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Article

Performance of Environmentally Friendly Concrete Containing Fly-Ash and Waste Face Mask Fibers

by
Adnan Nawaz
1,
Ameer Murad Khan
2,
Amorntep Jirasakjamroonsri
3,
Panumas Saingam
4,
Ali Ejaz
5,
Qudeer Hussain
6,
Hisham Mohamad
7 and
Phromphat Thansirichaisree
2,*
1
Department of Civil Engineering, COMSATS University Islamabad, Wah Campus, Wah Cantt 47040, Pakistan
2
Thammasat Research Unit in Infrastructure Inspection and Monitoring, Repair and Strengthening (IIMRAS), Faculty of Engineering, Thammasat School of Engineering, Thammasat University Rangsit, Klong Luang, Pathumthani 12121, Thailand
3
Department of Sustainable Development Technology, Faculty of Science and Technology, Thammasat University, Klong Luang, Pathumthani 12121, Thailand
4
Department of Civil Engineering, School of Engineering, King Mongkut’s Institute of Technology Ladkrabang, Bangkok 10520, Thailand
5
National Institute of Transportation, National University of Sciences and Technology (NUST), Islamabad 44000, Pakistan
6
Civil Engineering Department, Kasem Bundit University, Minburi, Bangkok 10510, Thailand
7
Civil & Environmental Engineering Department, Universiti Teknologi, PETRONAS, Seri Iskandar 32610, Malaysia
*
Author to whom correspondence should be addressed.
Sustainability 2024, 16(23), 10385; https://doi.org/10.3390/su162310385
Submission received: 4 October 2024 / Revised: 13 November 2024 / Accepted: 22 November 2024 / Published: 27 November 2024
(This article belongs to the Special Issue Sustainable Approaches for Developing Concrete and Mortar)
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Abstract

:
This work was carried out to explore the potential use of used face masks in concrete to develop sustainable green concrete. In this experimental study, used face masks were cut up, removing the ear stripes and internal nose steel wire, to prepare elongated fibers. These fibers were incorporated in cement fly ash mixtures as an additive to determine the response of M20-grade concrete. The Class F fly ash (FA) was employed as a fractional substitute of cement up to 25% by weight, whereas the addition of face masks occurred at 0%, 0.125%, and 0.25% by volume of concrete. The testing scheme focused on the mechanical and durability characteristics of the cement FA mixtures carried out after 3, 28, and 60 days of curing. The inclusion of FA and face mask fibers reduced the density of concrete specimens. The compressive, splitting tensile, and flexural strengths of mixes were also reduced at an early age; however, the strength characteristics improved at later ages, compared to the control mix. The combination of both materials in concrete mixtures resulted in lower water absorption, lower bulk water sorption, and lower mass loss values against acid attack at later ages. Similarly, the electrical resistance of concrete substantially enhanced by increasing the percentage of both materials. The experimental results demonstrated that processed face masks can be utilized in cement fly ash mixes without significantly compromising the resultant concrete characteristics.

