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Article

Performance Requirements and Optimum Mix Proportion of High-Volume Fly Ash 3D Printable Concrete

by
Hatice Gizem Şahin
1,
Ali Mardani
1,* and
Naz Mardani
2
1
Department of Civil Engineering, Faculty of Engineering, Bursa Uludag University, Bursa 16059, Turkey
2
Department of Mathematics Education, Bursa Uludag University, Bursa 16059, Turkey
*
Author to whom correspondence should be addressed.
Buildings 2024, 14(7), 2069; https://doi.org/10.3390/buildings14072069
Submission received: 3 June 2024 / Revised: 30 June 2024 / Accepted: 5 July 2024 / Published: 6 July 2024
(This article belongs to the Section Building Materials, and Repair & Renovation)
Browse Figures
Versions Notes

Abstract

:
In this study, a procedure for mixture design was proposed with the aim of meeting the requirements of extrudability, buildability, and shape stability in 3D printable concrete. Optimum water/binder ratio, sand/binder ratio, binder type, utilization ratio, aggregate particle distribution and quantity, and type and utilization ratio of chemical admixtures were determined for 3D printable concrete in terms of print quality and shape stability criteria. A total of 32 different mixtures were produced. It was determined that mixtures produced using a binder content with approximately 40% fly ash, a w/b ratio of 0.35, and aggregates with Dmax of 1 mm exhibit acceptable characteristics. Investigations were also conducted into the thixotropic behavior, rheological characteristics, and mechanical properties of the mixes that were deemed acceptable. As a result, it was determined that the increase in the amount of fly ash usage positively affected the buildability of the printed layers. Additionally, the dynamic yield stress ranging from 114 to 204 Pa, viscosity ranging from 22 to 43 Pa.s, and structural build-up value ranges suitable for the production of 3D printable concrete mixtures were determined.

