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Mixing Water for ConcreteMixing Water for Concrete

11

�� Almost any natural water that is drinkable and has no Almost any natural water that is drinkable and has no

pronounced taste or odor can be used as mixing water pronounced taste or odor can be used as mixing water

for making concrete. However, some waters that are not for making concrete. However, some waters that are not

fit for drinking may be suitable for use in concrete.fit for drinking may be suitable for use in concrete.

�� Water of questionable suitability can be used for making Water of questionable suitability can be used for making

concrete if mortar cubes (ASTM C concrete if mortar cubes (ASTM C 109 109 or AASHTO T or AASHTO T

106106) made with it have ) made with it have 77--day strengths equal to at least day strengths equal to at least

9090% of companion specimens made with drinkable or % of companion specimens made with drinkable or

distilled water. In addition, ASTM C distilled water. In addition, ASTM C 191 191 (AASHTO T (AASHTO T

131131) tests should be made to ensure that impurities in ) tests should be made to ensure that impurities in

the mixing water do not adversely shorten or extend the the mixing water do not adversely shorten or extend the

setting time of the cement. setting time of the cement.

22

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�� Acceptable criteria for water to be used in concrete are Acceptable criteria for water to be used in concrete are

given in ASTM C given in ASTM C 94 94 (AASHTO M (AASHTO M 157157) and AASHTO T ) and AASHTO T 2626..

�� Excessive impurities in mixing water not only may affect Excessive impurities in mixing water not only may affect

setting time and concrete strength, but also may cause setting time and concrete strength, but also may cause

efflorescence, staining, corrosion of reinforcement, volume efflorescence, staining, corrosion of reinforcement, volume

instability, and reduced durability. Therefore, certain instability, and reduced durability. Therefore, certain

optional limits may be set on chlorides, sulfates, optional limits may be set on chlorides, sulfates, alkaliesalkalies, ,

and solids in the mixing water or appropriate tests can be and solids in the mixing water or appropriate tests can be

performed to determine the effect the impurity has on performed to determine the effect the impurity has on

various properties. Some impurities may have little effect various properties. Some impurities may have little effect

on strength and setting time, yet they can adversely affect on strength and setting time, yet they can adversely affect

durability and other properties.durability and other properties.

33

�� Water containing less than Water containing less than 2000 2000 parts per million (parts per million (ppmppm) )

of total dissolved solids can generally be used of total dissolved solids can generally be used

satisfactorily for making concrete. Water containing more satisfactorily for making concrete. Water containing more

than than 2000 2000 ppmppm of dissolved solids should be tested for of dissolved solids should be tested for

its effect on strength and time of set. its effect on strength and time of set.

44

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Water QualityWater Quality

55

�� There is much more bad concrete made through using There is much more bad concrete made through using

too much goodtoo much good--quality water than there is using the right quality water than there is using the right

amount of pooramount of poor--quality water.quality water.

�� Rule of thumb:Rule of thumb:

'If you can drink it, you can make concrete with it''If you can drink it, you can make concrete with it'

�� Good quality concrete can be made with water that would Good quality concrete can be made with water that would

not pass normal standards for drinking waternot pass normal standards for drinking water

Uses of Water in Concrete ProductionUses of Water in Concrete Production

66

�� Mixing Water: Hydration, WorkabilityMixing Water: Hydration, Workability

�� Curing Water: EvaporationCuring Water: Evaporation

�� Wash Water:Wash Water:

�� Aggregates should be free of clay, silt and very fine Aggregates should be free of clay, silt and very fine

particles or organic impuritiesparticles or organic impurities

�� Organic impurities may interfere with setting and Organic impurities may interfere with setting and

hardening of concretehardening of concrete

�� Very fine particles increase water requirement and Very fine particles increase water requirement and

affect bonding propertiesaffect bonding properties

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Impurities in WaterImpurities in Water

77

�� FreshFresh ConcreteConcrete

DependingDepending onon typetype andand amount,amount, impuritiesimpurities maymay affectaffect

raterate ofof reactionreaction b/wb/w cementcement andand waterwater.. ThusThus;; workabilityworkability

andand settingsetting timestimes ofof concreteconcrete areare affectedaffected

�� HardenedHardened ConcreteConcrete

RateRate ofof strengthstrength gaingain ofof thethe cementcement pastepaste whichwhich coverscovers thethe

surfacessurfaces ofof thethe aggregatesaggregates andand fillfill thethe voidsvoids betweenbetween them,them,

dependsdepends onon thethe raterate andand amountamount ofof hydrationhydration reactionreaction..

