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![Table 2 Particle size distribution of standardized sand as [58]](profile/Mitsuhiro-Shigeishi/publication/319334619/figure/tbl2/AS:614117320716288@1523428387022/Particle-size-distribution-of-standardized-sand-as-58_Q320.jpg)
Performance of drying shrinkage, flow rate, mechanical properties, and microstructure of three materials - alkali-activated fly ash (FA); ground granulated blast-furnaced slag (GGBFS); and un-densified micro-silica (M) are investigated. Mixtures used herein are referred to as AAM - alkali activated materials - of four types according to composition...
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... Low calcium fly ash improves some properties of AAM, such as workability [10], and provides volumetric stability [11][12][13], but their setting needs a longer time [14]. Incorporation of slag with fly ash not only decreases the setting time [10] but can also improve the strength [5,10,15] and durability [16] of the material. Conversely, the drying shrinkage of the AAM is increased with the increment of slag in the mixture [17]. ...
... Therefore, an optimum mix proportion must be considered to overcome the aforementioned problems. Besides fly ash and slag, silica fume is also used to modify the properties of the AAM [15]. ...
... Sodium metasilicate pentahydrate (Na 2 SiO 3 .5H 2 O) and its anhydrous form (Na 2 SiO 3 ) that has a (SiO 2 /Na 2 O) modulus of 1 are frequently used by researchers to characterize one-parted AAM [24,[27][28][29][30] This may be due to their abundant existence in a dry state. But conventional AAM is usually made by a high concentrated sodium disilicate that has the modulus of around 2 [10,[14][15][16]. ...
Alkali-activated materials are conventionally produced by a two-part mixing in which alkalis are used as aqueous solutions that create applicability problems. To overcome the problem, one-part alkali-activated materials (AAM) are being studied. In this study, the influence of aluminosilicate precursors, sodium hydroxide (NaOH), alkaline activators (AA) ratio (Na2SiO3: NaOH), and production method on flowability, compressive and flexural strength, and drying shrinkage properties of one-part AAM was studied. Ground granulated blast-furnace slag (GGBFS) increased the strength but negatively influenced the flowability and drying shrinkage of the AAM. Fly ash improved the flowability and decreased the drying shrinkage but the material had much lower reactivity at ambient temperature to improve the strength. AA ratio improved the flowability but reduced the strength. High-concentrated NaOH decreased the flowability and strength of the material. One-part AAM had much lower strength compared to conventional and two-part AAM. This is attributed to a lack of better reaction between aluminosilicate precursors and AA in the one-part mixture.
... Oxide composition (wt.%) SG (g/cc) hydroxide ratio of 1.5 [26,27]. The precursors (fly ash, GGBFS, microsilica) were mixed with the alkali solution and fine aggregate and compacted, cured, and demoulded [8]. ...
This study uses the Weibull analysis to predict the robustness of various mortars based on a fracture process analysis through a flexural test recorded by an acoustic emission sensor. Alkali-activated materials (AAMs) are an alternative to Portland cement that can decrease the amount of emitted CO2. This study aimed to characterise and compare the properties of AAM cement mortars to those of the commonly used ordinary Portland cement (OPC) mortars using the Weibull distribution to clarify the reliability and robustness of the prepared AAM cements; four different AAM cement mortar compositions—with fly ash (F), ground-granulated blast-furnace slag (G), and micro silica (M) alkali activation (sodium hydroxide (NaOH) and sodium silicate(Na2SiO3))—was considered in this study. The fracture process under a flexural loading of AAMswas based on four combinations of F/G/M activated by the alkaline solution—AAM-IV, AAM-V, AAM-VI, and AAM-VII, with OPC as control. The Weibull analysis showed that AAMs were more robust than the OPC mortar and possessed minor fractures compared to the OPC mortar.
... The compressive strength of the resulting AAM paste is also presented along with the morphology behavior and compound of resulting specimens using XRD and SEM characterization methods. 28 The Application of Microbes to the Fly Ash-Based Alkali-Activated … 249 ...
... The highest achieved by F50S50 that increases its compressive strength by ± 50%. This proved that addition of GGBFS showed increasing the early compressive strength of resulting AAM [28][29][30]. ...
