Fly Ash Materials Research Articles

Physical and mechanical performance of cement-based renders with different contents of fly ash, expanded cork granules and expanded clay

In recent decades, there has been a demand for new cladding solutions with higher thermal efficiency. Mortars with an improved thermal performance are one such solution. The biggest challenge in developing these mortars consists in achieving a lower thermal conductivity, while still maintaining an appropriate mechanical and water resistance performance with a low environmental impact.The aim of this study is to analyse the physical and mechanical performance of 20 cement-based coating mortars (renders) with different contents of a SCM – supplementary cementitious material (fly ash) used to replace cement, and of two insulating aggregates (expanded cork granules, expanded clay or a mix of both) replacing sand.The reduction of cement binder and sand aggregate contents led to lower thermal conductivity and a decrease of the mechanical properties. However, the balance between the physical and mechanical performance allows different applications, reaching thermal mortars with distinct EN 998 classes: (i) thermal conductivity T1 or T2; (ii) compressive strength CSI or CSII; (iii) water capillary absorption W0 or W1.

Tentative Optimum Proportion of Supplementary Cementitious Materials in Blended Cement to Perform Better under Tannery Wastewater

The present research studies the compressive strength of cement mortar cubes prepared from different proportions of supplementary cementitious materials (Fly Ash and Slag) in blended cement. This research aims to find the tentative optimum composition of supplementary cementitious material that shows better performance under tannery wastewater condition, such as that in effluent treatment plants. Synthetic tannery wastewater was simulated in laboratory after collecting wastewater sample from local tannery industry. Eight types of cement compositions (varying supplementary materials proportions) have been chosen. Compressive strength test has been conducted on mortar cubes over a period of three months. Test results revealed that slag addition had shown significantly stronger effects than that of fly ash addition. Also, the combined effect of fly ash and slag and their order of variation on strength were studied. The observations made from this research will be helpful for selection of blended cement proportions in future structures exposed to similar severe conditions.

Response of Sandy Soil Stabilized by Polymer Additives

Traditional sandy soil stabilizers such as lime cement, fly ash and bituminous materials, etc., usually require long curing time. Hence now a day, polymer stabilizer is used more extensively because of its stable chemical property and shorter curing time. For the developing organization, it is important to judge the performance of stabilized soil during its developing stages only. This paper aims to highlight a quick and easy test to evaluate the mechanical performance of such polymer based stabilized soil. For this study, three different kinds of polymer stabilizers at developing stage were evaluated against a market ready product. The analysis of the test result include a comparison of the strength, moisture loss rate and strain energy under different curing time, polymer type, polymer additive amount and test conditions. This study shows that the strength of the stabilized sandy soil is significantly increased both under wet and dry conditions by using the polymer additives. With the procedure mentioned in the paper it was easier to identify the relative merits and demerits of each product.

Use of anthropogenic soils in securing unstable road embankment

In the article the problem of anthropogenic soils from thermal treatment of waste in terms of their use in road construction is discussed. As part of the research, the basic physical and mechanical properties of the anthropogenic soils were determined. PN-S-02205: 1998, the analyzed ground material (fly ash and slag mixture) qualifies as useful for embedding into the lower layers of the embankment below the freezing zone, provided they are in dry places or are insulated from water. The next step was to model an exemplary, unstable road embankment in the MIDAS GTS NX. The results point out that the strength and physical properties of the anthropogenic soils may be used to secure unstable road embankments with simple soil and water conditions. It should be remembered that analysed anthropogenic soils should also be subjected to rigorous testing for their chemical composition. The obtained results will allow us to determine the possibilities of their use in road construction in terms of their strength properties.

Optimization of superplasticizer MasterGlenium SKY 8614 with added materials fly ash, steel slag, and silica fume for high strength concrete

Indonesia as a developing country continues build various infrastructures such as high storey building, bridge, highway, or fly over. Most of the construction project in Indonesia use concrete as the main material. Various problems arise as the ongoing developments such as reduced the natural resources to market demand require the concrete can be used one day after the project completion. The research is trying to solve this problem. The use of fly ash as substitute material to reduce the amount of cement use due to its chemical properties of silica and alumina, the use of steel slag instead of 50% coarse aggregate, and use of silica fume so greatly affect the compressive strength of concrete. The result of concrete compressive strength in 3 samples from first mix design with code AR were 29.16 MPa, 29.72 MPa, and 30.12 MPa. Fly ash, steel slag, and silica fume can increase the compressive strength which is much higher than design compressive strength of 15 MPa and with this mix design only use 51% of total cement requirement with normal mix design of ACI method.

