effective applications of retarding admixture to improve the

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EFFECTIVE APPLICATIONS OF RETARDING ADMIXTURE TO IMPROVE THE

PERFORMANCE OF CONCRETE IN HOT WEATHER

ABSTRACT

The fresh concrete should have a suitable composition in terms of quality and quantity of cement, aggregate,

water and admixtures in order to achieve good performance in terms of shape, finish, strength, durability,

shrinkage and creep. It should also satisfy a number of requirements from the mixing stage till it is

transported, placed in formwork and compacted. Concreting in hot weather is a challenge to the constructionindustry. There is a need to design optimum concrete mixes in an era of economically tight policies. The use

of admixture offers an improvement not economically attainable by adjusting the proportion of cement and

aggregates. This paper has been devoted to the study of the influence of a retarding admixture on the

properties of fresh and hardened concrete, like water absorption, porosity, density of concrete, compressive

strength, flexure strength, and workability etc. This study has provided results, which show remarkable

improvement in different properties of concrete in fresh and hardened state, and should be very helpful for

designing an economical concrete mix for hot weather conditions.

INTRODUCTION

The erformance requirements of hardened concrete are defined with respect to shape, finish, strength,

durability, shrinkage and creep. To achieve these objectives economically, the fresh concrete should have a

suitable composition in terms of quality and quantity of cement, aggregate, water and admixtures !"#$. It

should also satisfy a number of requirements from the mixing stage till it is transported, placed in a formwork

and compacted.

The requirements to achieve good quality of concrete may be summarised as follows%

&i' The mix should be able to produce homogeneous fresh concrete from the constituent material of the batch

under the action of the mixing forces.

&ii The mix should be stable, in that it should not segregate during transportation and placing when it is

subjected to forces during handling operation of limited nature.

&iii' The mix should be cohesive and sufficiently mobile to be placed in the form around the reinforcement. It

should also be able to be cast into the required shape without losing continuity or its homogeneous state under

the available techniques of placing the concrete at a particular job.

&iv' The mix should be amenable to proper and thorough compaction to make a dense and compact concrete

with minimum voids under the existing facilities of compaction at the site.

&v' It should be possible to attain a satisfactory surface finish without honeycombing or blowing holes from

the formwork and free surface by trowelling and other processes.

Investigations have shown that very fne cracks at the interace between coarse aggregate andcement paste exist even prior to application o load on the concrete. They are probably due to

the inevitable dierences in mechanical properties between the coarse aggregate and the

hydrated cement paste, coupled with shrinkage or thermal movement.

The observation that micro-cracking is initiated at the interace between coarse aggregate and

the surrounding mortar and that at ailure, the crack pattern includes the interace, points to

the importance o this part o the concrete. It is thereore necessary to understand the

properties and behaviour o the interace one sometimes called the transition one. !uring

mixing dry bulk o the cement particles are unable to become closely packed against the

relatively large particles o the aggregate. This situation is similar to the wall-eect at thesurace o cast concrete suraces although on a much smaller scale. There is thus less cement

present to hydrate and fll the original voids. It"s a conse#uence the interace one has much

higher porosity than the hydrated cement paste urther away rom the coarse aggregate.



Concreting In Hot Weather

The weather conditions while casting and curing concrete may not always be ideal, but concreting is often

necessary due to time constraints, environmental factors, etc. Casting and curing concrete in a hot

environment requires special precautions to reduce the effects hot weather may have on the concrete. In

some cases, it has been reported that both the initial and final setting times are halved when the temperature

of cement mortar with water(cement &w(c' ratio of #.) is increased from *+ oC to -.- oC and other difficulties

like decrease of slump, plastic shrinkage cracking etc. may also arise !$. The chemical hydration reaction between the ortland cement and water is the major contributing factor that makes it difficult to cast and cure

concrete in hot environments.