1. Introduction

Three-dimensional printing technology is used to minimize the disadvantages of traditional construction methods, such as high labor requirements and occupational accident rates, slow production, high mold cost, and limited design freedom [1]. In 3D concrete printing technology, it was determined that the selection of materials, especially binders, is an important factor in obtaining the desired properties in 3D printable concrete (3DPC) mixtures [2]. Studies in the literature have stated that the amount of cement usage was increased in order to meet the necessary criteria for 3DPC mixtures [3]. It is known that this situation may negatively affect the performance of mixtures in terms of ecological, economic, and drying-shrinkage behavior [4]. In order to eliminate this negative situation in 3DPC mixtures and to increase the strength performance of the mixtures, supplementary cementitious materials, such as fly ash, are generally substituted for Portland cement [5]. It was reported by researchers that fly ash reduces the friction force between cement particles due to its spherical shape [6,7]. This effect is called the ball-bearing effect [8] and generally causes the rheological values of 3DPC mixtures to decrease. However, since it is thought that the use of fly ash, which positively affects late-age strength, may cause a decrease in early-age strength, it was stated that it imposes limitations on the use of mineral additives and mixture design in 3DPC mixtures [9]. It was emphasized by Zhang et al. [10] that conventional concrete standards are not sufficient for the design of 3DPC. As a result, various trial-and-error studies are being conducted to produce 3DPC mixtures with optimal fresh and hardened state properties [11].
Recently, several studies were conducted to determine the mix design and the rheological, fresh, and hardened state properties of 3DPC [12,13]. These studies have highlighted that the rheological properties of 3DPC significantly differ from those of conventional concrete. In this regard, Ref. [14] reported that 3DPCs need to have a high static yield stress value to resist structural deformations caused by their own weight, the weight of upper layers, and extrusion pressure. However, Ref. [15] emphasized that in order to improve the print quality of the printed layers, the yield stress and viscosity values should not be excessively high.
In determining the rheological properties of 3DPC, Ref. [16] stated that, unlike conventional concrete mixtures, in addition to yield stress and viscosity properties, the structural build-up (thixotropic) behavior should also be examined. The thixotropic behavior of 3DPC was defined as the ability of the structure to maintain stability during the process from extrusion to hardening [17]. Additionally, Yuan et al. [18] reported that this behavior is the most significant parameter affecting the buildability of 3DPC mixtures. In addition to the rheological requirements, certain criteria need to be met in terms of fresh state properties in 3DPC mixtures. These criteria are generally classified under three headings: (i) extrudability [19,20,21,22], (ii) buildability [23,24], and (iii) shape stability [25,26]. Extrudability is defined as the ability of 3DPC mixtures to be easily printed through a nozzle without causing any clogging or damage [27]. Xiao et al. [28] reported that extrudability is influenced by the design of the extrusion system and the rheological properties of 3DPC. It was stated that the “buildability” criterion needs to be met to prevent deformation in the printed layers after extrusion [29]. Buildability is defined as the ability of the 3DPC mixture to be printed in its layered structure without experiencing collapse or surface roughness [30]. Xiao et al. [28] mentioned that optimization methods need to be developed to meet the buildability criterion. The shape stability criterion is defined as the requirement for the printed 3DPC mixtures to have desired width, length, and height values within specified ranges and for these values not to be negatively affected by time and additional loads [30]. The shape stability of 3DPC is reported by Yang et al. [31] to be significantly influenced by nozzle size, shape, and movement speed. While the use of larger nozzles may lead to settling issues in 3DPC mixtures, it is emphasized that smaller nozzles may negatively impact the continuity of the structure. In a study conducted by Shakor et al. [32], it was determined that the shape stability of 3DPC is also influenced by the nozzle position. Improper selection of the nozzle distance was found to result in irregular extrusion flow, leading to increased deformation of the layers and potential degradation of shape stability. Consequently, it is understood from the literature that multiple parameters are influential in determining the optimal mixture proportions for 3DPC. Numerous studies were conducted on the subject. However, due to the high number of influential parameters and the absence of any existing standard, there is no precise procedure for determining the optimum mixture ratio of 3DPC. In this study, the optimum water/binder ratio, sand/binder ratio, binder type, usage rate, aggregate particle distribution, quantity, type of chemical admixture, and utilization ratio were determined for 3DPC mixtures in terms of extrudability, buildability, and shape stability criteria. The rheological and thixotropic properties of the selected optimum mixtures were examined. Additionally, the 28-day compressive and flexural strength values of the mixtures were also investigated.

2. Material and Methods

2.1. Materials

In this study, CEM I 42.5R Portland cement and class F fly ash were used as binders. Table 1 displays the characteristics of the manufacturer’s supplied binder ingredients.
In order to investigate the effect of aggregate particle size distribution on the fresh properties of 3DPC mixtures, crushed limestone aggregates with maximum particle diameters (Dmax) of 1 mm and 2 mm were used. The specific gravity and water absorption capacity of the aggregates were determined as 2.58 and 0.4% according to the EN1097-6 Standard [33], respectively. SEM images of the cement, fly ash, and aggregate used in the study are shown in Figure 1. In Figure 1b, the spherical structure of fly ash is clearly understood.
Table 2 presents some properties of the water-reducing (WRA) and viscosity-modifying admixture (VMA) used to ensure the required workability [34,35] and viscosity in 3DPC mixtures, as shared by the manufacturer.

2.2. Method

2.2.1. Preparation of Mixtures

Three steps were involved in the preparation of 3DPC mixes. During one minute at a speed of 62.5 rpm, cement, fly ash, and fine aggregate were combined in the first stage. Water and admixture were added to the mixture in the second stage, and it was mixed for a minute at a speed of 62.5 rpm. In the third stage, the mixture was mixed at 125 rpm for 2 min (Figure 2). Immediately after the mixture was prepared, it was extruded in layers.

