Fly Ash Materials Research Articles

Design Experiment for Leveraging Material Value Coal Ash as Material Mixture of Paving Block

The coal-fired thermal power plant is the main source of coal ash production. Coal ash collected at the bottom of the furnace (boiler) is called coal bottom ash (CBA) and fly ash remaining combustion called coal fly ash (CFA). In Indonesia, the utilization of bottom ash and fly ash generally is still limited to landfill material due to the value of the material too low. The objective of this research is to leverage the value of the utilization of bottom ash and fly ash materials as a mixer of construction industry products. Design of Experiment (DoE) was conducted on paving block product using various experimental factors such as composition of sand, cement, bottom ash, fly ash, and curing period of product. This Design of Experiment (DoE) applied orthogonal array to finding the best mixed compositions that affect the quality of the end result. After it, the proof was performed with a compressive strength test and water absorption test to meet the standard requirements. Testing compressive strength of paving block was done at 7 days, 14 days and 28 days to get the best result.

Properties and thermal insulation performance of light-weight concrete

The building energy performance is becoming increasingly important, because of environmental restrictions and rising costs of fuel end energy. Therefore, improve the thermal insulation performance of wall covers of buildings is crucial. The present study evaluated the combined effects of two types of materials of expanded polystyrene (EPS) beads and unprocessed fly ash (FA) in Vietnam on properties of light-weight concrete (LWC). The calculation of mixture proportions of LWC is applied in accordance with the absolute volume method. Twelve different concrete mixtures with a water to bind ratio of 0.3 and superplasticizer SR 5000F to Portland cement ratio of 0.02 were used. The EPS beads and FA were partially replaced with the volume of fresh concrete and cement, respectively. The engineering properties, including workability, density, compressive strength, tensile strength, modulus of elasticity and basic physical properties were investigated in 12 patterns of tested LWC and its correlations were made. In addition, the definition of temperature distribution over the thickness of the experimental wall cover was applied by the ANSYS 18 software. According to the experimental results, there is a decrease in dry density and mechanical properties with increasing these EPS beads and FA contents in LWC. The results by ANSYS 18 are shown that at the same thickness of 250 mm, a wall with the blocks LWC brick has better insulation than the wall made of other materials such as solid clay brick, clay hollow brick and solid brick with slag concrete.

Trial to Determine Durability and Serviceability for Swine Farm in Thailand

In agricultural construction, the most frequently used construction material is concrete. In particular swine farm, traditional concrete flooring system in the business is conventional concrete. However, the conventional concrete floor has several key issues on its surface. They are easily to be spalled and cracked, pig scour, rough areas, and low wear resistance of acid from animal feed. This research involves study in the ratio between Portland cement and supplementary materials (fly ash and silica fume) that is the most resistant to abrasion. Concrete samples were cured in water for 28 days, then submersed in lactic acid solution at 30 °C (pH 2-3). After exposure to the acid solution, every 7, 14, 28, and 56 days, the samples will be test for attrition on the face of concrete in accordance with ASTM C944 to simulate the acceleration reaction refer to animal behaviour and corrosion from acid of feed. From experiment, it was found that increasing the volume of fly ash and silica fume can increase concrete resistance to corrosion due to acid derived from feed.

Enhancement of low-cement self-compacting concrete with dolomite powder

This study aims at exploring the benefits of using dolomite powder (DP) to improve the engineering performance of low-cement self-compacting concrete (SCC) with cementitious materials comprised of 50 wt% of ordinary Portland cement (OPC) and 50 wt% pozzolanic materials of ground granulated blast furnace slag (GGBFS/slag) and low calcium fly ash (FA). Experimental results showed that the DP addition to partially substitute for the pozzolanic materials had no impact on the setting properties of pastes with blended binder of slag and OPC while significantly improved those of the pastes with that of FA and OPC or ternary mixture of slag, FA, and OPC binder. In addition, the adjustment of DP addition to the above-mentioned three binders had successfully manufactured the self-compacting mortars (SCMs) with significant increase in the flowing ability and compressive strength, in which the DP addition of 30 wt% substituting for the total amount of pozzolanic materials resulted in the hardened mortars with highest compressive strengths after ages of 7 days. The improvement of compressive strengths of hardened SCMs can be obtained by the DP addition up to 50 wt%. The SCCs produced from the appropriate proportions of the resulting DP modified SCMs had the engineering properties mostly satisfying the technical requirements for practical concrete structures.

