Introduction

In September 2015, world leaders adopted 17 Social Development Goals (SDGs) of the 2030 Agenda for Sustainable Development; these goals aimed to enhance the world and call out action to save our planet [1]. Many SDGs are linked and effectively influencing our topic; however, the main focus stands on goals 6, 9, 11, and 12; Clean water and sanitation, industry, innovation, infrastructure, sustainable cities, and communities. Since the targeted problem in our research and the MENA region is reducing water scarcity; a continuously growing issue, especially in recent years, thus, new techniques are required to tackle the issues aligning with the long-term vision in the construction industry and sustainability for concrete production [1].

Water scarcity is a global issue that is evolving and prevalent as water demand is rising due to growing populations. On the other hand, resources like rivers and groundwater are depleting due to climate change, over-exploitation, and pollution. Thus, there is a need to reduce the water quantity used in the construction industry without compromising on the quality. United Nations [2] reports that despite the precautionary measures taken by governments toward saving water resources and the tremendously increasing population, the crisis would be rising and more than 1.6 billion people lack safely managed drinking water for health and living. MENA region is one of the world’s highest-density population regions where more than 600 million people live in an area of less than 15 million square kilometers, which is considered a high-water stress area. According to Aamer [3], “the annual average water availability per person in this region stands at only 1200 m3, almost six times less than the global average of 7000 m3.” Egypt’s water status, for instance, would suffer from a water crisis after the Egyptian–Ethiopian conflict arose against the El Nahda dam and their share of water.

Recently, the use of treated wastewater (TW) in concrete has become of good alternative and has high potential environmental benefits [4]. However, little is known about the possible long-term effects of using TW in concrete. Asadollahfardi and Mahdavi [4] investigated the feasibility of using treated industrial wastewater to produce concrete and mortar. Their investigation encountered cement type II, which showed a delay in final setting time by 17 min. They recommended from their reported results that this would be usefully used in case of hot weather. Nevertheless, the compressive strength values for the cube specimen to a similar mix revealed slightly less than 95% of the control specimen. Ghrair et al. [5] reported that using graywater slightly affected the physical and mechanical properties of mortar while using cement type II in the mix. The initial setting time increased significantly; however, the negative impact on compressive strength could be negligible since it was up to 10%. Furthermore, their results revealed that no effect on the mortar soundness. Upon their investigation, it was recommended that using treated and non-treated graywater is a high-potential alternative in concrete and mortar production. Sandrolini and Franzoni [6] suggested the usage of non-treated waste wash water from ready-mixed concrete plants; despite the high solid content which might be within the upper limit as specified by ASTM C94 [7]. Moreover, the 28-day compressive strength results reported values just less than 4% lower than those of control with potable water. The authors quoted that “poor confidence of users in concrete containing waste wash water does not seem well-grounded.”

Taha et al. [8] used production and brackish water collected from 8 different treatment plants in Oman to investigate their influence on concrete and mortar. Taha et al. [8] found out that compressive strength would have the usual strength development as those produced using potable water after one year and a half of curing. Moreover, some of these results exceed the values of compressive strength from cube specimens with tap water. Abushanab and Alnahhal [9] examined the combined effect of treated domestic wastewater, fly ash, and calcium nitride on concrete mixture and mortar; only cement type I was used in this research. The results revealed that the initial and final setting time increased by around 21% and 29%, respectively, when using treated wastewater. It was also recorded that treated domestic wastewater had a positive effect on the compressive strength of mortar at the age of 28 days and the enhancement ranged between 2% and 6%. Al-Joulani [10] confirmed similar results when studying the effect of wastewater type on the properties of concrete and mortar. The results showed an increase in compressive strength after 7 days of curing while using stone slurry water with 5% and 10% salty water showed negligible effect on the compressive strength of the cube specimens. Nevertheless, when using tanning water and 5% oily water, results have shown a slight negative change when using 10% oily water and treated wastewater. All types of water were confronted with ASTM C94 [7]. Al-Joulani [10] suggested that the classification of wastewater should be performed based on the chemical composition analysis and precautions should be added for each class differently.