1. Introduction

Subsequent to the advent of the COVID-19 virus, plastic-related equipment and items have been remarkably increased, mainly due to the need for disposable personal protective equipment (PPE), packaging, and single-use medical items to mitigate virus transmission. Face masks have been extensively used during the pandemic to control the virus’s spread. Several countries enforced compulsory wearing of face masks in public locations during the COVID-19 virus, leading to widespread adoption of this practice in the daily life of people even in the post-pandemic era. The excessive use of disposable single-use face masks led to an upsurge in plastic waste production throughout the globe, threatening wildlife, terrestrial ecosystems, and marine ecosystems, consequently polluting the environment [1,2,3]. Hence, the possible methods and techniques to reuse face masks have been of interest to reduce the adverse environmental impacts.
Integrating face masks (FMs) in concrete can provide a green solution to this issue, considering concrete is the most extensively produced building substance globally with steadily increasing demand in the building sector over time. Further, single-use face masks essentially consist of polypropylene [4], and incorporating polypropylene fibers (PF) in concrete can enhance some of its properties [5,6,7,8]. Sun and Zu [9] studied the physical and mechanical characteristics of PF-reinforced concrete, determining that integrating PF in concrete modifies the concrete microstructure by forming a network of PF, consequently reducing micro-voids and micro-cracking and enhancing mechanical and durability performance. Haq et al. [10] investigated the mechanical and durability performance of concrete mixtures by adding supplementary cementitious materials (SCMs) and PF, observing that up to 0.5% PF content improved the compressive, tensile, and flexural strengths. Afridi et al. [11] showed a substantial enhancement in the ductility of mortar specimens containing up to 1% PF without compromising the strength characteristics. Karahan and Atis [12] and Fallah and Nematzadeh [13] also indicated improved mechanical and durability performance of concrete mixes integrating PF and SCMs.
Although several research works have investigated the utilization of PF in concrete, very few works have examined the impact of integrating single-use FM fibers in cement mixtures. Win et al. [14] reported that integrating 0.15% FM fibers in mortar can increase the flexural and tensile strength of the cement mixes. Kilmartin-Lynch et al. [15] observed improved compressive and indirect tensile properties due to the incorporation of 0.2% shredded single-use FM fibers. Avudaiappan et al. [16] determined that the compressive, flexural, and tensile strengths improved when up to 1% of the shredded FM fibers were incorporated in a mortar. Ahmed et al. [17] also experienced enhanced mechanical properties of FM-fiber-incorporated concrete mixtures at an optimal dosage of 2% PF. Koniorczyk et al. [18] integrated recycled FM fibers in concrete mixtures and indicated that though the tensile strength decreased slightly, the compressive strength of the test mixtures exhibited a 5% improvement. Wang et al. [19] produced fiber-reinforced recycled aggregate concrete by introducing FM fibers in concrete mixes and observed improved properties of concrete. Miah et al. [20] added FM fibers in mortar mixes and experienced increased voids along with reduced compressive strength and rate of water absorption. Previous studies have shown that these fibers, steel slags, steel clamps, bentonites and slaked lime help control cracking, increase ductility, and enhance the overall performance of concrete [21,22,23]. The investigation of the FM fibers and their impact on the characteristics of concrete is still in the preliminary phase. Though some works have been performed on the inclusion of FM fibers in mortars and conventional concrete mixtures, the integration of FM fibers in concrete mixes containing SCMs is yet to be investigated. The utilization of SCMs like fly ash (FA), ground granulated blast furnace slag, silica fume, etc., in concrete provides some beneficial alternatives to partially replace ordinary Portland cement (OPC) in concrete mixtures [24,25]. SCMs enhance the concrete’s resistance to aggressive chemicals, such as sulfates and chlorides, improving longevity. Using SCMs can lower the heat of hydration in concrete, which is beneficial in mass concrete applications where thermal cracking can be a concern. The presence of SCMs can alter the phase assemblage ferroaluminate cement. Therefore, the current study was conducted to explore the effect of FM fibers on the mechanical and durability properties of concrete with or without FA as a fractional cement alternative. The mechanical and durability performance of the resulting concrete mixes, comprising dry density; compressive, splitting tensile, and flexural strengths; water absorption; bulk water sorptivity; resistivity against acid attack; and bulk electrical resistivity were examined. The research hypothesis for this study could be state as described as follows: (1) incorporation of processed used face masks as an additive in cement fly ash mixtures will improve the mechanical and durability characteristics of concrete compared to conventional concrete without face mask fibers, and (2) the compressive, splitting tensile, and flexural strengths of the concrete mixtures will show significant improvement at ages.

2. Materials and Methods

2.1. Materials

Ordinary Portland cement (OPC Type 1) and Class F FA were utilized as binders in this study. The specific gravity of OPC and FA turned out to be 3.15 and 2.34, respectively. Unused FMs were used in this study for the reasons of cleanliness and safety. Initially, the metal strips and ear traps were detached from the face masks (Figure 1a). Afterwards, the masks were manually sliced into thinner pieces or fibers (10 mm × 20 mm) as shown in Figure 1b. Natural fine aggregate (sand) was procured from Lawrencepur, Attock, Pakistan. The bulk specific gravity and fineness modulus of sand were 2.71 and 2.34, respectively. The maximum size of coarse aggregates was limited to 19 mm. The specific gravity and water absorption of coarse aggregates were 2.65 and 0.61%, respectively. Locally available coarse aggregates were utilized. Tap water accessible in the laboratory was utilized for mix preparation and curing of samples.