OPTIMASI RASIO Si/Al, RASIO PADATAN/CAIRAN, KONSENTRASI NaOH DAN JENIS AGREGAT DALAM SINTESA BETON GEOPOLIMER DENGAN METODE TAGUCHI

The optimization synthezised of geopolymer based on fly ash materials have been done by using Taguchi method. The experimental design was done with 4 factors and 3 levels, that were the influence of Si/Al ratio, solid/liquid ratio, NaOH and the type of aggregate. Geopolymers were synthesized by sol gel method at room temperature, using fly ash as aluminasilica source and alkaline activator solutions thain consist of NaOH and Na2SiO3. The influence of Si/Al ratio studied at level of 4.00, 4.25, 4,50, solid/liquid ratio at level of 1.50, 2.33, 4.00. NaOH (%wt/%v) of 0.24, 0.40, 0.56, and the type of aggregate of Malang sand, Bojonegoro sand and granite. Based on SNR analysis and the characterization determination of higher is better, the geopolymer optimum composition was Si/Al factor at level of 3 (4.50), solid/liquid ratio level at 2 (2.33), NaOH level at 1 (0.24) and type of aggregate level at 3 (granite). The calculation of compressive strength prediction was determined at 21.01 Mpa, while the optimum compressive strength of the experimental result was found at 21 Mpa. Keywords: Geopolymer, Taguchi Method, Si/Al, Solid/Liquid, NaOH, Type of agreggate

Leaching Behavior and Immobilization of Heavy Metals in Geopolymer Synthesized from Red Mud and Fly Ash

Fly ash is an industrial waste from coal-fired thermal power plants whereas red mud is an industrial waste generated during aluminum production from bauxite. If both fly ash and red mud are not properly managed, they could cause negative impact on the environment. This study utilized red mud and fly ash in combination with sodium silicate solution to produce a geopolymer-based material which can be used as building materials. This study focussed on the leachability of heavy metals in the raw materials and the geopolymer as this would be significant in assessing the environmental impact of the product. Leachability of heavy metals such as Cu, Zn, Cd, Pb, Fe, and Cr was evaluated based on European standard (EN 124572 – 2, EU CEN TC292/ CEN TC 308) with pH values at 7. The results showed that raw materials (red mud and fly ash) have higher leachability than geopolymer specimens. And the values of leaching tests for heavy metals in the geopolymer - based materials belonged to limits of EULFD and USEPA.

Mechanical properties of ambient cured one-part hybrid OPC-geopolymer concrete

To produce geopolymers, a large amount of highly corrosive and hygroscopic alkaline activators, i.e, sodium hydroxide and potassium hydroxide, are commonly used. In this study, one-part hybrid ordinary Portland cement (OPC)-geopolymer concrete mixes were developed, in which solid potassium carbonate (7.5 wt% of the total geopolymeric raw materials) was used as the main activator and the OPC as a source of silicate and poly silicate was blended with geopolymeric raw materials (fly ash and ground granulated blast furnace slag) in different proportions. The influence of OPC content on the workability, setting time, compressive strength development and microstructure of the concrete mixes was investigated. It was found that the inclusion of OPC in geopolymer mixes reduced the workability and setting time but significantly increased the early age and ultimate compressive strength due to the quick reaction of OPC with alkali activators. By the inclusion of just 10% OPC in the binder system, the compressive strength at 28 days increased from 11.4 MPa to 33.4 MPa. Furthermore, control OPC concrete mixes were also prepared and tested. It was found that the percentage of strength increase at 28 days due to alkali activation decreased from 82.5% to 24.4% as the OPC content increased from 10% to 60%. Microstructural analysis was also conducted, which confirmed the coexistence of geopolymeric and CSH gels in the one-part hybrid OPC-geopolymer binder system.

