scholarly journals Cooling treatment of alkali solution to prolong the setting time of high calcium fly ash based geopolymers

2019 ◽  
Vol 669 ◽  
pp. 012024
Author(s):  
O K Wattimena ◽  
A Antoni ◽  
R T Surja ◽  
R Mintura ◽  
D Hardjito
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Alkali Solution ◽  
High Calcium ◽  
High Calcium Fly Ash

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.

Influences of the Ratios of High-Calcium Fly Ash to Low-Calcium Fly Ash on the Strength and Drying Shrinkage of Geopolymer Mortar

2014 ◽  
Vol 931-932 ◽  
pp. 416-420 ◽  
Author(s):  
Ridtirud Charoenchai ◽  
Prinya Chindaprasirt
Keyword(s):  
Fly Ash ◽  
Power Plants ◽  
Setting Time ◽  
Drying Shrinkage ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Class C ◽  
Class F Fly Ash ◽  
By Products ◽  
Class F

New types of binders are being developed as an alternative to traditional cement. These alternatives are developed to have better properties and to be more environmentally friendly. Geopolymer is a novel binder that is produced from by-products such as fly ash, rich hushes ash and bio mass ash. In this experiment, fly ash, which was a by-product from electrical-generating power plants, was used during the synthesis of geopolymer. According to ASTM standard C168, fly ash is categorized into two types: class F and class C. This research focuses on the effects of using both types of fly ashes on mechanical properties of geopolymer. The experiment studies the changes on setting time, drying shrinkage and compressive strength of geopolymer mortar when 0, 25, 50, 75 and 100 percent of total weight of class F fly ash (LCF) is substituted with class C counterpart (HCF). The study used sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) as alkali activators. The samples were cured for 24 hours either at an ambient temperature of 25°C or at an elevated temperature of 60°C.The result showed that the setting time of pure LCF geopolymer mortar was 6 times longer than that of the pure HCF ones. In addition to setting time, the specimens with 25 percent of their total binders weight replaced by HCF appeared to have the highest strength. However, the increase in HCF also increased the drying shrinkage by 6 and 12times when the specimens were cured at25°C and at 60°C respectively

Setting Time, Strength, and Bond of High-Calcium Fly Ash Geopolymer Concrete

2015 ◽  
Vol 27 (7) ◽  
pp. 04014198 ◽  
Author(s):  
Pattanapong Topark-Ngarm ◽  
Prinya Chindaprasirt ◽  
Vanchai Sata
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Geopolymer Concrete ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Time Strength

scholarly journals Influence of Chemical Additives on the Properties of Composite Materials Based on Fine-Dispersed High-Calcium Fly Ash

2020 ◽  
pp. 395-407
Author(s):  
Olga M. Sharonova ◽  
Valerii M. Kirilets ◽  
Leonid A. Solovyov ◽  
Alexander G. Anshits
Keyword(s):  
Composite Materials ◽  
Fly Ash ◽  
Citric Acid ◽  
Sodium Sulfate ◽  
Setting Time ◽  
Strength Properties ◽  
Sodium Tetraborate ◽  
Chemical Additives ◽  
High Calcium ◽  
High Calcium Fly Ash

Composite materials (CM) were obtained on the basis of fine- dispersed high-calcium fly ash (HCFA), selected from the 4th field of electrostatic precipitators of Krasnoyarsk TPP-2, with the addition of Melflux 5581F superplasticizer at the water: binder ratio W/B = 0.25. The influence of the concentration of superplasticizer in the range 0.06-0.6 wt. % on the strength properties of composite materials was studied. The effect of the addition of sodium sulfate as an accelerator of hydration hardening and additives-retarders of sodium phosphate, sodium tetraborate and citric acid, were studied. The optimal concentration of superplasticizer was established (0.3 wt. %). It was determined that sodium sulfate helps to improve the strength of CM, and the addition of sodium tetraborate and citric acid can effectively regulate the setting time

scholarly journals Durability of concrete containing ternary blends of high calcium fly ash and slag

2021 ◽  
Author(s):  
Seyon Kandasamy
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Sulfate Attack ◽  
Alkali Silica Reaction ◽  
Ternary Blends ◽  
Fresh Properties ◽  
Freeze Thaw ◽  
Salt Scaling ◽  
High Calcium ◽  
High Calcium Fly Ash

