Reaction Products in Fly Ash Concrete

1984 ◽  
Vol 43 ◽  
Author(s):  
Mark D. Baker ◽  
Joakim G. Laguros
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Calcium Hydroxide ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Hydration Process ◽  
Reaction Products ◽  
Fly Ash Concrete ◽  
Xrd Studies ◽  
One Year

AbstractThe setting and strength gaining process of PC concrete containing Class C high lime fly ash were related to the reaction products identified using XRD and SEM. Four fly ash concrete mixes (20, 30, 40, and 50 percent replacement of cement by fly ash) and similar paste mixes were compared to control mixes for curing periods up to one year. Setting time and early compressive strength were adversely affected by the addition of fly ash. Beyond one week all of the fly ash concrete mixes gained strength at a faster rate than the corresponding control mixes. XRD studies suggest that the retardation mechanism may be associated with the high levels of ettringite formed early in the hydration process and its conversion to monosulfoaluminate. A decrease in the level of calcium hydroxide, typical of pozzolanic activity, was not in evidence. SEM micrographs of fly ash spheres in concrete at the various stages of hydration reveal an intricate crystal framework. A simple heat of hydration test is presented which helps explain the strength gains observed.

Advancements in Properties of Cement Containing Pulverised Fly Ash and Nanomaterials by Blending and Ultrasonication Method (Review - Part I)

2018 ◽  
Vol 19 ◽  
pp. 1-11 ◽  
Author(s):  
Mehmet Serkan Kirgiz
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Water Demand ◽  
Review Paper ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Strength Gain ◽  
Hydration Properties ◽  
Carbon Nano Tube

This review research aims to discuss the results obtained researches on cement containing pure cement, pulverised fly ash, and nanoparticles, in order for eliminating negative side effects underlie the substitution of by–products for pure Portland cement. Nanoparticles (NP) used in these researches are nanoTiO2, nanoSiO2, nanoCaCO3, fibers of carbon nano tube (CNT), nanolimestone (nanoCaCO3), nanoZrO2, nanoclays, and nanometakaolin (nMK) for improving properties of cement systems. Published manuscripts explains two methods regarding on the usage of nanoparticles for cement system: blending and ultrasonication for dispersion of nanoparticles. However, differences between blending and ultrasonication methods suggested by various researchers are also discussed. Experiments reported these papers include the water demand, the density, the setting–times, the heat of hydration, the fluidity, the compressive strength and the flexural strength. According to these results, nanoparticles increase the water demand and heat of hydration of cement; it decreases the density and fluidity for cement mortars, evidently. The most effective nanoparticles on early compressive and flexural strengths are fibers of carbon nano tube and nanoCaCO3. These papers also point effects of these nanoparticles on the strength gain of cement. This review paper inform us until Effect of nanomaterial on water demand and density section in this Part I. Second part of this review paper will explain Hydration properties of Portland pulverised fly ash cement section, Effect of nanomaterial on setting–time section, Effect of nanomaterial on heat of hydration section, Strength gain mechanisms for hardened Portland pulverised fly ash cement paste and mortar section, Effect of nanomaterial on compressive strength section, Effect of nanomaterial on flexural strength (Bending) section, and Conclusion section.

scholarly journals Effect of the Sodium Silicate Modulus and Slag Content on Fresh and Hardened Properties of Alkali-Activated Fly Ash/Slag

Minerals ◽  
2019 ◽  
Vol 10 (1) ◽  
pp. 15 ◽  
Author(s):  
Xiaowei Ouyang ◽  
Yuwei Ma ◽  
Ziyang Liu ◽  
Jianjun Liang ◽  
Guang Ye
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Pore Structure ◽  
Heat Release ◽  
Setting Time ◽  
Heat Evolution ◽  
Reaction Products ◽  
Hardened Properties ◽  
Alkali Activated ◽  
Slag Content