A cheap mesoporous silica from fly ash as an outstanding adsorbent for sulfate in water

This research describes the development of a very cheap mesoporous silica material similar to hexagonal mesoporous silica (HMS) and using a silicate extract as precursor. This precursor is obtained from cheap fly ash by an easy calcination process at 850 °C and a green extraction with water. The obtained mesoporous fly ash material had a surface area of 282 m2 g−1 and a pore size of 5.7 nm. It was functionalized with ethylene diamino moieties via the well-known SAMMS method, followed by a DRIFT analysis that clearly showed the successful functionalization. An excellent adsorbent was obtained for the adsorption of sulfate anions by the solid's modification with copper forming a copper-ethylenediamine complex. The adsorption of sulfates was studied in a batch system where the pH at highest adsorption 8 was and the adsorption time remarkably fast (5 min). The kinetic data were fitted according to a pseudo-second order model with a high coefficient of linear regression at different initial concentrations. The adsorption isotherm that best fitted the experimental data was the Freundlich model. The maximum sulfate adsorption capacity of this very cheap fly ash based adsorbent was 146.1 mg g−1, 3 times greater than the values reported in literature and commercial adsorbent materials.

Evaluation of the Use of Fly Ash as a Low Cost Technology for Phosphorus Removal in Wastewater Treatment

“Pozzolan” is a slag from the burning of coal in power plants which has the potential to assist as a low-cost adsorbent for wastewater treatment. The excess of Phosphorus (P) in the environment can promote chemical pollution and harm ecosystems, especially water. It is therefore necessary to implement inexpensive techniques and processes for the efficient treatment of water and wastewater. In this context, this study evaluated the use of the pozzolanic fly ash material for P removal from wastewater for the development of low-cost treatment technologies for environmental restoration and remediation of water resources. The treatment systems were developed in batch configuration. The removal tests from a synthetic sample with a known concentration of P reached a maximum of 30% removal in concentration, even varying the pH and performing different treatments of the pozzolanic material. This low removal efficiency of Phosphorus led to a comparative test between different lots of pozzolan in order to verify if the results obtained were characteristic of the material itself or of the lot obtained. Also the P adsorption isotherms were constructed with the two lots achieving adsorption capacities from 0.87 mg g-1 to 74 mg g-1. This difference indicates that the low P removal efficiency in the preliminary tests is due to the characteristics of the substrate of the first lot. Tests on a real effluent using the pozzolan from the second sample lot indicated a 99% efficiency of P removal, with an initial concentration of Phosphorus in the effluent of 5.5 mg L-1.

Reduction of Radon Gas in Concrete Using Admixtures and Additives

Abstract The second largest cause of lung cancer is related to radon (222Rn) and its progenies in our environment. Building materials, such as concrete, contribute to the production of radon gas through the natural decay of 238U from its constituents. The Swedish Cement and Concrete Research Institute (CBI) has examined three concrete recipes where only an additive as well as fly ash were added as single constituents to a reference recipe and compared to a reference concrete. The inputs of an additive as well as a supplementary cementitious material (fly ash) were made as a mean to investigate their potential influence on the radon exhalation rates of the concrete. Measurements were performed with an ATMOS 33 ionizing pulsation chamber for at least five different occasions for each recipe during a 22 month period. The results indicate a reduction of the exhalation rate by approximately 30-35 % for each altered recipe. This means roughly 1.5-2 mSv per year decrease in effective dose to a human using an additive or a supplementary cementitious material such as fly ash in relation to the investigated standard concrete.

Stabilization of Cr-rich tannery waste in fly ash matrices.

In the present work, the stabilization/solidification of a Cr-rich ash obtained from the anoxic incineration of tannery hazardous wastes was studied. Chromium in the starting waste was exclusively in amorphous form and in trivalent state. The waste was embedded in fly ash-based cementitious material matrices. Calcium and sodium hydroxides, as well as sodium silicate, were used as activators. The proposed process combines mechanical activation with hydrothermal curing. Successful immobilization of chromium was achieved, as attested by standard leaching tests. Backscattered electron images revealed the existence of the C-S-H gel, and elemental mapping by energy dispersive X-ray spectroscopy showed a good interdispersion of chromate and aluminosilicate species, verifying that chromium was well distributed in the final amorphous cementitious matrix. X-ray diffraction confirmed the absence of Cr-rich crystalline phases of calcium aluminosilicates, where chromium can enter in hexavalent state. The stiffness of the stabilized samples was reduced with increasing the amount of added Cr-rich ash, as attested by measurements of the dynamic Young's modulus.

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.

