Mix Design for Concrete Roads as Per IRC_15-2011
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10/21/2015 Mix Design For Concrete Roads As Per IRC:152011
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Mix Design For Concrete Roads As Per IRC:152011Posted in Mix Design, Research Papers | Email This Post |
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ByKaushal Kishore, Materials Engineer, Roorkee
ABSTRACT:The stresses induced in concrete pavements are mainly flexural. Therefore flexural strength is more often specified than compressive strength in thedesign of concrete mixes for pavement construction. A simple method of concrete mix design based on flexural strength for normal weight concretemixes is described in the paper.
INTRODUCTION:Usual criterion for the strength of concrete in the building industry is the compressive strength, which is considered as a measure of quality concrete.However, in pavement constructions, such as highway and airport runway, the flexural strength of concrete is considered more important, as the stressesinduced in concrete pavements are mainly flexural. Therefore, flexural strength is more often specified than compressive strength in the design ofconcrete mixes for pavement construction. It is not perfectly reliable to predict flexural strength from compressive strength. Further, various codes of theworld specified that the paving concrete mixes should preferably be designed in the laboratory and controlled in the field on the basis of its flexuralstrength. Therefore, there is a need to design concrete mixes based on flexural strength.
The type of aggregate can have a predominant effect, crushed rock aggregate resulting in concrete with higher flexural strength than uncrushed (gravel)aggregates for comparable mixes, assuming that sound materials are used. The strength of cement influences the compressive and flexural strength ofconcrete i.e. with the same watercement ratio, higher strength cement will produce concrete of higher compressive and flexural strength.
MIX DESIGN DETAILSIRC: 152011 specified that for concrete roads OPC should be used. This code also allowed PPC as per IS: 1489 (Part1) with flyash content not morethan 20 percent by weight of PPC. Accordingly OPC + fly ash may be used in concrete roads. Flyash shall be not more than 20 percent by weight ofcementitious material. However, IS: 4562000 specified that fly ash conforming to grade1 of IS” 3812 may be used as part replacement of OPCprovided uniform blended with cement is essential. The construction sites where batching plants are used this may be practicable. In ordinary sites wheremixer or hand mixing are done uniform blending of fly ash with cement is not practicable. At such construction sites, PPC may be used. PPC should beused with caution where rapid construction methods like slip form is being used. Joints cutting also need early strength.
1 Characteristic Flexural Strengthat 28 days
: 4.5 N/mm2
2 Cement : Three mixes are to be designedMIXA
With PPC (Flyash 18 percent based)conforming to IS:1489partI1991. 7 daysstrength 37.5 N/mm2. Specific Gravity :3.00
MIXB
With OPC43 Grade conforming to IS:81121989. 7 days strength 40.5 n/mm2.Specific Gravity : 3.15
MIXC
With OPC of MixB and Fly ashconforming to IS:3812 (PartI)2003Specific Gravity : 2.20
Note: Requirements of all the three mixesare the same. Fine Aggregate, CoarseAggregate and Retarder Super plasticizerare the same for all the three mixes.
3 Fly ash replacement : 20% Fly ash is required to be replaced withthe total cementitious materials.
4 Maximum nominal size ofaggregates
: 31.5 mm Crushed aggregate
5 Fine aggregate and coarseaggregate grading
: Given in Table 1
6 Minimum cement content for 4.5N/mm2 characteristic flexuralstrength:
: (a) OPC shall not be less than 360 kg/m3.
(b) PPC shall not be less than 425 kg/m3.
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Fly ash in it 20% maximum by weight oftotal cementitious materials
(c) OPC + Fly ash mix OPC shall not beless than 340 kg/m3. Fly ash 20% maximumby weight of cementations material
7 Maximum free W/C Ratio : (a) For OPC 0.45
(b) For PPC 0.50
8 Workability : 40 mm slump at pour the concrete will betransported from central batching plantthrough transit mixer, at a distance of 15Km during June, July months. The averagetemperature last year during these monthswas 300C.
9 Exposure condition : Moderate10 Method of placing : Fully mechanised construction11 Degree of supervision : Good12 Maximum of cement content : (a) OPC 425 kg/m3
(b) PPC 425 kg/m3
13 Chemical admixture : Retarder Super plasticizer conforming toIS:91031999. With the given requirementsand materials, the manufacturer of RetarderSuper plasticizer recommends dosages of1% bw of OPC, which will reduce 15% ofwater without loss of workability. For flyash included cement dosages will berequired to be adjusted by experience/trials.2% maximum by weight ofcementitious material
14 Values of Z x (for NationalHighway)
: 1.96 x 0.40
TEST DATA FOR MATERIALS AND OTHER DETAILS1. The grading of fine aggregate, 1 & 2 aggregates are as given in Table. 1.2. Properties of aggregates
Tests Fine aggregate Aggregate 1 Aggregate 2
Specific Gravity2.65 2.65 2.65
Water Absorption %0.8 0.5 0.5
3. Target average flexural strength for all A, B and C mixesS = S+ Zq=4.5 + 1.96 x 0.40= 5.3 N/mm2 at 28 days age4. For Mix A, B and C free W/C ratio with crushed aggregate and required average flexural target strength of 5.3 N/mm2 at 28 days from Fig. 1 Curve Dfound to be 0.42. This is lower than specified maximum W/C ratio value of 0.45 for OPC and 0.50 for PPC.