El-Nawawy and Ahmad [11], one of the oldest and pioneering researchers, explored the effect of treated wastewater in concrete mixing. The research focused on the potential effect of the arid climate in Qatar on water replacement in the concrete mixture. The mechanical properties results were revealed in harmony with the aforementioned literature. Reddy et al. [12] used CEM I and treated wastewater collected from 4 different plants in India to explore the feasibility of using wastewater in cement. The results showed variance in initial setting time ranging between + 15 and −22 min compared to distilled water, while final setting times ranged between + 73 and −2 min. This variance can be explained by the difference in the chemical composition of raw wastewater provided by the 4 plants. The authors found that the compressive and flexural strengths within the permissible limits mentioned by BS: 3148 [13]. Furthermore, the X-ray diffraction (XRD) analysis was carried out and showed that new compounds further than neutrally formed compounds in hydrated cement exist. These compounds were CaCO3 and CaCl3. Thus, the presence of bicarbonates and chlorides present in the treated wastewater was the justification for these compounds.

Zahra Bouaich et al. [14] focused also on the feasibility of using treated wastewater in mortar mixtures. Their results showed a slight increase in initial setting time and a minor impact on mortar fresh density. The results also found that CEM III has a high success probability in terms of compressive strength and specific initial and final setting time when used to produce mortar using treated wastewater. They reported that the bending stress was slightly increased in specimens made using treated wastewater. The authors performed also non-destructive testing (NDT) to measure the dynamic elastic modulus with different cement types using treated wastewater. The values of NDT testing recorded a slight increase to those in the control specimens. The research did not stop on evaluating the NDT testing, mechanical and physical properties but also a microstructural analysis was carried out through scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential thermogravimetric analysis (DTA) to analyze hardened mortar made using treated wastewater. According to the findings, it was concluded that mortar produced using treated wastewater is considered durable, acceptable, and surprising results in terms of physical and mechanical properties compared to mortar performed using distilled water.

To sum up, many researchers suggested and highly recommended setting up codes and limitations to legalize the use of different types of treated wastewater in mixing mortar and concrete [5, 10]. It was found that the setting time of cement was affected when using treated wastewater and increased significantly but with compliance with different codes and limitations [4, 5, 9, 13]. There are also many calls to investigate the possible corrosive effect of treated water by conclusive and non-questionable methods [8, 9]. It is also important to mention that many researchers [6, 9] referenced their compressive strength results to ASTM C94 [7] and their results acceptably satisfied the standard. It is important to note that many of the mentioned researchers [4, 6, 8, 9, 11, 12, 14] used special types of wastewater and different types of cement such as I, II, and III. Most suggested that CEM III had better results than other types when using treated wastewater.

Research significance

This research is considered a part of a project that the construction-scientific community has to minimize the tremendous usage of drinkable water in the industry for the sake of saving the globe from negative influence. The research aims to explore the influence of different types of cement and different sources of treated domestic wastewater on the setting time of different cement pastes and mortar mechanical properties. Using treated wastewater from different sources may show whether the input for the treatment has an effect on the effluent and consequently affects the properties of cement paste and mortar. Furthermore, tackling the different cement types in the market and experimenting with the suitable cement type may influence the properties of cement paste and mortar when using treated domestic wastewater from different sources.

Experimental program

This study is part of an experimental research program that aims to tackle the effects of replacing potable water with treated domestic wastewater in cementitious products. The part presented in this paper focuses on testing cement paste and mortar made using different treated wastewater from 4 different sources with different levels of treatment (3 secondary treated samples and a tertiary treated sample) with 3 different types of cement to see if there is an effect of the treatment plant or cement type on the properties of mortar with reference of the control sample of water. 15 mixtures were made with mixing water source and cement type illustrated in Table 1. The practical work was carried out in the laboratory of the Misr Beni-Suef cement factory.

Table 1 XRF results for cement samples
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Materials

Cement

In the study, three different types of cement were used: OPC (CEM I), Cement type III (CEM III/A), and Cement type IV (CEM IV/A-P) with grade 42.5 N for all types. CEM I is the most commonly used cement and is primarily composed of clinker, gypsum, and small amounts of other materials such as limestone or pozzolanic ash. CEM III/A and CEM IV/A-P, on the other hand, are blended cement made from Portland cement clinker, pozzolanic or slag materials, and gypsum. CEM III/A contains 60% granulated blast furnace slag as its pozzolanic material, while Cement IV uses fly ash.