Adsorption study of modified coal fly ash with sulfonic acid as a potential adsorbent for the removal of toxic reactive dyes from aqueous solution: Kinetics and thermodynamics

Great emphasis is being put in to develop green, efficient and inexpensive adsorbent in recent years. In this study, we demonstrate the potential of coal fly ash (CFA) materials as environmental pollutant adsorbent. The Sulfonic acid functionalized heat and alkali treated CFA (HATF-SO3H), is synthesized by condensation of 3-mercaptopropyltrimethoxysilane (3-MPTS) and heat and alkali treated CFA (HATF) followed by oxidation of surface thiol groups by H2O2 to sulfonic acid groups. The as-synthesized product is used to remove toxic and reactive dyes i.e. Malachite green (MG) and Rhodamine 6G (R6G), which are the main contaminant from the dye manufacturing and textile finishing. The efficiency of the dye adsorption on HATF-SO3H surface was investigated under various experimental parameter such as adsorbent dose, contact time, stirring speed, pH, and temperature. The proficient sorption efficacy of HATF-SO3H qm towards toxic and reactive dyes (efficiency of MG removal, 99.20%; maximum specific removal qm 233.30 mg g−1: efficiency of R6G removal, 98.70%; maximum specific removal 381.70 mg g−1) can be explained from the perspective of both electrostatic and H-bonding interactions between the surface of HATF-SO3H and dye molecules.

Adsorption of heavy metal ions using zeolite materials of municipal solid waste incineration fly ash modified by microwave-assisted hydrothermal treatment

In this work, microwave-assisted hydrothermal process was applied to modify the municipal solid waste incineration (MSWI) fly ash and get zeolitic production. The condition of hydrothermal process was fixed at 200 °C and 30 min. The 1 mol/L Na2HPO4 was selected as the additive, and the liquid to solid ratio was 3 ml/g. X-ray diffraction results revealed that analogous zeolite crystals formed by the MSWI fly ash during the hydrothermal process. The cation exchange capacity (CEC) was 0.498 meq/g of the modified fly ash, which increased about 22 times compared to the raw MSWI fly ash. To obtain the adsorption mechanism of the modified fly ash, the experiments of adsorption isotherm and kinetics were researched. The adsorption isotherms of heavy metal cations in mixed solution could be described by Langmuir isotherm equations, with a high correlation coefficient value. The experimental products were better fitted by the pseudo second-order kinetics rather than the pseudo first-order kinetics. Although the adsorption capacity of the modified fly ash needs to be promoted, it is a potential utilization for MSWI fly ash to be the original materials as adsorbents.

Performance of Nitrogen and Phosphorus Removal in Petrochemical Wastewater by Zeolited Fly Ash

The zeolitized fly ash was synthesized by alkali melt hydrothermal method. The cation exchange capacity of zeolitized fly ash was far greater than the raw material fly ash. The main component was NaP1 zeolite (Na6Al6Si10O32·12H2O), followed by mullite, and a small amount of heterozygous crystals. The effect of synthetic zeolite dosage, pH value, adsorption time and reaction temperature on the effect of nitrogen and phosphorus removal in petrochemical wastewater were investigated. The results showed that when the zeolitized fly ash dosage was 9 g/L, the petrochemical wastewater pH value was 6∼8, adsorption time was 30 min and the reaction temperature was 30°C, the synthetic zeolite had the best effect on the removal of TN and TP in petrochemical wastewater, and the removal was 65.5%, 91.4% respectively. Besides, the concentrations of TN and TP in the effluent were 11.04 mg/L, 0.31 mg/L respectively. The concentrations met the sewage discharge standard in petrochemical industry of "Liaoning sewage comprehensive discharge standard" (DB21 1627-2008). This study was to realize the comprehensive utilization of solid waste and achieve the purpose of waste and waste.

Flexural performance and tension-stiffening evaluation of reinforced concrete beam incorporating recycled aggregate and fly ash

This paper presents the effect of fly ash in recycled aggregate concrete (RAC with 100% recycled coarse aggregates) on the flexural performance of reinforced concrete (RC) beam. Particle packing method (PPM) of mixture proportioning is used in a novel way for the flexure study. This method by principle accounts for the excess adhered mortar present on the outer surface of recycled coarse aggregates (RCA) while calculating maximum packing density and consequently minimize the requirement of fresh mortar. The parameters such as materials (aggregate type and fly ash), mix design method and reinforcement percentages are considered for evaluation of moment carrying capacity, deflection, and failure pattern. Based on experimental results, the constitutive relation for cracked RAC and natural aggregate concrete (NAC) is evaluated numerically showing tension stiffening effect. The results conclude mostly comparable moment carrying capacity of RAC incorporating fly ash beams and NAC beams at ultimate limit state. The maximum mid-span deflection has been observed to be higher, but the variation is not substantial at service load due to the effect of fly ash and PPM in RAC. The reduced tension-stiffening effect, as observed from the derived stress–strain relation of cracked concrete justifies the higher mid-span deflection in RAC. The applicability of existing code provisions for NAC beam is assessed for RAC with fly ash beams. The results suggest the potential application of 100% recycled coarse aggregates and up to 30% fly ash in a reinforced concrete beam without compromising its flexure performance.