2.2.2. Workflow

The workflow applied to determine the fresh state requirements of 3DPC mixtures is shown in Figure 3. The characteristics of the printed layer were taken into account in creating this workflow. Thus, the proposed workflow can be applied to different 3DPC mixtures. Previous studies [36,37,38] on the subject were considered in the preparation of the trial mixtures. It was reported that 3DPC mixtures generally contain high binder content and fine aggregate [39]. Based on the literature, the fresh state requirements were examined in terms of print quality and shape stability parameters in the prepared mixtures. For this purpose, in the first stage, the extrudability and buildability requirements of the mixtures were ensured. Mixtures with easily printable layers were considered extrudable. It was understood that three requirements must be met in order to ensure the buildability parameter. These requirements are that at least 5 layers of printing are possible, dimensional conformity is ensured, and there is no roughness on the surface. In the second stage, shape stability was evaluated using Equation (1) for mixtures considered to have acceptable print quality [40]. A 3DPC mixture with a shape stability value greater than 95% was considered to meet the fresh state requirements [16].
S S   % = b l a y e r b n o z z l e · 100
where SS represents the shape stability (%), b l a y e r represents the layer width after extrusion (mm), and b n o z z l e represents the nozzle width (42 mm).

2.2.3. Rheological Measurement

The rheological properties and structural build-up of the accepted mixtures were examined. In this study, an MCR52-Anton Paar rheometer with an 8 mm ball diameter was used [31,41]. The ambient temperature during the measurements was maintained at 20 ± 2 °C. The applied rheological measurement process is shown in Figure 4. The rheological measurement method used was created by modifying two different rheological measurement methods suggested by Mardani-Aghabaglou [41] and Yao et al. [13].
Detailed explanations of the periods applied in the rheological measurement method are given below.
  • 1st period: This period was applied to eliminate shear history during mixing in the mixer. With a constant shear rate of 5 s−1, the ball was rotated in the mixture for 30 s.
  • 2nd period: This period is used to create the output part of the flow curve. The shear rate was increased from 0 to 30 s−1. Measurements were taken every 5 s for a total of 150 s.
  • 3rd period: This period is made to create the downward part of the flow curve. The shear rate is reduced from 30 to 0 s−1. Measurements were taken every 5 s for a total of 150 s. Dynamic yield stress and viscosity values of 3DPC mixtures were obtained from this period.
On the basis of the raw data collected in the third period, the Herschel–Buckley model (Equation (2)) was used to create shear stress-shear rate and VS-shear rate graphs for each mixture.
τ = τ 0 + b γ ˙ p
where τ is the shear stress (Pa), τ 0 is the yield stress (Pa), b is the Herschel–Bulkley consistency coefficient, γ ˙ is the shear rate (s−1), and p is the Herschel–Bulkley index.
  • 4th period: This period was applied to recover the 3DPC mixtures before static measurement. The mixtures were kept for 30 s without being exposed to any shear rate.
  • 5th period: In this period, moment measurements were taken every 2 s for a total of 15 times for 30 s with a constant shear rate of the mixture (0.02 s−1). During this period, the static (at rest) yield stress of the material was measured.
  • 6th period: In this period, the mixtures were kept for 480 s without being exposed to any shear rate in order to measure the structural build-up rate.
  • 7th period: In this period, moment measurements were taken every 2 s for a total of 15 times for 30 s with a constant shear rate of the mixture (0.02 s−1). During this period, the static (at rest) yield stress of the material was measured.
After the dynamic measurement, the mixture was left for 30 s. Then, initial static measurements were performed for 30 s at a constant shear rate of 0.02 s−1. After the mixtures were left for 480 s, final static measurements were conducted for 30 s at a constant shear rate of 0.02 s−1. Structural build-up (Athix) was determined using the obtained static yield stresses from this test. The corresponding value was calculated using Equation (3).
A t h i x = τ s , f − τ s , i t d
where A t h i x represents structural build-up (Pa/s), τ s , f represents static yield stress value obtained from the 7th period (Pa), τ s , i represents static yield stress value obtained from the 5th period (Pa), and t d represents the resting time (s). Images of the rheometer device and sample mixture used in the study are shown in Figure 5.
The 28-day compressive strength and three-point flexural strength performance properties of 3D-printed concrete mixtures were measured as mechanical properties. The strength performance of the samples was determined by making some changes in the dimensions and loading directions specified in the EN 196-1 Standard [39]. Specimens were loaded on 40 mm × 40 mm surfaces, and their compressive strength was determined. Also, the flexural strength of the printed samples was determined by performing a three-point bending test on 40 mm × 40 mm × 160 mm prism samples. The representation of the samples produced and tested within the scope of the study is summarized in Figure 6.