2.2. Mix Design, Composition, and Preparation

In this work, the response surface method (RSM) was employed to enhance the process of mix design. RSM is an efficient approach for the optimization of complex problems by developing statistical relations between the input variables and output responses. In this process, experiments are designed systematically for different combinations and the responses are gathered by performing the experimental work. Ultimately, models are developed for each response that can be used for predicting the response. The most widely used method of RSM for the above procedure is central composite design (CCD) [26]. The data points are selected such that the space of input variables contains the low and high levels. Ten concrete mixtures were produced based on the CCD of the RSM using commercially available software Design Expert 11 [27]. The mixes included a control mixture in addition to mixtures containing face masks and FA in varying quantities. Table 1 displays the two factors (independent variables) studied in this study, i.e., FA (0–25%) and face masks (0–0.25%), and their corresponding codes and levels. Although in previous studies the face mask fibers and FA were used with different replacement ratios. In this study, the specific percentages of FA and face masks were selected on trial basis. After 28 days of curing, the control mix was intended to exhibit a compressive strength of 20 MPa. Water-to-cement ratio (w/c) of 0.50 remained constant in the preparation of all mixes. FA was employed as a fractional substitute of cement in the mixes, with percentages ranging from 0% to 25% by mass. The face mask fibers were incorporated at a rate of 0.125 and 0.25 percent by volume of concrete. Table 2 shows the design of all the mixes where the letters “C” and “F” denote cement and FA, respectively, each followed by its percentage as binder, and the letter “M” denotes face mask followed by the numeric indicating its percentage incorporated in the mix. For instance, the control mix was represented by “C100F0M0”, illustrating that 100% cement was used as a binder with no FA and face mask content. To prepare concrete mixes, initially, the coarse and fine aggregates were included to a pan mix for dry mixing of one minute. Then, cement, FA, and face mask fibers were introduced to the mixture and dry mixed for one more minute. Lastly, the mixing water was gradually mixed with the mixer and blended for 2–3 min to guarantee a mix of uniform workability.

2.3. Samples Casting and Curing

The procedure followed for molding and curing all the samples was according to ASTM C192/C192M [28]. A pan mixer was used for mixing and preparing samples of different mixes. Molds were cleaned and oiled before casting the samples. Cylindrical samples of 100 × 200 mm and beam prisms of 100 × 100 × 500 mm were fabricated as per the standard specifications and then taken out of the molds after 24 h for water curing. After 3, 28, and 60 days of curing, different tests were performed on the samples. The curing period was extended to 60 days to observe the behavior of Class F FA mixtures, as they are pozzolans and contribute to strength more at later ages [29,30,31].

2.4. Testing Methods

The different tests conducted on the concrete samples are given in Table 3 along with the specimen’s shape, size, and age of testing. The dry density of the mixtures was noted at the age of 60 days in accordance with ASTM C642 [32] employing cylindrical samples of 100 × 200 mm. The compressive strength test was performed as per ASTM C39 [33] utilizing a universal testing machine of 1000 kN capacity. Cylindrical samples of 100 × 200 mm were used for compressive strength determination after 3, 28, and 60 days of curing. The samples were tested at a rate of 0.20 MPa/s up to failure. The splitting tensile strength test was conducted as per ASTM C496 [34] on cylinder samples of size 100 × 200 mm at 3, 28, and 60 days. The samples were tested at a rate of 0.25 MPa/s. The flexural strength test was conducted following ASTM C293 [35]. A central point loading at a rate of 0.9 to 1.2 MPa/min was applied to the beam samples of 100 × 100 × 500 mm. The water absorption test was conducted on 100 × 200 mm cylindrical specimens as per ASTM C642 [32], whereas the cylindrical disk specimens of 100 × 50 mm were employed to determine the bulk water sorption following the ASTM C1757 [36] specifications. The resistance of concrete to acids, an important durability characteristic, was found in terms of the mass loss and residual compressive strength of 100 × 200 mm cylindrical specimens as per ASTM C267 [37]. For acid resistance measurement, 5% of dilute sulphuric acid (H2SO4) by volume of the water, having a pH number of approximately 2, was utilized. The specimens were dipped in sulphuric acid solution for 28 days. The mass loss (%) of the specimens was determined after 3, 7, 14, and 28 days, whereas the residual compressive strength of the samples was found after 28 days. The bulk electrical resistance of a hardened concrete sample in saturated condition indicates the resistivity of concrete to aggressive ions penetration. The electrical resistivity of the tested concrete specimens was determined according to ASTM C1760 [38] employing cylindrical specimens of 100 × 200 mm. For each test, three samples were tested following particular ASTM standards, and the average results were reported in this study.

