Alternatives for Fresh Water in Cement-Based Materials: A Review

Abstract

Huge amounts of fresh water are used in the concrete industry every day. The quantity and quality of water play important roles in determining the quality, strength, setting time, and durability of cement-based materials (CBMs), such as paste, mortar, and concrete. Freshwater systems are under pressure due to climate changes, industrialisation, population growth, urbanisation, and the lack of proper water resource management. The lack of potable water has resulted in the search for possible alternatives, such as seawater, treated industrial wastewater, treated sewage wastewater, carwash service station wastewater, wastewater from ready-mix concrete plants, and wastewater from the stone-cutting industry. All of these water resources can be used in concrete to achieve adequate industry standards for the physical and chemical characteristics of concrete. This study is a comprehensive review of the existing information regarding the effects of alternate water resources on the fresh, physical, strength, and durability properties of CBMs. The review shows that the research on the utilisation of wastewater in CBMs is limited. The development of different procedures and methods is urgently needed to utilise various wastewaters in concrete production. The usage of various wastewaters in concrete construction overcomes their adverse impacts on the environment and human health.

1. Introduction

Water has prime importance in the production of cement-based materials (CBMs), such as paste, mortar, and concrete [1]. Concrete is produced by mixing binding materials (Portland cement or asphalt) and inert materials (coarse and fine aggregates) with water [2]. Globally, concrete requires around 1 trillion gallons of water yearly [3]. Less water produces better concrete; however, concrete needs an adequate amount of water to provide a workable mixture that can be mixed, placed, consolidated, and finished without complications [4]. Water is used for the production and processing of concrete, washing of concrete aggregates, concrete batching plant, and washing of a concrete truck mixer [5].

The water-to-cement ratio (w/c) is the key factor in controlling most of the properties of fresh and hardened concrete, as well as its strength, durability, and sustainability [6]. Water causes the hardening of CBM through a process called hydration [7]. Thus, its quality and quantity play important physical and chemical roles in determining the quality, strength, setting time, and durability of CBMs [8].

Any potable water is suitable to be used in the production of CBMs [9]. The water should be clean and free from injurious amounts of acids, salts, alkalis, oils, sugar, and organic materials [10]. Highly acidic or alkaline water [11], water mixed with algae [12], and water containing large amounts of chlorides [13] should be avoided because they may have adverse effects on the setting, hardening, and strength development of concrete.

Suitable water for concrete should not change its setting time (about 30 min) and strength reduction (greater than 20%) compared to the specimens prepared using potable water. The compressive strength of concrete cubes made with unknown suitable water should not be less than 90% of the cubes made using potable water [14]. The pH value of this water should be greater than 6 and preferably slightly basic between 7.2 and 7.6 [10,15]. However, appropriate steps should be taken when only nonpotable water is available to encompass the possible adverse effects on the final product of CBMs [16].

A concrete mix is around 10–15% cement, 60–75% aggregate, and 15–20% water [17]. Estimations show that the annual demand for concrete for construction will increase by up to 18 billion tons by the year 2050 [18]. By 2050, approximately 75% of the water demand for concrete production will probably occur in regions that will likely experience water stress. This is a substantial amount of water, especially in water-scarce areas [19].

Freshwater systems are under pressure due to climate changes, industrialisation, population growth, urbanisation, and the lack of proper water resource management [20]. Water consumption is growing at twice the rate of the global population [21]. Some researchers have described the chances of water war occurring at a range from 75 to 95% in the next 50–100 years due to water conflicts between various regions, such as the Middle East, the east coast of Canada, Bazile, Thailand, Bolivia, the Nile River basin, and Cauvery basin countries [22].

The lack of potable water has resulted in the search for possible alternatives [23]. Other water resources, such as seawater, treated industrial wastewater, treated sewage wastewater, carwash service station wastewater, wastewater from ready-mix concrete plants, and wastewater from the stone-cutting industry have higher levels of dissolved chemicals and suspended solids [24]. However, all of these water resources can be used in concrete production with acceptable strength and durability [5].

In the construction industry, the rate of consumption of concrete is almost the same as that of consumption of water [10]. Therefore, various types of partially and fully treated wastewaters may help in the production of concrete and prevent the high costs of its treatment [25]. The usage of wastewater in concrete construction overcomes its adverse impacts on the environment and human health.