/etarding admixtures or retarders are highly recommended for use in all concrete where a delay in rate of

hardening is necessary !"$. There are also problems related to early volume changes and cracking. 0ore

specifically, fresh concrete that is allowed to prematurely dry experiences plastic shrinkage, which is

essentially contraction of the concrete. 1ue to this effect, cracks may develop in the surface of concrete after

the first few hours of placement. /etarders do not alter the composition or identity of products of hydration

!+$. /etarders tend to increase plastic shrinkage because the duration of the plastic stage is extended but

drying shrinkage is not affected !$. 2ir temperature also affects the performance of admixture !3$. The use of

retarding admixtures is important where thin concrete sections are present. The retarding admixtures provide

more uniform setting characteristics. 4ince concrete setting times are dramatically influenced by ambient

temperature, the uses of retarding admixtures are strongly recommended during hot weather. These

admixtures allow for normal setting times under these conditions. The use of retarding admixtures usually

leads to higher ultimate strength in concrete.

MATERIALS USED

Cement: Ordinary Portland cement manufactured by an Omani company.

Fine aggregate$ %ocally available in &uscat.

Coarse aggregate% 5ocally available in 0uscat.

Water % otable water supplied by 0uscat municipality.

Admixture o66olith

'oolith is an admixture, which is used to enhance the properties o concrete. It is a versatile

product, which can be utilied to maintain workability and eect water reduction throughout a

range o concrete mix designs. In this study dierent percentages o 'oolith are added to the

concrete mix and the variations in properties are reported. The physical properties o 'oolith

are given in Table()*.

Table [1] Physical Properties of Poolith

Colour% 1ark brown(black liquid

4pecific gravity% "." at *-7C



2ir entrainment% "8*9 dependent on dosage.

Chloride content% :il to ;4 -#+-

:itrate content :il

<ree6ing point%+. an be reconstituted i stirred

ater leaving to thaw.

<lashpoint% :one

!"THODO#O$%

In this study all the results are conducted based on the guidelines o ritish /tandards 0/ 1231

and /)44)5. The conditions o hot weather are generated by keeping the temperature in the

laboratory between 617 and 827.

oncrete cubes o dimension )12mm )12mm )12mm were prepared with proportions o

)$+$8.

oncrete beams o )22mm )22mm 122 mm were prepared.

The water9cement ratio is kept constant at 2.1.

The coarse aggregate used is well graded. Three types o fne aggregate are used: 0i5 well

graded, 0ii5 less than ;22 m, 0iii5 greater than ;22 m.

The admixture is added to the concrete varying rom 2.+<-).+< by weight o cement.

The water added to the concrete is at room temperature.

The strength o concrete is tested ater curing or +4 days.

RESULTS

The normal consistency of cement paste was determined and was found to be =-.+9. The variations in

properties of concrete in the plastic as well as hardened state are measured for different percentages of

o66olith and are presented in the tables below.

T!"#e $ E%%e&t 'n initi!# (ettin) time

Per&ent!)e '%

P'**'#it+ ,-.

Initi!# (ettin)

time ,minute(.

# 3-

#.* 3

#. -

T!"#e / E%%e&t 'n 0'r1!"i#it2 '% &'n&rete

Per&ent!)e '%

P'**'#it+ ,-.

W'r1!"i#it2

,mm.

# =*

#.* -

#. )+



#.) "#*

#.3 "#3

".# """

".* ""*

#.) #

#.3 "##

".# """

".* "*#

T!"#e 3 E%%e&t 'n 0!ter !"('r4ti'n '% &'n&rete

Per&ent!)e '% P'**'#it+ ,-.

W!ter!"('r"ed ,-.

# ".=-

#.* ".*)

#. "."

#.) #.)

#.3 #.3

".# #.+-

".* #.+

T!"#e 5 E%%e&t 'n &'m4re((i6e (tren)t+ '% &'n&rete

Per&ent!)e '% P'**'#it+ ,-.

C'm4re((i6e(tren)t+ ,N7mm$.

# ).-

#.* +."

#. 3.#

#.) .=

#.3 -".#

".# -*.=

".* -=.

T!"#e 8 E%%e&t 'n %#exur!# (tren)t+ '% &'n&rete

Per&ent!)e '%

P'**'#it+ ,-.

A6er!)e %#exur!#

(tren)t+,N7mm$.

# =.=-

#.* =.)

#. =.-3

#.) =.)*

#.3 =.)-

".# =.)

".* =.+*

T!"#e 9 E%%e&t 'n 4er%'rm!n&e '% %ine !))re)!te

Si*e '%

%ine

!))re)!te

Per&ent!)e

'% P'**'#it+

,-.

A6er!)e

C'm4re((i6e

(tren)t+

,N7mm$.