3. Results and Discussion

This study aimed to determine the 3DPC mixing ratios with optimum properties in terms of economic, ecological, and fresh-state requirements. In this direction, a total of 32 different 3DPC mixtures were prepared by changing the parameters of water/binder ratio, sand/binder ratio, binder type, usage ratio, aggregate particle distribution, amount, chemical admixture type, and utilization ratio. The amount of material used in the production of 1 m3 of 3DPC mixture is shown in Table 3. In determining these material ratios, the criteria and revision rules specified in Figure 3 were taken into consideration. Compared to the literature, a mixture design was made using a relatively lower amount of cement and a higher percentage of fly ash in mixture no. 1. [42,43,44,45]. In this mixture, aggregate with a maximum particle diameter of 2 mm, which is recommended in the literature, was used. WRA and VMA at the rate of 0.4% of the total binder weight were used. The capacity of the mortar injection gun used was considered in the selection of these values. The produced mixture no. 1 caused a blockage in the nozzle because it was excessively solid and cohesive. Thus, the extrudability parameter, which is one of the print quality criteria, is not provided in the 1st mixture. For this reason, mixtures 2, 3, and 4 were prepared, respectively, by increasing the w/b ratio from 0.32 to 0.33, 0.34, and 0.35, which is the first of the changes suggested in Figure 3. However, the extrudability parameter was not provided in the mentioned mixtures. According to the literature, the w/b ratio is generally below 0.35 in the production of 3DPC [46,47]. For this reason, in this study, the w/b ratio was kept constant at 0.35, and the second suggested change was applied. For this purpose, mixtures of 5, 6, 7, 8, 9, and 10 were prepared by reducing the VMA dosage between 6% and 60%. However, the extrudability parameter is not provided in these mixtures. In this regard, the third suggested change was implemented. In this context, by increasing the WRA dosage from 16% to 133%, mixtures numbered 11, 12, 13, 14, 15, 16, 17, and 18 were produced. It was determined that in these mixtures, the extrudability parameter is achieved, but the buildability parameter is not achieved (a five-layer structure could not be formed) (Figure 7a). It was expressed by Sanjayan et al. [48] that as the usage rate of WRA increases, in addition to the positive impact on workability, the layer surface will remain moist for a longer period. It was reported that this condition will positively affect buildability performance by increasing the interlayer bonding strength. Furthermore, an increase in the usage rate of WRA leads to the formation of a more fluid mixture, resulting in an increase in layer thickness. Thus, Ref. [49] stated that an increase in the contact surface between two layers will result in a larger effective bonding area. Therefore, the second and third suggested changes were implemented. As a result, mixtures numbered 19 and 20 were prepared by increasing the dosage of WRA without the use of VMA. It was observed that in these mixtures, the extrudability parameter is achieved, and a five-layer structure can be formed.
However, the smoothness requirement, which is another criterion for buildability, could not be achieved. It can be understood from Figure 7b that mixtures 19 and 20 have excessively rough surfaces (red circles). The surface roughness of the mixture is significantly influenced by the aggregate volume and size. For this purpose, in the first stage, the cement content was increased with the aim of reducing the sand/binder ratio. For this purpose, a mixture numbered 21 was prepared by increasing the cement usage rate by 10%. However, in this particular mixture, the increase in cement content has negatively affected the extrudability due to the corresponding increase in water demand. Therefore, mixtures numbered 22, 23, and 24 were prepared by increasing the dosage of WRA by 4% to 10%. In mixture number 24, both the extrudability and buildability criteria are met. To ensure the economic and ecological aspects of the mixtures, a mixture numbered 25 was prepared by keeping the total binder content at 750 kg/m3 while reducing the cement content and increasing the fly ash content due to excessive flow performance (Figure 7c). Thus, the buildability criterion could not be achieved. For this purpose, a mixture numbered 26 was produced by reducing the usage of WRA by 3.5%. In the mentioned mixture, a five-layer structure could be achieved; however, it was observed that the surface roughness prevented the fulfillment of the buildability criterion. For this purpose, it was decided to modify the parameter of the maximum aggregate particle size, which has an impact on surface roughness [46,50,51]. In line with this, a mixture numbered 27 was produced using aggregate with a maximum particle size of 1 mm. However, in this particular mixture, the increase in the proportion of fine materials led to an increase in the total surface area, resulting in the failure to meet the extrudability criterion. Therefore, mixtures numbered 28, 29, and 30 were produced by increasing the usage rate of WRA between 3.5% and 10%. It was determined that both the extrudability and buildability criteria were met in the mentioned mixtures. From an economic standpoint, it is understood that the order of the mixtures is 28, 29, and 30. Considering the pump power, the selection order for producing a more fluid mixture is 30, 29, and 28.
It is known that for the widespread adoption of 3DPC mixtures in construction applications, the materials used in the mixture need to be sustainable [52,53,54]. In line with this, the study aimed to achieve sustainability by using fly ash at a proportion of 40% of the binder content. For this purpose, mixtures numbered 31 and 32 were prepared by increasing the fly ash usage rate by 10% and 17%, respectively. Both the extrudability and buildability criteria were met in the mentioned mixtures as well. In mixtures 28–32, where the criteria for print quality are met, the criterion of shape stability was examined. In all of the mentioned mixtures, the shape stability value was measured to be above 95%. Therefore, it is understood that the criterion of shape stability is met in the mentioned mixtures.