Each alternative source of water must be subjected to a series of tests and meet acceptable industry standards regarding the physical and chemical characteristics of concrete to avoid detrimental effects [26]. This study reviews existing information about the reported alternatives for fresh water in CBMs and their effects on the fresh, physical, mechanical, and durability properties. This study helps researchers understand the status and possibility of using alternatives for fresh water and its technical advantages and disadvantages.

2. Using Seawater in CBMs

Natural seawater has negative and positive effects on CBMs, such as mortar and concrete. Currently, the use of seawater in concrete has expanded predominantly due to the freshwater deficiency and vast economic development worldwide. Therefore, the effects of seawater on the properties of concrete must be examined [27].

Seawater is a complex mixture consisting of 96.5% water, 2.5% salts, traces of dissolved inorganic and organic materials, and a few atmospheric gases [28]. Salt in seawater can weaken the durability and strength of the concrete exposed to it by affecting it physically, chemically, and mechanically [29]. The physical actions of seawater include sea waves, freeze–thaw cycles, ocean currents, temperature gradients, and tides. Chemical damages include the deterioration of the cement matrix and corrosion of steel reinforcement. Mechanical damages include the loss of strength, cyclic drag, and abrasions [27]. The overall damages to the concrete exposed to seawater are shown in Figure 1 [28]. The effects of seawater on the fresh, hardened, and durable properties of CBMs, such as paste, mortar, and concrete, are listed in

Table 1. Effects of seawater on the fresh, physical, strength, and durability properties of CBMs.

S. No.	Main Findings	References
Fresh properties of CBMs
1	The workability of concrete containing supplementary cementitious materials (SCMs) and seawater decreased compared to plain concrete.	[30,31]
2	The workability of concrete mixed with seawater was unaffected compared with plain concrete prepared with tap water.	[32]
3	The workability of concrete mixes can vary using seawater and sea sand from various regions.	[32]
4	The workability of concrete reduces by using seawater in its mixing.	[33]
Physical properties of CBMs
1	The setting time of the cement paste was unaffected by using seawater.	[34]
2	The initial and final setting times of cement decreased with the increase in the concentration of seawater.	[32,35]
3	Setting time of cement paste with seawater decreased by about 30% compared to that with normal potable water due to the fast hydration process of cement.	[33]
4	The weight of the concrete with seawater increased by around 2% after 28 days. It can be controlled by using SCMs, such as coal bottom ash because it decays the penetration of harmful salts and reduces the setting time of CBMs.	[31]
5	Concrete mixed and cured with seawater had a minimum water penetration depth of 25 mm due to the crystallisation of salts.	[36]
6	The density and modulus of the elasticity of concrete mixed and cured with seawater were unaffected compared with normal concrete.	[36]
7	Seawater does not affect the air content and density of CBMs because the density of seawater is 2%–3% higher than that of fresh tap water.	[33]
8	Concrete specimens (1.7% volume) exposed to the freeze–thaw action in the marine environment decreased by the effect of seawater, and their colours changed from dark grey to light grey.	[28]
Strength properties of CBMs
1	The early strength-gaining rate of concrete made and cured with seawater increased rapidly at 7 days due to chlorides in the seawater that accelerated the setting of cement and improved the strength.	[30,37]
2	The strength-gaining rate was observed to be reduced at 14, 28, and 90 days due to leaching out of soft hydration products or sulphates in seawater that retarded the setting of cement.	[38,39,40]
3	The strength of concrete containing seawater was observed to be reduced by around 15% compared to similar concrete specimens made and cured with fresh water at 90 days.	[38,41]
4	Concrete mixed and cured in seawater had higher compressive, tensile, flexural, and bond strengths than concrete mixed and cured in fresh water at the early ages of 7 and 14 days. The strengths after 28 and 90 days for concrete mixes mixed and cured in fresh water increased slowly.	[24,42]
5	The tensile properties of concrete were weakened by the sulphate salts present in the seawater.	[43]
6	The seawater and sea sand concretes were slightly more brittle than ordinary concrete.	[44]
7	Seawater had an enhanced effect on the early strength development of sea sand concrete.	[44]
Durability properties of CBMs
1	The usage of fly ash with a low w/c ratio made the concrete more chloride-resistant against seawater.	[45]
2	Chloride salts in the seawater caused the deterioration of concrete due to the chloride-induced corrosion of steel.	[43]
3	No effect was observed on the stress–strain performance of seawater-cured concrete compared with the freshwater-cured concrete.	[28]
4	Seawater was responsible for the corrosion of concrete reinforcement.	[46]
5	The usage of corrosion inhibitors, such as fibre-reinforced polymers, was suggested to overcome the negative effects of seawater.	[47]
6	A negligible effect of seawater was observed on the carbonation process of concrete.	[32]
7	Concretes with seawater had more resistance against drying shrinkage and less against the freeze–thaw action due to the presence of chlorides.	[32]
8	The permeability of concrete produced through seawater mixing was not influenced.	[33]
9	Shrinkage was recorded to be 5% more than the conventional concrete produced through normal water mixing.	[33]
10	Chloride ingression resistance was unaffected by seawater. A rapid chloride permeability test was performed on freshwater and seawater concretes, and the results were approximately the same for the two concretes.	[33]
11	The same pore structure was found for freshwater-cured concrete and seawater-cured concrete.	[48]
12	The use of SCMs improved the serviceability and life of concrete exposed to the marine environment.	[31]

