Influence of water, alkali activators, and curing regime on the workability and compressive strength of the alkali activated mortar

2019 ◽  
Author(s):  
Eslam Gomaa ◽  
Simon Sargon ◽  
Cedric Kashosi ◽  
Ahmed Gheni ◽  
Mohamed ElGawady
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Calcium Content ◽  
Chemical Compositions ◽  
Heat Curing ◽  
High Calcium ◽  
Influence Of Water ◽  
Curing Regime ◽  
Curing Regimes ◽  
Alkali Activated

<p>The effect of the water to fly ash (W/FA), alkali activators to fly ash (Alk/FA), and curing regimes on the workability and compressive strength of the alkali-activated mortar (AAM) was studied. Three high calcium fly ashes (FAs) having different chemical compositions were used. Sodium hydroxide (SH) and sodium silicate (SS) were used as the alkali activators. The two alkali activators were mixed together at ratio of 1.0. Two curing regimes, elevated heat curing in an electric oven at 70°C for 24 hr and ambient curing at 23 ± 2°C, were applied. The water to fly ash (W/FA) ratios were 0.350, 0.375, and 0.400. However, the alkali activators to fly ash (Alk/FA) ratios were 0.250, 0.275 and 0.300. The results revealed that the workability and the compressive strength of the oven cured specimens were decreased with increasing the calcium content of FA in the mixture. However, the compressive strength of the specimens that cured under the ambient temperature increased with increasing the calcium content. The workability increased with increasing the W/FA and decreasing the Alk/FA. The compressive strength based on both curing regimes decreased with increasing the W/FA. The optimum Alk/FA was 0.275 with W/FA of 0.400.</p>

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.

scholarly journals Compressive Strength Performance of Alkali Activated Concretes under Different Curing Conditions

2021 ◽  
Author(s):  
Anıl Niş ◽  
İlhan Altındal
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Strength Performance ◽  
Curing Conditions ◽  
Standardization Process ◽  
Water Curing ◽  
Curing Regimes ◽  
Alkali Activated Concrete ◽  
Alkali Activated ◽  
Ambient Curing

This study investigated the influence of different curing conditions on the compressive strength (CS) of the different alkali activated concrete (AAC) specimens at the ages of 2, 28, and 90 days for the structural utilization and standardization process of AAC instead of OPC concrete. For this aim, 100% slag (S100), 75% slag and 25% fly ash (S75FA25), and 50% slag and 50% fly ash based (S50FA50) AAC specimens were produced. Based on the oven-curing (O), water-curing (W), and ambient-curing (A) methods, the influence of 2O for 2 days, 26A2O, 2O26A, 28A, 28W, 26W2O, and 2O26W for 28 days, and 88A2O, 2O88A, 90A, 88W2O, 2O88W, 90W for 90 days on the CS of the AAC were examined in details. In addition, the influence of delayed oven-curing conditions on CS development was also investigated. The results indicated that curing conditions significantly affected on the CS and the water-curing condition could provide a better CS for those of AAC at 90 days. Although, the oven-curing enhanced CS of the S100 specimens at initial ages (first oven-curing applied), delayed oven-curing (oven-curing applied later) was found significant for S75FA25 and S50FA50 specimens. The delayed oven-curing affected more on the CS of the AAC when fly ash content increased. The most of AAC specimens with oven-curing had significantly enhanced the CS at 28 days, but S50FA50 at the age of 90 days decreased. Different curing regimes were proposed for the superior compressive strength values for each AAC specimens at the ages of 28 and 90 days.

scholarly journals Workability and Strength Properties of Class C Fly Ash-Based Geopolymer Mortar

2019 ◽  
Vol 258 ◽  
pp. 01009
Author(s):  
Remigildus Cornelis ◽  
Henricus Priyosulistyo ◽  
Iman Satyarno ◽  
Rochmadi
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Strength Properties ◽  
Mass Ratio ◽  
Heat Curing ◽  
Absolute Volume ◽  
High Calcium ◽  
Class C ◽  
Direct Tensile ◽  
Ambient Curing