Impurities in WaterImpurities in Water

88

�� FreshFresh ConcreteConcrete

DependingDepending onon typetype andand amount,amount, impuritiesimpurities maymay affectaffect

raterate ofof reactionreaction b/wb/w cementcement andand waterwater.. ThusThus;; workabilityworkability

andand settingsetting timestimes ofof concreteconcrete areare affectedaffected

�� HardenedHardened ConcreteConcrete

RateRate ofof strengthstrength gaingain ofof thethe cementcement pastepaste whichwhich coverscovers thethe

surfacessurfaces ofof thethe aggregatesaggregates andand fillfill thethe voidsvoids betweenbetween them,them,

dependsdepends onon thethe raterate andand amountamount ofof hydrationhydration reactionreaction..

�� StrengthStrength:: SlowSlow hydrationhydration ——►► slowslow raterate ofof CC--SS--HH formationformation

——►► highhigh amountamount ofof capillarycapillary porespores ——►► lowlow strengthstrength

�� DurabilityDurability:: SlowSlow hydrationhydration ——►► slowslow raterate ofof CC--SS--HH

formationformation ——►► highhigh amountamount ofof capillarycapillary porespores ——►► highhigh

permeability,permeability, porosityporosity andand absorptionabsorption --►► externalexternal waterwater

infiltrationinfiltration (may(may containcontain sulphatessulphates,, acids)acids)

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ALKALI CARBONATE AND BICARBONATEALKALI CARBONATE AND BICARBONATE

99

�� Carbonates and bicarbonates of sodium and potassium have Carbonates and bicarbonates of sodium and potassium have

different effects on the setting times of different cements. different effects on the setting times of different cements.

Sodium carbonate can cause very rapid setting, bicarbonates Sodium carbonate can cause very rapid setting, bicarbonates

can either accelerate or retard the set. In large can either accelerate or retard the set. In large

concentrations, these salts can materially reduce concrete concentrations, these salts can materially reduce concrete

strength. When the sum of the dissolved salts exceeds strength. When the sum of the dissolved salts exceeds 1000 1000

ppmppm, tests for their effect on setting time and , tests for their effect on setting time and 2828--day strength day strength

should be made. The possibility of aggravated alkalishould be made. The possibility of aggravated alkali--

aggregate reactions should also be consideredaggregate reactions should also be considered

CHLORIDECHLORIDE

1010

�� Concern over a high chloride content in mixing water is chiefly Concern over a high chloride content in mixing water is chiefly

due to the possible adverse effect of chloride ions on the due to the possible adverse effect of chloride ions on the

corrosion of reinforcing steel or precorrosion of reinforcing steel or pre--stressing strands. stressing strands.

Chloride ions attack the protective oxide film formed on the Chloride ions attack the protective oxide film formed on the

steel by the highly alkaline (pH greater than steel by the highly alkaline (pH greater than 1212..55) chemical ) chemical

environment present in concrete. The acidenvironment present in concrete. The acid-- soluble chloride soluble chloride

ion level at which steel reinforcement corrosion begins in ion level at which steel reinforcement corrosion begins in

concrete is about concrete is about 00..22% to % to 00..44% by mass of cement (% by mass of cement (00..1515% to % to

00..33% water soluble). % water soluble).

�� Of the total chlorideOf the total chloride--ion content in concrete, only about ion content in concrete, only about 5050% %

to to 8585% is water soluble; the rest becomes chemically % is water soluble; the rest becomes chemically

combined in cement reactionscombined in cement reactions

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CHLORIDECHLORIDE

1111

�� Chlorides can be introduced into concrete with the separate Chlorides can be introduced into concrete with the separate

mixture ingredients admixtures, aggregates, mixture ingredients admixtures, aggregates, cementitiouscementitious

materials, and mixing water or through exposure to deicing materials, and mixing water or through exposure to deicing

salts, seawater, or saltsalts, seawater, or salt--laden air in coastal environments. laden air in coastal environments.