Note:In absence of cement strength, but cement conforming to IS Codes, assume from Fig. 1
Curve C and D for OPC 43 Grade
Take curves C and D for PPC, as PPC is being manufactured in minimum of 43 Grade of strength.
5. Other data’s: The Mixes are to be designed on the basis of saturated and surface dry aggregates. At the time of concreting, moisture content of siteaggregates are to be determine. If it carries surface moisture this is to be deducted from the mixing water and if it is dry add in mixing water the quantityof water required for absorption. The weight of aggregates are also adjusted accordingly.
DESIGN OF MIXA WITH PPCa) Free W/C ratio for the target flexural strength of 5.3 N/mm2 as worked out is 0.42 for first trial.
b) Free water for 40 mm slump from Table 2 for 31.5 mm maximum size of aggregate.2/3×170 + 1/3×200= 180 kg/m3
From trials it is found that Retarder Super plasticizer at a dosages of 1.3% bw of PPC may reduce 15% water without loss of workabilityThen water = 180 – (180 x 0.15) = 153 kg/m3
c) PPC = 153/0.42 = 364 kg/m3 (Required minimum PPC is 425 kg/m3)
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d) Formula for calculation of fresh concrete weight in kg/m3
Um = 10 x Ga (100 – A) + Cm(1 – Ga/Gc) – Wm (Ga – 1)Where,Um=Weight of fresh concrete kg/m3Ga=Weighted average specific gravity of combined fine and coarse aggregate bulk, SSDGc=Specific gravity of cement. Determine actual value, in absence assume 3.15 for OPC and 3.00 for PPC (Fly ash based)A=Air content, percent. Assume for trial entrapped air 1.5%
For 31.5 mm maximum size of aggregateThere is always entrapped air in concrete. Therefore ignoring entrapped air value as NIL will lead the calculation of higher value of density. Take exactvalue of air as obtained in the testWm=Mixing water required in kg/m3
Cm=Cement required, kg/m3
Note: The exact density may be obtained by filling and fully compacting constant volume suitable metal container from the trial batches of calculateddesign mixes. The mix be altered with the actual obtained density of the mix.
Um =10 x Ga (100 – A) + Cm (1 – Ga/Gc) – Wm (Ga – 1)=10 x 2.65 (100 – 1.5) + 425(1 2.65/3.00) – 153 (2.65 1)=2409 kg/m3
e) Aggregates = 2409 – 425 – 153 = 1831 kg/m3
f) Fine aggregate = 1831 x 0.45 = 824 kg/m3
Aggregate 1 = 1831 x 0.29 = 531 kg/m3
Aggregate 2 = 1831 x 0.26 = 476 kg/m3
g) Thus for 4.5 N/mm2 flexural strength quantity of materials per cu.m. of concrete on the basis of saturated and surface dry aggregates:
Water = 153 kg/m3
PPC = 425 kg/m3
Fine Aggregate (sand) = 824 kg/m3
Aggregate (1) = 531 kg/m3
Aggregate (2) = 476 kg/m3
Retarder Super Plasticizer 1.3% bw of PPC = 5.525 kg/m3
MIX B WITH OPCa) Water = 180 – (180 x 0.15) = 153 kg/m3
b) OPC = 153/0.42 = 364 kg/m3
c) Density: 10 x 2.65 (100 – 1.5) + 364 (1 – 2.65/3.15) – 153 (2.65 – 1)= 2416 kg/m3
d) Total Aggregates = 2416 – 364 – 153 = 1899 kg/m3
Aggregate 1 = 1899 x 0.29 = 551 kg/m3
Aggregate 2 = 1899 x 0.26 = 494 kg/m3
Fine Aggregate = 1899 x 0.45 = 854 kg/m3
e) Thus for 4.5 N/mm2 flexural strength quantity of materials per cu.m of concrete on the basis of SSD aggregates are given below:Water = 153 kg/m3
OPC = 364 kg/m3
Fine Aggregate (sand) = 854 kg/m3
Aggregate (1) = 551 kg/m3
Aggregate (2) = 494 kg/m3
Retarder Super Plasticizer 1% bw OPC = 3.640 kg/m3
MIXC WITH OPC + FLY ASHWith a total cementitious material of 430 kg/m3,OPC = 430 x 0.80 = 344 kg/m3
Fly ash = 430 x 0.20 = 86 kg/m3
Mix on the basis of SSD Aggregates,(1) Water as worked out earlier = 153 kg/m3
(2) OPC = 344 kg/m3
(3) Fly ash = 86 kg/m3Density = 10 x 2.65 (100 – 1.5) + 430 (1 – 2.65/3.00) – 153 (2.65 – 1) = 2410 kg/m3
Total Aggregates = 2410 – 153 – 344 – 86 = 1827 kg/m3
(4) Fine aggregate 0.45 x 1827 = 822 kg/m3
(5) Aggregate (1) 0.29 x 1827 = 530 kg/m3
(6) Aggregate (2) 0.26 x 1827 = 475 kg/m3
(7) Retarder super plasticizer 1.5% bw of cementitious material = 6.450 kg/m3
Note:(1) Cementitious material worked out as per IRC : 152011, which specified: In case fly ash (as per IS: 3912 Part 1) is blended at site, the quantity of flyash shall be restricted to 20 percent by weight of cementitious material and the quantity of OPC in such a blend shall not be less than 340 kg/m3 .