Microbial agents are often used to enhance the performance of cementitious material. This study presents the utilization of microbes to the properties of fly ash (FA)-based alkali-activated material (AAM) paste, with ground granulated blast furnace slag (GGBFS) as partially FA substitution. Variations of GGBFS-to-FA weight ratio were between 0 and 50%. Raw material and specimens are characterized with X-ray fluorescence, X-ray diffraction, scanning electron microscope, compression test, porosity test, workability test, and setting time. Supplement of microbes to FA-based AAM enhances the strength in a limited amount up to 20% slag replacement due to its workability. AAM without GGBFS addition showed a 28-day compressive strength of 23.00 MPa. The 28-day compressive strength of 20% GGBFS substitution without and with microbes addition was 32.90 MPa and 33.50 MPa, respectively. Microbes application to 20% GGBFS substitution in AAM resulting total porosity (pf) of 19% which was lower than without microbes addition. Microbes increased the workability but fastened the setting time of fresh AAM. The X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis showed the microbes image and precipitation dominated by calcite.KeywordsAlkali-activated materialFly ashGGBFSMicrobesCalcite
... In addition to precast applications, the production of geopolymer concrete by curing at room temperature would enable its usage in castin-situ applications. Early age strength growth of fly ashbased geopolymer concrete cured at room temperature was less than that of heat-cured specimens [14], [15]. At ambient temperature, the main disadvantages of fly ashbased geopolymer concrete are its slow setting and strength growth. ...
... The proportions of the concrete mixtures were based on earlier research on geopolymer concrete cured at ambient temperature [10], [11], [14], [15], [18], [19]. During the investigation, the following characteristics were considered: aggregate content, alkaline activator solution, sodium silicate to NaOH ratio, the molarity of NaOH solution, and curing process. ...
... 100 mm in diameter and 200 mm in height geopolymer concrete specimens were cast and cured in ambient conditions at 15-20°C and 70±10% relative humidity. 100 mm in diameter and 200 mm in height cylinder specimens were cast for compressive strength (14) and change in mass testing. 7day-old prism samples were submerged in a 5% magnesium sulphate solution for length change testing. ...
... The alkaline solution consisted of 8M Sodium hydroxide (NaOH) and 56% sodium silicate gel. Sodium silicate was composed of 36% SiO 2 , 18% Na 2 O, and 46% H 2 O. Fixed alkali solution concentration dosage with a ratio of sodium silicate to sodium hydroxide was 1.5 for all the samples [18,19] The precursors ( y ash, GGBFS, Micro-silica) were mixed with an alkali solution and ne aggregate as [3] in a 2-liter batch mixer. Table 1 Speci c gravity (SG) and oxide composition of materials in weight percentage [3]. ...
This paper focuses on using Weibull analysis to predict various mortars' robustness based on the fracture process analysis through the flexural test which was recorded by the sensor of Acoustic Emission. Weibull distribution is used to clarify the reliability and robustness of cement by mortar characterization made from fly ash (F), ground granulated blast-furnace slag (GGBFS or G), and micro-silica (M) alkali activation compared with Ordinary Portland Cement (OPC) Mortars. This mortar production aims to characterize and compare alkali-activated materials (AAMs) properties with the cement type commonly used, OPC. AAMs are an alternative to Portland cement, that can decrease the amount of CO2 emission.
The fracture process under flexural loading of AAMs was made from 4 combinations of F/G/M activated by the alkaline solution. Four variations are AAM-IV, AAM-V, AAM-VI, AAM-VII, and OPC as a control. Weibull analysis showed that AAMs were more robust than OPC mortar and possessed minor fractures compared to OPC mortar.
... According to the molar ratio (MR = SiO 2 : Na 2 O), sodium silicate has several types such as sodium metasilicate (MR = 1) and sodium disilicate (MR = 2) [14]. Conventionally, water glass is used at a concentration of around 50% [9,[15][16][17][18], which makes the solution to be viscose and sticky, and this causes AAM to have a workability problem. Sodium silicate solution not only provides an alkaline environment to dissolve the aluminosilicate precursors, but they are a source of silica and contribute significantly to developing mechanical strength [19]. ...
... Incorporating the slag with fly ash improves the reactivity of the aluminosilicate precursors that result in a decrease in the hardening or setting time of the samples at ambient temperature and modifies some other properties of concrete such as compressive strength, flexural strength, and density of AAM [17]. As the slag is very active and increases the reactivity and hydration of the materials [22], this causes the materials to emit a higher amount of heat during the reaction process [23]. ...