3.1. Rheological Properties of Mixtures

The rheological parameters of mixtures 28–32, where it was determined that the criteria for print quality and shape stability are met, were measured. For this purpose, shear stress/viscosity–shear rate graphs were created for each mixture [55,56] (Figure 8). The values of dynamic yield stress (DYS), viscosity (VS), and structural build-up obtained from Figure 8 are shown in Table 4. It can be inferred from the results that fly ash, which has a spherical structure, leads to a decrease in the values of yield stress and structural build-up in 3DPC mixtures due to the balling effect [57,58]. Alghamdi et al. [59] reported similar outcomes as well. Additionally, studies have shown that these effects are influenced by fly ash dosage, specific gravity, fineness, and surface characteristics [60].
Based on the literature [11,42], mixture 32, which has relatively low DYS and VS values and a higher substitution rate of fly ash, is suitable for use in 3DPC applications. It can be understood from the table that mixtures with a DYS ranging from 114 to 204 Pa, viscosity ranging from 22 to 43 Pa·s, and structural build-up ranging from 0.61 to 1.49 Pa/s may be suitable for 3DPC. However, it should be noted that the values mentioned can vary in a wider range depending on the materials and their properties used in the mixture. The relationship between shape stability and rheological properties of the mixtures is shown in Table 5. As can be seen from the table, there is a very strong correlation between the shape stability and viscosity value of the mixtures (r = 0.9). Other parameters affecting shape stability were DYS and Athix, respectively.

3.2. Mechanical Properties of Mixtures

The 28-day compressive and flexural strength results of mixtures 28–32 produced within the scope of the study are shown in Figure 9 and Figure 10, respectively. It was determined that the compressive strength values of the mixtures varied between 32.63 and 34.86 MPa, and the flexural strength values varied between 10.34 and 10.87. Since the amount of cement used in the mixtures is constant, it was observed that the difference between the strengths is quite small and generally depends on the amount of fly ash. As a result of the data obtained within the scope of the study, it was determined that the compressive strength values increased by 4–7% with the increase in the amount of fly ash used in the mixtures. No significant change was observed in the flexural strength values of the mixtures. It was measured that the mixtures with the highest compressive strength values were those with 330 and 350 kg/m3 fly ash content. This situation is thought to be due to the physico-chemical properties of fly ash [61,62,63,64]. Fly ash, which has a physically finer structure than cement, fills the voids [65,66], makes the microstructure of the paste denser, and provides a tighter structure [67,68,69]. These positive effects reduce the permeability of concrete and increase its strength [70,71,72,73]. Also, chemically, fly ash has a pozzolanic reaction with Ca(OH)2 [74]. It was reported by various researchers that this reaction leads to the formation of more calcium silicate hydrate (C-S-H) gel, resulting in an increase in the advanced age strength of concrete [74,75].

