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Cement And Water Saving With Water Reducers

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

In India 0.93 kg of CO2 is emitted in the production of one kg of cement. In the financial year 2009-10 India produces 200 million tonnes of cement. In the production of this cement 186 million tonnes of CO2 was emitted in the atmosphere during financial year of 2009-10.

The availability of water in India per person per year in 1950 was 5177 cu.m. In the year 2009 it is reduces to 1700 cu.m.

If 50 million tonnes cement in making concrete uses water reducers 7500000 tonnes of cement can be saved. 3750000 kl of potable water will be saved and the saving of Rs. 3300 crores per year to construction industry. This amount is worked out after adjusting the cost of water reducers. Less cement used means less cement required to be produce by the cement factories resulting 6975000 tonnes of CO2 will be prevented to be emitted to the atmosphere. These are worked out with an average saving of 15% cement and 15% water.

CO2 emission is word problem, but for India in addition to CO2 it has problems of Air, Water, Soil, Food and Noise pollutions. Less densily populated countries may cope with these problems but for India it is of the top concern. The population figures of 2009 is, India 350 person per sq.km, China 132 person per sq.km and USA only 34 person per sq.km. The figures of 2006 CO¬2 emissions are USA 658.60 tonnes per sq.km, China 611.76 tonnes per sq.km and India 459.35 tonnes per sq.km. Every one should contribute his or her efforts to save the environment from pollution. Those involve in the construction activities can contribute their share by proper design of concrete Mixes. This is best illustrated by the following examples.
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Concrete Mix Design – M70 Grade of Concrete (OPC 53 Grade)

Concrete mix design – M70 grade of concrete provided here is for reference purpose only. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

A. Design Stipulation:
Characteristic comprehensive Strength @ 28 days = 70 N/mm2
Maximum size of aggregate = 20 mm
Degree of workability = Collapsible
Degree of quality control = Good
Type of exposure = Severe
Minimum cement content as per is 456-2000

B. Test data for concrete ingredients
Specific gravity of cement = 3.15
Specific gravity of fly ash = 2.24
Specific gravity of microsilica = 2.21
Setting time of cement initial = 165 min, final = 270min
Cement compressive strength =
39.0 N/mm2 @ 3 days
51.0 N/mm2 @ 7 days
64.2 N/mm2 @ 28 days
Specific gravity of coarse aggregates (ca) and fine aggregates (fa)
20 mm 2.729
10 mm 2.747
R/sand 2.751
C/sand 2.697

Water absorption
20 mm 1.540, 10mm 1.780, R/sand 3.780, C/sand 4.490

Characteristic strength @ 28 days 70 N/mm2
Target mean strength : Depend upon degree of quality control “good” and considering (std. Dev.As 5 N/mm2)

Characteristic strength given by the relation 70 +(1.65 *5 ) = 78.25 N/mm2

C. Quantities of ingredients (By Absolute Volume Method )
Actual cement used = 486 kg/cum
Actual fly ash used = 90 kg/cum
Actual microsilica used = 24 kg/cum
W/C fixed = 0.26
Absolute volume of cement = 0.154
Absolute volume of air = 0.02
Absolute vol of water. = 0.156
Absolute vol of fly ash. = 0.040
Absolute vol of microsilica = 0.011

Total volume of CA and FA used = 1.00-(0.155+0.044+0.022+0.02 +0.154)
= 0.619 Cum

D. Aggregate percent used.
20 Mm = 24, 10 mm = 36, r/sand = 20, c/sand = 20

(2.729*0.24) + (2.747*0.36) +(2.751* 0.20 )+(2.697*0.20) *0.619*1000
405+612+340+334=1691

Aggt: cement = 2.82 : 1

Mix proportion = 0.26:1:0.57:0.56:1.02:0.67

E. Abstract:
20 mm = 405 kg/cum
10 mm = 612 kg/cum
r/sand = 340 kg /cum
c/sand = 334 kg/cum
water = 154 kg/cum

Admixture 0.50 % BY WT OF (C+F+MS) ASTP-1 OF BASF

Cube Compressive Strength (N/mm2)
3 days = 49.13
7 Days = 59.57
28 Days = 81.49

Note: Mix design is same for Crane bucket and Pump concrete only admixture dosage will fine tuned by 0.05 to 0.10%
We are thankful to Deshmukh D S for submitting this very useful mix design information to us.

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Concrete Mix Design – M60 Grade Of Concrete (OPC 53 Grade)

Concrete mix design – M60 grade of concrete provided here is for reference purpose only. Actual site conditions vary and thus this should be adjusted as per the location and other factors.

A. Design Stipulation:
Charastaristic comprehensive Strength @ 28 days = 60 N/mm2
Maximum size of aggregate = 20 mm
Degree of workability = Collapsible
Degree of quality control = Good
Type of exposure = Severe
Minimum cement content as per is 456-2000

B. Test data for concrete ingredients
Specific gravity of cement = 3.15
Specific gravity of fly ash = 2.24
Specific gravity of microsilica = 2.21
Setting time of cement initial = 120 min, final = 185 min
Cement compressive strength =
45.21 N/mm2 @ 3 days
54.82 N/mm2 @ 7 days
69.32 N/mm2 @ 28 days
Specific gravity of coarse aggregates (ca) and fine aggregates (fa)
20 mm 2.729
10 mm 2.747
R/sand 2.751
C/sand 2.697

Water absorption
20 mm 1.540, 10mm 1.780, R/sand 3.780, C/sand 4.490

Characterstic strength @ 28 days 60 N/mm2
Target mean strength : Depend upon degree of quality control “good” and considering (std. Dev.As 5 N/mm2)