This paper presents the results of an experimental study performed to investigate the effect of activator modulus (SiO2/Na2O) and slag addition on the fresh and hardened properties of alkali-activated fly ash/slag (AAFS) pastes. Four activator moduli (SiO2/Na2O), i.e., 0.0, 1.0, 1.5, and 2.0, and five slag-to-binder ratios, i.e., 0, 0.3, 0.5, 0.7, 1.0, were used to prepare AAFS mixtures. The setting time, flowability, heat evolution, compressive strength, microstructure, and reaction products of AAFS pastes were studied. The results showed that the activator modulus and slag content had a combined effect on the setting behavior and workability of AAFS mixtures. Both the activator modulus and slag content affected the types of reaction products formed in AAFS. The coexistence of N–A–S–H gel and C–A–S–H gel was identified in AAFS activated with high pH but low SiO2 content (low modulus). C–A–S–H gel had a higher space-filling ability than N–A–S–H gel. Thus, AAFS with higher slag content had a finer pore structure and higher heat release (degree of reaction), corresponding to a higher compressive strength. The dissolution of slag was more pronounced when NaOH (modulus of 0.0) was applied as the activator. The use of Na2SiO3 as activator significantly refined the pores in AAFS by incorporating soluble Si in the activator, while further increasing the modulus from 1.5 to 2.0 prohibited the reaction process of AAFS, resulting in a lower heat release, coarser pore structure, and reduced compressive strength. Therefore, in view of the strength and microstructure, the optimum modulus is 1.5.

scholarly journals Effect of Chemical Composition and Network of Fly Ash Glass on the Hydration Process and Properties of Portland-Fly Ash Cement

2021 ◽  
Author(s):  
Ewelina Tkaczewska
Keyword(s):  
Fly Ash ◽  
Chemical Composition ◽  
Strength Class ◽  
Saturation Index ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Point Of View ◽  
Hydration Process ◽  
Initial Setting Time ◽  
Aluminum Ions

AbstractIn the experiment, the aluminosilicate glasses with aluminum saturation index (ASI), defined as the Al2O3/(Na2O+K2O+2CaO), equal to 0.74, 1.72. 2.52, or 4.05 were synthesized. The spectroscopy tests (MIR and 27Al MAS-NMR) confirm that in glass with ASI < 1, the aluminum ions occur in the [AlO4]5- only. In glasses with ASI > 1, the aluminum ions create mainly [AlO4]5-, but part of them occurs in the form of [AlO6]9-. The content of [AlO6]9- octahedrons increases successively for ASI from 1.72 to 4.05. Glass with ASI equal to 4.05 demonstrates the highest content of pozzolanic active Al2O3. Model ashes were prepared by mixing 70 wt.% of glass, 20 wt.% of synthetic mullite and 10 wt.% of SiO2 as an equivalent of quartz. Then Portland cement CEM I 42.5R was milled together with 20 wt.% of each of model ashes to Blaine’s specific surface area of 4,200±50 cm2 g-1. It was found that the addition of ash with higher content of [AlO6]9- octahedrons in the structure of glass accelerates the hydration process of cement blend, which, in turn, positively affects its usable features (heat of hydration, initial setting time and compressive strength). According to the requirements of PN-EN 197-1:2012 standard, the introduction of ash with ASI coefficient equal to 4.05 gives cement blend of strength class of 52.5N. Cement blends with the ash of ASI value equal to 1.72 and 2.52 correspond to strength class of 32.5R, whereas the cement blend with the ash of ASI value equal to 0.74 does not achieve the minimum value of strength for any cement strength class. Results show that the change in chemical composition of fly ash glass and resulting from this diversified structure are essential from the point of view of hydration and properties of cement containing fly ashes in its composition.

Advancements in Properties of Cements Containing Pulverised Fly Ash and Nanomaterials by Blending and Ultrasonication Method (Review- Part II)

2019 ◽  
Vol 24 ◽  
pp. 37-44 ◽  
Author(s):  
Mehmet Serkan Kirgiz
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Review Paper ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Strength Gain ◽  
Hydration Properties ◽  
Setting Times ◽  
Current Article