Placing an acceptable limit on chloride content for any one Placing an acceptable limit on chloride content for any one

ingredient, such as mixing water, is difficult considering the ingredient, such as mixing water, is difficult considering the

several possible sources of chloride ions in concrete. An several possible sources of chloride ions in concrete. An

acceptable limit in the concrete depends primarily upon the acceptable limit in the concrete depends primarily upon the

type of structure and the environment to which it is exposed type of structure and the environment to which it is exposed

during its service life.during its service life.

CHLORIDECHLORIDE

1212

�� A high dissolved solids content of a natural water is A high dissolved solids content of a natural water is

sometimes due to a high content of sodium chloride or sometimes due to a high content of sodium chloride or

sodium sulfate. Both can be tolerated in rather large sodium sulfate. Both can be tolerated in rather large

quantities. Concentrations of quantities. Concentrations of 2020,,000 000 ppmppm of sodium chloride of sodium chloride

are generally tolerable in concrete that will be dry in service are generally tolerable in concrete that will be dry in service

and has low potential for corrosive reactions. Water used in and has low potential for corrosive reactions. Water used in

prepre--stressed concrete or in concrete that is to have aluminum stressed concrete or in concrete that is to have aluminum

embedmentsembedments should not contain deleterious amounts of should not contain deleterious amounts of

chloride ion. The contribution of chlorides from ingredients chloride ion. The contribution of chlorides from ingredients

other than water should also be considered. Calcium chloride other than water should also be considered. Calcium chloride

admixtures should be avoided in steel reinforced concrete.admixtures should be avoided in steel reinforced concrete.

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CHLORIDECHLORIDE

1313

�� The ACI The ACI 318318building code limits water soluble building code limits water soluble chlochlo--ride ion ride ion

content in reinforced concrete to the followingcontent in reinforced concrete to the following

�� percentages by mass of cement:percentages by mass of cement:

�� PrePre--stressed concrete stressed concrete 00..0606%%

�� Reinforced concrete exposed to chloride in service Reinforced concrete exposed to chloride in service 00..1515%%

�� Reinforced concrete that will be dry or protected from Reinforced concrete that will be dry or protected from

moisture in service moisture in service 11..0000%%

�� Other reinforced concrete construction Other reinforced concrete construction 00..3030%%

�� ACI ACI 318 318 does not limit the amount of chlorides in plain does not limit the amount of chlorides in plain

concrete, that is concrete not containing steel.concrete, that is concrete not containing steel.

OTHER COMMON SALTSOTHER COMMON SALTS

1414

�� Carbonates of calcium and magnesium are not very soluble in Carbonates of calcium and magnesium are not very soluble in

water and are seldom found in sufficient concentration to affect water and are seldom found in sufficient concentration to affect

the strength of concrete.the strength of concrete.

�� Bicarbonates of calcium and magnesium are present in some Bicarbonates of calcium and magnesium are present in some

municipal waters. Concentrations up to municipal waters. Concentrations up to 400 400 ppmppm of bicarbonate of bicarbonate

in these forms are not considered harmful.in these forms are not considered harmful.

�� Magnesium sulfate and magnesium chloride can be present in Magnesium sulfate and magnesium chloride can be present in

high concentrations without harmful effects on strength. Good high concentrations without harmful effects on strength. Good

strengths have been obtained using water with concentrations strengths have been obtained using water with concentrations

up to up to 4040,,000 000 ppmppm of magnesium chloride. of magnesium chloride.

�� Concentrations of magnesium sulfate should be less than Concentrations of magnesium sulfate should be less than

2525,,000 000 ppmppm..

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IRON SALTSIRON SALTS

1515

�� Natural ground waters seldom contain more than Natural ground waters seldom contain more than 20 20 to to 30 30 ppmppm

of iron; however, acid mine waters may carry rather large of iron; however, acid mine waters may carry rather large

quantities. Iron salts in concentrations up to quantities. Iron salts in concentrations up to 4040,,000 000 ppmppm do not do not

usually affect concrete strengths adversely. usually affect concrete strengths adversely.