>)## m

#.# *-.=

#.3 *.)

?ell

graded

#.# ).-

#.3 -".+

@ )##m

#.# =."

#.3 -.-

DISCUSSION OF RESULTS

Effect of Pozzolith on initial setting time

The test results obtained to study the effect of o66olith on initial setting time of cement are presented in

Table * which shows an increase in the initial setting time of cement from 3- minutes without o66olith to

""* minutes with ".*9 o66olith. This retardation of initial setting time will be very advantageous in the case

of concreting in hot weather. In case of transporting concrete from the ready8mix plant to the construction site,it will be advantageous to have a high initial setting time. It will also be helpful in placing concrete with a

good bond in different layers.

Effect on workability and water-cement ratio



To study the effect of o66olith on workability of cement, concrete mixes of "%*% were prepared with

different percentages of o66olith. 4lump test was used to determine the workability and the results presented

in Table = and <ig. " show an increase in slump value with an increase in the percentage of o66olith. This

improvement in workability enhances the chance of getting a concrete mix of high workability with less

water8cement ratio. In normal conditions it was observed that to achieve a slump value of )+ a water8cement

ratio of #.) is required. Aence there is a saving of .9 water by adding only #.9 of o66olith.

Effect on water absorption

Concrete cubes were weighed before and after curing for *3 days. The results obtained for water absorption asa percentage of concrete are shown in Table and <ig. *. These results clearly indicate that water absorption

is inversely proportional to percentage of o66olith. 2 decrease in water absorption indicates a decrease in

porosity, which in turn increases the density of concrete. This will definitely help to reduce the permeability of

concrete and hence improvement in water8tightness of concrete.

Effect on compressive strength

The compressive strength of concrete was tested after curing the cubes for *3 days. The average value of

compressive strength as shown in Table - and <ig. = is increased from ).- :(mm* to -=. :(mm* with an

increase in percentage of o66olith associated with high workability. This will help to design a concrete mix

of high strength with less water8cement ratio.

Effect on flexural strength

Table ) and <ig. represent the variations in flexural strength of concrete as a result of adding different

percentages of o66olith. These results also show an increase in the value of flexural strength from =.=*

:(mm* to =.+* :(mm* with an increase in the percentage of o66olith from #9 to ".*9 by weight of cement.

Effect on performance of fine aggregate

1ifferent types of fine aggregates &>)## m, well graded and @)## m' were used to study the effect of

o66olith on the performance of fine aggregate. The results given in Table + show an increase in the

compressive strength by adding o66olith. The fine aggregate >)## m requires more water in normal

conditions whereas by the addition of o66olith the water requirement is reduced. The use of fine aggregate

will produce concrete of high density and less porosity, which will greatly enhance the related properties ofconcrete.

CONCLUSIONS

Concreting in hot weather is a challenge to the construction industry. Bn the basis of the results obtained in

this study there is a clear indication of improvement in the properties of fresh and hardened concrete under hot

weather conditions. This study provides a basis for producing economical concrete mixes with a high

workability, high strength and low water8cement ratio. The addition of o66olith will also reduce the water

required for the curing of concrete. The retardation of the initial setting will play an important role in placing

the concrete as well as the transport of concrete from the ready8mix plant to the construction site. There will

be great saving of precious potable water, which is in high demand in countries with high temperatures formost of the year. It will help to prevent the cold joints. It can be predicted that the chances of corrosion will

also be reduced, as the water retained in the core will be small.



Fi)ure : E%%e&t 'n W'r1!"i#it2 '% &'n&rete

Fi)ure $ E%%e&t 'n 0!ter !"('r4ti'n

Fi)ure / E%%e&t 'n &'m4re((i6e (tren)t+ Fi)ure 3 E%%e&t 'n %#exur!# (tren)t+

WATER ;UALIT< EFFECT ON CONCRETE COMPRESSIVE STRENGTH

OGUNPA STREAM WATER CASE STUD<

benga 0atthew 2yininuola

1epartment of Civil Dngineering Eniversity of Ibadan, Ibadan

ayigbengaFyahoo.com or gm.ayininuolaFmail.ui.edu.ng

G*=3#-)"="))*

A"(tr!&t

The study centred on the effect of water quality on concrete compressive strength development with

Bgunpa stream water as a case study. Two concrete mixes "%"%* and "%".-%= with water ( cement ratio of #.)

