Performance Of Fly Ash Concrete Research Articles

Numerical Study on Static and Fatigue Behavior of Alkali-Activated Fly Ash Concrete Modelled using Concrete Damage Plasticity (CDP) Model

Abstract Alkali-activated concretes (AAC) are considered as an alternative to Portland cement concretes because of their much lower carbon emissions. To study its characteristics is of utmost importance. In the present research, an attempt is made to create a numerical model to analyze the static and fatigue flexural behavior of alkali-activated fly ash concrete (FC) and compare them with ordinary Portland cement concrete (PCC). Three-point bending tests are simulated for the monotonic load to obtain the static behavior of a 2D notched rectangular beam. A 2D beam specimen of size 262.5 mm x 75 mm, with a notch of size 15 mm x 3 mm was provided at the bottom middle. Fly ash-based alkali-activated concrete (FC) and corresponding PCC of similar strength are modeled in ABAQUS CAE using the concrete damage plasticity (CDP) model. The ultimate loads, maximum deflection, and CMOD for each of them were obtained from the history output manager. The results of monotonic tests are utilized for creating a sinusoidal load cycle for fatigue tests with various loading frequencies and stress ratios. Different structural responses are examined under the fatigue test. The results showed that FC performs better than PCC under static and fatigue tests. Fatigue performance of both FC and PCC is influenced by the frequency of loading and fatigue life increases at higher frequencies. It is also found that stress reversal negatively impacts the fatigue life of both FC and PCC.

Strength and Durability Performance of Fly Ash Concrete with and without Superplasticizer

Strength and Durability Performance of Fly Ash Concrete with and without Superplasticizer

Chloride Penetration Resistance, Electrical Resistivity, and Compressive Strength of Concrete with Calcined Kaolinite Clay, Fly Ash, and Limestone Powder

This study aims to examine the chloride penetration resistance, chloride binding capacity, electrical resistivity, and compressive strength of multibinder systems, including ordinary portland cement (OPC), calcined kaolinite clay (C), fly ash (F), and limestone powder (L). At all tested ages, the results revealed that calcined kaolinite clay concrete had better chloride penetration resistance and chloride binding ability compared with the control OPC concrete. Moreover, at all tested ages, calcined kaolinite clay concrete had greater compressive strength compared with the control OPC concrete and fly ash concrete. At the curing age of 91 days, improved performance of fly ash concrete was observed. The overall performance of the ternary binder system of cement-fly ash-calcined kaolinite clay surpassed that of the binary binder systems. Among the tested combinations of binders, the ternary binder C30F15 (55% OPC+30% C+15% F) demonstrated the best overall performance. The test results also indicate that fly ash can be beneficially integrated into the cement-calcined kaolinite clay binder system to obtain a ternary binder system, which is better than the ternary binder system of cement, calcined kaolinite clay, and limestone powder, at both tested early and later ages.

Performance of Fly Ash Concrete with Nickel Slag Fine Aggregate in the Marine Environment

This research aims to assess the feasibility of the mechanical strength and the durability of the concrete containing 50% nickel slag and a combination of 15% and 30% fly ash with a water-cement ratio of 0.25 and 0.45 in a marine environment. Four types of concrete, namely OPC-sand (C) as control concrete, OPC-50GNS (S), 15FA-50GNS (F1), and 30FA-50GNS (F2) as comparison concrete, were tested with a 100×200 mm cylindrical specimen. The results showed an increase in the mechanical strength and potential resistance of the comparison concrete at the age of 28 days. While at the age of 180 days, fluctuating changes were found. The compressive strength of S concrete increased by 36.9 and 9.3% respectively, F1 concrete by 37.7% and 1.7%, F2 by 33.7% and 5.9% at ratio 0.45 and 0.25. Likewise, the value of the split tensile strength and modulus of elasticity of concrete. This result was followed by reduced porosity, sorptivity, and chloride penetration resistance as an indication of better concrete durability. Fly ash appears to have a greater positive impact on potential durability than mechanical strength at a water cement ratio of 0.25 versus 0.45. Although the chloride penetration resistance is decent, the compressive strength of concrete with a water-cement ratio of 0.45 does not qualify for application in the marine environment. In contrast, concrete with a water-cement ratio of 0.25 containing 50% nickel slag and the addition of class C fly ash up to 30% was declared suitable for application to concrete in the marine environment zone C2 according to ACI 318-19. Doi: 10.28991/CEJ-2022-08-12-010 Full Text: PDF

Performance of fly ash concrete with ferronickel slag fine aggregate against alkali-silica reaction and chloride diffusion

Ferronickel slag (FNS) is an industrial by-product of ferronickel alloy production at a high temperature which can be a promising potential to be used as fine aggregate to produce more sustainable concrete. In this study, the performance of concrete containing ferronickel slag sand and fly ash relating to alkali-silica reaction (ASR) and chloride contamination was investigated. ASR-induced expansion, chloride diffusion resistance, and chloride binding capacity of FNS concrete were determined through concrete prism tests (CPT), accelerated diffusion test, and bulk diffusion test. Thermogravimetric analysis (TGA) was conducted to measure the amount of Portlandite and Friedel's salt in concrete. Concrete with 50 wt% FNS sand as fine natural aggregate replacement and 25 wt% of cement replacement by fly ash showed a remarkable potential to be used not only as a low-carbon concrete with comparable mechanical properties to conventional concrete but also with a better performance against ASR and chloride contamination.