CEM I was obtained from Misr Beni-Suef cement factory, CEM IV/A-P was supplied by Lafarge commercial name “AL-Mokawem,” with 20–23% natural siliceous pozzolanic, and CEM III/A with 60% slag powder was also supplied by Lafarge. X-ray fluorescence (XRF) analysis was performed to include the chemical composition of the cement used. Generally, cement is a complex material composed of various chemical compounds, and its quality and performance depend on its chemical composition. The XRF technique allows for rapid and accurate determination of the major and minor oxides present in samples to assess their quality and suitability for different applications. Table 1 provides the chemical composition of the cement types used in this study.

Treated wastewater

Generally, there are three different stages of treated wastewater: primary, secondary, and tertiary treated wastewater. These stages represent the different levels of treatment that domestic and industrial wastewater undergoes before it is released back into the environment.

The first stage of the treatment process is the primary treatment, which involves screening the wastewater to remove large objects and then settling or floating to remove suspended solids and organic matter. This process removes up to 60% of the solids and organic matter in the wastewater, but it does not remove dissolved pollutants or nutrients like nitrogen and phosphorus. Primary treated wastewater is typically used for non-potable purposes such as irrigation or industrial cooling water.

The next stage of the treatment process is secondary treatment, which involves further treating the primary treated wastewater with biological processes to remove dissolved and suspended organic matter, nutrients, and pathogens. This process removes up to 90% of the pollutants in the wastewater, making it suitable for reuse in some applications such as irrigation, industrial processes, or even some non-potable urban uses.

The final stage of the treatment process is tertiary treatment, which involves additional treatment of the secondary treated wastewater to remove any remaining pollutants, such as nitrogen and phosphorus, that may be harmful to the environment. This process can involve physical, biological, or chemical treatment methods, such as filtration, disinfection, or membrane treatment. Tertiary treated wastewater is typically used for potable purposes, such as drinking water or indirect potable reuse.

Recalling, the study focused on comparing the influence of treated wastewater from different sources and stages of treatment on the properties of mortar and cement paste. The study evaluated the performance under the usage of 3 different sources of secondary treated wastewater as mentioned in Table 1 and also 1 source of tertiary treated wastewater and a control sample using distilled water.

Standard sand

Standard sand is the typical type of sand that is commonly used in the construction industry to test the strength and durability of concrete and mortar. The sand is carefully manufactured to meet strict specifications, ensuring that it has a consistent particle size, shape, and texture. Societe Nouvelle Du Littoral’s standard sand was supplied and rigorously tested to meet the highest quality standards. Figure 1 shows the sand used in the mixes.

Fig. 1
figure 1

The standardized sand

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Mix designs

The experimental program is divided into two phases: Phase I for evaluating the setting time, initial and final and Phase II to evaluate the compressive strength of the mortar for the crossing pastes. It should be mentioned that the mixtures differ in two main parameters cement types and different stages of treated wastewater. For phase I, 15 sets of mixtures were designed to evaluate the setting time as well as the mechanical properties of the mortars performed. Table 2 shows the sets of mixes designed for cement paste. This requires the knowledge of the amount of water used through the plunger needle in the Vicat apparatus to determine the consistency of the paste as per BS EN 196-3 [15]. The mix ID relies on the level of treated water from different plants in Egypt, which stands from 1, 2, 3, 4, and 5. While the cement types denoted by A, B, and C stand for CEM I, cement types IV and CEM III/A. For Phases, I and II, Phase I was denoted by ‘P” for paste, and Phase II was symbolized by ‘M’ for mortar. Thus, mix P1A stands for paste with cement type I, CEM I, and distilled water which represents the control.

Table 2 The mixture sets for Phase I: paste
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On the other hand. Phase II was set with one mixture but of the same set of mixes. Table 3 shows the mixtures of Phase II including the portions assigned as per BS EN 196-1 [16]. The amount of the cement is assumed at first, and then, the sand was considered as 3 times the cement amount while the w/c ratio was of value 0.50. The total number of prims cast was 90 specimens, 6 for each mix.