Fly ash-based geopolymer mortar normally achieves expected properties by heat curing. This becomes one of the obstacles for in-situ applications. The development of high calcium fly ash-based geopolymer mortar, suitable for ambient curing, will gain the applicability of such a material in civil structures. This article reports the results of an experimental study on mortar workability and the increasing of compressive strength of class C fly ash-based geopolymer mortar created in ambient curing condition. The main synthesis parameters such as alkali to the cementitious mass ratio varied from 30% to 40% by an increment of 5% and absolute volume of paste to absolute volume of voids of the aggregate ratio varied from 1 to 2 by an increment of 0.25. These parameters were designed to figure out their individual effects on mortar workability and the mechanical properties for the production of geopolymer mortar. The results suggested that the workability of mortar generally increased by using alkali to the cementitious mass ratio. The compressive strength of 60 MPa and the direct tensile strength of 2.8 MPa, the ratio of alkali to the cementitious mass of 0.35 and absolute volume of paste to absolute volume of voids of the aggregate ratio was 1.5; it was obtained at ambient temperature after 28 days of age. The results will be useful for developing the knowledge for the use of class C fly ash in producing geopolymer concrete, which is currently in progress. Hopefully, this contribution of research will improve the applications of such new binding material in the future.

scholarly journals A Mix Design Procedure for Alkali-Activated High-Calcium Fly Ash Concrete Cured at Ambient Temperature

2018 ◽  
Vol 2018 ◽  
pp. 1-13 ◽  
Author(s):  
Tanakorn Phoo-ngernkham ◽  
Chattarika Phiangphimai ◽  
Nattapong Damrongwiriyanupap ◽  
Sakonwan Hanjitsuwan ◽  
Jaksada Thumrongvut ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Design Methodology ◽  
Design Procedure ◽  
Mix Design ◽  
Fly Ash Concrete ◽  
High Calcium ◽  
High Calcium Fly Ash ◽  
Alkaline Activator ◽  
Alkali Activated

This research focuses on developing a mix design methodology for alkali-activated high-calcium fly ash concrete (AAHFAC). High-calcium fly ash (FA) from the Mae Moh power plant in northern Thailand was used as a starting material. Sodium hydroxide and sodium silicate were used as alkaline activator solutions (AAS). Many parameters, namely, NaOH concentration, alkaline activator solution-to-fly ash (AAS/FA) ratio, and coarse aggregate size, were investigated. The 28-day compressive strength was tested to validate the mix design proposed. The mix design methodology of the proposed AAHFAC mixes was given step by step, and it was modified from ACI standards. Test results showed that the 28-day compressive strength of 15–35 MPa was obtained. After modifying mix design of the AAHFAC mixes by updating the AAS/FA ratio from laboratory experiments, it was found that they met the strength requirement.

scholarly journals Aggregates Obtained by Alkali Activation of Fly Ash: The Effect of Granulation, Pelletization Methods and Curing Regimes

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 776 ◽  
Author(s):  
Ognjen Rudić ◽  
Vilma Ducman ◽  
Mirjana Malešev ◽  
Vlastimir Radonjanin ◽  
Suzana Draganić ◽  
...  
Keyword(s):  
Fly Ash ◽  
Energy Dispersive Spectrometer ◽  
Textural Properties ◽  
Alkali Activation ◽  
X Ray Diffraction ◽  
Scattered Electron ◽  
Curing Regime ◽  
Class F Fly Ash ◽  
Curing Regimes ◽  
Alkali Activated

This paper presents results regarding the phase composition, microstructure and textural properties of two types of aggregates, which were prepared via crushing or pelletization of alkali-activated Class F fly ash and cured under different conditions. The alkali activator was the same for aggregate products, containing an alkaline solution consisting of 8 M NaOH and Na-silicate (8 M NaOH/Na-silicate = 1:2.5 mass ratio). The aforementioned properties were influenced by two different preparation procedures combined with varying curing regimes (under normal conditions at 20 °C, RH 40–60% for 28 and 120 days and under an accelerated regime, at 65 °C for 5 days). Aggregates were characterized using X-ray diffraction (XRD), Fourier-transform transmission infrared spectroscopy (FTIR), back scattered electron microscopy with energy dispersive spectrometer (BSE-EDS) analyses and mercury intrusion porosimetry (MIP). The results showed noteworthy structural and textural diversities between the two types of aggregate. The method of preparation and curing regime affected the formation of the N-A-S-H structure and the texture of the alkali-activated fly ash product, with the crushing method giving an advantage.