were investigated. ?ater samples from two sections of Bgunpa stream and Eniversity of Ibadan ?ater

mailto:[email protected]






Treatment lant &potable water' were used to cast *33 concrete cubes. The cured cubes were crushed on day

+, ", *", *3, -) and 3 for compressive strength estimation. The chemical constituents of the water samples

were determined in the laboratory. The results showed that the compressive strength of concrete cubes made

with potable water increased with days while those of Bgunpa stream declined after " day of concreting. The

chemical analyses revealed that Bgunpa stream contained high concentrations of sodium :a, potassium H,

chloride Cl8, and carbonate CB=8 amongst others which led to concrete strength reduction. Consequently, proper

water analysis should be encouraged before choosing water for concrete work.

=e20'rd water analyses, potable water, stream water, compressive strength, concrete mixes, concrete cubes

INTRODUCTION

The properties of concrete are vital factors, which determine to a great extent the strength and

serviceability of structures. Concrete is plastic and malleable in green state but strong and durable when

hardened. These qualities explained why concrete can be used for constructing skyscrapers, bridges, etc

&ortland Cement 2ssociation, *##-'. There are many factors that determine the quality of concrete and its

strength. These include the type of cement used, aggregate quality and grading, the degree of compaction,

quality and quantity of water used in concreting, curing method, type of reinforcement embedded including itssi6es, arrangement and spacing, etc.

Bf important at present is the quality of the mixing water. 2ccording to :eville &")', the quality of

water plays a significant role impurities in water may interfere with the setting of the cement paste adversely

affect the strength of the concrete or cause straining on its surface, corrosion of the reinforcement. 4teinour

&")#' agreed that some waters which adversely affect hardened concrete may be harmless or beneficial when

in mixing. In drawing specifications for many civil engineering projects, the water requirement is covered in a

clause saying it must be fitted for drinking.

?ater fitted for drinking is generally satisfactory, but there are exceptional cases. <or instance, in some

arid areas, local drinking water is saline and may contain an excessive amount of chloride, undesirable amount

of alkali carbonates and bicarbonates, which could contribute to the alkali8silica reaction &:eville, ")'.

Aowever, some waters that are not fit for drinking may be suitable for concrete production &ortland Cement

2ssociation, *##-'. 0cCoy &"+3' opined that water with pA range of ).# to 3.# is good for concreting.

0cCoy &"-)' suggested the use of water with pA .#, which does not taste brackish in concrete work.

<urthermore, mixing water with high content of suspended solids needs to stand in a settling basin

before use a turbidity limit of *###ppm has been suggested by E.4. ;ureau of /eclamation &"+-'. :atural

waters that are slightly acid are harmless, but water containing humic or other organic acids may adversely

affect the hardening of concrete &:eville, ")'. 1ifferent ions have separate effect on concrete &4teinour,

")#'. 1oell &"-' investigated the effect of algae on concrete, which resulted to entrainment of air with a

consequent loss of concrete strength. ;uilding /esearch 4tation &"-)' reported the success recorded in the use

of water with higher salts contents such as chloride &higher than -##ppm' and trioxosulphate v &higher than

"###ppm'.Thomas and 5isk &"+#' suggested that sea water slightly accelerates the setting time of cement. ?ater

containing large quantities of chlorides &sea water' tends to cause dampness and surface efflorescence. 4uch

water should not be used where appearance of concrete is of importance or where a plaster finish is to be

applied &5ea, "-)'. The presence of chlorides in concrete containing embedded steel can lead to steel

corrosion &:eville, ")'. Tests on mixes with ranges of water suitable for use in concrete showed no effect on

the structure of the hydrated cement paste &horab et al. "3'. 2l80anaseer et al &"33' showed that water

containing very percentages of salts of sodium, potassium, calcium and magnesium used in making concrete

containing ortland cement blended with fly ash did not affect the strength of concrete. Chatveera et al &*##)'

utilised and recycled sludge water as mixing water for concrete production and found that concrete slump and

strength reduced drastically.

