scholarly journals The Influence of Calcareous Fly Ash on the Effectiveness of Plasticizers and Superplasticizers

Materials ◽  
2020 ◽  
Vol 13 (10) ◽  
pp. 2245
Author(s):  
Jacek Gołaszewski ◽  
Tomasz Ponikiewski ◽  
Aleksandra Kostrzanowska-Siedlarz ◽  
Patrycja Miera
Keyword(s):  
Sustainable Development ◽  
Fly Ash ◽  
Rheological Properties ◽  
Water Demand ◽  
High Water ◽  
Heat Of Hydration ◽  
Yield Value ◽  
High Calcium ◽  
Concrete Mix ◽  
Polycarboxylate Ether

Due to the rational shaping of the environment and the management of environmental resources in accordance with the principle of sustainable development, calcareous fly ash (CFA)—high-calcium as a by-product of lignite combustion—is a valuable addition to concrete. This additive, however, due to its high-water demand lowers the workability of the concrete mix, which is a problem, especially in the first 90 min after mixing the components of the mix. In order to meet this challenge, plasticizers (P) and superplasticizers (SP) for concrete are used with various effects which are designed to reduce the yield value and plastic viscosity. To check the technical efficiency of admixtures P and SP with different chemical bases, the main objective of this research was to investigate the influence of raw and ground CFA on the rheological properties and other side effects of admixtures, such as the amount of air in the mixture and the amount of heat of hydration. The use of P, particularly SP, effectively improves the workability of the mortar containing CFA, especially ground CFA. With these admixtures, it is possible to obtain mortars containing ground CFA with similar rheological properties to mortars without its addition. To obtain a specific workability of mortar with CFA, it is usually necessary to introduce a higher dose of P or SP than used for mortars without CFA. The presence of raw CFA does not alter the effectiveness of P and strongly reduces the effectiveness of SP. The reduced effectiveness of SP manifests primarily as a high workability lost. The presence of ground CFA does not change the effectiveness of P (or is higher). The effectiveness of the superplasticizer SNF (with a chemical base of naphthalene sulfonate) and PE (with a chemical base of polycarboxylate ether) is slightly lower or does not change. The effectiveness of the superplasticizer SMF (with a chemical base of melamine sulfonates) is significantly lower. We found that the presence of ash affects the efficiency of P and SP, while processing via the grinding of ash makes the effect negligible. These results are novel in both their cognitive and practical aspects.

scholarly journals Effect of Calcareous Fly-ash Processing Methods on Rheological Properties of Mortars

2018 ◽  
Author(s):  
Jacek Gołaszewski ◽  
Zbigniew Giergiczny ◽  
Tomasz Ponikiewski ◽  
Aleksandra Kostrzanowska-Siedlarz ◽  
Patrycja Miera
Keyword(s):  
Fly Ash ◽  
Rheological Properties ◽  
Negative Influence ◽  
Plastic Viscosity ◽  
Processing Methods ◽  
Yield Value ◽  
Selective Collection

The paper presents the results of research into the influence of calcareous fly ash (CFA) processing methods on the rheological properties of mortars. The study consisted of a comparison of changes of the rheological properties (plastic viscosity and yield value) of the mortars during 90 minutes when CFA, unprocessed or processed by grinding, grain separation, or selective collection from the filter, was used as a substitute for a part of the cement. The results show that processing of CFA decreases its negative influence on the rheological properties; the efficient methods are separation or grinding, while the effect of selective collection is almost insignificant.

Retardation Effects in the Hydration of Cement-Fly Ash Pastes

1984 ◽  
Vol 43 ◽  
Author(s):  
Michael W. Grutzeck ◽  
Wei Fajun ◽  
Della M. Roy
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Solid Phase ◽  
Heat Of Hydration ◽  
Type I ◽  
Fly Ashes ◽  
Solution Composition ◽  
Early Hydration ◽  
High Calcium ◽  
Phase Characterization

AbstractThe hydration of high-calcium and low-calcium fly ash-cementmixtures was investigated to determine the effect of fly ash upon the hydration of a Type I portland cement, and to determine the associated mechanisms of hydration. When blended with portland cement, both fly ashes retarded the early hydration process, the high-Ca more so than the low-Ca. Analyses of solution compositions and calorimetric (heat of hydration) measurements were made. The retardation and hydration effects are discussed in terms of solution composition data and solid phase characterization. The hydration effects were interpreted and compared with the results of previous work.

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.