3. Experimental Findings

3.1. Dry Density

The dry density of the hardened concrete samples was calculated after samples were cured for 60 days, and the average results are shown in Figure 2 and Figure 3. It may be noted that the dry density of concrete slightly lowered with the FM and FA incorporation. The dry density of the concrete produced by utilizing either of these materials exhibited a decreasing trend as the quantity of these materials enhanced in the mixture. The control mix (C100F0M0) showed the maximum dry density of 2448 kg/m3 whereas, in contrast, the mix C75F25M25 demonstrated the lowest dry density of 2358 kg/m3, around 3.6% lower than the control concrete. The lowering in dry density can be ascribed to the lower specific gravity of the incorporated materials related to OPC. Similar results of reduced dry density of concrete with the addition of polypropylene fibers and FA were reported in the previous studies [12,39].

3.2. Compressive Strength

Figure 4 demonstrates the compressive strength results of the concrete mixtures at various curing ages. Figure 5 presents the relative percentage average compressive strength of mixtures after 3, 28, and 60 days, whereas a 3D response surface diagram of compressive strength is illustrated in Figure 6. At the age of 3 days, the control mix (C100F0M0) exhibited the highest strength, and a reduction in compressive strength was noted for both FA and face mask fibers mixtures. A slight strength reduction (0.8%) was noticed due to the incorporation of 0.125% face mask fibers (C100F0M12.5) compared to the control mix, which further reduced for 0.25% addition (C100F0M25). The reduction in strength at 3 days was more prominent for the FA mixtures related to the control mix.
After 28 days, all mixtures exhibited a consistent pattern of reduced compressive strength values analogous to that observed at 3 days, despite the rate of decrease in strength was decreased related to the control mixture. These results were observed to be consistent with past research studies [12,40,41,42,43,44,45], where the compressive strength at 28 days decreased owing to the inclusion of FA and polypropylene fibers. The reduction in the compressive strength owing to the higher percentage of face mask fibers in the mix could be credited to the voids in the microstructure due to fibers inclusion causing weaker interfacial connection among the fiber and cement–FA grains [40]. In the case of FA mixtures, the reduced strength can be ascribed to the incorporation of F FA, a pozzolanic material, which generally requires more time to interact with the calcium hydroxide obtained during the hydration reaction to produce secondary cementitious products [31,46,47,48].
At later ages of 60 days, the mix containing FA only and the 0.125% FM fibers mix exhibited improved strength compared to the control mix, with compressive strength higher by 6.4% (C100F0M12.5), 21.7% (C87.5F12.5M0), and 3.8% (C75F25M0). The enhancement in compressive strength caused by FA at a later time is ascribed to the prolonged pozzolanic resistance of FA with calcium hydroxide emitted from the hydration reaction in concrete [31,48,49,50,51]. The reaction of carbon dioxide with calcium hydroxide can lead to the formation of calcium carbonate, which may contribute to the long-term strength and durability of concrete. The improvements in concrete after 60 days are primarily driven by continued hydration and microstructural changes, along with potential reactions involving relevant materials and environmental factors. Moreover, the compressive strengths of the other mixtures were lower than those of the control which may be ascribed to the higher quantity of face mask fibers in the mixture creating more voids in the microstructure due to fibers and subsequently causing weaker bonds [40].