Table 3 The mixture sets for Phase II: Mortar
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Test methods

This section describes a detailed procedure for investigating the initial and final setting times of the cement samples using the Vicat apparatus. The test follows the standardized procedure for measuring the setting time of cement according to BS EN196-3 [15]. The initial setting time test was performed using a needle with a diameter of 1.13 mm. The final setting time test was performed by placing a standard needle with an ending frustum of 10 mm in diameter and 50 mm in length on the surface of the cement paste, as shown in Fig. 2. The time taken for the paste to reach the initial and final setting points was recorded. It is important to note that a consistency test was not held for cement samples, and unified water amounts were used.

Fig. 2
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The Vicat’s apparatus with the two needles while measuring for (a) initial and (b) final setting time

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From Table 3, quantities were calculated to perform flexural prisms specimen evaluating the flexural and compressive strengths of the mixes as per BS EN 196-1 [16]. The specimen dimension was 40 mm × 40 mm × 160 mm, with a span-to-depth ratio of 3:1. The specimens were cured in a moist room at a temperature of 20 ± 2 °C until the tests were held after 2 and 28 days of curing. The specimens were subjected to a loading rate of 0.5 mm/min until failure, and the flexural strength was calculated based on the maximum load and the dimensions of the specimen, as shown in Eq. (1) and Fig. 3.

$${R}_{{\text{f}}}=\frac{1.5*{F}_{{\text{f}}}*I}{{b}^{3}}$$
(1)

where Rf is the flexural strength, in megapascals; b is the side of the square section of the prism, in millimeters; Ff is the load applied to the middle of the prism at fracture, in newtons; and l is the distance between the supports, in millimeters.

Fig. 3
figure 3

The flexural prism while testing for evaluating the flexural strength

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The same prismatic specimens were used to determine the compressive strength of the mixes by using the other half split of the flexural prism specimens, following the procedure outlined in Annex B of BS EN196-1 [16]. The compressive strength was calculated using the flexural strength and the dimensions of the specimen, according to the formula given in the standard, as shown in Eq. (2) and Fig. 4.

$${R}_{{\text{C}}}=\frac{{F}_{{\text{C}}}}{1600}$$
(2)

where Rc is the compressive strength, in megapascals; Fc is the maximum load at fracture, in newtons; and 1600 is the area of the platens or auxiliary plates (40 mm × 40 mm), in square millimeters. Figures 3 and 4 represent the adopted method for testing both flexural and compressive strengths on prism specimens according to BS EN196-1 [16]. It should be mentioned that for each mix 6 prisms were cast to determine the compressive and flexural strengths at 2 and 28 days of age after water curing.

Fig. 4
figure 4

The half flexural prism while testing for evaluating the compressive strength as per BS EN 196-1 [16]

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Test results and discussion

This section discusses the results of setting times and mechanical properties represented in compressive and flexural strength of pastes and mortars mentioned in Tables 2 and 3.

Setting time

The initial and final setting times of the resulting cement paste mixtures were recorded and are compiled into Table 4. The observations and analysis of the experimental data reveal that both cement type and the type of treated wastewater have a significant impact on the initial and final setting times of the cement paste mixtures.

Table 4 Initial and final setting time results for 15 mixes
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Generally, the initial and final setting times for CEM I mixtures are longer than those for CEM IV/A-P and 60% of CEM III/A mixtures. The initial setting time for 60% CEM III/A mixtures provides a shorter time than those for CEM I and CEM IV/A-P mixtures. The final setting times for CEM I and 60% CEM III/A mixtures are generally longer than those for CEM IV/A-P mixtures. This could be noticed in mixtures P1A, P1B, and P1C where the cement types were only the controlling parameter, and the water used was distilled water.

The type of treated wastewater used also has a significant impact on the setting times of the cement paste mixtures. The initial and final setting times for distilled water are longer than those for treated wastewater. The P1A mixture has the longest initial setting time and the second-longest final setting time. The P5C mixture has the shortest final setting time among all the mixtures. It has to be mentioned that the amount of water used influenced the setting time of cement paste mixtures significantly. For instance, the 60% CEM III/A mixtures had flash setting due to relatively low water content, this also may indicate that treated wastewater has almost the same effect as the typically used water types in the construction industry.