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(2) After the first trial mix, its actual density is to be determined, as specified elase where in this paper. The mix proportions shall then be worked outaccordingly including the water content, the dosages of Retarder SP for required workability keeping the free w/c ratio with in the permissible limits andadjusting it according to the required flexural strength.
(3) The mix proportions given in this paper are for first trial and to be adjusted as per actual site materials, conditions and requirements.
For 4.5 N/mm2 flexural strength quantity of material per cu.m of concrete on the basis of saturated and surface dry aggregates of Mix ‘A’, ‘B’and ‘c’ are given below:
Materials MIX. ‘A’ with PPC Mix. ‘B’ with OPC Mix. ‘C’ withOPC+Flyash
Water kg/m3153 153 153
PPC kg/m3425 — —
OPC kg/m3— 364 344
Flyash kg/m3— — 86
Fine Agg. kg/m3824 854 822
Agg. (1) kg/m3531 551 530
Agg. (2) kg/m3476 494 475
Retarder Super plasticizerkg/m3 5.525 3.640 6.450
W/ Cementitious ratio0.36 0.42 0.356
Note:1. For exact W/C ratio the water in admixture should also be taken into account.2. PPC reduces 5% water demand. If this is found by trial then take reduce water for calculation.3. If the trial mixes does not gives the required properties of the mix, it is then required to be altered accordingly. However, when the experiences growswith the particular set of materials and site conditions very few trials will be required, and a expert of such site very rarely will be required a 2nd trial.
CONCLUSION1. For 4.5 N/mm2 flexural strength concrete having same material and requirement, but without water reducer, the OPC required will be 180/0.42 = 429kg/m3
2. With the use of superplasticizer the saving in OPC is 65 kg/m3 and water 27 lit/m3.
3. In the financial year 20092010 India has produces 200 million tonnes of cement. In India one kg of cement produce emitted 0.93 kg of CO2. Thus theproduction of 200 million tonnes of cement had emitted 200 x 0.93 = 186 million tonnes of CO2 to the atmosphere.
4. If 50 million tonnes cement in making concrete uses Water Reducers 7500000 tonnes of cement can be saved. 3750000 KL of potable water will besaved and the saving of Rs. 3300 crores per year to the construction Industry. 6975000 tonnes of CO2 will be prevented to be emitted to the atmosphere.The benefits in the uses of water reducers not limited to this. When water reduces shrinkage and porosity of concrete are reduces which provides thedurability to concrete structures.
5. India is facing serious air, water, soil, food and noise pollution problems. Every efforts therefore are necessary to prevent pollution on top prioritybasis.
6. As the stress induced in concrete pavements are mainly flexural, it is desirable that their design is based on the flexural strength of concrete. Thequality of concrete is normally assessed by measuring its compressive strength. For pavings, however, it is the flexural strength rather than thecompression strength of concrete which determine the degree of cracking and thus the performance of road, and it is imperative to control the quality onthe basis of flexural strength.
7. As per IRC: 152011, in case of small size projects, where facilities for testing beams with three print loading are not available, in such cases, the mixdesign may be carried out by using compressive strength values and there after flexural strength will be determined as per correlation between flexuralstrength with compressive strength given the following equation.
Where fcr is the flexural strength in MPa or N/mm2 and fck is the characteristic compressive strength in MPa or N/mm2 as per IS: 4562000.