.

3. Using Treated Industrial Wastewater in CBMs

Industrial wastewater is a great difficulty to environmental progress in human civilisation. Carelessly discharging wastewater into water bodies affects the physical, chemical, and biological changes to the environment. The typical steps for industrial wastewater treatment are shown in Figure 2 [49].

Industrial wastewater, such as textile factory wastewater, fertiliser factory wastewater, and sugar factory wastewater, affects the mechanical and durability properties of concrete, such as compressive strength, splitting tensile strength, water absorption, and chloride migration [50]. The effects of treated industrial wastewater on the fresh, hardened, and durable properties of CBMs, such as paste, mortar, and concrete, are listed in

Table 2. Effects of treated industrial wastewater on the fresh, physical, strength, and durability properties of CBMs.

S. No.	Main Findings	References
Fresh properties of CBMs
1	The use of treated industrial wastewater has a minimal effect on the air content of freshly mixed concrete.	[5]
2	The workability of concrete decreased by using tertiary and secondary-treated wastewaters; however, it can be improved by adding plasticisers.	[51]
Physical properties of CBMs
1	The use of treated industrial wastewater has a minimal effect on the normal consistency of hydraulic cement and the density of concrete.	[5]
2	The use of treated industrial wastewater in the cement paste postponed the final setting time to 17 min.	[5]
3	Concrete with treated industrial wastewater has regular and well-formed crystals compared with concrete that has drinking water in accordance with the scanning electron microscopy images.	[5]
Strength properties of CBMs
1	Textile factory wastewater presented higher compressive and split tensile strengths than concrete with potable water.	[50]
2	The compressive strengths of concrete samples made with 100%drinking water were higher than concrete samples mixed withwater containing 25 to 100% of treated wastewater.	[52]
3	The compressive strength of concrete with treated industrial wastewater decreased by an average of 6.9% than the compressive strength of cement mortar with drinking water.	[5]
4	The use of treated industrial wastewater in concrete production decreased the tensile strength of concrete by 11.8% at 90 days.	[5]
5	The compressive strengths of concrete ranged from 85% to 94% ofnormal concrete by replacing 100% tap water with tertiary-treated wastewater and curing in tap water with tertiary wastewater.	[51]
6	The use of industrial wastewater had a minor effect on the strength properties of concrete.	[53]
Durability properties of CBMs
1	Amongst the five various types of wastewaters separately used for the mixing of concrete (textile factory wastewater, fertiliserfactory wastewater, domestic sewerage wastewater, service station wastewater, and sugar factory wastewater), fertiliser factory wastewater showed the highest mass loss and chloride penetration.	[50]
2	An increase of about 7.7% was observed in the electrical resistivity of concrete with treated industrial wastewater than using drinking water in concrete production.	[5]
3	The carbonation resistance of concrete decreased by using tertiary-treated water as a replacement for tap water.	[51]
4	The use of tertiary wastewater with tap water for curing or only tertiary wastewater for the curing of concrete increased the abrasion resistance.	[51]

.

