Use of Ash after Denitrification as an Additive to Concrete Based on Alcali-Activated Slag

2021 ◽  
Vol 322 ◽  
pp. 78-83
Author(s):  
Lukáš Procházka ◽  
Jana Boháčová
Keyword(s):  
Blast Furnace ◽  
Fly Ash ◽  
Partial Replacement ◽  
Negative Effects ◽  
Concrete Mixtures ◽  
Granulated Slag ◽  
Activated Slag ◽  
Alkali Activated Concrete ◽  
Alkali Activated ◽  
Reference Mixture

This paper deals with the possibility of using fly ash after denitrification by the SNCR method a partial replacement in alkali-activated concrete based on blast furnace granulated slag. Previous research has verified the use of fly ash after denitrification in alkali-activated materials based on blast furnace granulated slag, and so far no negative effects on the properties of these mixtures have been found. The tests were performed on cement test specimens. As part of the preparation of concrete mixtures, two recipes were prepared. The first reference mixture contained only blast furnace granulated slag activated by sodium water glass with silicate modulus of 2. The second recipe was modified by replacing of 30% slag by fly ash after denitrification by SNCR method. Within the strength characteristics, the reference mixture always achieved better results. Very slow increases in strength were recorded for the mixture with 30% slag replacement by fly ash, when the compressive strength after 7 days of maturation was only 4.5 MPa.

scholarly journals Effect of Admixtures on Durability Characteristics of Fly Ash Alkali-activated Material

2020 ◽  
Vol 4 (6) ◽  
pp. 493-502
Author(s):  
Lukáš Procházka ◽  
Jana Boháčová
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Fly Ash ◽  
Flexural Strength ◽  
Frost Resistance ◽  
Granulated Slag ◽  
Furnace Slag ◽  
Alkali Activated ◽  
Reference Mixture ◽  
Denitrification Process

This paper deals with the possibility of partial replacement of blast furnace slag with fly ash and fly ash after denitrification by SNCR method in alkali-activated materials based on granulated blast furnace slag. The aim of this paper is to verify the effect of fly ash on properties of alkali-activated materials based on blast furnace granulated slag. Frost resistance and resistance to aggressive environments, represented by demineralized water were tested. The reference mixture was based on blast furnace granulated slag activated by sodium water glass with silicate modulus of 2. Mixtures with an ash content of 10, 20, and 30% were then compared with the reference mixture. The influence of the denitrification process on fly ash and its use in mixed alkali activated materials was also compared. As a part of the experiment, alkali-activated pastes were also prepared. Infrared spectroscopy with Furier transformation was subsequently determined on these pastes. The reference mixture achieved the highest compressive strength in the experiment and the strength decreased with increasing amount of fly ash. In terms of flexural strength, the highest values were reached for mixtures with 10% slag replacement by fly ash. In the case of frost resistance, the significant increase of flexural strength, which was 50% for the reference mixture, is particularly interesting. For compressive strength, the frost resistance coefficient ranged from 0.95 to 1.00. In the case of resistance to aggressive environments, no differences were observed in the compressive strength, on the other hand, flexural strength decrease of up to 20% was detected for 10 and 20 percent replacement of slag with fly ash that did not undergo denitrification. Monitored properties did not show any negative effect of the denitrification process on fly ash properties. Infrared spectroscopy identified the main hydration product in the region of 945 cm-1which is a C-(A)-S-H gel and in combined mixtures with fly ash also N-A-S-H gel. Doi: 10.28991/esj-2020-01247 Full Text: PDF

scholarly journals Alkali-Activated Slag/ Fly Ash Concrete: Mechanism, Properties, Hydration Product and Curing Temperature

2020 ◽  
Vol 9 (9) ◽  
pp. 204-215
Keyword(s):  
Fly Ash ◽  
Hydration Product ◽  
Test Methods ◽  
Curing Temperature ◽  
Environmental Friendliness ◽  
Alkali Activated Slag ◽  
Fly Ash Concrete ◽  
Activated Slag ◽  
Alkali Activated Concrete ◽  
Alkali Activated