3.3. Splitting Tensile Strength

The findings of the average splitting tensile strength test of concrete mixtures at curing ages of 3, 28, and 60 days are shown in Figure 7 and Figure 8, whereas the 3D response surface diagram of splitting tensile strength is illustrated in Figure 9. After 3 days of curing, it may be noted that analogous to the compressive strength results, the splitting tensile strength reduced with the inclusion of FM fibers and FA related to the control similar to the compressive strength results. After 28 days of curing, the splitting tensile strength of the mixes decreased relative to the control mix, except the mix C75F25M0 containing 25% FA without FM, which demonstrated an 18% enhancement in splitting tensile strength. At 60 days, an analogous behavior of reduction in splitting tensile strength was observed for all of the mixes in relation to the control, except for the FA mixes C87.5F12.5M0 and C75F25M0, which exhibited higher tensile strength compared to the control. As discussed earlier, FA is a pozzolan, and it reacts at later ages with cement to produce the secondary C-S-H gel that enhances the microstructure and results in higher strength [31,48,49,50,51]. The results of blended mixes (i.e., containing both FA and FM) at 60 days demonstrated that mix C75F25M25 showed higher splitting tensile strength than other blended mixes. This enhancement in splitting tensile strength could be ascribed to the resistance the fibers in concrete mixes provide against the opening and progression of early cracks, as indicated in previous studies [52,53,54,55].

3.4. Flexural Strength

The average flexural strength findings of mixtures at 28 and 60 days are reported in Figure 10 and Figure 11, whereas the 3D response surface diagram of flexural strength is illustrated in Figure 12. It may be noted that the addition of FM fibers and FA decreased the flexural strength after a 28-day curing. The control mixture exhibited the highest flexural strength of 4.78 MPa at 28 days compared to other mixes. FM fiber mixes C100F0M12.5 and C100F0M25 experienced reduced flexural strengths, i.e., 23% and 45% lower than the control mix, respectively. Similarly, at 28 days, the FA mixes C87.5F12.5M0 and C75F25M0 demonstrated decreased flexural strength (37% and 31.8%), respectively, when related to the control mix. Furthermore, the flexural strength values of the blended mixes were lower than the control.
At 60 days, the FA mix C75F25M0 showed 14% greater flexural strength related to the control mix, while all the other mixes depicted lower flexural strength, though the rate of decrease in strength reduced. In blended mixes, the mix C87.5F12.5M12.5 exhibited the highest flexural strength which was close to the control mix. As discussed earlier, the enhancement in the flexural strength at a later age of 60 days can be credited to the contribution of F FA in producing SCMs, owing to the pozzolanic reaction that results in denser microstructure and subsequently improved mechanical properties [48,49,50,51]. The ultimate failure modes of specimens are shown in Figure 13.

3.5. Water Absorption

Figure 14 and Figure 15 depict the average water absorption test results after 60 days. It can be noticed that introducing FM fibers into the concrete caused higher water absorption when related to the control mixture, which was similar to the previous research [56,57,58]. When contrasted to the control mixture, the mix C87.5F12.5M0 containing 12.5% FA without FM fibers exhibited somewhat greater water absorption. The water-absorption potential reduced when more FA was added to the mix as in C75F25M0, but this impact was reversed when a high percentage of FMs was added compared to the control. When FA and FM fibers were included simultaneously to the mix at the proportions of 25% and 0.125%, respectively, there was a slight reduction in the water absorption compared to the control mix, i.e., 7.88% lower than the control mix. The increase in water absorption owing to the incorporation of fibers has been reported in the previous studies that can be ascribed to greater void volume created owing to the incorporation of fibers in concrete mixes [56,57,58].

3.6. Bulk Water Sorption

The results of average bulk water sorption measured at 60 days are displayed in Figure 16 and Figure 17. The control mix exhibited a bulk sorption of 0.44 mm. Increased water sorption was observed with the incorporation of FM fibers, which was correlated to the quantity of FM fibers mixed in the mixture, similar to findings of previous research [59], suggesting a more permeable pore micro-structure. The bulk water sorption demonstrated a decreasing trend after the incorporation of FA in the mix. The mix C75F25M0 with 25% FA and 0% FM fibers experienced the lowest water sorption related to other mixtures. In the case of blended mixes incorporating both FA and FM, the water sorption of the mix C87.5FA12.5FM12.5 was almost analogous to that of the control mix. As discussed earlier, the increased water sorption can be ascribed to the higher pore volume created by the fibers [59,60,61], whereas the reduced water sorption values can be credited to the denser microstructure developed due to the fabrication of SCMs, owing to the pozzolanic reaction of FA [48,49,50,51].