4. Using Treated Sewage Wastewater in CBMs

Treated sewage wastewater involves domestic, municipal, or some industrial wastewater in which all the contaminants and suspended solids are removed before their disposal in the environment [54]. Various physical, chemical, and biological processes are involved to remove the contaminants for producing treated effluent that is safe to release into the environment [55]. A by-product of sewage treatment is a semi-solid waste called sewage sludge that undergoes further treatment before being suitable for disposal on the land [54]. Preliminary, secondary, and tertiary-treated sewage wastewaters can be used as mixing waters in concrete [56,57]. The effects of treated sewage wastewater on the fresh, hardened, and durable properties of CBMs, such as paste, mortar, and concrete, are listed in

Table 3. Effects of treated sewage wastewater on the fresh, physical, strength, and durability properties of CBMs.

S. No.	Main Findings	References
Fresh properties of CBMs
1	The slump of concrete was unaffected by the type of mixing water, such as preliminary-, secondary-, and tertiary-treated sewage wastewaters.	[56]
2	For primary, secondary, and domestic wastewaters and potable water, the slump value of concrete changed between 90 and 100 mm.	[58]
3	The initial and final setting times of cement paste were the same for potable water and secondary-treated wastewater, whereas they decreased for primary-treated wastewater.	[58]
4	A reduction in concrete workability was observed using domestic primary-treated wastewater.	[59]
5	The use of treated domestic wastewater increased the setting time of cement related to using drinking water in concrete.	[60]
6	The use of domestic wastewater in concrete did not cause any remarkable deterioration in its fresh and hardened properties.	[61]
7	The use of wastewaters from small-scale water treatment plants in residential buildings did not affect the initial setting time of OPC; however, a considerable change was observed in its final setting time.	[10]
Physical properties of CBMs
1	The density of concrete was unaffected by the type of mixing water, such as preliminary, secondary, and tertiary-treated sewage wastewaters.	[56]
2	Initial and final setting times of concrete were found to increase with deteriorating water quality. Preliminary and secondary-treated wastewaters had more effects on retarding the setting times.	[56]
3	A considerable increase in the initial setting time of up to 16.7% was observed in the concrete using domestic primary-treated wastewater compared with potable wastewater.	[59]
4	No considerable effect was observed on the use of domestic primary- or secondary-treated wastewater on the soundness value of mortar.	[59]
Strength properties of CBMs
1	Concrete with domestic sewerage wastewater showed a reduction of about 50% in compressive strength due to the water absorption property of mixed organic waste than that of the compressive strength of concrete made by using potable water.	[50]
2	Concrete mixes with domestic sewerage wastewater showed a maximum split tensile strength of 92.3% compared with that of concrete having potable water.	[50]
3	Concrete with preliminary and secondary sewage-treated wastewaters showed lower strengths for ages of up to 1 year than concrete made with potable water.	[56]
4	The compressive strength of mortar and concrete improved at 28 and 60 days by mixing secondary-treated wastewater, respectively. However, no improvement was observed in the tensile and flexural strengths of mortar and concrete by mixing secondary-treated wastewater compared with potable water.	[58]
5	No negative effect was observed on the compressive strength of mortar made with domestic secondary-treated wastewater at a curing age of 200 days. However, a reduction of about 16.2% was found in the compressive strength of mortar using domestic primary-treated wastewater.	[59]
6	The type of mixing water, such as domestic primary- and secondary-treated wastewater, distilled water, and fresh water did not affect the continuous increase in the concrete and mortar’s compressive strength. However, the compressive strength growth rate is dependent on the type of mixing water.	[59]
7	Concrete cast with treated sewage wastewater obtained higher compressive strength compared with concrete treated with potable water for up to 28 days.	[62]
8	The compressive strength of concrete under rapid freezing and thawing decreased by about 10% by using treated domestic wastewater in place of using drinking water.	[60]
9	The use of secondary-treated sewage wastewater had a negligible effect on the strength properties of concrete.	[53]
10	The compressive and flexural strengths of OPC pastes made with wastewaters from small-scale water treatment plants in residential buildings were less than the samples made with distilled water. However, they were within the limits as per code IS: 456-2000 and BS: 3148-1980.	[10]
Durability properties of CBMs
1	Water absorption of the concrete with domestic sewerage wastewater was about 114.05% at 28 days and 120.65% at 90 days than that of concrete with potable water.	[50]
2	Concrete with domestic sewerage wastewater showed the highest mass loss of about 103.3% due to the acid attack at the testing age of 120 days compared with that of the concrete with potable water.	[50]
3	Concrete with domestic sewerage wastewater showed a maximum chloride penetration of 101.7% compared with that of concrete having potable water at 120 days.	[50]
4	The possibility of steel corrosion increased by using sewage-treated wastewater.	[56]
5	The effects of domestic primary- and secondary-treated wastewater on concrete water absorption and durability were insignificant.	[59]
6	Concrete samples produced and cured with treated domestic wastewater did not have remarkable effects on water absorption and surface electrical resistivity compared to concrete samples using drinking water.	[60]
7	Chloride permeability was high for sewage-treated wastewater concrete compared to potable water concrete at 14 and 28 days.	[62]

