogypsum–lime–fly ash (PLF) mixture were designed, first, according to orthogonal tests. The comprehensive performance of the PLF mixture was tested by the compression rebound modulus test, unconfined compressive strength test, flexural tensile strength test, dry shrinkage test, and temperature shrinkage test, respectively. The results show that adding crushed stone to the PLF mixture can effectively improve the compression rebound modulus, unconfined compressive strength, and flexural tensile strength. The high content of PG in the mixture can also improve the dry shrinkage and temperature shrinkage properties of the mixture. According to the road layer requirements, the optimum proportion of the PLF mixture is recommended, which may benefit the road construction and PG resources.

Effects of free lime content in fly ash on sulfate expansion of cement–fly ash mixtures

Effects of free lime content in fly ash on sulfate expansion of cement–fly ash mixtures

Optimization of equivalent modulus of RAP-geopolymer-soil mixtures using response surface methodology

This study focuses on assessing the resilient characteristics of a clayey soil modified with a fly ash (FA)-based geopolymer and reclaimed asphalt pavement (RAP) as an unpaved road material. RAP-geopolymer-soil mixtures were designed using the response surface methodology-central composite design with 0–40% RAP and 0–25% FA. The repeated-load California bearing ratio (CBR) testing method was used to determine the recoverable and permanent deformations and then obtain the equivalent (resilient) modulus (Mequ). The Mequ values were used to develop predictive models and determine the optimum soil–RAP–geopolymer mixture. The effects of the load level and soaking period on the stiffness of the optimum mixture were also investigated. The results revealed that the geopolymer binder played a significant role in enhancing the stiffness of the mixtures, with the maximum Mequ obtained at 25% FA and 0% RAP. However, it was determined that RAP has an adverse effect on the stiffness for almost all the studied cases and more significantly for the 40% RAP and 0% FA mixture. The optimal mixture was found to be 25% FA and 30% RAP. The developed model exhibited excellent predictive capability based on ANOVA results. The optimum mixture exhibited stress-softening behavior at an increased load level. No clear trend was observed in the effect of the soaking period on the resilient modulus within the examined soaking period range. Overall, this study agrees with several pavement design guidelines to limit the RAP content used in road applications owing to uncertain adequacy. Additionally, it suggests that the geopolymer binder is an effective stabilizer with excellent environmental and economic potential.

Improvement of Strength Characteristics of a Highly Plastic Expansive Soil with Fly Ash

Highly plastic expansive clays swell or shrink due to change in moisture content and they often have very low bearing capacity. Construction of engineering structures particularly pavements and lightweight buildings on problematic soils such as highly plastic expansive clays may create severe structural problems due to poor engineering properties of that kind of soil. This study focused on the influence of fly ash on strength properties of highly expansive clays which are problematic soils due to their undesirable engineering characteristics such as high plasticity index, liquid limit, swelling and shrinkage characteristics, and low bearing capacity. Atterberg’s limit tests and hydrometer tests were conducted to obtain consistency limits and grain-size distribution of the highly plastic expansive clay. Standard proctor tests for clay samples with different fly ash contents such as 10%, 15%, and 20% were performed to determine maximum dry densities and optimum water contents of the mixtures of clay and fly ash. The clay and fly ash mixtures were prepared at optimum water content and maximum dry density for unconfined compression strength (UCS) and California Bearing Ratio (CBR) tests. Effects of fly0ash content on the strength characteristics of a highly plastic expansive clay were investigated through unconfined compression and CBR tests. The experiment results showed that fly0ash is a promising additive to enhance strength characteristics of highly plastic expansive clays. An approximately 66% increase in UCS and CBR values was observed with the addition of 20% fly ash into the clay mixture in weight.

Fly ash-based frit as a sintering aid for ceramic body

Coal fly ash is characterized by high silica and alumina contents, making it suitable as a raw material for alumosilicate ceramics. However, direct use of fly ash reveals obstacles such as high porosity, black core, cracking, and swelling. This work synthesized frit by melting a mixture of fly ash, quartz, limestone, and soda. TG-DSC analysis showed that the glass transition point of the frit occurs at approximately 600 degrees Celsius. Ceramic bodies from raw mixes containing various frit amounts were prepared and characterized. The results showed that with 4% being frit, the firing temperature could be reduced by 30 degrees Celsius, along with decreased water absorption and increased flexural strength. Besides, no swelling, cracks, or black cores occur. These observations indicate that fly ash-based frit is viable a sintering aid in ceramic production.