27Al NMR MAS Spectral Studies Inferring the Initiation of Geopolymerization Reaction on Together Mechanochemical Grinding of Raw Materials

Chemical shifts and intensities of the 27Al NMR signals provide structural information about the environment of Al nuclei in presence of an external magnetic field. This paper analyzes the structural information of the aluminum nuclei present in the precursor material after mechanochemical co‐grinding of the raw materials, namely fly ash, NaOH, and amorphous tricalcium phosphate [Ca3(PO4)2], with the help of 27Al MAS NMR spectral studies. The results indicate transformation of the sixfold coordination Al ions with oxygen AlQ6 present in aluminosilicate material fly ash to fourfold AlQ4 and fivefold AlQ5 in the precursor material. The variation in chemical shift is between δ 64 and 65 ppm. This indicates that, in addition to direct bonding to the oxygen atom, the Al tetrahedron is also bonded to Si as [AlQ4(4Si)]. Thus, the mechanochemical co‐grinding of the raw materials initiates a solid‐state chemical reaction among them. The addition of water alone to this precursor material results in the formation of the geopolymeric material unlike the conventional geopolymeric system which requires the addition of a highly alkaline aqueous solution to fly ash. This study helps in the determination of the reaction mechanism during the mechanochemical transformation of raw materials into the geopolymeric product by a novel process.

Flexural strength reduction of cement pastes exposed to CaCl2 solutions

Calcium chloride (CaCl2) can react with calcium hydroxide (Ca(OH)2) to form calcium oxychloride which can reduce flexural strength and damage concrete. This paper aims to characterize the reduction in flexural strength of cement pastes exposed to CaCl2 solutions using the ball-on-three-balls test. The amounts of Ca(OH)2 and calcium oxychloride in the cement paste are measured using thermogravimetric analysis and low-temperature differential scanning calorimetry, respectively. The volume change that occurs as a result of the reactions between the cement paste and CaCl2 is also measured. The reduction in flexural strength increases as the concentration of the CaCl2 solution increases and the exposure temperature decreases. The flexural strength reduction can be mitigated by increasing the amount of supplementary cementitious materials (fly ash) in the cement pastes. Lowering the water-cementitious materials ratio also reduces the flexural strength reduction. The flexural strength reduction is correlated with the amount of calcium oxychloride and the volume change in the cement pastes exposed to the CaCl2 solution. While the flexural strength reduction is believed to be primarily due to the formation of calcium oxychloride, the formation of Friedel's salt and Kuzel's salt also contributes to the flexural strength reduction.

Design of rapid hardening engineered cementitious composites for sustainable construction

Abstract This paper deals with design of environmentally friendly Rapid Hardening Engineered Cementitious Composite (RHECC) nanomodified with ultrafine mineral additives, polycarboxylate ether based superplasticizer, calcium hydrosilicate nanoparticles and dispersal reinforced by fibers. The incremental coefficient of surface activity was proposed in order to estimation of ultrafine supplementary materials (fly ash, methakaolin, microsilica) efficiency. A characterization of RHECC’s compressive and flexural properties at different ages is reported in this paper. Early compressive strength of ECC is 45-50 MPa, standard strength – 84-95 MPa and parameter Rc2/Rc28 – 65–70%. The microstructure of the cement matrix and RHECC was investigated. The use of ultrafine mineral supplementary materials provides reinforcement of structure on micro- and nanoscale level (cementing matrix) due to formation of sub-microreinforcing hydrate phase as AFt- and C-S-H phases in unclinker part of cement matrix, resulting in the phenomena of “self-reinforcement” on the microstructure level. Designed RHECC may be regarded as lower brittle since the crack resistance coefficient is higher comparison to conventional fine grain concrete.

Reduction/immobilization of chromite ore processing residue using composite materials based geopolymer coupled with zero-valent iron

Chromite ore processing residue (COPR) is a hazardous waste due to the presence of highly mobile Cr(VI). In this paper, the reduction/immobilization of COPR using composite materials (fly ash, blast furnace slag and metakaolin) based geopolymer coupled with zero-valent iron (ZVI) was investigated. The effects of ZVI and acid dosages on the reduction of Cr(VI) in COPR had been analysed. The immobilization of original COPR samples and reduced COPR samples were prepared. The immobilization effect was evaluated by compressive strength and leaching tests. The results showed that geopolymer with reduced COPR had better immobilization effect as compared to original COPR. According to mechanical and leaching properties of geopolymer with reduced COPR samples as well as X-ray diffraction, scanning electron microscope with energy dispersive spectrometer and Fourier transform infrared spectrometry analyses, COPR was effectively immobilized.