3.7. Resistant to Acid Attach

The average mass loss values of the concrete mixes owing to the acidic solution are displayed in Figure 18, Figure 19 and Figure 20. It may be noted that the mass loss of mixtures enhanced by increasing the exposure duration to the acid solution. The mass loss of the control mixture was greater than the mixture containing FM fibers and FA. The mass loss decreased when the FM fibers and FA were incorporated into the mixes at all ages. The combined mix, C75F25M25, which contains 25% FA and 0.25% FM, exhibited the lowest mass loss at all ages. This smaller mass loss can be ascribed to the refined microstructure due to FA secondary C-S-H gel formation that resisted the entry of acid solution into the concrete, thus resulting in lower deterioration [48,49,50,51]. The residual compressive strength findings of the samples after a 28-day exposure period to the acid solution are presented in Figure 18.

3.8. Bulk Eelectrical Resistivity

The average relative bulk electrical resistance of the mixes determined after curing for 60 days is presented in Figure 21 and Figure 22. It may be noted that improving the FA and FM fibers content resulted in higher electrical resistivity related to the control mix. The impact of incorporating FM fibers appeared to be more profound than that of FA, as the electrical resistivity of mixes with only FM fibers was greater than that of the FA-only mixes. The maximum electrical resistance value was observed for the mix C75F25M25, which was 56% greater than the control mixture. This increase in electrical resistivity may be ascribed to the reduced cracking and discontinuity in the cement paste mixture due to the inclusion of fibers, as indicated in the previous studies [62,63]. The addition of face mask fibers significantly alters the fiber–matrix interaction in concrete, providing multiple benefits that enhance durability. By improving load distribution, minimizing crack propagation, and increasing resistivity, these fibers contribute to the overall performance and longevity of concrete structures. Researchers often consider the electrical resistance of concrete as a means to determine the durability of concrete mixtures, and it has been established in the previous literature that higher electrical resistivity can lead to better durability characteristics [64,65,66,67,68].

3.9. Microstructural Study of Hardened Concrete

The microstructure of the selected concrete samples was examined utilizing the scanning electron microscopy (SEM) method. Based on the optimum strength results, the control mix (C100F0M0) and the FA mixtures (C87.5F12.5M0 and C75F25M0) were selected for the microstructure investigation. The SEM images of the tested specimens at 60 days of curing are illustrated in Figure 23, Figure 24 and Figure 25. The control mix SEM image (Figure 23) exhibits the presence of micro cracks and voids that may lead to lower strength values and compromised durability properties. The SEM images of FA mixes (Figure 23, Figure 24 and Figure 25) demonstrated a denser microstructure with fewer void spaces that can subsequently lead to improved mechanical and durability characteristics [48,49,50,51].

4. Conclusions

This work evaluated the experimental data to examine the impact of FA and face mask fibers incorporation on the mechanical and durability characteristics of concrete mixes. It may be summarized based on the findings of this study.
  • The dry density of the concrete mixes was lowered owing to the incorporation of FA and FM fibers.
  • At 3 and 28 days, the compression strength decreased for FA and FM fiber mixes. However, at the later age of 60 days, the compressive strength exhibited enhancements for the mixes containing 0.125% FM fibers as well as for mixes incorporating up to 25% FA.
  • FA and FM fibers exhibited lower splitting tensile and flexural strength at 3 and 28 days compared to the control mixture, which tend to improve at a later age of 60 days.
  • The enhancement in FM fiber content leads to higher water absorption and bulk water sorption, whereas these values tend to decrease in the case of FA incorporation.
  • The addition of FM fibers and FA to the concrete mixes reduced the mass loss when compared to the control mix.
  • The electrical resistivity of concrete mixes increased with the FM fibers incorporation when related to the control mix.