REFERENCES:
1 IS : 3831970 Specifications for coarse and fine aggregatesfrom natural sources for concrete (secondrevision) BIS, New Delhi
2 IS: 4562000 Code of practice for plain and reinforced
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concrete (fourth revision), BIS, New Delhi3 IS: 91031999 Specification for admixtures for concrete (first
revision) BIS, New Delhi4 IS: 81121989 Specifications for 43 Grade ordinary portland
cement (first revision) BIS, New Delhi5 IS: 2386 (PartIII) 1963 method of test for aggregate for concrete.
Specific gravity, density, voids, absorption andbulking, BIS, New Delhi
6 IS: 3812 (PartI) 2003 Specification for pulverized fuel ash: PartI foruse as pozzolana in cement, cement mortar andconcrete (second revision) BIS, New Delhi
7 IS: 1489PartI 1991 Specifications for portland pozzolana cement(PartI) Flyash based. (Third revision), BIS,New Delhi
8 IRC: 152011 – Standard specifications and code of practice for construction ofconcrete road (Fourth revision)
9 Kishore Kaushal, “Concrete Mix Design Based on Flexural strength for AirEntrained Concrete”, Proceeding of 13th Conference on our World in Concreteand Structures, 2526, August, 1988, Singapore.
10 Kishore Kaushal, “Method of Concrete Mix Design Based on FlexuralStrength”, Proceeding of the International Conference on Road and RoadTransport Problems ICORT, 1215 December, 1988, New Delhi, pp. 296305.
11 Kishore Kaushal, “Mix Design Based on Flexural Strength of AirEntrainedConcrete”. The Indian Concrete Journal, February, 1989, pp. 9397.
12 Kishore Kaushal, “Concrete Mix Design Containing Chemical Admixtures”,Journal of the National Building Organization, April, 1990, pp. 112.
13 Kishore Kaushal, “Concrete Mix Design for Road Bridges”, INDIANHIGHWAYS, Vol. 19, No. 11, November, 1991, pp. 3137
14 Kishore Kaushal, “ Mix Design for Pumped Concrete”, Journal of Central Boardof Irrigation and Power, Vol. 49, No.2, April, 1992, pp. 8192
15 Kishore Kaushal, “Concrete Mix Design with Fly Ash”, Indian Construction,January, 1995, pp. 1617
16 Kishore Kaushal, “HighStrength Concrete”, Bulletin of Indian ConcreteInstitute No. 51, AprilJune, 1995, pp. 2931
17 Kishore Kaushal, “Concrete Mix Design Simplified”, Indian Concrete InstituteBulletin No. 56, JulySeptember, 1996, pp.2530.
18 Kishore Kaushal, “Concrete Mix Design with Fly Ash & Superplasticizer”, ICIBulletin No. 59, AprilJune 1997, pp. 2930
19 Kishore Kaushal. “Mix Design for Pumped Concrete”, CE & CR October, 2006,pp. 4450.
Table. 1: Grading of Aggregates
IS SieveDesignation Percentage of passing by mass
Fineaggregatefrom river
45%
Crushed aggregate Combinedgrading ofmix
IRC: 152011recommended gradingof combined aggregatesfor pavement qualityconcrete (PQC)
(1)
29%
(2)
26%
31.50 mm100 100 100 100 100
26.50 mm100 100 98 99 85 – 95
19.0 mm100 100 25 81 68 – 88
9.50 mm100 46 0 58 45 – 65
4.75 mm94 5 44 30 – 55
600 micron42 0 19 8 – 30
150 micron10 5 5 – 15
75 micron2 1 0 – 5
Table. 2: Approximate freewater content (kg/m3) required to give various levels of workability for nonairentrained (with normal entrappedair) concrete.
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Maximum size ofaggregate (mm) Type of
aggregateSlump (mm)
25 + 1040 + 1031.5
Uncrushed
Crushed
160
190
170
200
Note: When coarse and fine aggregate of different types are used, the free water content is estimated by the expression.2/3Wf+1/3WcWhere,Wfsub>= Free water content appropriate to type of fine Aggregate
And Wc= Free water content appropriate to type of coarse aggregate.
We at engineeringcivil.com are thankful to Er. Kaushal Kishore for submitting the revised mix design as per IRC:152011. This will be of great help toall civil engineering students and faculty who are seeking information on mix design based on revised IRC.
More Entries :
Mix Design For M35 Grade Of ConcreteUnderstanding Nominal and Design MixesMix Design M50 GradeMix Design For Concrete Roads As Per IRC152002Mix Design With SuperplasticizersMix Design M40 GradeList Of Research Publications Of Kaushal KishoreConcrete Mix Design M60
Comments
Farhan July 20, 2013 at 1:35 pm
Thank you sir for your valuable information
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Reply Link QuoteOmona Richard November 4, 2013 at 12:33 pm
What is volume of materials to be used in 1cubic meter of concreteOne (1 cubic meter) of concrete is how many kilograme of materials inside
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