Response of concrete with blended binders and nanoparticles to sulfuric acid attack

Concrete has long been the most popular material for the construction of key infrastructural elements such as sewerage pipes, water treatment facilities, industrial floors and foundations, which can be chemically vulnerable to damage by sulfuric acid attack. Since high alkalinity is required for stability of the cementitious matrix, concrete is susceptible to attack by acidic media, which may disintegrate the hydrated cement paste to various levels based on the prevailing exposure conditions and key mixture design parameters of concrete. This study investigated the response, in terms of physico-mechanical and microstructural features, of concrete comprising different types of cement (general-use or Portland limestone cement (PLC)) with various combinations of supplementary cementitious materials (fly ash, silica fume and nanosilica) to severe sulfuric acid exposure (immersion of test specimens in 5% sulfuric acid solution with a maximum pH threshold of 2·0 for 90 d). The results revealed that the surface degradation (mass loss) of concrete under severe sulfuric acid attack was independent of its penetrability (physical resistance), since very dense cementitious matrices (low penetrability) suffered severe deterioration. PLC may slightly improve the resistance of concrete to sulfuric acid attack whereas, among the blended binders tested, binary binders comprising 30% fly ash particularly improved the resistance of concrete to sulfuric acid attack due to an inert filler effect of fly ash particles at the exposed surface.

Use of cement-chelated, solidified, municipal solid waste incinerator (MSWI) fly ash for pavement material: mechanical and environmental evaluations

As a by-product from the incineration of municipal solid waste (MSW), fly ash usually contains mobile heavy metals that may engender severe pollution when reused. In this study, fly ash was solidified with cement and a chelating agent to immobilize these polluting elements. The possibility of using the solidified fly ash for pavement materials was also assessed through mechanical and environmental perspectives. According to the results, the strength of solidified fly ash was found proportional to both the cement/fly ash ratio and curing time. This indicated that the increase of fly ash loading reduced the concentration of products from cement hydration, and thus destroyed the structure of the products of hydration. With the increase of freeze–thaw cycles, the compressive strength of cement-stabilized fly ash decreased between days 7 and 14, and then increased between days 14 and 28. Subsequently, the finite element analysis showed that placing the solidified fly ash layer as a pavement material between an unbound base course and subgrade was beneficial to prolong fatigue life and reduce rutting distress of asphalt pavements. Finally, leachability of metals from the mixtures was tested, which showed that leaching concentration decreased as the cement/ash ratio, curing time, and chelating agent content increased.

Influence of Foaming Agent/Water Ratio and Foam/Geopolymer Paste Ratio to the Properties of Fly Ash-based Lightweight Geopolymer for Brick Application

Nowadays, the demand for lightweight building materials has been growing worldwide. This paper presents an investigation on the use of waste materials of fly ash as a source materials for the production of lightweight geopolymer by using foaming agents. The key properties for the foamed geopolymer namely density, compressive strength, and water absorption were investigated. The chemical composition of materials and morphology analysis were studied to find the microstructure properties of foamed geopolymer. The foamed geopolymer were prepared by combination of 12 M Sodium Hydroxide (NaOH) solution and Sodium Silicate (Na2SiO3) solution. The ratio of Na2SiO3/NaOH and ratio of fly ash/alkaline activator were kept constant at 2.5 and 2.0, by mass respectively. The effect of different ratio of foaming agent/water and foam/geopolymer paste were investigated at 7 days of ageing and cured at 80�C for 24 hours. In general, the results showed that the fly ash-based lightweight geopolymer has good potential as brick application.

Strength, elastic and microstructural properties of SCCs’ with colloidal nano silica addition

One of the concerns regarding the elastic behavior of self-compacting concretes (SCC) is their lower stiffness tendency compared to conventional concretes (CC). Because of mixture design methods applied, SCC mixtures, in general, contains higher amounts of fine materials. The use of high volume of fine materials causes a decrease in the amount of total aggregates which have an important role on the strength and elastic properties of concretes. This paper discusses the results of an experimental study which investigated the strength, elastic and microstructural properties of SCC mixtures modified with different particle sizes of colloidal nano-SiO2 (CNS). CNS samples, having 35, 17, and 5 nm average particle size, were used with the aim of reducing the total fine material (fly ash) content in SCC designs. With the help of CNS, the amount of fly ash in reference SCC mixture design was gradually reduced and replaced with aggregates. The mixtures which fulfill desired fresh SCC properties were subjected to compressive tests at 28th and 120th days. Moduli of elasticity of concrete specimens were also measured. Results have shown that, although the use of CNS in reduced-fly ash content mixtures could not compensate the strength decrement, the stiffness of SCC mixtures containing CNS together with fly ash has been strikingly improved even the increase in total aggregate content is not noteworthy. Microscopic investigations has indicated the development of a dense C-S-H gel and interfacial transition zone.