These observations suggest that the use of different cement types and treated wastewater can be tailored to achieve desired setting times for concrete mixtures, which can be important for construction projects with specific requirements for concrete placement and curing times. However, it is important to note that the setting times are only one of the factors that affect the performance of concrete, and other properties such as strength, durability, and workability should also be considered in the selection of cement and treated wastewater for concrete production.

As shown in Table 4, the initial setting time of mixes P1C, P2C, P3C, P4C, and P5C is too short to satisfy the ES 4756-1 [17] limits and standards which should be greater than or equal to 60 min at the grade of 42.5 N and are not accepted for construction did not comply with the requirements of ES 4756-1 [17].

Mechanical properties

After water curing at room temperature (20 ± 2 °C), the results of the flexural and compressive strength were recorded at 2 and 38 days after testing them according to BS EN 196:1 [16]. As elaborated in Table 5, flexural and compressive strengths were evaluated after 2 and 28 days of curing to assess the mechanical performance of mortar samples prepared with different cement types and water sources. Flexural strength ranged from 1.9 to 4.67 MPa and 7.395 to 9.435 MPa after 2 and 28 days, respectively. Mix M2B exhibited the highest early flexural strength of 4.67 MPa at 2 days, while mix M1C showed the lowest value of 1.9 MP at the same age. At 28 days, mix M3C displayed superior flexural strength of value 9.435 MPa compared to all other samples, while mix M5A exhibited the lowest value of 7.395 MPa.

Table 5 Flexural and compressive strength results at 2 and 28 days of age
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For compressive strength, 2-day results varied between 7.2 and 21 MPa. Mix M2B achieved the maximum early compressive strength of a value of 21 MPa, whereas mix M1C had the minimum with a value of 7.2 MPa. After 28 days, compressive strengths ranged from 35.525 to 44.725 MPa, with mix M1A demonstrating the highest value of 44.725 MPa and mix M1C providing the lowest value of 35.525 MPa.

Both flexural and compressive strengths displayed an increasing trend with curing duration, indicative of the progressive development of a stronger and more rigid mortar structure over time. These results are limited to only 28 days of age; it is recommended to investigate the long-term strength development as well at 56 and 90 days of age.

Comparing cement types, mixes containing type IV cement showed consistently higher flexural and compressive strengths at both 2 and 28 days compared to cement A (CEM I) and C (CEM III/A). This implies that the specific composition and properties of type IV cement may promote enhanced mechanical performance in concrete. Though no distinct correlation was discernible, the water source utilized also appeared to influence strength development. For instance, mix M1C exhibits poor strength regardless of the curing age. Further studies are needed to conclusively establish the relationship between water source and concrete strength.

In general, flexural and compressive strengths correlated positively, with mixes having higher flexural strength tending to show greater compressive strength as well. However, this trend was not universal, suggesting that other parameters like cement type and water source also play pivotal roles in governing mortar strength. Considerable variation was noted in the mechanical properties between samples, highlighting the complex interplay of several factors including but not limited to cement characteristics and water quality as well. Additional investigations aided by statistical analysis are imperative to elucidate the specific contributions of these variables and their interactions in determining concrete strength.

Figure 5 presents the percentage changes in the flexural and compressive strengths of mortar. Comparing the results at 2 and 28 days of curing provides insights into the early and later age strength development of the different concrete mixtures while considering the control mix in each set of 5 mixes; M1A, M1B, and M1C, the percentile changes in flexural and compressive strength were deduced.

Fig. 5
figure 5

The percentile change in (a) flexural and (b) compressive strengths of the prisms specimen considering the control mix for each cement type; mix M1A, M1B, and M1C

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For cement type A (CEM I), the majority of samples showed reduced flexural and compressive strengths compared to the control mix M1A at both 2 and 28 days. Mixes M2A and 5A exhibited marginal increases in early strength, while all other mixtures displayed lower strengths. The reductions were particularly significant for mix M4A, with around 24% and 8% lower flexural and compressive strengths, respectively, at 2 days compared to values of mix M1A. At 28 days, most mixes had inferior mechanical properties than the control, barring M2A which showed slightly higher compressive strength. This indicates that the water sources generally had an unfavorable effect on the strength evolution of cement A (CEM I).