The role of zinc sulphate as a retarder for alkali activated binders and its influence on the rheological, setting and mechanical behaviour

Alkali activated materials are alternative cementitious materials that have demonstrated good mechanical and durability properties. However, these materials exhibit quick setting and poor workable times. To address this issue, in this study, zinc sulphate was used as a retarder to alkali activated ground granulated blast furnace slag and fly ash (AASFA) mixtures. The rheological, setting and mechanical behaviour of AASFA mixtures with different molar modulus, proportion of fly ash and dosage of ZnSO4·7H2O were investigated. Delay in setting time, increase in workable time, reduction in yield stress and apparent viscosity, and absence or minimal secondary increase in storage modulus of AASFA mixtures were observed with an increase in the dosage of ZnSO4·7H2O from 0 to 3%. The compressive strength of AASFA mixtures at early ages decreased with an increase in the content of zinc sulphate and attained more than 80% of the control strength at 28 days and above.

Correlating field and laboratory investigations for preventing ASR in concrete – The LNEC cube study (Part I – Project plan and laboratory results)

As part of the Norwegian R&D project “ASR - Reliable concept for performance testing (KPN-ASR)” and of the RILEM TC 258-AAA activities, a study was launched in 2015 with the aim of correlating the results of field and laboratory investigations for selecting appropriate preventive measures against deleterious alkali-silica reaction (ASR) in concrete. Three coarse aggregates, i.e. New Mexico polymictic gravel, Ottersbo cataclasite, and a non-reactive limestone aggregate, were used to manufacture cubes (300×300×300 mm3) from air-entrained, control (high-alkali cement; normal alkali cement) and ASTM Class F fly ash (20 and 30 % replacement levels of the high-alkali cement) concrete mixtures. The cubes were then shipped to be placed on the study participants’ outdoor exposure sites, where they are being monitored for long-term expansion and cracking development (Canada; France; Germany; Iceland; Norway; Portugal; USA). Companion laboratory cubic specimens (for compressive strength and air-void spacing factor determination on hardened concrete) and test prisms were cast from the above mixtures. The prisms were subjected to RILEM AAR–3.1 and RILEM AAR-4.1 testing at LNEC's laboratory; their expansion was monitored over 205 and 28 weeks, respectively. Selected control and fly ash mixtures, without air-entrainment, were repeated at SINTEF following the 38 °C Norwegian concrete prism test (NCPT, prism size 100×100×450 mm3) and RILEM AAR-4.1. This paper, the first of the LNEC cube study, gives an overview of the project, lists the project's main objectives, provides a summary of the activities already developed in the project, and presents and discusses the results obtained thus far in the laboratory investigations. As expected, excessive expansions were obtained for the control high-alkali concretes, whereas addition of fly ash reduced the expansion to a low level. However, the expansion attained for the fly ash mixtures depended on the CPT procedure used.

Leaching and transport of technetium from reducing cementitious waste forms in field lysimeters

Field lysimeters tests examined leaching of technetium-99 (99Tc) from two types of cementitious waste forms and found that the presence of blast furnace slag reduced the overall leaching of 99Tc from the waste form. The two cementitious waste forms were a slag-grout 45%/45%/10% mixture of fly ash, blast furnace slag, and cement, respectively, referred to as slag-grout or a 55%/45% mixture of cement and fly ash, respectively, referred to here simply as cement. Duplicate sources of each composition were buried in four lysimeters for approximately 10 months to evaluate leaching characteristics under natural meteorological conditions in South Carolina, USA. Effluent samples were collected four times during the experiment, and the distribution of 99Tc in the sediment was determined by destructively segmenting the lysimeters at the end of the experiment.The transport of Tc within the lysimeter was simulated by assuming advection, dispersion, and sorption in partially saturated porous media, and by using a shrinking-core type approximation for the release of Tc from the source. The shrinking-core model predicted that the oxidation front created by the oxygenated infiltrating groundwater moved into the cementitious source at a rate of 14 μm/day. As this front moved through the source, Tc(IV) was oxidized to the highly mobile Tc(VII) (as TcO4−) species, which then was transported through the sediment primarily via advection due to a small partitioning coefficient (Csolid/Caq; Kd = 0.14 mL/g). The simulations predicted a cycle of accumulation of Tc in sediment at the source between rainfall events, followed by downward advection due to infiltration during rainfall events. The anomalous upward movement of Tc peak was predicted to be due to upward flux caused by evaporation after the experiment was terminated by capping the lysimeter. These experiments demonstrate that Tc leaching from cementitious waste forms under simulated vadose zone oxidizing conditions can be reasonably approximated by the shrinking core model, and the migration of Tc through the sediment is profoundly influenced by the presence of slag in the grout formulation and hydraulic conditions due to the low sorption affinity of TcO4−.