Author Contributions

Conceptualization, A.N., A.M.K., A.J., P.S., A.E., Q.H., H.M. and P.T.; methodology, A.N., A.M.K., A.J., P.S., A.E., Q.H., H.M. and P.T.; investigation, A.N., A.M.K., A.J., P.S., A.E., Q.H., H.M. and P.T.; writing—original draft preparation, A.N., A.M.K., A.J., P.S., A.E., Q.H., H.M. and P.T.; writing—review and editing, A.N., A.M.K., A.J., P.S., A.E., Q.H., H.M. and P.T. All authors have read and agreed to the published version of the manuscript.

Funding

This research project was supported by the Thailand Science Research and Innovation Fundamental Fund Fiscal Year 2024, Thammasat University, Thailand.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Data are contained within the article.

Acknowledgments

This research project was supported by the Thailand Science Research and Innovation Fundamental Fund Fiscal Year 2024, Thammasat University. Thanks are extended to COMSATS University Islamabad Pakistan for supporting partial test facilities.

Conflicts of Interest

The authors declare no conflicts of interest.

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Figure 1. (a) Face masks and (b) face mask fibers.
Figure 1. (a) Face masks and (b) face mask fibers.
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Figure 2. Dry density of concrete mixtures after 60 days.
Figure 2. Dry density of concrete mixtures after 60 days.
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Figure 3. Three-dimensional surface diagram of dry density of concrete mixes after 60 days.
Figure 3. Three-dimensional surface diagram of dry density of concrete mixes after 60 days.
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Figure 4. Compressive strength results of mixes at different times.
Figure 4. Compressive strength results of mixes at different times.
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Figure 5. Relative compressive strength of mixtures.
Figure 5. Relative compressive strength of mixtures.
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Figure 6. Three-dimensional response surface diagram of compressive strength at 28 days.
Figure 6. Three-dimensional response surface diagram of compressive strength at 28 days.
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Figure 7. Splitting tensile strength findings of mixtures at different times.
Figure 7. Splitting tensile strength findings of mixtures at different times.
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Figure 8. Relative splitting tensile strength of mixtures.
Figure 8. Relative splitting tensile strength of mixtures.
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Figure 9. Three-dimensional response surface diagram of splitting tensile strength at 28 days.
Figure 9. Three-dimensional response surface diagram of splitting tensile strength at 28 days.
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Figure 10. Flexural strength results of mixes at different ages.
Figure 10. Flexural strength results of mixes at different ages.
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Figure 11. Relative flexural strength of mixes.
Figure 11. Relative flexural strength of mixes.
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Figure 12. Three-dimensional response surface diagram of flexural strength at 28 days.
Figure 12. Three-dimensional response surface diagram of flexural strength at 28 days.
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Figure 13. Ultimate failure modes (a) compression, (b) flexure, and (c) splitting.
Figure 13. Ultimate failure modes (a) compression, (b) flexure, and (c) splitting.
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Figure 14. Water absorption results of mixes at 60 days.
Figure 14. Water absorption results of mixes at 60 days.
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Figure 15. Three-dimensional response surface diagram of water absorption of mixes.
Figure 15. Three-dimensional response surface diagram of water absorption of mixes.
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Figure 16. Variation in bulk water sorption of mixes.
Figure 16. Variation in bulk water sorption of mixes.
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Figure 17. Three-dimensional response surface diagram of bulk sorption of mixes.
Figure 17. Three-dimensional response surface diagram of bulk sorption of mixes.
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Figure 18. Mass loss results of mixes due to acid attack.
Figure 18. Mass loss results of mixes due to acid attack.
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Figure 19. Three-dimensional response surface diagram of mass loss of mixes at 28 days.
Figure 19. Three-dimensional response surface diagram of mass loss of mixes at 28 days.
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Figure 20. Residual compressive strength of tested specimens after acid attack.
Figure 20. Residual compressive strength of tested specimens after acid attack.
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Figure 21. Electrical resistivity results of concrete mixes at 60 days.
Figure 21. Electrical resistivity results of concrete mixes at 60 days.
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Figure 22. Three-dimensional response surface illustration of electrical resistivity of mixes at 60 days.
Figure 22. Three-dimensional response surface illustration of electrical resistivity of mixes at 60 days.
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Figure 23. SEM results of control concrete (C100F0M0).
Figure 23. SEM results of control concrete (C100F0M0).
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Figure 24. SEM results of FA concrete sample (C87.5F12.5M0).
Figure 24. SEM results of FA concrete sample (C87.5F12.5M0).
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Figure 25. SEM results of FA concrete (C75F25M0).
Figure 25. SEM results of FA concrete (C75F25M0).
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Table 1. Levels of independent variables in RSM.
Table 1. Levels of independent variables in RSM.
FactorCodeLevels (%)
Low (−1)MeanHigh (+1)
Face mask (FM)X100.1250.25
Fly ash X2012.525
Table 2. Mix composition (kg/m3).
Table 2. Mix composition (kg/m3).
Mix No.Mix CodeCement
(kg)		Fly Ash
(kg)		Sand
(kg)		Coarse Aggregates
(kg)		Water
(kg)		Face Masks
(% by Concrete Volume)
1C100F0M0400060012002000
2C100F0M12.5400060012002000.125
3C100F0M25400060012002000.25
4C87.5F12.5M03505060012002000
5C87.5F12.5M12.53505060012002000.125
6C87.5F12.5M12.53505060012002000.125
7C87.5F12.5M253505060012002000.25
8C75F25M030010060012002000
9C75F25M12.530010060012002000.125
10C75F25M2530010060012002000.25
Table 3. Tests conducted with respective standards, sample size, and age of testing.
Table 3. Tests conducted with respective standards, sample size, and age of testing.
TestASTM StandardSample ShapeSample Dimensions (mm)Test Age (Days)
Density of hardened concreteASTM C642 [32]Cylinder 100 × 20060
Compressive strength testASTM C39/C39 [33]Cylinder100 × 200 3, 28, 60
Splitting tensile strength testASTM C496 [34]Cylinder100 × 200 3, 28, 60
Flexural strength testASTM C293 [35]Prism beam100 × 100 × 50028, 60
Water absorption testASTM C642 [32]Cylinder100 × 20060
Bulk water sorption testASTM C1757 [36]Cylindrical disk100 × 5060
Acid resistance testASTM C267 [37]Cylinder100 × 2003, 7, 14, 28
Bulk electrical resistivityASTM C1760 [38]Cylinder100 × 20060
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MDPI and ACS Style