Regarding cement B (CEM IV/A-P), the early flexural and compressive strengths increased for all samples relative to the control mix M1B, except mix M4B. Mix M2B displayed a maximum improvement of approximately 17% in both flexural and compressive strengths at 2 days. After 28 days, the effects were less pronounced, with mixes M2B, M3B, and M4B continuing to show enhanced strengths over M1B. Thus, the water sources helped improve early as well as later age strengths for most mixtures with cement B (CEM IV/A-P).

For cement C (CEM III/A), substantial early strength gains were observed for all samples compared to control mix M1C, with improvements ranging from 9% to 51% in flexural strength and 9% to 36% in compressive strength at 2 days. Mixes M2C and M3C exhibited the highest early strength increases. At 28 days, the influences were less remarkable but still mostly beneficial, with samples maintaining higher mechanical properties than M1C. Hence, the different water sources consistently enhanced the early and later age strength evolution for cement C (CEM III/A).

Comparing the cement types, the water sources had the most positive impact on the mechanical properties of concrete containing cement C (CEM III/A), followed by cement B (CEM IV/A-P). For cement A (CEM I), the influences were mostly unfavorable. This implies that the specific chemical and physical interactions between the cement composition and water quality played a key role in determining the strength development. A microstructural and deeper analysis (thermogravimetric analyzer, TGA, etc.) might be required.

The early age results were variable, indicating that the water sources had a greater influence on the hydration reactions and microstructural formation during the initial curing period. The 28-day strengths evened out to an extent, suggesting that the long-term pozzolanic and hydration effects counteracted some of the early differences arising from the water sources.

Overall, this comparative analysis provides valuable insights into the complex interplay between cement type, water source, and mortar strength evolution. While cement B (CEM IV/A-P) and C (CEM III/A) were compatible with the different water sources in enhancing mechanical properties, cement A (CEM I) displayed reduced performance in most cases. Further microscopy and spectroscopic studies are imperative to elucidate the microstructural mechanisms underlying these macroscopic strength trends. Statistical quantification of the results will also help ascertain the significance of the observed variations. This can aid in optimizing mixture design and curing practices for specific cement–water combinations to maximize concrete durability and mechanical integrity.

Conclusions

This study investigated the influence of both cement types and variable water sources on the setting time and mechanical properties of the pastes and mortars designed. Fifteen mixtures were designed including 15 setting time tests were carried out to determine their initial and final setting time. A total of 90 prism specimens were cast; 6 prisms for each mixture to evaluate the compressive and flexural strengths of mortars. Generally, cement type and water source both showed significant impacts on the setting times of concrete mixtures. CEM III/A displayed the shortest initial setting times, while CEM I had the longest. Treated wastewater mixtures generally set faster than those with distilled water.

  1. 1.

    Mechanical properties including flexural and compressive strengths were also influenced by cement type and water source. CEM IV/A-P provided superior strength performance compared to CEM I and CEM III/A.

  2. 2.

    Water source effects depended on the cement type. For CEM I, most treated water sources reduced strengths, while similar sources provided enhancement for the properties of CEM IV/A-P and CEM III/A, especially at early ages.

  3. 3.

    The highest strength improvements of over 50% in flexural and 35% in compressive strength occurred with CEM IV/A-P and treated wastewaters compared to CEM I control with distilled water.

  4. 4.

    Considerable variability in mechanical properties highlights the complex interactions between materials and mixture factors influencing concrete performance.

  5. 5.

    Microstructural studies are required to elucidate mechanisms behind the strength trends arising from cement–water interactions.

  6. 6.

    With testing and validation, non-conventional waters could potentially substitute for scarce freshwater resources in concrete construction using optimized cement types.

Further coupled chemical-microstructural research, expanded experimental matrices and durability testing are vital to build on the insights gained in this work. Overall, the study successfully demonstrated the feasibility of a tailored selection of compatible cement–water combinations to enhance the sustainable development of mortar using locally available materials.