Compressive strength, mineralogy, chloride ingress, and corrosion of steel bars embedded in concretemade with seawater and tap water were investigated based on the several long8term exposure under tidal

environment. 4eawater8mixed concrete showed earlier strength gain. 2fter *# years of exposure, no significant

difference in the compressive strength of concrete was observed for concrete mixed with seawater and tap

water &0ohammed et al, *##'. Islam and Haushik &"-' studied the mixing and curing effect of sea water

on setting time, compressive strength of cement8sand mortar and corresponding concrete, rebar corrosion,



chloride content and variation of alkalinity over a period of "3 months in a laboratory simulated splash(tidal

6one of marine environment. The test results indicate that sea water was not suitable for the mixing and curing

of both plain and reinforced concrete in marine conditions.

4u et al &*##*' described the effect of different types of mixing water on properties of mortar and

concrete such as compressive strength, setting times and workability. The compressive strength of concrete

mixed with wash water or underground water was as good as that with tap water. Therefore, it was suggested

that underground water should be considered as mixing water for concrete and wash water be recycled where

tap water resources are scarce. The potential use of groundwater and oily production water in flowable fills

was investigated by 2l8Aarthy et al &*##-'. <lowable fill blends prepared using brackish groundwater gavehigher strength than mixes prepared using oily production water. Humar &*###' studied the effects of the

quality of mixing water and initial curing on the strength of concrete exposed to seawater attack in marine

environment for a period of "year. /esults of this study showed that the use of precasting in place of casting8

in8situ mitigated the effect of marine environments on concrete specimens considerably.

Dven though, the basic requirement for water for concreting is its potability the question that comes to

mind is the availability of potable water for concreting. In developing countries, provision of water to meet

domestic demand has not been fulfilled. In urban areas, such as Ibadan, 5agos Hano etc in :igeria, only few

percentages of the populace have access to potable or wholesome water. Ibadan city, the biggest city in ?est

2frican countries is facing with scarcity of potable water supply. The two water treatment plants are not

adequate to produce the water need. The plants are producing below installation capacities due to inadequate

power supply and other problems. If the potable water available can not meet the domestic requirement, it will be difficult for an average contractor to comply with the requirement for mixing water in contract document.

The contractors would seek for alternative means by using available surface water once it is clean, clear and of

little or no odour for concrete work without testing its suitability.

The city of Ibadan has one major stream called Bgunpa that serves as major drain. Bccasional flooding

of the stream occurred in early "3#s that instigated the need to carry out channelisation of the stream and

construction of bridges over the stream. The project started few years ago and later abandoned. resently the

contract has been re8awarded, which involves about a several cubic metre of concrete. The quantity of water

required for the concrete works will be enormous and as such temptation may arise on the part of the

contractors to use Bgunpa stream water. Consequently, the research was conducted to determine suitability of

Bgunpa stream water for concrete work

METHODOLOG<

Samples Preparation

?ell graded granite coarse aggregate of maximum si6e "mm was obtained from a granite quarry

located in Ibadan and stockpiled. The fine aggregate, marine deposit was obtained from a stream located in the

Eniversity of Ibadan, air dried and stockpiled. 2bout four bags of ordinary ortland cement were purchased for

the research work. Dnough formworks &moulds' made of wood of si6e "-#mm x "-#mm x "-#mm were

prepared with the inside coated with oil.The concentration of chemicals in the stream water was expected to be higher during dry weather flow

than in wet weather. 2lso, the dry weather flow in Ibadan would reach its peak in January. Consequently,

water for the research was collected in the month of January at two designated points in Bgunpa stream. The

collection points were &i' <elele &lower Bgunpa' labelled 2 and &ii' Bgunpa market Bke ;ola area &0iddle

Bgunpa' labelled ;. otable water was also collected at the Eniversity of Ibadan ?ater treatment lant labelled

C for production of controlled concrete cubes. The water samples were stored in three different black kegs.

/epresentative samples from the three black kegs were set aside for chemical analyses.

Concrete Production

Two major concrete mix ratios were investigated namely "%"%* and "%%=. The batching of materials for

concreting was done by weighing. The mixing of concrete constituents &water, cement and aggregate' was

manually done on a hard surface to produce homogeneous fresh concrete. ?ater ( cement ratio of #.) wasadopted throughout the concrete cubes production.

Concrete cubes production was carried out in accordance with ;4 "33"% art "#3% "3=. Dach layer of

concrete received =- strokes of a *-mm square steel prunner. The cubes *33 in number still in moulds were left

overnight at room temperature. 2t the end of this period, the moulds were stripped and the cubes were further



cured in bath filled with potable water by completely immersion throughout the cubes compressive strength

determination period.