4. Conclusions

Materials utilized in the investigation and the conducted experiments produced the following outcomes:
  • The optimum w/b ratio should be 0.35 in 3DPC, where extrudability, buildability, and shape stability requirements are met. DYS, VS, and structural build-up values were measured as 114–204 Pa, 22–43 Pa·s, and 0.61–1.49 Pa/s, respectively, in 3DPC mixtures where these criteria were met.
  • It was observed that extrudability and buildability criteria were negatively affected in mixtures with high s/b ratio (>1.50) and Dmax value (2 mm).
  • Fresh state requirements of 3DPC were positively affected by the utilization of F-type fly ash at the rate of 40% of the total binder weight.
  • It was observed that the buildability was positively affected due to the increase in the surface moisture of the printed layers with the increase in the use of WRA and fly ash. The surface roughness of the mixtures decreased significantly with the decrease in the aggregate maximum particle size from 2 mm to 1 mm.
  • It was determined that the compressive strength values of the mixtures increased by 4–7% with the increase in the amount of fly ash used.

Author Contributions

Conceptualization, H.G.Ş., A.M. and N.M.; methodology, H.G.Ş., A.M. and N.M.; software, H.G.Ş., A.M. and N.M.; validation, H.G.Ş., A.M. and N.M.; writing—original draft preparation, H.G.Ş., A.M. and N.M.; writing—review and editing, A.M.; supervision, A.M.; project administration, A.M. All authors have read and agreed to the published version of the manuscript.

Funding

The Bursa Uludag University Science and Technology Center was supported by Grant Number FAY-2021-579.

Data Availability Statement

The original contributions presented in the study are included in the article, further inquiries can be directed to the corresponding author.

Acknowledgments

TUBITAK 2211-A is acknowledged by the primary author.

Conflicts of Interest

The authors declare no conflict of interest.