This thesis investigates the performance of ternary blends containing high calcium fly ash (HCFA) and slag against: sulfate attack, alkali-silica reaction (ASR), salt scaling, and freeze-thaw damage. In addition, compressive strength, permeability and fresh properties were evaluated. In terms of sulfate attack, the performance of HCFA was significantly enhanced when slag was added to the mix, and the same was found for ASR. The high efficacy in resisting ASR of HCFA/slag blends was found to be a result of the blends' ability to bind and retain alkalis. Regarding the salt scaling, the tested ternary concretes failed the Ministry of Transportation Ontario limit, 0.8 kg/m²; however, enhanced performance was achieved when the samples were cured by wrapping with plastic sheets. Ternary blends achieved high resistance to freezing/thawing and less bleeding compared to those of the control mix without slag or HCFA; however, setting time was dragged by about an hour.

scholarly journals Durability of concrete containing ternary blends of high calcium fly ash and slag

2021 ◽  
Author(s):  
Seyon Kandasamy
Keyword(s):  
Fly Ash ◽  
Setting Time ◽  
Sulfate Attack ◽  
Alkali Silica Reaction ◽  
Ternary Blends ◽  
Fresh Properties ◽  
Freeze Thaw ◽  
Salt Scaling ◽  
High Calcium ◽  
High Calcium Fly Ash

This thesis investigates the performance of ternary blends containing high calcium fly ash (HCFA) and slag against: sulfate attack, alkali-silica reaction (ASR), salt scaling, and freeze-thaw damage. In addition, compressive strength, permeability and fresh properties were evaluated. In terms of sulfate attack, the performance of HCFA was significantly enhanced when slag was added to the mix, and the same was found for ASR. The high efficacy in resisting ASR of HCFA/slag blends was found to be a result of the blends' ability to bind and retain alkalis. Regarding the salt scaling, the tested ternary concretes failed the Ministry of Transportation Ontario limit, 0.8 kg/m²; however, enhanced performance was achieved when the samples were cured by wrapping with plastic sheets. Ternary blends achieved high resistance to freezing/thawing and less bleeding compared to those of the control mix without slag or HCFA; however, setting time was dragged by about an hour.

scholarly journals The Use of Borax in Deterring Flash Setting of High Calcium Fly Ash Based Geopolymer

2016 ◽  
Vol 857 ◽  
pp. 416-420 ◽  
Author(s):  
Antoni ◽  
Stephen Wibiatma Wijaya ◽  
Juan Satria ◽  
Agung Sugiarto ◽  
Djwantoro Hardjito
Keyword(s):  
Particle Size ◽  
Compressive Strength ◽  
Fly Ash ◽  
Chemical Composition ◽  
Setting Time ◽  
Chemical Properties ◽  
Physico Chemical ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Positive Effect

Geopolymer that was made with high CaO content fly ash was found to have higher compressive strength than the low CaO fly ash, using the same mixture composition. This effect could be due to the physico-chemical properties of the fly ash, in respect to its particle size or the chemical composition. Although it was not widely published, the occurrence of flash setting of geopolymer was known to occur when using high CaO content fly ash as the precursor. Geopolymer paste may solidify within minutes after the addition of alkali activators, making it very difficult to cast in big volume. This paper investigate the effect of borax addition to the high calcium fly ash-based geopolymer mixture to reduce the occurrence of flash setting. It was found that the setting time can be extended significantly, with the addition of 5% borax, by mass, of fly ash. The addition of borax also have positive effect on increasing the compressive strength of geopolymer.

The Investigation on Setting Time and Strength of High Calcium Fly Ash Based Geopolymer

2018 ◽  
Vol 881 ◽  
pp. 158-164 ◽  
Author(s):  
Remigildus Cornelis ◽  
Henricus Priyosulistyo ◽  
Iman Satyarno ◽  
Rochmadi
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Setting Time ◽  
Solid Ratio ◽  
Synthesis Parameters ◽  
Heat Curing ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Ambient Curing

Fly ash based geopolymer normally gets the optimum strength by heat curing. This is considered as a hindrance to in-situ applications. Therefore, development of fly ash based geopolymer that suitable for ambient curing will widen the application to the concrete structure. This paper reports the results of an experimental study on setting time and development of compressive strength of class C fly ash based geopolymer paste produced in ambient curing condition. The main synthesis parameters such as water to the geopolymer solid ratio, alkali to cementitious ratio and molarity of NaOH were varied to understand their individual effect on setting time and the mechanical properties of the resulting geopolymer. The results suggested that generally the setting time increased with the NaOH molarity and the compressive strength of 59 MPa was obtained for geopolymer mixture cured at ambient temperature for 28 days with alkali to a cementitious ratio of 0.35 and 10 M NaOH. The results will be useful for developing the knowledge of the use of high calcium fly ash in producing geopolymer. This would be beneficial to the understanding the future applications of this material as new binding material.

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