... As the slag is very active and increases the reactivity and hydration of the materials [22], this causes the materials to emit a higher amount of heat during the reaction process [23]. erefore, the drying shrinkage of alkali-activated materials with slag is much higher than the other types [17,18]. ...
Low-calcium Fly ash-based alkali-activated materials (AAM) have some extraordinary properties such as high fire resistance and low shrinkage. However, they have lower strength and high setting time when curing at ambient temperature conditions. Therefore, this research aimed to improve the strength and setting time of low-calcium fly ash-based AAM curing at ambient temperature conditions. The effect of the changes in concentration and modulus of sodium silicate and curing condition of the materials were studied on the properties of the AAM. Fly ash type II, 32% sodium metasilicate pentahydrate, 32 and 56% sodium disilicate solution, 8M sodium hydroxide, and standardized were used. Using 32% sodium disilicate solution significantly improved the flowability of mortar. Moreover, it increased the compressive strength and remarkably decreased the setting time of AAM at ambient temperature curing. The decrease in the concentration of sodium disilicate has a significant influence on the reactivity of fly ash.
... Therefore, they are cured at higher temperatures [36,37]. Incorporating slag with fly ash increases the reactivity of aluminum silicate precursors that results in quick hardening of the samples at ambient temperature and modifies other properties of concrete, such as compressive strength, flexural strength, and density of concrete [38]. As the slag is very active and increases the reactivity and hydration of the materials [39], its addition causes quick solidification of the material that in some cases causes difficulty in casting the fresh AAM in molds. ...
... It was due to the low reactivity of low-calcium fly ash or fly ash type II [37] which caused the extremely low chemical reaction rate between the precursor and the alkaline solution, therefore, a lower amount of the aqueous solution was consumed during the reaction process. There was a decrease in the flowability of slag and microsilica due to their higher reactivity [38,39]. The mortar with 30% of slag had the lowest flow value of 114 mm M3 and M1 had a flowability of 122 and 120 mm, respectively. ...
... Compressive strength of more than 40 MPa and flexural strength of 6 MPa were achieved using 32% concentrated sodium metasilicate solution, which is much lower than the concentration of sodium silicate solution used in making traditional geopolymer and AAMs [11,37,38,47,48,49]. ...
This research investigates the properties of alkali-activated materials (AAMs) using sodium metasilicate, with the ratio of SiO2:Na2O equals 1. This study was conducted to achieve the following three aims. Firstly, to understand the solubility mechanism of granular sodium metasilicate pentahydrate (Na2SiO3.5H2O) when used in a one-part mixing method. Secondly, to investigate the properties of AAMs when a sodium metasilicate aqueous solution is used as an alkaline material and as a source of silica. Lastly, to study the retardation effect of sucrose on AAMs. This research used aluminum silicate precursors, such as low-calcium fly ash, slag, and micros silica, alkali activators, such as NaOH pellets and Na2SiO3.5H2O, and standardized sand. The alkaline activators were first dissolved in water using a water bath shaker to achieve the alkaline solution. Sucrose, which is about 2% of the weight of the solid precursors, was added to modify the reaction process between the precursors and the alkaline materials. Four types of samples were prepared: M1, M2, M3, and M4, with the fly ash, slag, and silica fume ratios of 80:20:0, 70:30:0, 75:20:5, and 100:0:0, respectively. The research conducted solubility test of the alkaline materials, flowability, 7-, 28-, 56-day compressive and flexural tests, drying shrinkage test of mortar samples, and the setting tests of pastes with and without sucrose. The results show that the dissolution time of the NaOH was much shorter, whereas Na2SiO3.5H2O needed a solvent with a temperature of around 40°C to be fully dissolved. This problem of solubility decreases the quality of AAMs formed using the one-part mixing method. Among the mortar samples, the M4 had the highest flow rate, while M3 had the lowest flow rate. M2 had the highest compressive and flexural strength of 43.4 MPa and 6.1 MPa, respectively. The setting time test shows that sucrose retards the reaction process in AAM.