.

5. Using Carwash Service Station Wastewater in CBMs

Carwash wastewater may contain many pollutants, such as detergents, oil, grease, sand, dust, chemicals, solvent-based solutions, heavy metals, and volatile organic matter [63,64]. Therefore, it can be harmful to humans and the environment if released untreated to the surface water bodies. Reusing carwash wastewater in concrete mixes aims to create a sustainable environment and a means to recover a substantial amount of wastewater directly discharged into rivers and oceans [65].

The authors [52] used carwash wastewater to manufacture concrete and found that the characteristics of this wastewater are within the American Society for Testing and Materials standard limits. They used carwash wastewater in the concrete mix ranging from 25 to 100%. Their experimental results show that the compressive strength of concrete increases with curing age regardless of the amount of carwash service station wastewater used. The use of carwash service station wastewater can raise the possibility of corrosion and sulphate attacks in reinforced concrete structures. All concrete mixtures with various amounts of carwash service station wastewaters (up to 100% in the replacement of potable tap water) showed similar water absorption rates to the control mixture.

The authors [50] noted that the concrete that had carwash service station wastewater showed a mass loss of about 115.32% due to acid attack and maximum chloride penetration of 110.61% at the testing age of 120 days compared with the concrete with potable water. The maximum compressive strength of a concrete mixed with carwash service station wastewater is about 4% less than that of concrete with potable water. The authors [66] stated that concrete with 20% carwash wastewater achieves the highest compressive strength and modulus of elasticity compared with other compositions of wastewater.

6. Using Wastewater from Ready-Mix Concrete Plants in CBMs

Global concrete production is about 11 billion tons annually, which needs around 1.87 billion m³ of fresh water as mixing water and generates 748 million m³ of wastewater from its ready-mix plants [67]. Each cubic meter of ready-mix concrete requires approximately 175 L of mixing water and approximately 70 L of water to wash the mixer trucks, concrete pumps, and equipment at later stages [68]. Wastewater from ready-mix concrete plants contains heavy metals, high dissolved solids ≥ 9000 mg/L, and pH ≥ 12. Its discharge into the environment is a great problem for sustainability, water pollution, and human health [69].

From a ready-mix concrete plant, most water samples are hazardous due to the pH value of 11.5. Therefore, they should not be disposed directly to the environment in accordance with European and US legislation [70]. Although a recycling water system is used in the specific ready-mixed concrete plant, extremely small portions of water (0–20%) are used only after overflowing and neutralisation.

Ready-mix concrete plants are facing great challenges due to the water shortage, high cost of fresh water, and wastewater disposal. Therefore, a new revolution to produce zero waste from the ready-mix concrete industry by filtering and treating its wastewater for reuse as mixing water in ready-mix concrete plants will have a positive impact on the environment worldwide [68]. The separated solid powder can be collected and recycled in cement clinker or asphalt mixtures. The filtered wash water after pre-treatment for the removal of metals and reduction of pH can be reused for several applications or delivered to a municipal wastewater network [71].