Performance of high-volume fly ash concrete after exposure to elevated temperature

The purpose of the present research is to investigate the sustainable performance of fly ash concrete at elevated temperature. Initially, the optimum level of cement replacement with class F fly ash was determined. The concrete mixes, i.e., plain concrete (0% fly ash), 25% fly ash, and optimum level of cement replacement with fly ash (i.e., 40%), were chosen to determine the residual compressive strength of concrete after a single heating-cooling cycle of elevated temperature ranging from ambient to 400 °Cat an interval of 200 °C under unstressed and stressed conditions. The microstructure by scanning electron microscopy (SEM) was also examined for all the concrete mixes. During the heating-cooling process, the hysteresis loop at 400 °C is found larger than the hysteresis loop at 200 °C and ambient temperature. The 40% fly ash concrete showed a lower reduction in the residual compressive strength after heating at 400 °C under the unstressed condition. The 40% fly ash concrete has shown maximum residual compressive strength than 25% fly ash and plain concrete after heating at 200 °C and 400 °C under the unstressed and stressed conditions. The SEM analysis indicates a massive change in the morphology at 400 °C for plain and fly ash concrete mixes.

휨 시험을 이용한 PE섬유 및 PVA섬유보강 플라이 애시 콘크리트의 자기치유 성능평가

휨 시험을 이용한 PE섬유 및 PVA섬유보강 플라이 애시 콘크리트의 자기치유 성능평가

Degradation of fly ash concrete under the coupled effect of carbonation and chloride aerosol ingress

This paper presents an experimental investigation regarding the coupled effect of carbonation and chloride aerosol ingress on the durability performance of fly ash concrete. Test results demonstrate that carbonation significantly affects the chloride ingress profile, reduces the chloride binding capacity, and accelerates the rate of chloride ion diffusion. On the other hand, the carbonation rate of fly ash concrete is reduced by the presence of chlorides aerosol. The interaction nature between concrete carbonation and chloride aerosol ingress is also demonstrated by the microscopic analysis results obtained from scanning electron microscope and mercury intrusion porosimetry.

Experimental study on durability improvement of fly ash concrete with durability improving admixture.

In order to improve the durability of fly ash concrete, a series of experimental studies are carried out, where durability improving admixture is used to reduce drying shrinkage and improve freezing-thawing resistance. The effects of durability improving admixture, air content, water-binder ratio, and fly ash replacement ratio on the performance of fly ash concrete are discussed in this paper. The results show that by using durability improving admixture in nonair-entraining fly ash concrete, the compressive strength of fly ash concrete can be improved by 10%–20%, and the drying shrinkage is reduced by 60%. Carbonation resistance of concrete is roughly proportional to water-cement ratio regardless of water-binder ratio and fly ash replacement ratio. For the specimens cured in air for 2 weeks, the freezing-thawing resistance is improved. In addition, by making use of durability improving admixture, it is easier to control the air content and make fly ash concrete into nonair-entraining one. The quality of fly ash concrete is thereby optimized.

Accelerated engineering properties of high and low volume fly ash concretes reinforced with glued steel fibers

The present study focuses on the improvement of pozzolanic reaction of fly ash particles with the cement hydration products. Low and high volume fly ash concrete mixtures were studied systematically with the addition of accelerating admixtures and accelerated curing of the concrete specimens in a steam chamber for 18 h at 75°C. Also, the reinforcing effects of glued steel fibers addition on the compressive and flexural performance of fly ash concrete were investigated. The test results indicated that the addition of accelerator improved the rate of hardening and the inclusion of steel fibers provided higher flexural performance. Also, it can be noted that the high volume fly ash (50%) addition in concrete showed a reduction in strength; however, the addition of accelerator has compensated the deceleration in strength gain. The proper selection of concrete ingredients, addition of accelerator and initial steam curing for 18 h showed better improvement on the engineering properties in fly ash concrete. A maximum increase (41.7%) in compressive strength of fly ash concrete around 52.90 MPa was noticed for 25% fly ash substitution and 1.5% steel fibers addition. Dynamic elastic modulus was also calculated in loaded concrete specimen using ultrasonic pulse velocity test and showed a good agreement with the experimental value.

養生の相違がフライアッシュコンクリートの物質移動抵抗性および空隙組織構造に与える影響

The aim of this research is to reveal the effect of curing conditions on carbonation and chloride diffusion of normal concrete and fly ash replacement concrete. Sealed curing, air curing and curing under the wind and sunlight were compared to normal water curing. As the result, better curing made carbonation depth, chloride diffusion coefficient and void ratio of cement matrix were low, and in case of fly ash replacement concrete, mass transfer resistant was lower by comparison of same void ratio of normal concrete. According to the analysis of binarized concrete CT image by homogenization methods, magnitude relation of tortuosity between normal concrete and fly ash concrete is differ in the difference of water to powder ratio. This fact implies that the mechanism of high mass transfer resistance performance of fly ash concrete is different in differ of pore structure of each solid.