Alkali-activated concrete (AAC) is mounting as a feasible alternative to OPC assimilated to reduce greenhouse gas emanated during the production of OPC. Use of pozzolana results in gel over-strengthening and fabricate less quantity of Ca(OH)2 which provide confrontation to concrete against hostile environment. (AAC) is potential due to inheriting the property of disbursing CO2 instantly from the composition. Contrastingly an option to ordinary Portland cement (OPC), keeping this fact in mind the goal to evacuate CO2 emits and beneficiate industrial by-products into building material have been taken into consideration. Production of alkali-activated cement emanates CO2 nearly 50-80% less than OPC. This paper is the general assessment of current report on the fresh and hardened properties of alkali-activated fly ash (AAF), alkali-activated slag (AAS), and alkali activated slag and fly ash (AASF) concrete. In the recent epoch, there has been a progression to blend slag with fly ash to fabricate ambient cured alkali-activated concrete. Along with that the factors like environmental friendliness, advanced studies and investigation are also mandatorily required on the alkali activated slag and fly ash concrete. In this way, the slag to fly ash proportion impacts the essential properties and practical design of AAC. This discusses and reports the issue in an intensive manner in the following sections. This will entail providing a good considerate of the following virtues like workability, compressive strength, tensile strength, durability issues, ambient and elevated-temperature curing of AAC which will improve further investigation to elaborate the correct test methods and to commercialize it.

Influence of Industrial By-Products on Shrinkage of Alkali-Activated Slag

2014 ◽  
Vol 1000 ◽  
pp. 137-140
Author(s):  
Vlastimil Bílek Jr. ◽  
Lukáš Kalina ◽  
Eva Bartoníčková ◽  
Tomáš Opravil
Keyword(s):  
Fly Ash ◽  
Partial Replacement ◽  
Cement Kiln ◽  
Hydration Products ◽  
Fluidized Bed Combustion ◽  
Alkali Activated Slag ◽  
Activated Slag ◽  
Kiln Dust ◽  
By Products ◽  
Alkali Activated

One of the highest shortages of alkali-activated slag (AAS) is high shrinkage, both autogenous and drying. One of the possibilities of lowering the shrinkage is partial replacement of slag by suitable admixtures, which can act for example through the forming of expansive hydration products. In this study, 0–50 % of slag was replaced by by-pass cement kiln dust and fluidized bed combustion fly ash. Promising results were obtained especially in the case of fly ash. By using admixtures at higher dosages compressive strengths were reduced.

Chloride Resistance of Alkali Activated Slag Pastes with Fly Ash Replacement

2016 ◽  
Vol 851 ◽  
pp. 98-103
Author(s):  
Ladislav Pařízek ◽  
Vlastimil Bílek Jr. ◽  
Matěj Březina
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Raw Materials ◽  
High Energy ◽  
Partial Replacement ◽  
Alkali Activated Slag ◽  
Practical Applications ◽  
Chloride Resistance ◽  
Activated Slag ◽  
Alkali Activated

High energy requirements due to producing of Portland cement leads to a tendency to use secondary raw materials or completely new kind of materials. One of the possibilities is using the materials based on alkali activated slag (AAS). In this paper the influence of partial replacement of ground granulated blast furnace slag by fly ash in AAS pastes on mechanical properties and porosity of was investigated. For practical applications it is also necessary to know their resistance to environment such as salty water. Chloride resistance was investigated by setting the experiment as external chloride attack and measuring the changes of mechanical properties, porosity and composition of the pastes.

scholarly journals The Compressive Strength and Microstructure of Alkali-Activated Binary Cements Developed by Combining Ceramic Sanitaryware with Fly Ash or Blast Furnace Slag

Minerals ◽  
2018 ◽  
Vol 8 (8) ◽  
pp. 337 ◽  
Author(s):  
Juan Cosa ◽  
Lourdes Soriano ◽  
María Borrachero ◽  
Lucía Reig ◽  
Jordi Payá ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Fly Ash ◽  
Blast Furnace Slag ◽  
Calcium Content ◽  
Partial Replacement ◽  
Alkali Activation ◽  
High Calcium ◽  
Furnace Slag ◽  
Alkali Activated