The second part of this review paper will explain Hydration properties of Portland pulverised fly ash cement section, Effect of nanomaterial on setting–time section, Effect of nanomaterial on heat of hydration section, Strength gain mechanisms for hardened Portland pulverised fly ash cement paste and mortar section, Effect of nanomaterial on compressive strength section, Effect of nanomaterial on flexural strength (Bending) section, and Conclusion section. Experiments reported include the setting–times, the heat of hydration, the compressive strength gain, and the flexural strength gain in the current article. According to the result, nanoparticles, especially the GNP, increase the heat of hydration of cement, and accelerate the time of setting evidently, both initial and final setting-time. The most effective nanoparticle on early compressive strength gain and flexural strength gain is the GNP. The article also points the effects of the nanoparticles on the strength gain of cement comprehensively. Consequently, the prominent cement technology can use the nanoparticles dispersed in liquid by ultrasonication method to increase the properties of cement based materials effectively.

scholarly journals Effect of Waste Glass on the Properties and Microstructure of Magnesium Potassium Phosphate Cement

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 2073
Author(s):  
Qiubai Deng ◽  
Zhenyu Lai ◽  
Rui Xiao ◽  
Jie Wu ◽  
Mengliang Liu ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Glass Powder ◽  
Setting Time ◽  
Potassium Phosphate ◽  
Heat Of Hydration ◽  
Waste Glass ◽  
Hydration Heat ◽  
Magnesium Potassium Phosphate Cement ◽  
The Matrix ◽  
Powder Content

Waste glass is a bulk solid waste, and its utilization is of great consequence for environmental protection; the application of waste glass to magnesium phosphate cement can also play a prominent role in its recycling. The purpose of this study is to evaluate the effect of glass powder (GP) on the mechanical and working properties of magnesium potassium phosphate cement (MKPC). Moreover, a 40mm × 40mm × 40mm mold was used in this experiment, the workability, setting time, strength, hydration heat release, porosity, and microstructure of the specimens were evaluated. The results indicated that the addition of glass powder prolonged the setting time of MKPC, reduced the workability of the matrix, and effectively lowered the hydration heat of the MKPC. Compared to an M/P ratio (MgO/KH2PO4 mass ratio) of 1:1, the workability of the MKPC with M/P ratios of 2:1 and 3:1 was reduced by 1% and 2.1%, respectively, and the peak hydration temperatures were reduced by 0.5% and 14.6%, respectively. The compressive strength of MKPC increased with an increase in the glass powder content at the M/P ratio of 1:1, and the addition of glass powder reduced the porosity of the matrix, effectively increased the yield of struvite-K, and affected the morphology of the hydration products. With an increase in the M/P ratio, the struvite-K content decreased, many tiny pores were more prevalent on the surface of the matrix, and the bonding integrity between the MKPC was weakened, thereby reducing the compressive strength of the matrix. At less than 40 wt.% glass powder content, the performance of MKPC improved at an M/P ratio of 1:1. In general, the addition of glass powders improved the mechanical properties of MKPC and reduced the heat of hydration.

Effects of Elevated Temperatures on the Compressive Strength of HFCC

2011 ◽  
Vol 261-263 ◽  
pp. 416-420 ◽  
Author(s):  
Fu Ping Jia ◽  
Heng Lin Lv ◽  
Yi Bing Sun ◽  
Bu Yu Cao ◽  
Shi Ning Ding
Keyword(s):  
Compressive Strength ◽  
Elevated Temperature ◽  
Fly Ash ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Relative Strength ◽  
Ordinary Concrete ◽  
Residual Compressive Strength ◽  
Fly Ash Concrete ◽  
The Relationship

This paper presents the results of elevated temperatures on the compressive of high fly ash content concrete (HFCC). The specimens were prepared with three different replacements of cement by fly ash 30%, 40% and 50% by mass and the residual compressive strength was tested after exposure to elevated temperature 250, 450, 550 and 650°C and room temperature respectively. The results showed that the compressive strength apparently decreased with the elevated temperature increased. The presence of fly ash was effective for improvement of the relative strength, which was the ratio of residual compressive strength after exposure to elevated temperature and ordinary concrete. The relative compressive strength of fly ash concrete was higher than those of ordinary concrete. Based on the experiments results, the alternating simulation formula to determine the relationship among relative strength, elevated temperature and fly ash replacement is developed by using regression of results, which provides the theoretical basis for the evaluation and repair of HFCC after elevated temperature.