The recycling of ready-mixed concrete wastewater in various ratios with fresh water can be utilised for concrete production [72,73]. The authors [74] reported that the use of recycled wastewater from a concrete plant as a partial replacement of mixing water (from 20 to 50% for mortar production) did not affect the mechanical properties of mortar but reduced its setting time by 15 min. The authors [75] described that the use of concrete wash water to produce concrete samples had no remarkable effect on their compressive strength, flexural strength, specific gravity, and air content.

The authors [70] stated that the mortars prepared using treated waste wash water from a ready-mix concrete plant at the curing ages of 7, 28, 120, and 200 days showed no negative effects on the compressive strength. However, the use of raw waste wash water from a ready-mix concrete plant (i.e., used as mixing water in mortars) led to a reduction in compressive strength (up to 10% at 28 days). Concrete made with raw waste wash water from a ready-mix concrete plant showed a reduction in compressive strength of up to 13.9% at 120 days. In accordance with the research report by authors [70], wastewater samples from ready-mix concrete plants used in concrete specimens with and without admixtures did not lower the concrete’s workability and slump value. No remarkable differences were observed in the setting times of cement pastes with and without wastewater from ready-mix concrete plants.

The authors [76] noted that a partial or full replacement of ready-mix concrete plant wastewater with municipal water as mixing water in mortar and concrete showed a reduction of up to 10 mm in the workability. However, the hydration heat output and air permeability were unaffected. The initial and final setting times of plain concrete were reduced by 20 and 35 min, respectively, and the compressive strength increased by 8% using 100% ready-mix concrete plant wastewater as mixing water.

7. Using Wastewater from the Stone-Cutting Industry in CBMs

The cutting, moulding, and finishing of stones release dust and slurry sludge. This slurry sludge is prohibited from being discharged into the public sanitary system [77]. The slurry sludge contains high amounts of water; therefore, its reuse decreases the cost of production and cleans the environment [78]. Currently, this slurry sludge is recycled and used as a source of water in the concrete production. The authors [77] reported that the use of a stone slurry sludge as a water source in concrete production reduced its slump value by 58% and increased its compressive and flexural strengths by 21 and 18%.

In accordance with the research report by authors [66], the compressive strength of concrete mixed with stone slurry water was in the range of 81–98% of the control mix with fresh water. The authors [79] stated that the replacement of tap water with stone slurry wastewater caused a considerable slump reduction at the w/cs of 0.6 and 0.7, but a minor effect on the slump was noticed at the w/c of 0.5. The use of wastewater from stone slurry waste at the w/c of 0.7 in concrete mixtures had no remarkable effect on their compressive strength at 28 days. However, the comprehensive strengths of concrete mixtures at w/cs of 0.5 and 0.6 were reduced in 28 days.

8. Conclusions

This study presents a detailed literature review regarding the effects of various water types, such as seawater, treated industrial wastewater, treated sewage wastewater, carwash service station wastewater, wastewater from ready-mix concrete plants, and wastewater from the stone-cutting industry on the fresh, physical, mechanical, and durability properties of CBMs. The conclusions are summarised as follows:

• Seawater does not considerably affect the air content, density, chloride ingression, pore structure, permeability, and carbonation of CBMs; however, it reduces the setting time.
• Industrial wastewater can be used (up to 100%) as a replacement for normal water in CBMs after treatment. However, the compressive and tensile strengths can be decreased by up to 15 and 7% by using it as a full replacement for normal water, respectively, and by postponing the setting time. Industrial wastewater decreases workability but has a negligible effect on the air content of fresh concrete.
• The secondary-treated domestic sewerage wastewater is suitable for producing cement mortars and concretes in accordance with the allowable limits of mixing water for concrete compared with primary-treated domestic sewerage wastewater.
• The use of carwash service wastewater in CBMs may have adverse effects on their mechanical and durability properties, such as compressive strength, corrosion, chloride penetration, acid attack, sulphate attack, and water absorption, because they may contain many pollutants. Carwash service wastewater should be used partially as a replacement for potable water in CBMs for its safe usage.
• The use of raw waste wash water from a ready-mix concrete plant reduces the compressive strength of concrete by about 10%, and the use of recycled ready-mixed concrete wastewater for mortars and concrete does not have harmful effects on their properties. However, it reduces the setting times.
• Wastewater from the stone-cutting industry used in concrete production reduces the slump value by about 58% and increases its compressive and flexural strengths by 21 and 18% at 28 days, respectively.