The properties of a binder developed by the alkali-activation of a single waste material can improve when it is blended with different industrial by-products. This research aimed to investigate the influence of blast furnace slag (BFS) and fly ash (FA) (0–50 wt %) on the microstructure and compressive strength of alkali-activated ceramic sanitaryware (CSW). 4 wt % Ca(OH)2 was added to the CSW/FA blended samples and, given the high calcium content of BFS, the influence of BFS was analyzed with and without adding Ca(OH)2. Mortars were used to assess the compressive strength of the blended cements, and their microstructure was investigated in pastes by X-ray diffraction, thermogravimetry, and field emission scanning electron microscopy. All the samples were cured at 20 °C for 28 and 90 days and at 65 °C for 7 days. The results show that the partial replacement of CSW with BFS or FA allowed CSW to be activated at 20 °C. The CSW/BFS systems exhibited better mechanical properties than the CSW/FA blended mortars, so that maximum strength values of 54.3 MPa and 29.4 MPa were obtained in the samples prepared with 50 wt % BFS and FA, respectively, cured at 20 °C for 90 days.

Rheological Characteristics of Alkali Activated Fly-Ash Concrete Mixtures

2016 ◽  
Vol 677 ◽  
pp. 86-92
Author(s):  
Tomáš Váchal ◽  
Rostislav Šulc ◽  
Pavel Svoboda
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Fresh Concrete ◽  
Rheological Characteristics ◽  
Fresh Mixture ◽  
Fly Ash Concrete ◽  
Concrete Mixtures ◽  
Alkali Activated Concrete ◽  
Alkali Activated

This paper describes rheological characteristics of concrete mixtures based on alkali-activated fly ash. There are shown relationships between workability of fly-ash fresh concrete mixtures and water–fly-ash ratio in fresh alkali-activated concrete. In addition, there is described relationship between workability in fresh mixture on compressive strength of alkali-activated concrete.

Effect of Specimen Size and Curing Condition on the Compressive Strength of Alkali-Activated Concrete

2017 ◽  
Vol 2629 (1) ◽  
pp. 9-14 ◽  
Author(s):  
Robert James Thomas ◽  
Sulapha Peethamparan
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Specimen Size ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Slag Cement ◽  
Fly Ash Concrete ◽  
Activated Slag ◽  
Alkali Activated Concrete ◽  
Alkali Activated

Alkali-activated concrete is a rapidly emerging sustainable alternative to portland cement concrete. The compressive strength behavior of alkali-activated concrete has been reported by various studies to a limited extent, but these discussions have been based on minimal evidence. Furthermore, although it is known that specimen size has a distinct effect on the apparent compressive strength of concrete, this effect has yet to be modeled for alkali-activated concrete. This paper presents the results of a comprehensive study of the effects of curing condition (i.e., moist-cured at ambient temperature for 28 days or heat-cured at 50çC for 48 h) and specimen size on the compressive strength of sodium silicate–activated fly ash and slag cement concrete. The heat-cured strength of alkali-activated slag cement concrete was linearly related to the moist-cured strength; the former was about 5% greater than the latter. Heat curing also improved the strength of alkali-activated fly ash concrete, although the effect was greatly magnified for lower-strength mixtures and was much less significant at higher strengths. Existing size effect laws employed for portland cement concrete proved reasonably accurate in describing the effect of specimen size on the apparent strength of alkali-activated slag cement concrete. However, these existing models greatly underestimated the size effect in alkali-activated fly ash concrete; the authors suggest that this finding was the result of significant microcracking in the alkali-activated fly ash concrete.

Freeze-Thaw Resistance with Sodium Chloride Solution of Fly-Ash Concrete Mixtures

2015 ◽  
Vol 1124 ◽  
pp. 137-144
Author(s):  
Tomáš Váchal ◽  
Rostislav Šulc ◽  
Pavel Svoboda
Keyword(s):  
Fly Ash ◽  
Sodium Chloride ◽  
Chloride Solution ◽  
Sodium Chloride Solution ◽  
Freeze Thaw ◽  
Fly Ash Concrete ◽  
Air Content ◽  
Concrete Mixtures ◽  
Alkali Activated Concrete ◽  
Alkali Activated

This paper describes freeze-thaw resistance with sodium chloride solution of concrete mixtures based on alkali-activated fly ash. There are shown relationships between freeze-thaw resistance with sodium chloride solution and air content in fresh alkali-activated concrete and relationship between freeze-thaw resistance with sodium chloride solution and spacing factor of alkali-activated concrete. Also there is described relationship between air content in fresh mixture and compressive strength of alkali-activated concrete.

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