Nawaz, A.; Khan, A.M.; Jirasakjamroonsri, A.; Saingam, P.; Ejaz, A.; Hussain, Q.; Mohamad, H.; Thansirichaisree, P. Performance of Environmentally Friendly Concrete Containing Fly-Ash and Waste Face Mask Fibers. Sustainability 2024, 16, 10385. https://doi.org/10.3390/su162310385

AMA Style

Nawaz A, Khan AM, Jirasakjamroonsri A, Saingam P, Ejaz A, Hussain Q, Mohamad H, Thansirichaisree P. Performance of Environmentally Friendly Concrete Containing Fly-Ash and Waste Face Mask Fibers. Sustainability. 2024; 16(23):10385. https://doi.org/10.3390/su162310385

Chicago/Turabian Style

Nawaz, Adnan, Ameer Murad Khan, Amorntep Jirasakjamroonsri, Panumas Saingam, Ali Ejaz, Qudeer Hussain, Hisham Mohamad, and Phromphat Thansirichaisree. 2024. "Performance of Environmentally Friendly Concrete Containing Fly-Ash and Waste Face Mask Fibers" Sustainability 16, no. 23: 10385. https://doi.org/10.3390/su162310385

APA Style

Nawaz, A., Khan, A. M., Jirasakjamroonsri, A., Saingam, P., Ejaz, A., Hussain, Q., Mohamad, H., & Thansirichaisree, P. (2024). Performance of Environmentally Friendly Concrete Containing Fly-Ash and Waste Face Mask Fibers. Sustainability, 16(23), 10385. https://doi.org/10.3390/su162310385

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