Compressive Strength est

The cured cube was placed with the cast faces in contact with the platens of the universal testing

machine electrically operated. In accordance with ;4 "33"% art "")%"3=, the load on the cube was applied at

constant rate of stress equal to #.*)0a(sec. The force or load that resulted to failure of each cube was taken

and used in calculating the compressive strength. The test was carried out at end of +th, "th, *"st, *3th, -)th and

3th day of concreting.

Water Samples !nalyses

These representative water samples were taken to laboratory for analyses. The parameters monitored

were sodium :a, potassium H, calcium Ca, sulphate 4B*8, nitrate :B=

8, carbonate CB=8, bicarbonate ACB=

8,

chloride Cl8, fluoride <l8, phosphate B8, iron <e, acidity, pA, manganese levels amongst others.

The level of acidity of water sample was obtained by titrating a known quantity of tested sample with

barium hydroxide. The presence of nitrate was determined by the addition of phenol8di8sulphonic acid with

potassium hydroxide to a known quantity of tested sample. The colour formed was compared with standard

colours. The chloride content of each water sample was measured by adding to a known sample volume of

".-ml of H *CrB and titrating the resulting solution with silver nitrate solution. The amount of iron, manganese

and other metals in each water sample were determined by adding a colouring agent to the sample and

comparing with solution of known amount of metal. Bther monitored parameters were determined in line withlaid down standard.

RESULTS AND DISCUSSIONS

The chemical constituents of the three water samples were determined immediately the cubes were

cast. The results of the chemical properties of the water samples are displayed in Table ". 2t the end of +th,

"th, *"st, *3th, -)th and 3th days, eights cubes from each mix type and water sample were taking for

compressive strength determination. 2ltogether, 3 cubes were crushed at every test day. 2t the end of 3th

day, *33 cubes had been crushed. The results of the compressive strength of concrete cubes were displayed in

Table *.

T!"#e : W!ter te(t re(u#t(

arameter tested EI potable 0iddle Bgunpa 5ower Bgunpa

&mg(l' water water water

4odium, :a *=#.# )-#.# +*#.#

otassium, H ="#.# +)#.# +3#.#

Calcium, Ca *##.# ="#.# =-#.#

4ulphate, 4B*8 "-." ".- *#.=

:itrate, :B= #."" #." #."3

Carbonate, CB= *+#.# -#.# -*#.#

;icarbonate, ACB= *)#.# +#.# "#"#.#

Chloride, Cl **#.# *+#.# =*#.#

<luoride, <l "." ".) ".+

hosphate, B *+.- =3.# #.#

Iron, <e ".= ".+ ".3

Copper, Cu ".= ".3 ".

0agnesium, 0g #. "." ".-

0anganese, 0n "." ".= ".-Kinc, Kn ".= ".- ".+

5ead, b #."" ".* ".

Cadmium, Cd #.# ". ".)

2cidity #.#) #." #.")

pA ).+ .) .3



Dxcept pA and level of acidity, the unit is mg(l

T!"#e $ T+e &u"e( &'m4re((i6e (tren)t+

eriod of ?ater Concrete Compressive 4trength &:(mm*'

cube sample mix minimum maximum mean

crushing type

+th day EI water "%"%* *.* *+.+ *).#

0B water *.# *-.* *. 5B water **. *." *=.*

EI water "%".-%= ".3 **.) *".

0B water *#." *".- *#.

5B water ".= *#.+ *#.*

"th day EI water "%"%* *+. =#.- *.#

0B water *). *3.= *+.*

5B water *-.) *).3 *)."

EI water "%".-%= *-. *+.+ *).)

0B water *".+ *=.) *=.)

5B water *"." **.= *".

*"st day EI water "%"%* =." =).= =-."

0B water *=.+ *-.* *."

5B water **. *.# *=.-

EI water "%".-%= *3.+ =".3 =#.-

0B water *".3 *=.+ **.

5B water *#.+ **." *".-

*3th day EI water "%"%* ".- .+ =.*

0B water **.) *." *=.+

5B water "3.+ *#. ".3

EI water "%".-%= ==." =.# =."