scholarly journals Influence of Water Content on Mechanical Strength and Microstructure of Alkali-Activated Fly Ash/GGBFS Mortars Cured at Cold and Polar Regions

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 138 ◽  
Author(s):  
Xiaobin Wei ◽  
Feng Ming ◽  
Dongqing Li ◽  
Lei Chen ◽  
Yuhang Liu
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Water Content ◽  
Negative Temperature ◽  
Polar Regions ◽  
Uniaxial Compression Strength ◽  
Influence Of Water ◽  
Strength And Durability ◽  
Alkali Activated Binders ◽  
Alkali Activated

Negative temperature curing is a very harmful factor for geopolymer mortar or concrete, which will decrease the strength and durability. The water in the geopolymer mixture may be frozen into ice, and the water content is a crucial factor. The purpose of this paper is to explore the influence of water content on the properties of alkali-activated binders mortar cured at −5 °C. Fly ash (FA) and ground granulated blast furnace slag (GGBFS) were used as binders. Three groups of experiments with different water content were carried out. The prepared samples were investigated through uniaxial compression strength test, Scanning electron microscopy (SEM), and X-ray diffraction (XRD) for the determination of their compressive strength, microstructural features, phase, and composition. The results indicated that, the compressive strength of samples basically maintained 25.78 MPa–27.10 MPa at an age of 28 days; for 90 days, the values reached 33.4 MPa–34.04 MPa. The results showed that lower water content is beneficial to improving the early strength of mortar at −5 °C curing condition, while it has little impact on long-term strength. These results may provide references for the design and construction of geopolymer concrete in cold regions.

scholarly journals The effect of water binder ratio on strength development of class C fly ash geopolymer mortar prepared by dry geopolymer powder

2019 ◽  
Vol 258 ◽  
pp. 05032 ◽  
Author(s):  
Arie Wardhono
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Calcium Content ◽  
Strength Properties ◽  
Strength Development ◽  
Effect Of Water ◽  
High Calcium ◽  
Binder Ratio ◽  
Geopolymer Binder ◽  
Water Binder Ratio

The use of geopolymer binder as cement replacement material can reduce the amount of carbon dioxide gas produced during the Portland Cement manufacturing process. However, the main issue of geopolymer binder is in the mixing process of sodium silicate and NaOH which requires specialized knowledge and strict supervision. This paper reports the effect of water binder ratio on strength development of fly ash geopolymer mortar using dry geopolymer powder. Fly ash with high calcium content was used as primary material. The dry geopolymer powder was prepared by wet mixing method which was made by drying a mixture of NaOH solution and limestone for 24 hours. The variations of water to binder ratio were 0.30, 0.35, 0.40, 0.45, and 0.50. Strength properties were measured by compressive strength at the age of 7, 14 and 28 days. The results showed that the water binder ratio significantly affect the strength development of geopolymer mortar prepared by dry geopolymer powder. The water binder ratio of 0.40 gives the highest compressive strength of 10.3 MPa at 28 days. This suggests that the use of dry geopolymer powder on geopolymer mortar production can overcome the difficulties of geopolymer mortar mixing on site.

scholarly journals Fresh properties and compressive strength of high calcium alkali activated fly ash mortar

2017 ◽  
Vol 29 (4) ◽  
pp. 356-364 ◽  
Author(s):  
Eslam Gomaa ◽  
Simon Sargon ◽  
Cedric Kashosi ◽  
Mohamed ElGawady
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Fresh Properties ◽  
High Calcium ◽  
Alkali Activated

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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