Freezing and thawing resistance of cellular concrete containing binary and ternary cementitious mixtures

Cellular concrete (CC) is a foamed low-density and low-strength material made with cement and/or lime, silica-rich material (sand, slag, or fly ash), water, fine aggregate and a foaming agent. The CC containing millions of evenly distributed, uniformly sized macroscopic air-voids of approximately 0.1–1 mm in size is considered to have good freeze-thaw (F-T) resistance. In the present study, the CC of binary and ternary cementitious mixtures with varying proportions of portland cement, fly ash, and lime were explored in a comprehensive laboratory test program related to porosity, water absorption, dry density, compressive strength, and resistance to F-T including durability factor and loss of mass. For selected mixtures, air-void spacing factor and air-void distribution had been determined. Test results showed that compressive strength of CC was primarily as a function of the porosity and density regardless of type of cementitious material with respect to the combination of binary and ternary cementitious mixture. It was also found that higher porosity did not necessarily result in higher water absorption. CC was generally found to present good F-T resistance compared to non-aerated concrete although the CC with high porosity did not necessarily result in higher resistance of F-T. The addition of fly ash to mixture led to a decrease in the number of air voids smaller than 300 µm. It was also found the F-T resistance of CC was more affected by the size of the air-void. The number of air-voids smaller than 300 µm played a critical role on reducing the F-T damage in CC.

Ultrasound-enhanced electrokinetic remediation for removal of Zn, Pb, Cu and Cd in municipal solid waste incineration fly ashes

Low-frequency ultrasound generated by a transducer was investigated to activate the raw municipal solid waste incineration (MSWI) fly ashes in the electrokinetic process, aiming at enhancing heavy metal (HM) removal and achieving better remedial efficacy. The maximum removal efficiencies of 69.84%, 64.24%, 67.74% and 59.93% were obtained in the orthogonal tests of ultrasonication for Zn, Pb, Cu and Cd, respectively. The acoustic time of 30 min and controlling temperature of 45 °C in the operating parameters were quantitatively determined to optimize the ultrasonication of the MSWI fly ash matrices. The changes of acoustic time had a significant effect on the extraction efficiencies of all the four heavy metal elements in the sonication optimal experiments. The longer running time was preferred for the pretreatment of the fly ashes in according to the marginal mean removal results. The voltage gradient of 2 V/cm was most likely to improve the removals of four HMs during the electrokinetics in the range of 0.5–2 V/cm. The synergetic application of acidification and ultrasonication for the media treatment was demonstrated to be most effective in enhancing the remedial efficiencies in the further electrokinetic experiments compared with the other activation systems. Correspondingly, the leaching concentrations of Zn, Pb, Cu and Cd in the samples were reduced by 85.92%, 98.22%, 88.53% and 98.34%, respectively. The contaminants were continuously extracted from the solid grains of the fly ashes by the protonic attack and bubble implosion. The obtained risk-assessment-code values indicated the adoption of AUS-EKR system reduced the environmental toxicity for the fly ashes to the maximum extent.

Closing the material cycle of biomass-derived fly ashes: a regional case study of natural ageing in Finland

The amount of biomass-derived ashes is expected to rise in the EU due to targets to increase the use of renewable energy resources. To promote the reuse of biomass ashes, a regional case study of natural ageing of approximately 1 year was carried out on two landfill fly ash materials originating from wood and wood/peat. The results showed that leaching behaviour differed considerably between the fly ashes. Natural ageing had beneficial effects on the leaching properties of wood fly ash. The leached concentrations of sulphate, chloride, Cr and Mo decreased significantly in this residue. In peat and wood-derived fly ash, natural ageing decreased the leaching of Cr, but had no significant effect on the leaching of Mo and chloride. It was also notable that the leaching of sulphate increased in wood/peat fly ash by more than 130%, exceeding the upper limit value given in national legislation for a paved structure. To comply with the limit values of national legislation concerning the recovery of waste in earth construction, natural ageing alone was not shown to be a sufficient method to reduce the leaching of harmful elements in biomass-derived fly ashes and, thus, further treatments are required.