0B water *#." **.# *#.) 5B water "3. *#.# ".*

-)th day EI water "%"%* +.) .= 3.-

0B water "3. *#.= ".+

5B water "3.* ".+ ".=

EI water "%".-%= =3. ".+ #."

0B water "3.+ *#.3 "."

5B water "3." ". "3.3

3th day EI water "%"%* .) -*." -".)

0B water "+. ". "3.3

5B water ").3 "3.* "+.3

EI water "%".-%= *.) .3 =.* 0B water "). "3.# "+.)

5B water ").* "+.- ").+

0B L 0iddle Bgunpa 5B L 5ower Bgunpa

The results got from the chemical analyses showed that the three water samples have different

concentrations of chemical composition. The concentrations of chemicals in water sample at 5ower Bgunpa

stream were higher than that of the middle one as a result of discharging of more wastewater into the stream at

this section. 0oreover, the chemical properties of potable water from the Eniversity of Ibadan ?ater

Treatment lant were lower than that of water from Bgunpa stream. The concentration of :a and H of Bgunpa

stream almost doubled that of potable water. The level of acidity, pA, CB=8 and ACB=

8 of water at 5ower

Bgunpa were higher than that of 0iddle one due to presence of more impurities as water moves downstream.The compressive strength of cubes produced with potable water increased with ages as shown in

<igures " and *. re8*3 days, the increment in strength was very rapid but beyond, its rate of strength

development reduces as expected for a normal concrete. Bn the other hand, the strength development of cubes

cast with Bgunpa stream water was not as that rapid on comparing with those of potable water as shown in

<igures " and *. The cubes started to loose compressive strength after "th day of concreting. The highest



compressive strength for concrete cubes of mix ratio "%"%* cast with water got from 0iddle Bgunpa was

*+.*:(mm* whilst that of 5ower Bgunpa was *).":(mm*.

/eferring to Table * for concrete mix ratio of "%"%*, the expected compressive strength should be

#:(mm* or thereabout. Bnly cubes cast with potable water have mean compressive strength of =.*:(mm*.

Bn the other hand, the *3th day mean compressive strengths of concrete cubes of mix ratio "%".-%= cast with

water from 0iddle and 5ower Bgunpa were *#.) and ".*:(mm* respectively. <or a normal concrete cube of

mix ratio "%".-%=, the expected *3th day compressive strength should be =#:(mm* or thereabout. This shows

clearly that the water from Bgunpa stream contains chemicals that retard development of concrete compressive

strength. Bn comparing with chemical constituents of portable water, these can be attributed to the presence of very high concentrations of :a, H, 4B

*8, Cl8, CB=8, ACB=

8 and B8 . In addition, the level of acidity of

Bgunpa stream water was higher than that of potable water. 0oreover, the Bgunpa stream water has high pA

value prohibiting its usefulness in concrete production. The compressive strength values of cubes cast with

water from 5ower Bgunpa stream were lower than that of 0iddle Bgunpa. This can traced to presence of

higher concentrations of H, :a, 4B*8, CB=

8 and Cl8 in water at 5ower Bgunpa stream section.

<igure "% Compressive strength of concrete cubes with mix "%"%*



<igure *% Compressive strength of concrete cubes with mix "%".-%=

C'n&#u(i'n(

2n in8depth study of the effect of water obtained from two sections of Bgunpa stream on concrete

compressive strength has been carried out. The following facts emerged%

Bgunpa stream water contains high concentration of chemicals that inhibit the development of

concrete compressive strength.

In general, for all construction that involves using concrete, the need to investigate suitability of water

proposed for concrete work prior to commencement of work should be strengthened by all structural and

civil engineers.

otable water is relatively scarced in developing and third world countries, the temptation is always

there to use available water. The engineers8in8charge of construction work should ensure that contractors

comply strictly with specification of water for concrete work

Re%eren&e(

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5ondon.

;4 "33"% art "#3 &"3='% 0ethod for making test cubes from fresh concrete, ;ritish 4tandard Institute,

5ondon.



;4 "33"% art "") &"3='% 0ethod for determination of compressive strength of concrete, ;ritish 4tandard

Institute, 5ondon.

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on properties and durability of concrete, Dlsevier, Cement and Concrete Composities, *3&-'%" M -#.

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effective applications of retarding admixture to improve the

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