ACI Design Mix Example

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ACI Mix Design ExamplePublish date: August 13, 2007 | Author: Pavement Interactive

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A concrete mi! is to be designed "or use in a 2#0 mm $10 inch% thic& 'PCP (avement) he

desired (ro(erties are:

• *lum( + 2# mm $1)0 inch%

• Average 2-da. "le!ural strength o" at least /)# Pa $#0 (si%

• Coarse aggregate: nominal ma!imum sie + 37)# mm $1)# inch%, dr.-rodded eight +

100 &g4m3 $100 lb4"t3%, s(eci"ic gravit. + 2), moisture content + 1)0 (ercent,

absor(tion + 0)# (ercent

• 5ine aggregate: "ineness modulus + 2)0, s(eci"ic gravit. + 2)/, moisture content + #

(ercent, absor(tion + 0)7 (ercent

• Air content: /)# 6 )# (ercent

• a!imum alloable ater-cement ratio + 0)//

• inimum cement content + 33# &g $## lb%

• ensit. o" ater + 1000 &g4m3 $2)/ lb4"t3%

• *(eci"ic gravit. o" (ortland cement + 3)1# $t.(icall. assumed value%

Slump

*(eci"ied as 2# mm $1)0 inch%) his is t.(ical "or (avement PCC)

Maximum Aggregate Size

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*(eci"ied as 37)# mm $1)# inches%) his is ell ithin the general ACI recommendation that the

nominal ma!imum sie be limited to 143 o" slab de(th) 8o rein"orcing steel ill be used so the

thumbrule (ertaining to clear s(ace beteen rein"orcing bars is not a((licable)

Mixing Water and Air Content Estimation

In order to achieve an air content above 2 6 3 (ercent, PCC must be air-entrained) here"ore,

using the mi!ing ater and air content estimation table, air-entrained PCC ith a target 2# mm

$1 inch% slum( and a 37)# mm $1)# inch% nominal ma!imum aggregate sie ill re9uire about1/ &g4m3 $2#0 lb4.d3% o" mi!ing ater) Enough air-entraining admi!ture ill be added to

achieve a #)# (ercent air content $in the middle o" the s(eci"ied /)# 6 )# (ercent band%) ee( in

mind that ater-reducing admi!tures can reduce ater re9uirements b. about # 6 10 (ercent andseveral ill also increase the entrained air content b. about 0)# 6 1 (ercent)

Converting eight to volume, the recommended volume o" mi!ing ater in one cubic meter $one

cubic .ard% o" PCC is 0)1/ m3 $/)00 "t3%) he amount o" entrained air ill be #)# (ercent o" the

total volume or 0)0## m3 $1)/; "t3%)

Water-Cement Ratio

*ince the s(eci"ied strength is "le!ural strength, a conversion "actor must be used to obtain an

a((ro!imate com(ressive strength in order to use the ater-cement ratio vs) com(ressive

strength table) A good rule-o"-thumb $as used in the ACI Code% is:

here: + com(ressive strength

*olving "or com(ressive strength, e get about #1)7 Pa $7,#00 (si%) his value is not listed in

able 17 "or determining ater-cement ratios) here"ore, a more involved determination o" theater-cement ratio is needed)


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he recommended volume o" (ortland cement in one cubic meter $one cubic .ard% o" PCC is:

$etric% $English%

Coarse Aggregate Content

>sing the coarse aggregate content table ith the given nominal ma!imum aggregate sie o"

37)# mm $1)# inches% and the given "ine aggregate "ineness modulus o" 2)0, the recommended

volume "raction o" coarse aggregate is 0)71) his means that the coarse aggregate should occu(.71 (ercent o" the total volume) ?oever, this volume o" aggregate includes the volume o" air

beteen the aggregate (articles) here"ore, this 71 (ercent volume must be converted to a

eight o" aggregate) @iven the 100 &g4m3 $100 lb4"t3% dr.-rodded unit eight, this e9uates to:

$etric% $English%

8o, the recommended volume o" coarse aggregate $hich is no onl. the solid volume o"

coarse aggregate% in one cubic meter $one cubic .ard% o" PCC is:

$etric% $English%

Fine Aggregate Content

he "ine aggregate content can be "ound b. subtracting the other constituent volumes "rom the

unit volume:

$etric% $English%>nit volume $1 m3 or .d3% 1)000 m3 27)00 "t3

- olume o" mi!ing ater - 0)1/ m3 - /)00 "t3

- olume o" air - 0)0## m3 - 1)/; "t3

- olume o" (ortland cement - 0)121 m3 - 3)2 "t3

- olume o" coarse aggregate - 0)/2/ m3 - 11)/ "t3

+ olume o" "ine aggregate + 0)2#2 m3 + )7; "t3

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here"ore, the eight o" "ine aggregate (er unit volume is:

$etric% $English%

Adjustments for Aggregate Moisture

*ince there is moisture in both the coarse and "ine aggregate their trial batch eights must be

adBusted)

$etric% $English%

Coarse aggregate: 113 ! 1)01 + 11/7 &g4m3 1;17 ! 1)01 + 1;3 lb4.d3

5ine aggregate: # ! 1)0# + ; &g4m3 111; ! 1)0# + 117# lb4.d3

Also, the amount o" mi!ing ater needs to be adBusted because both the coarse and "ineaggregate are et and ill contribute ater to the cement (aste)

$etric% $English%

Coarse aggregate: 113 ! $0)01 6 0)00#% + #)7 &g4m3 1;17 ! $0)01 6 0)00#% + 10 lb4.d3

5ine aggregate: # ! $0)0# 6 0)007% + 2) &g4m3 111; ! $0)0# 6 0)007% + / lb4.d3

here"ore, the amount o" mi!ing ater to be added is:

1/ &g 6 #)7 &g 6 2) &g+ 113)7 &g2#0 lb 6 10 lb 6 / lb+ 1;2 lb

Summary

he "inal trial batch amounts (er unit volume $1 m3 or .d3% are:

$etric% English%

i!ing ater 11/ &g 1;2 lb

Portland cement 30 &g /1 lbCoarse aggregate 11/7 &g 1;3 lb

5ine aggregate ; &g 117# lb

>suall., to ma&e trial batches, something less than the unit volume is made 6 a t.(ical trial batch

sie is 0)03 m3 $1 "t3%) nce the trial batch is made it can be tested "or slum(, air content,

"le!ural strength, com(ressive strength and an. other re9uired (ro(ert.)


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