Properties and behavior of self-compacting concrete produced with GBFS and FA additives subjected to high temperatures

This paper presents an experimental investigation on the performance of self-compacting concrete (SCC) subjected to high temperatures. For this purpose, Portland cement was replaced with fly ash (FA) and granulated blast furnace slag (GBFS) in various proportions with and without polypropylene (PP) fibers and the PP fiber content was 2 kg/m 3 for the mixtures that contained fibers. When the specimens were 56 days old, they were heated to elevated temperatures (200, 400, 600 or 800 °C). Afterword, tests were conducted to determine the weight loss and the compressive strength. Moreover, the change in the ultrasonic pulse velocity (UPV) was determined, and observations for surface cracks were made after the specimens were exposed to elevated temperatures. A severe strength loss was observed for all of the concretes after 600 °C, particularly for the concretes that contained PP fibers; however, the fibers reduced and eliminated the risk of explosive spalling. Based on the test results, it can be concluded that the performance of FA concrete is better than that of the GBFS concrete.

Technical Research on Quality Control of Fly Ash Concrete

Based on comprehensive quality management theory, we have studied quality factors of fly ash high-performance concrete in construction, put forward the method of beforehand control, course control and afterwards control. From the project construction of the actual conditions, the raw material selection, mixture design and try gradation and concrete performance of fly ash concrete, has been comprehensively studied and analysised. The optimal dosage of fly ash has been determined with good workability of different fly ash concrete strength grade and mechanical properties meeting the design requirements and good durability, which demonstrates the good effect of the high-performance concrete implementation of total quality control management through the engineering practice.

Assessment of curing efficiency and effect of moist curing on performance of fly ash concrete

This study was conducted to evaluate the sensitivity of compressive strength, water permeability and electrical resistance of near-surface layer concrete with different fly ash contents to curing conditions. It is shown that the sensitivity to curing condition and fly ash content descends in the following order: difference between internal and surface resistivity (ρ) at 28 days, water permeability and compressive strength; both of longer duration of moist curing and use of fly ash in concrete enhanced the water penetration resistance. It is indicated that the resistivity difference ρ at 28 days can reflect accurately the curing history of fly ash concrete regardless of mix proportions; and use of fly ash in concrete requires longer moist curing duration.

Enhanced durability performance of fly ash concrete for concrete-faced rockfill dam application

The main purpose of this research was to enhance the durability in both the design and construction of dams. Especially, in case of rockfill dams, the durability of face slab concrete in a concrete-faced rockfill dam (CFRD) is achieved by optimizing the fly ash replacement for cement. The effect on durability corresponding to the increasing replacement of fly ash was evaluated, and the optimum value of fly ash replacement was recommended. The results show that 15% of fly ash replacement was found to be an optimum level and demonstrated excellent performance in durability.

Chloride thresholds in marine concrete

This paper reports results from an ongoing study of the performance of fly ash concrete in marine exposure. Reinforced concrete specimens exposed to tidal conditions were retrieved at ages ranging from 1 to 4 years. Steel reinforcement mass losses are compared with chloride contents at the location of the bar for concrete specimens of various strength grades and with a range of fly ash levels. The maximum level of chloride that could be tolerated without significant mass loss due to corrosion was found to vary with fly ash content. This threshold chloride level decreased with increasing fly ash content; values obtained were 0.70%, 0.65%, 0.50% and 0.20% acid-soluble chloride (by mass of cementitious material) for concrete with 0%, 15%, 30% and 50% ash, respectively. Despite the lower threshold values, fly ash concrete was found to provide better protection to the steel under these conditions, due to its increased resistance to chloride ion penetration.

Effect of Cement Replacement, Content, and Type on the Durability Performance of Fly Ash Concrete in the Middle East

Abstract The low durability of concrete construction in the Middle East caused by corrosion of reinforcement, sulfate attack, environmental cracking, and aggregate-cement reactivity necessitates that mix design techniques be formulated to yield dense and impervious concrete with as little heat of hydration as possible; it should also have enhanced resistance to salt attack and possible cement-aggregate reactivity. These objectives present fly ash as a potentially useful admixture from the standpoint of improving the durability of concrete construction in the aggressive service environment of the Gulf seaboard. This investigation presents data on the strength, general quality, and durability performance of fly-ash portland-cement concrete against sulfate/chloride attack. The variables used for this study are fly ash additions as cement replacement from 0 to 40%, cement factors of 300, 360 and 450 kg/m3 (500, 600, and 750 lb/yd3) and tricalcium aluminate (C3A) phase ranging from 0 to 9.5%. Results show that 20% replacement by fly as shows the best performance in terms of rate of strength gain, ultimate strength, absorptive characteristics, and resistance to sulfate/chloride attack. The strength gain is superior in lean mixes, and the effect of fly ash addition on sulfate resistance of concrete is more pronounced for higher C3A cements. An increase in the cement factor without attendant changes in water/cement ratio does not necessarily provide better durability performance.