Post on 17-Jul-2016
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Mixing Water for ConcreteMixing Water for Concrete
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�� 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.
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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.
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�� 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.
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Water QualityWater Quality
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�� 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
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�� 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
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�� 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
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�� 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
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�� 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
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�� 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
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�� 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.
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MISCELLANEOUS INORGANIC SALTSMISCELLANEOUS INORGANIC SALTS
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�� 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.
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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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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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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.