The Effect of Substituting Rdf on the Physical and Environmental Properties of Coal Fly Ash

1988 ◽  
Vol 136 ◽  
Author(s):  
Ashaari B. Mohamad ◽  
David L. Gress
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Physical Properties ◽  
Activity Index ◽  
Coal Fly Ash ◽  
Pozzolanic Activity ◽  
Portland Cement Concrete ◽  
Fly Ash Concrete ◽  
Refuse Derived Fuel ◽  
Cadmium And Lead

ABSTRACTRefuse-derived-fuel (RDF) consisting mainly of waste paper and plastics is a viable fuel source for the production of power. An experimental test burn partially substituting coal with RDF was undertaken by the Public Service of New Hampshire at the Merrimack Power Station.Five percent and ten percent RDF were substituted, on a BTU basis, for coal in the test bums. The chemical and physical properties of the resulting fly ash were determined. Twelve test burn days were run with 4 days of 5% RDF and 8 days of 10% RDF. Emphasis was placed on investigating the effect of the RDF fly ash on Portland cement concrete.Most of the chemical and physical properties of the coal-RDF fly ash were found to be comparable with ordinary coal fly ash except for the amount of cadmium and lead, the pozzolanic activity index and the compressive strength of fly ash concrete. Cadmium and lead were at average levels of 5.1 ppm and 102.6 ppm for the 5% RDF, and 7.8 ppm and 198.3 ppm for the 10% RDF, respectively. Although the pozzolanic activity index of coal-RDF fly ash increases over normal coal fly ash, preliminary results show that the 28-day compressive strength of concrete with direct replacement of cement and sand decreases by up to 30%. Leaching tests on crushed concrete were conducted to evaluate the environmental effect of acid rain.

scholarly journals Influence of Particle Size Distribution of High Calcium Fly Ash on HVFA Mortar Properties

2018 ◽  
Vol 20 (2) ◽  
pp. 51
Author(s):  
Antoni . ◽  
Hendra Surya Wibawa ◽  
Djwantoro Hardjito
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Fly Ash ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Setting Time ◽  
High Volume ◽  
High Volume Fly Ash ◽  
High Calcium ◽  
High Calcium Fly Ash

This study evaluates the effect of particle size distribution (PSD) of high calcium fly ash on high volume fly ash (HVFA) mortar characteristics. Four PSD variations of high calcium fly ash used were: unclassified fly ash and fly ash passing sieve No. 200, No. 325 and No. 400, respectively. The fly ash replacement ratio of the cementitious material ranged between 50-70%. The results show that with smaller fly ash particles size and higher levels of fly ash replacement, the workability of the mixture was increased with longer setting time. There was an increase in mortar compressive strength with finer fly ash particle size, compared to those with unclassified ones, with the highest strength was found at those with fly ash passing mesh No. 325. The increase was found due to better compactability of the mixture. Higher fly ash replacement reduced the mortar’s compressive strength, however, the rate was reduced when finer fly ash particles was used.

scholarly journals Properties of non-standard fly ash – slag cements containing calcareous fly ash

2013 ◽  
Vol 12 (3) ◽  
pp. 215-222
Author(s):  
Katarzyna Synowiec
Keyword(s):  
Fly Ash ◽  
Blast Furnace Slag ◽  
Strength Class ◽  
Setting Time ◽  
Heat Of Hydration ◽  
Initial Setting Time ◽  
Granulated Blast Furnace Slag ◽  
Unfavorable Effect ◽  
Initial Setting ◽  
Furnace Slag

The paper presents the tests results of the properties of non - standard fly ash - slag cements composition. Both natural (unprocessed) and activated by grinding calcareous fly ash was used. It was found that the calcareous fly ash next to the granulated blast furnace slag may be a component of low - clinker cements (ca. 40%). Those cements are characterized by low heat of hydration and overdue of initial setting time in comparison with Ordinary Portland Cement, moreover they have an unfavorable effect on consistency and its upkeep in time. Production of fly ash - slag cements is possible for strength class 32,5 N when the component of cement is raw fly ash, and for strength classes 32,5 N, 32,5 R and 42,5 N when ground fly ash was used. Fly ash activated by grinding was characterized by higher activity.

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