Influence of mineral admixtures and aggregates on properties of different concretes under high temperature conditions I: Experimental study

Fire in concrete structures deteriorates mechanical properties of the material and leads to structural collapse under loads. Two types of spalling occurs in concrete when exposed to high temperature, namely explosive and thermal spalling. Explosive spalling occurs once the hydrostatic stress (developed in the pores) exceeds the tensile strength of the concrete. Where as thermal spalling of concrete happens due to degradation of material properties (elastic modulus, compressive and tensile strength) when exposed to high temperature. The present study comprises of an experimental (this manuscript) and analytical program (part II) to assess deformations due to high temperature in different concretes. Seven different concrete mixes have been made for this purpose and among the seven mixes, three mixes are self compacted concrete mixes (35MPa, 55MPa and 70MPa), a high volume fly ash concrete mix (45MPa), a normally vibrated OPC concrete mix (45MPa) and a heavy density concrete mix (25MPa). Two ages were selected to test these concretes to study the age effects, one at 28 days and other at 365 days. All these mixes were tested in three different test approaches, which are stressed (ST), unstressed (UST) and unstressed residual strength (URST) approach. Each approach has its specific purpose of extracting residual properties of concrete when exposed to high temperature. The findings indicate that both concrete with supplementary cementitious material (fly ash) and heavy density concrete (Haemetite) were gound to be structurally robust when exposed to high temperature.

Combined Use of Jute Geotextile-EPS Geofoam to Protect Flexible Buried Pipes: Experimental and Numerical Studies

This paper addresses the results of the experimental and numerical studies conducted on 4.2 mm thickness and 110 mm diameter high-density polyethylene (HDPE) pipes buried in fly ash material overlying stone dust beds. The model tests were performed using single and double layers of expanded polystyrene (EPS) geofoam as compressible inclusions. In addition to that, jute geotextile was used as a reinforcement for the infill fly ash along with EPS geofoam inclusion to obtain induced trench condition. The test beds were subjected to loading on the fly ash surface with the help of a rigid steel plate to simulate as a strip footing in different embedment depths of the pipe (1–3 times pipe diameter). The test results revealed that the pressure and strain values in the pipe reduced significantly in the presence of EPS geofoam and jute geotextile related to the location of the pipe. In the case of double layers of EPS geofoam could induce reduction of the pressure up to 87.2% and strain about 63.5% respectively depending on the density and width of EPS geofoam. Whereas, at the same burial depth, in the presence of jute geotextile together with EPS geofoam can be reduced up to 93.8 and 73.4% for pressure and strain respectively depending on EPS geofoam density and number of reinforcement. Moreover, the jute geotextile-EPS geofoam combination of model test results were validated with finite element program. A good agreement was observed on pressure-settlement response and pipe strain between experimental and numerical investigations. The numerical studies show that the jute geotextile distributes stresses in the lateral direction and then the stresses on the pipe significantly reduced.

Strength characteristics of fly ash stabilized with lime and modified with phosphogypsum

The paper presents the strength characteristics of fly ash stabilized with lime and phosphogypsum. A series of unconfined compression strength test and unconsolidated undrained triaxial tests were conducted on the reference mix composed of fly ash, 8% lime and 2% phosphogypsum. The specimens for these tests were prepared and cured for 7, 28, 56 and 90 days with three different curing methods termed as method M1, M2 and M3. The results of this study indicated that the unconfined compressive strength, deviator stress, cohesion, friction angle, initial tangent modulus and secant modulus increased with the increase in curing period. The increase in these parameters was highest for M3 method of curing followed by M1 and M2 respectively. Further to predict these parameters an empirical relationship is proposed which was found to predict the given parameters within acceptable error. It is anticipated that the results of present study will be useful in utilizing the waste materials (fly ash, phosphogypsum) for various geotechnical applications.