Seawater as Alkali Activator in Fly Ash Based Geopolymer

Indonesia as a maritime country in the world with 66% of its territory consists of maritime territory. A lot of potential that can be exploited, such as sea water. XRD characterization results indicate that the sea water from Tanjung Priok, North Jakarta, Indonesia has a compound Halite (NaCl) and Bassanite (CaSO4.5H2O) in the salt form. These compounds are alkaline thereby can influence the compressive strength of the geopolymer. Geopolymer is made up of aluminosilicate precursors which are activated by the alkaline activator solution, which usually combines sodium silicate and sodium hydroxide. The precursor material is waste from the coal based power plant called fly ash that produce 219.000 tonne per year and still underutilized but potentially as an alternative to cement. In this study, seawater was used to substitute the sodium hydroxide in alkali activator as an effort to reduce the manufacturing cost of Geopolymer. Geopolymer prepared by mixing fly ash as a precursor, silica sand as aggregates, with activator, then casted and cured by immersion. After 28 days compression test was conducted to measure the strength of resulting geopolymer. The sample consisted of a mixture of fly ash, silica sand, waterglass, and seawater produces strength of 16.60 MPa. X-Ray Diffraction characterization was conducted to study the compound formed from precursors activated with seawater alkali activator. Resulting diffractogram indicate the formation of anorthite compound as proof of Geopolymerization has been successfully occured.

Stabilization of Soil Using Fly Ash

Abstract: Soil is the basic foundation for any civil engineering structures. It is required to bear the loads without failure. In some places, soil may be weak which cannot resist the oncoming loads. In such cases, soil stabilization is needed .Numerous methods are available in the literature for soil stabilization, But sometimes, some of the methods like chemical stabilization; lime stabilization etc. adversely affects the chemical composition of the soil. In this study, fly ash mixes with clay soil to investigate the relative strength gain in terms of unconfined compression, bearing capacity and compaction. The effect of fly ash on the geotechnical characteristics of clay-fly ash was investigated by conducting standard Proctor compaction tests, unconfined compression test, CBR tests and permeability test. The tests were performed as per Indian Standard specifications. Index Terms: Soil, Fine Fly Ash Mixture, Soil Stabilization.

Effect of delayed placement of layers on permeability and durability of roller-compacted concrete containing fly ash

ABSTRACT Interlayer cold joint formation in roller compacted concrete (RCC) structures is inevitable because of typically applied in layers. In this study, the effect of interlayer cold joint formation on the water absorption and freeze–thaw resistance of RCC with fly ash was investigated. After the first layer of specimens is placed and compacted, the second layer was cast with a delay of 0, 60, 120 and 180 min in order to investigate the cold joint effects. In addition, RCC specimens were produced by applying the mortar between the layers to prevent interlayer cold joint formation. Water absorption and freeze–thaw experiments were performed on RCCs. According to the test results, cold joint formation arising from prolongation of delay increased the water absorption of RCCs and reduced freeze–thaw resistance. However, the application of mortar is an effective method to overcome the interlayer cold joint. Besides, partial substitution of aggregate with fly ash in mixtures improved the workability, impermeability, strength and freeze–thaw resistance of RCC. However, although partial replacement of the cement with fly ash improved the workability and freeze–thaw resistance of some of RCC mixtures, it increased the water absorption and decreased the compressive strength.

Study on the three body abrasive wear behaviour of EN8-steel before and after coating of wear resistance material

The effects of aluminum, zirconium, and fly-ash mixture additions on three-body abrasive wear behaviour of EN8- steel have been systematically investigated using a threebody abrasive machine and SiO<sub>2</sub> as abrasive.The coating material is preferred by using 49% aluminum and 49% zirconium is mixed by using 2% fly-ash, the fly ash works as a binder between aluminum and zirconium. Investigate the worn surface of EN8-steel specimen before and after coating of Al<sub>2</sub>O<sub>3</sub>, ZrSiO<sub>4</sub> and fly-ash mixture. The Al<sub>2</sub>O<sub>3</sub>, ZrSiO<sub>4</sub> and fly-ash coated working specimen will give less wear rate in grams compared to working specimen without coating. It clearly shows that using Al<sub>2</sub>O<sub>3</sub> and ZrSiO<sub>4</sub> will reduce the wear rate and increase life of EN8 steel.