SULFATESULFATE�� Concern over a high sulfate content in mix water is due to Concern over a high sulfate content in mix water is due to

possible expansive reactions and deterioration by sulfate possible expansive reactions and deterioration by sulfate

attack, especially in areas where the concrete will be exposed attack, especially in areas where the concrete will be exposed

to high sulfate soils or water. Although mixing waters containing to high sulfate soils or water. Although mixing waters containing

1010,,000 000 ppm of sodium sulfate have been used satisfactorily, the ppm of sodium sulfate have been used satisfactorily, the

limit in the following Table should be considered unless special limit in the following Table should be considered unless special

precautions are taken.precautions are taken.

1616

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MISCELLANEOUS INORGANIC SALTSMISCELLANEOUS INORGANIC SALTS

1717

�� Salts of manganese, tin, zinc, copper, and lead in mixing water Salts of manganese, tin, zinc, copper, and lead in mixing water

can cause a significant reduction in strength and large can cause a significant reduction in strength and large

variations in setting time. Of these, salts of zinc, copper, and variations in setting time. Of these, salts of zinc, copper, and

lead are the most active. Salts that are especially active as lead are the most active. Salts that are especially active as

retarders include sodium retarders include sodium iodateiodate, sodium phosphate, sodium , sodium phosphate, sodium

arsenate, and sodium borate. All can greatly retard both set and arsenate, and sodium borate. All can greatly retard both set and

strength development when present in concentrations of a few strength development when present in concentrations of a few

tenths percent by mass of the cement. Generally, tenths percent by mass of the cement. Generally,

concentrations of these salts up to concentrations of these salts up to 500 500 ppmppm can be tolerated in can be tolerated in

mixing water.mixing water.

�� Another salt that may be detrimental to concrete is sodium Another salt that may be detrimental to concrete is sodium

sulfide; even the presence of sulfide; even the presence of 100 100 ppmppm warrants testing. warrants testing.

Additional information on the effects of other salts can be found Additional information on the effects of other salts can be found

in the references.in the references.

SEAWATERSEAWATER

1818

�� Seawater containing up to Seawater containing up to 3535,,000 000 ppmppm of dissolved salts is of dissolved salts is

generally suitable as mixing water for concrete not containing generally suitable as mixing water for concrete not containing

steel. About steel. About 7878% of the salt is sodium chloride, and % of the salt is sodium chloride, and 1515% is % is

chloride and sulfate of magnesium. Although concrete made chloride and sulfate of magnesium. Although concrete made

with seawater may have higher early strength than normal with seawater may have higher early strength than normal

concrete, strengths at later ages (after concrete, strengths at later ages (after 28 28 days) may be lower. days) may be lower.

This strength reduction can be compensated for by reducing This strength reduction can be compensated for by reducing

the waterthe water--cement ratio. cement ratio.

�� Seawater is not suitable for use in making steel reinSeawater is not suitable for use in making steel rein--forced forced

concrete and it should not be used in preconcrete and it should not be used in pre--stressed concrete due stressed concrete due

to the risk of corrosion of the reinforcement, particularly in warm to the risk of corrosion of the reinforcement, particularly in warm

and humid environments. If sea water is used in plain concrete and humid environments. If sea water is used in plain concrete

(no steel) in marine applications, moderate sulfate resistant (no steel) in marine applications, moderate sulfate resistant

cements, Types II or MS, should be used along with a low cements, Types II or MS, should be used along with a low

waterwater--cement ratio. cement ratio.

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1919

SEAWATERSEAWATER

�� Sodium or potassium in salts present in Sodium or potassium in salts present in seawater used seawater used for mix for mix

water can aggravate alkaliwater can aggravate alkali--aggregate aggregate reactivityreactivity. Thus, seawater . Thus, seawater

should not be used as mix water should not be used as mix water for concrete for concrete with potentially with potentially

alkalialkali--reactive aggregates.reactive aggregates.

�� Seawater used for mix water also tends to cause Seawater used for mix water also tends to cause efflorescence efflorescence

and dampness on concrete surfaces exposed and dampness on concrete surfaces exposed to air to air and and waterwater

2020

ACID WATERSACID WATERS

�� Acceptance of acid mixing water should be based on Acceptance of acid mixing water should be based on the the

concentration concentration (in parts per million) of acids in the water.(in parts per million) of acids in the water.