Effect of constituents on rheological properties of fresh concrete-A review

The rheology is an effective tool to characterize workability, consistency, flowability, and predict stability, pumpability, shootability, pressure of formwork, multi-layer casting. This paper presents a critical review on the rheological properties of fresh concrete in recent publications. The applicable rheological models for the flow of concrete are revealed. The effects of constituents of fresh concrete, including cement, supplementary cementitious materials (fly ash, ground blast furnace slag, and silica fume), limestone powder, coarse and fine aggregates, and chemical admixtures (superplasticizer, viscosity modifying agent and air-entraining agent) on the rheological properties are discussed in detail. The applications of rheograph and workability box in mixture proportioning and quality control are also illustrated.

Effect of PEI Impregnation on the CO2 Capture Performance of Activated Fly Ash

In the bid to develop cheaper adsorbents for CO2 capture applications, this work investigates the impact of polyethylenimine (PEI) impregnation on the performance of an activated fly ash material for CO2 capture. The fly ash was activated by fusing with NaOH and then subjecting to hydrothermal treatment to derive more porous zeolitic phases which were subsequently loaded with Polyethylenimine (PEI) using a wet impregnation technique. Two different PEI amines (MW∼600 and MW∼1200) were tested at varying concentrations (15%, 20%, and 25%) to study the effect of molecular weight of the PEI as well the loading percentage on the adsorption performance. The activation resulted in a significant increase in surface area from 11 m2/g in the fly ash to 270 m2/g in the activated fly ash, while the 25% PEI-600 sorbent was found to be the most efficient, giving the highest adsorption capacity of 26 mg/g adsorbent at 70 oC.

Correlation Analysis between Different Types of Corrosion of Concrete Containing Sulfate Resisting Cement

Utilization of pozzolanic materials (fly ash, slag, zeolite, metakaolin, microsilica and more) in the manufacturing of cement and concrete has increased considerably over the last decades. Another option is to use concrete containing sulfate resisting cement. This could help minimize the harmful impacts on concrete exposed to an aggressive environment. The issue of the deteriorative impact of the three types of concrete corrosion (acidic, sulfate and leaching) investigated using correlation analysis is presented in the paper. Concentrations of silicon and calcium leached out from the concrete samples into the liquid phase and the measured pH values were used as input data for a mathematical approach to the study of sulfate resisting cement. The performance of sulfate resisting cement-based concrete was improved when exposed to sulfate attack, but not in the case of leaching corrosion caused by water.

Correlation Analysis between Different Types of Corrosion of Concrete Containing Sulfate Resisting Cement

Utilization of pozzolanic materials (fly ash, slag, zeolite, metakaolin, microsilica and more) in the manufacturing of cement and concrete has increased considerably over the last decades. Another option is to use concrete containing sulfate resisting cement. This could help minimize the harmful impacts on concrete exposed to an aggressive environment. The issue of the deteriorative impact of the three types of concrete corrosion (acidic, sulfate and leaching) investigated using correlation analysis is presented in the paper. Concentrations of silicon and calcium leached out from the concrete samples into the liquid phase and the measured pH values were used as input data for a mathematical approach to the study of sulfate resisting cement. The performance of sulfate resisting cement-based concrete was improved when exposed to sulfate attack, but not in the case of leaching corrosion caused by water.

Effect of curing time on selected properties of soil stabilized with fly ash, marble dust and waste sand for road sub-base materials.

The properties of sub-base filling materials in highway construction are essential, as they can determine the performance of the road in service. Normally, the existing materials are removed and replaced with new materials that have adequate load-bearing capacity. Rising environmental concern and new environmental legislations have made construction professionals consider other methods. These methods include stabilizing the existing materials with other additives to improve their performance. Additives can be waste materials generated by different industries. In this work, the existing excavated soil is stabilized with waste materials. The wastes consisted of fly ash, marble dust and waste sand. The percentage addition of waste materials was 5%, 10%, 15% and 20% (by mass) of the existing soil. The soil/waste specimens were cured for 1, 7, 28, 56, 90 and 112 days before testing. Testing included the dry unit weight and unconfined compressive strength ( qu) as well as X-ray diffraction analysis and scanning electron microscopy observation. Also, the California Bearing Ratio values were obtained and are reported in this investigation. The results showed that the qu values increased with the increase in waste materials content. Also, there is tendency for the dry unit weight to increase with the increase in waste materials.