... Total 2% of solid precursor mass was used as the mass of air entrained-agent. The ratios of liquid and alkaline solution per solid precursor were fixed at 0.558 and 0.538 by weight for all AAM mixtures respectively [24]. ...
... Fig. 7 illustrates the average compressive strength of all specimens. The AAM-VI is plain geopolymer mortar as a reference to control fiber mortar AAM-F [24]. Fig. 8 illustrates average compressive strength for cylinder specimens which have the same composition with prismatic samples. ...
... The chemical analysis and specific gravity (SG)[24] Note: this table shows the proportion of solid precursors by weight of alkali-activated mortars with supplementary materials such as S= GGBFS, FA = fly ash, OPC=Ordinary Portland Cement and M= microsilica ...
... The GGBFS substitution on AAM4 can increase compressive strength. Substitution of reactive Si from micro-silica and Ca from GGBFS on AAM5 causes higher compressive strength than that of AAM3 at the 14-day age [17]. Class C fly ash mortar (AAM1) has a higher compressive strength than that of class F fly ash mortar (AAM3). ...
... SEM image of (a) Class C Fly ash from Indonesia, (c) Class F Fly ash from Japan, (d) GGBFS, (e) Micro-silica[17], (b) Sandblasting ...
This research is to find out the contribution of waste energy utilization in Indonesia as a binding agent of alkali-activated mortar. In a previous study, researchers investigated mortar made from class F fly ash/GGBFS/micro-silica in Japan. The inclusion of GGBFS is to shorten/normalize the setting time and micro-silica is to improve mortar performance. This research is then continued by using abundant waste material in Indonesia, namely class C fly ash, by making cubic mortar specimens. Setting time of class C fly ash paste from Indonesia is very fast, in contrast to that of class F fly ash paste from Japan. Sandblasting as abundant waste material in Indonesia is substituted to class C fly ash to lengthen the setting time of paste and to improve standard deviation of a compressive test of mortar specimens. On the other hand, the addition of sandblasting waste has a negative effect, because it reduces a compressive strength of mortar specimens.
... In previous work [10][11], the researcher investigated the utilization of low calcium fly ash for alkali-activated (geopolymer) matrices. Researchers developed low calcium fly ash, ground granulated blast furnace slag (GGBFS), and microsilica as binding materials for alkali-activated mortar [12][13]. There has been no paper discussing the reliability of strength of alkali-activated (geopolymer) mortars by using Acoustic Emission. ...
... AAM mortars are mixtures made from precursor materials (fly ash/GGBFS/micro-silica), mixed with a fixed alkaline solution (Na2SiO3+NaOH), and standardized sand. All of these materials are then compacted, demolded, cured as previous papers [10][11][12][13]. Fixed alkali solution ratio of Na2SiO3 to 8 M NaOH of 1.5 is used. ...
Alkali-activated materials or geopolymer technology is one of the material innovations that can provide several benefits by reducing the use of Portland cement. The source of precursor materials come from industrial by-products. This study investigated the reliability failure of seven-variation of alkali-activated fly ash/slag/micro-silica mortar (AAM) and one-type of Portland Cement (PC) mortar. Compressive strength test accompanied by acoustic emission is used to characterize cylindrical mortar specimens. Examination of fracture distribution according to stress level until final failure was then performed. The compressive strength of four-type of alkali-activated mortar AAM (AAM-IV, V, VI, and VII) at 14 and 28 days shows a slight strength increase, 61.9 to 63.6 MPa, 62.3 to 65.6 MPa, 64.8 to 68.3 MPa and 63.1 to 63.6 MPa, respectively. The slight increase of AAM compressive strength is caused by high early strength achieved due to the replacement of more than 40 % of fly ash with GGBFS. The presence of more CaO in the AAM mixture accelerates the reaction in early age. By contrast, PC mortar shows significantly strength increases from 55.2 MPa to 69.5 MPa during the same period. Amplitude filters greater than (50dB, 60dB, 70dB and 80 dB) is utilized to investigate the reliability of compressive strength of the mortar by acoustic emission. It was found that filter greater than 60dB is the most suitable filter. Alkali-activated mortars which contain raw material of 42.5% fly ash, 42.5% GGBFS, and 15% micro-silica has the lowest reliability of failure than those of other mortars whereas Portland cement mortar shows the highest reliability of failure than other alkali-activated mortars.