�� Occasionally, acceptance is based on the pH, which is Occasionally, acceptance is based on the pH, which is a a

measure measure of the hydrogenof the hydrogen--ion concentration on a log scale.ion concentration on a log scale.

�� The pH value is an intensity index and is not the The pH value is an intensity index and is not the best measure best measure

of potential acid or base reactivity. The pH of potential acid or base reactivity. The pH of neutral of neutral water is water is

77..00; values below ; values below 77..0 0 indicate acidity indicate acidity and those and those above above 77..0 0

alkalinity (a base).alkalinity (a base).

�� Generally, mixing waters containing Generally, mixing waters containing hydrochloric, sulfurichydrochloric, sulfuric, and , and

other common inorganic acids in other common inorganic acids in concentrations concentrations as high as as high as

1010,,000 000 ppmppm have no adverse effect have no adverse effect on strengthon strength. Acid waters . Acid waters

with pH values less than with pH values less than 33..0 0 may create may create handling problems and handling problems and

should be avoided if should be avoided if possiblepossible. Organic acids, such as tannic . Organic acids, such as tannic

acid, can have a acid, can have a significant significant effect on strength at higher effect on strength at higher

concentrations.concentrations.

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2121

Effect of tannic acid on the strength of concrete

2222

ALKALINE WATERSALKALINE WATERS

�� Waters with sodium hydroxide concentrations of Waters with sodium hydroxide concentrations of 00..55% % by mass by mass

of cement do not greatly affect concrete of cement do not greatly affect concrete strength provided strength provided quick quick

set is not induced. Higher set is not induced. Higher concentrations, howeverconcentrations, however, may reduce , may reduce

concrete strength.concrete strength.

�� Potassium hydroxide in concentrations up to Potassium hydroxide in concentrations up to 11..22% % by mass by mass of of

cement has little effect on the concrete cement has little effect on the concrete strength developed strength developed by by

some cements, but the same some cements, but the same concentration when concentration when used with used with

other cements may substantially other cements may substantially reduce the reduce the 2828--day strength.day strength.

�� The possibility for increased alkaliThe possibility for increased alkali--aggregate aggregate reactivity reactivity should should

be consideredbe considered..

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2323

INDUSTRIAL WASTEWATERINDUSTRIAL WASTEWATER

�� Most waters carrying industrial wastes have less Most waters carrying industrial wastes have less than than 4000 4000

ppmppm of total solids. When such water is used of total solids. When such water is used as mixing as mixing water in water in

concrete, the reduction in concrete, the reduction in compressive strength compressive strength is generally not is generally not

greater than about greater than about 1010%%--1515%.%.

�� Wastewaters such as those from tanneries, paint Wastewaters such as those from tanneries, paint factories, factories,

coke coke plants, and chemical and galvanizing plants plants, and chemical and galvanizing plants may contain may contain

harmful impurities. It is best to test any wasteharmful impurities. It is best to test any waste--water that water that

contains even a few hundred parts per contains even a few hundred parts per million of million of unusual solids.unusual solids.

2424

WATERS CARRYING SANITARY SEWAGEWATERS CARRYING SANITARY SEWAGE

�� A typical sewage may contain about A typical sewage may contain about 400 400 ppmppm of of organic matterorganic matter. .

After the sewage is diluted in a good After the sewage is diluted in a good disposal systemdisposal system, the , the

concentration is reduced to about concentration is reduced to about 20 20 ppmppm or lessor less. This amount . This amount

is too low to have any significant is too low to have any significant effect on effect on concrete strength.concrete strength.