Optimization of fly ash concrete mix – a solution for sustainable development

2020 ◽  
Vol 26 ◽  
pp. 3250-3256 ◽  
Author(s):  
A. Fuzail Hashmi ◽  
M. Shariq ◽  
A. Baqi ◽  
Moinul Haq
Keyword(s):  
Sustainable Development ◽  
Fly Ash ◽  
Fly Ash Concrete ◽  
Concrete Mix

scholarly journals Effect of Fly Ash and Fibres on Strength and Permeability Characteristics of Pervious Concrete

2019 ◽  
Vol 8 (4) ◽  
pp. 12089-12093
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Flexural Strength ◽  
Water Permeability ◽  
High Strength ◽  
High Water ◽  
Pervious Concrete ◽  
Storm Water ◽  
Water Runoff ◽  
Concrete Mix

Conventional normal cement concrete is generally used as construction material of buildings. The impervious nature of concrete contributes to the increased water runoff into drainage system, over-burdening the infrastructure and causing excessive flooding in built-up areas. Pervious concrete has become significantly popular during recent decades, because of its potential contribution in solving environmental issues. Pervious concrete is a type of concrete with significantly high water permeability compared to conventional concrete. It has been mainly developed for draining water from surface to underground, so that storm water runoff is reduced. Due to high water permeability then normal concrete, pervious concrete has very low compressive strength. The characteristic of high permeability of pervious concrete contributes to its advantage in storm water management. However, the mechanical property such as low compressive strength limits the application of pervious concrete to the roads having light volume traffic. It is observed form previous studies that the strength of pervious concrete can be enhanced by substituting some of the cement with other materials, such as fly ash and fibres. The objective of present study was to make pervious concrete mix with high strength and pore properties by partial replacement of cement with fly ash and using steel and glass fibres. For this purpose cubes beams were casted with and without replacement of cement with flyash and addition of steel and glass fiber by total weight of concrete mix. Test such as compressive strength, flexural strength, total porosity and Infiltration rate were performed. It was observed addition of fly ash decreased the compressive as well as flexural strength of the pervious concrete. Further, incorporation of 1% steel fibres by weight of concrete mix was found adequate in achieving high strength and permeability, when compared to control mix concrete

Optimization of Concrete with High Volume of Fly Ash

2016 ◽  
Vol 865 ◽  
pp. 249-254 ◽  
Author(s):  
Adam Hubáček ◽  
Martin Labaj ◽  
Martin Ťažký
Keyword(s):  
Mechanical Properties ◽  
Sustainable Development ◽  
Fly Ash ◽  
Portland Cement ◽  
Building Materials ◽  
Lower Cost ◽  
High Volume ◽  
Cement Production ◽  
High Volume Fly Ash ◽  
Concrete Mix

The demand for concrete structures grows worldwide, which raises fears about sustainable development of Portland cement production. Its carbon footprint is relatively small compared to alternative building materials, but still it is not negligible. This argument together with lower cost and possibility of utilization of material, which would otherwise be disposed as waste, lead the research towards concrete with higher content of Portland cement replaced with fly ash. The experiment is divided into two parts: the first one determines influence of high volume fly ash replacement of Portland cement on behavior and properties of cement paste and mortar. The second part optimizes composition of concrete mix, in particular the granulometry of the cement-fly ash system in order to achieve maximal possible values of mechanical properties at high dosage of fly ash.

Aluminum Sulfate Hydration Retarders for High-Calcium Fly Ash Used in Highway Construction

1986 ◽  
Vol 86 ◽  
Author(s):  
M. Tohidian ◽  
Joakim G. Laguros
Keyword(s):  
Fly Ash ◽  
Adverse Effects ◽  
Aluminum Sulfate ◽  
Highway Construction ◽  
Weight Ratio ◽  
Heat Of Hydration ◽  
Hydration Reaction ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Delayed Compaction

ABSTRACTThe rapid hydration and setting associated with the use of high-calcium fly ash as an additive in soil and aggregate base stabilization in highway construction imposes certain limitations in regards to operational time and volume of work executed. Aluminum sulfate and its ammonium salt were evaluated as hydration reaction retarders. Mixtures of Ottawa sand and Class C high lime fly ash in a 1:1 weight ratio were used for the evaluations. These additives minimized the adverse effects of delayed compaction by recovering some of the compressive strength lost to the rapid hydration, although in all cases the density of the mixes decreased. The recovery of strength was related to the heat of hydration, wherein the peak temperature was reduced from 90°F to the range of 86–78°F at 2 hours; further temperature decreases were observed as reaction time increased. The availability of the sulfate ions, as manifested by the presence of ettringite, helps the hydration process continue, minimizes the adverse effects of delayed compaction and assists positively in the reduction of the void area of mixes and in stratlingite formation, which contributes to a strong crystalline framework.

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