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Figure 1. SEM images of (a) cement, (b) fly ash, and (c) aggregate.
Figure 1. SEM images of (a) cement, (b) fly ash, and (c) aggregate.
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Figure 2. Preparation of 3DPC mixtures.
Figure 2. Preparation of 3DPC mixtures.
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Figure 3. Workflow used in the study.
Figure 3. Workflow used in the study.
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Figure 4. Rheological measurement process.
Figure 4. Rheological measurement process.
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Figure 5. (a) rheometer and (b) sample mixture.
Figure 5. (a) rheometer and (b) sample mixture.
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Figure 6. Illustration of produced and tested sample.
Figure 6. Illustration of produced and tested sample.
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Figure 7. Mixtures for which the buildability parameter is not met because (a) dimensional suitability and consistency are not ensured and the five-layer structure cannot be printed, (b) it has a rough surface, and (c) settlement occurs.
Figure 7. Mixtures for which the buildability parameter is not met because (a) dimensional suitability and consistency are not ensured and the five-layer structure cannot be printed, (b) it has a rough surface, and (c) settlement occurs.
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Figure 8. Shear stress/VS–shear rate graphs of suitable mixtures.
Figure 8. Shear stress/VS–shear rate graphs of suitable mixtures.
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Figure 9. Compressive strength values of mixtures.
Figure 9. Compressive strength values of mixtures.
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Figure 10. Flexural strength values of mixtures.
Figure 10. Flexural strength values of mixtures.
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Table 1. Chemical composition, physical, and mechanical properties of binder materials.
Table 1. Chemical composition, physical, and mechanical properties of binder materials.
Oxides (%)CementFly Ash
SiO21858.79
Al2O34.7522.51
Fe2O33.587.89
CaO633.7
MgO1.42.18
Na2O + 0.658 K2O0.71.93
SO33.110.29
Spesific gravity3.062.35
Spesific surface area (cm2/g)34414000
Compressive Strength (MPa)7-Day42.8-
28-Day51.8-
Pozzolanic activity index (%)28-Day-77.7
90-Day-92.5
Setting Time (min)Initial170-
Final240-
Table 2. Some properties of the VMA and WRA.
Table 2. Some properties of the VMA and WRA.
Admixture TypeDensity (g/cm3)Solid Content (%)pHChloride
Content (%)		Alkaline
Content, Na2O (%)
VMA1.010-9–11<0.1<1
WRA1.060322–5<0.1<10
Table 3. Amount of materials used in the production of 1 m3 3DPC and its compliance with acceptance criteria.
Table 3. Amount of materials used in the production of 1 m3 3DPC and its compliance with acceptance criteria.
Mixture No.Cement (kg/m3)Fly Ash (kg/m3)AggregateWRA (kg/m3)VMA (kg/m3)w/bs/bPrint QualitySS (%)
Dmax (mm)Content
(kg/m3)		ExtrudabilityBuildability
150025021211330.321.61XXX
250025021191.7330.331.59XXX
350025021172.4330.341.56XXX
450025021153330.351.54XXX
550025021153.632.80.351.54XXX
650025021154.332.50.351.54XXX
750025021155.6320.351.54XXX
850025021156.931.50.351.54XXX
950025021157.431.30.351.54XXX
1050025021157.831.130.351.54XXX
1150025021156.63.51.130.351.54XXX
1250025021155.441.130.351.54XXX
1350025021154.24.51.130.351.54XXX
145002502115351.130.351.54XXX
1550025021151.75.51.130.351.54√XX
1650025021150.561.130.351.53√XX
1750025021149.36.51.130.351.53√XX
1850025021148.171.130.351.53√XX
1950025021149.87.5-0.351.53√XX
2050025021149.37.7-0.351.53√XX
21550250210627.7-0.351.33√XX
2255025021061.28-0.351.33√XX
2355025021060.78.2-0.351.33√XX
24550250210608.5-0.351.33√XX
2545030021134.68.5-0.351.51√XX
2645030021135.38.2-0.351.51√XX
2745030011135.38.2-0.351.51XXX
2845030011134.68.5-0.351.51√√100
2945030011134.18.7-0.351.51√√97.6
3045030011133.49-0.351.51√√95.2
3145033011074.68.5-0.351.38√√100
3245035011034.58.5-0.351.29√√97.6
Table 4. Rheological properties of mixtures.
Table 4. Rheological properties of mixtures.
Mixture No.Dynamic Yield Stress (Pa)VS (Pa·s)Athix (Pa/s)
28204.726.21.2
29114.2300.61
30160431.49
31144.922.51.1
32130300.95
Table 5. Relationship between shape stability and rheological properties of mixtures.
Table 5. Relationship between shape stability and rheological properties of mixtures.
MethodSS-DYSSS-VSSS-Athix
Multiple R0.33510.95230.2397
R Square0.11230.90680.0575
Adjusted R Square−0.18360.8758−0.2567
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Şahin, H.G.; Mardani, A.; Mardani, N. Performance Requirements and Optimum Mix Proportion of High-Volume Fly Ash 3D Printable Concrete. Buildings 2024, 14, 2069. https://doi.org/10.3390/buildings14072069

AMA Style

Şahin HG, Mardani A, Mardani N. Performance Requirements and Optimum Mix Proportion of High-Volume Fly Ash 3D Printable Concrete. Buildings. 2024; 14(7):2069. https://doi.org/10.3390/buildings14072069

Chicago/Turabian Style

Şahin, Hatice Gizem, Ali Mardani, and Naz Mardani. 2024. "Performance Requirements and Optimum Mix Proportion of High-Volume Fly Ash 3D Printable Concrete" Buildings 14, no. 7: 2069. https://doi.org/10.3390/buildings14072069

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