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2525

ORGANIC IMPURITIESORGANIC IMPURITIES

�� The effect of organic substances on the setting time The effect of organic substances on the setting time of of portlandportland

cement or the ultimate strength of concrete is cement or the ultimate strength of concrete is a problem a problem of of

considerable complexity. Such substances, considerable complexity. Such substances, like surface like surface loams, loams,

can be found in natural waters. can be found in natural waters. Highly colored Highly colored waters, waters waters, waters

with a noticeable odor, or those with a noticeable odor, or those in which in which green or brown algae green or brown algae

are visible should be are visible should be regarded with regarded with suspicion and tested suspicion and tested

accordingly. Organic accordingly. Organic impurities are impurities are often of a humus nature often of a humus nature

containing containing tannatestannates or or tannic acidtannic acid

2626

SUGARSUGAR

�� Small amounts of sucrose, as little as Small amounts of sucrose, as little as 00..0303% to % to 00..1515% % by mass by mass

of cement, usually retard the setting of of cement, usually retard the setting of cement. The upper cement. The upper limit limit

of this range varies with different cements.of this range varies with different cements.

�� The The 77--day strength may be reduced while the day strength may be reduced while the 2828--day strength day strength

may be improved. Sugar in quantities of may be improved. Sugar in quantities of 00..2525% % or more or more by by

mass of cement may cause rapid setting and mass of cement may cause rapid setting and a substantial a substantial

reduction in reduction in 2828--day strength. Each type day strength. Each type of sugar of sugar influences influences

setting time and strength differently.setting time and strength differently.

�� Less than Less than 500 500 ppmppm of sugar in mix water of sugar in mix water generally has generally has no no

adverse effect on strength, but if the adverse effect on strength, but if the concentration exceeds concentration exceeds this this

amount, tests for setting time and amount, tests for setting time and strength should strength should be made.be made.

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2727

SILT OR SUSPENDED PARTICLESSILT OR SUSPENDED PARTICLES

�� About About 2000 2000 ppmppm of suspended clay or fine rock of suspended clay or fine rock particles can particles can be be

tolerated in mixing water. Higher amounts tolerated in mixing water. Higher amounts might not might not affect affect

strength but may influence other properties strength but may influence other properties of some of some concrete concrete

mixtures. Before use, muddy water mixtures. Before use, muddy water should be should be passed through passed through

settling basins or otherwise clarified settling basins or otherwise clarified to reduce to reduce the amount of silt the amount of silt

and clay added to the mixture and clay added to the mixture by way by way of the mix water. When of the mix water. When

cement fines are returned cement fines are returned to the to the concrete in reused wash concrete in reused wash

water, water, 5050,,000 000 ppmppm can can be toleratedbe tolerated..

2828

OILSOILS�� Various kinds of oil are occasionally present in Various kinds of oil are occasionally present in mixing water.mixing water.

Mineral oil (petroleum) not mixed with animal Mineral oil (petroleum) not mixed with animal or vegetable or vegetable oils oils

probably has less effect on strength probably has less effect on strength development development than other than other

oils. However, mineral oil in oils. However, mineral oil in concentrations concentrations greater than greater than 22..55% %

by mass of cement may by mass of cement may reduce strength reduce strength by more than by more than 2020%.%.

ALGAEALGAE�� Water containing algae is unsuited for making Water containing algae is unsuited for making concrete because concrete because

the algae can cause an excessive reduction the algae can cause an excessive reduction in strengthin strength. Algae in . Algae in

water leads to lower strengths either water leads to lower strengths either by influencing by influencing cement cement

hydration or by causing a hydration or by causing a large amount large amount of air to be entrained in the of air to be entrained in the

concrete. Algae concrete. Algae may also may also be present on aggregates, in which case be present on aggregates, in which case

the the bond between bond between the aggregate and cement paste is reducedthe aggregate and cement paste is reduced..

�� A maximum A maximum algae content of algae content of 1000 1000 ppmppm is recommended.is recommended.

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2929

INTERACTION WITH ADMIXTURESINTERACTION WITH ADMIXTURES

�� When evaluating waters for their effect on concrete When evaluating waters for their effect on concrete propertiesproperties, ,

it is important to also test the water with it is important to also test the water with chemical admixtures chemical admixtures

that will be used in the job concrete. that will be used in the job concrete. Certain compounds Certain compounds in in

water can influence the performance water can influence the performance and efficiency and efficiency of certain of certain

admixtures. For example, the admixtures. For example, the dosage of dosage of airair--entraining entraining

admixture may need to be admixture may need to be increased when increased when used with hard used with hard

waters containing high waters containing high concentrations concentrations of certain compounds or of certain compounds or

minerals.minerals.