Characteristic strength given by the relation 60 +(1.65 *5 ) = 68.25 N/mm2

C. Quantities of ingredients ( by absolute volume Method )
Actual cement used = 450 kg/cum
Actual fly ash used = 80 kg/cum
Actual microsilica used = 40 kg/cum
W/C fixed = 0.24
Absolute volume of cement = 0.143
Absolute volume of air = 0.02
Absolute vol of water. = 0.137
Absolute vol of fly ash. = 0.036
Absolute vol of microsilica = 0.018

Total volume of CA and FA used = 1.00-(0.143+0.036+0.018+0.02 +0.137)
= 0.619 Cum

D. Aggregate percent used.
20 Mm = 31, 10 mm = 25, r/sand = 34, c/sand = 10

(2.729*0.31) + (2.747*0.25) +(2.751* 0.34 )+(2.697*0.10) *0.619*1000
546+444+604+174=1768
Aggt: cement = 3.10 : 1

Mix proportion = 0.24:1:1.06:0.30:0.78:0.96

E. Abstract:
20 mm 546 kg/cum
10 mm 444 kg/cum
r/sand 604 kg /cum
c/sand 174 kg/cum
water 137 kg/cum

Admixture 1.80 % By wt of (C+F+MS) chemsonite SP 450XL-B

Cube Compressive Strength (N/mm2)
3 days = 40.98
7 Days = 57.71
28 Days = 70.96

Note: Mix design is same for crane bucket and pump concrete only admixture dosage will fine tuned by 0.10%.
We are thankful to Deshmukh D S for submitting this very useful mix design information to us.

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Mix Design For Concrete Roads As Per IRC-15-2002

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

Check out the Mix Design For Concrete Roads As Per IRC:15-2011

ABSTRACT:
The stresses induced in concrete pavements are mainly flexural. Therefore flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. A simple method of concrete mix design based on flexural strength for normal weight concrete mixes 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 stresses induced in concrete pavements are mainly flexural. Therefore, flexural strength is more often specified than compressive strength in the design of concrete mixes for pavement construction. It is not perfectly reliable to predict flexural strength from compressive strength. Further, various codes of the world specified that the paving concrete mixes should preferably be designed in the laboratory and controlled in the field on the basis of its flexural strength. 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 of concrete i.e. with the same water-cement ratio, higher strength cement will produce concrete of higher compressive and flexural strength.

MIX DESIGN DETAILS
IRC: 15-2002 specified that for concrete roads OPC should be used. This code also allowed PPC as per IS: 1489 may also be used. Accordingly OPC + fly ash may be used in concrete roads. However, IS: 456-2000 specified that fly ash conforming to grade-1 of IS-3812 may be used as part replacement of OPC provided uniform blended with cement is essential. The construction sites where batching plants are used this may be practicable. In ordinary sites where mixer or hand mixing are done uniform blending of fly ash with cement is not practicable. At such construction sites, PPC may be used.

1 Characteristic Flexural Strength at 28 days 4.5N/mm2
2 Cement Three mixes are to be designed
MIX-A
With PPC (Flyash based) conforming to IS:1489-part-I-1991. 7 days strength 37.5N/mm2. Specific Gravity: 3.00
MIX-B
With OPC-43- Grade conforming to IS: 8112-1989. 7 days strength 40.5N/mm2. Specific Gravity : 3.15
MIX-C
With OPC of Mix-B and Fly ash conforming to IS:3812 (Part-I)-2003 Specific Gravity : 2.20
Note Requirements of all the three mixes are the same. Fine Aggregate, Coarse Aggregate and Retarder Super plasticizer are the same for all the three mixes.
3 Fly ash replacement 25% Fly ash is required to be replaced with the total cementitious materials.
4 Maximum nominal size of aggregates 20 mm Crushed aggregate
5 Fine aggregate River sand of Zone-II as per IS:383-1970
6 Minimum cement content 350 kg/m3 including Fly ash
7 Maximum free W/C Ratio 0.50
8 Workability 30 mm slump at pour the concrete will be transported from central batching plant through transit mixer, at a distance of 20 Km during June, July months. The average temperature last year during these months was 400C.
9 Exposure condition Moderate
10 Method of placing Fully mechanized construction
11 Degree of supervision Good
12 Maximum of cement content (Fly ash not included) 425 kg/m3
13 Chemical admixture Retarder Super plasticizer conforming to IS:9103-1999. With the given requirements and materials, the manufacturer of Retarder Super plasticizer recommends dosages of 10 gm per kg of OPC, which will reduce 15% of water without loss of workability. For fly ash included cement dosages will be required to be adjusted by experience/ trials.
14 Values of Jaxo- 1.65 x 0.5 N/mm2

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How To Make Concrete At Site? M 25 Example

By
Er. Kaushal Kishore ,
Materials Engineer, Roorkee

PORTLAND CEMENT:
Joseph Aspdin, a mason at Leeds prepared a cement in 1824 by heating a mixture of finely-divided clay and hard limestone in a furnace until CO2 had been driven off; this temperature was much lower than that necessary for clinkering. The prototype of modern cement was made in 1845 by Isaac Johnson, who burnt a mixture of clay and chalk until clinkering, so that the reaction necessary for the formation of strongly cementitious compound took place. The name ‘Portland Cement’ was given due to the resemblance of the colour and quality of the hardened cement to Portland stone- a limestone quarried in Doset.

The process of manufacturing of cement consists essentially of grinding the raw materials ( calcareous materials such as limestone or chalk and argillaceous materials such as shale or clay), mixing them intimately in certain proportion and burning in a large rotary kiln at a temperature of upto about 14500C when the material sinters and partially fuses into balls known as clinker. The clinker is cooled and ground to a fine powder, with some gypsum added, and the resulting product is the commercial Portland Cement so widely used throughout the world.

MAKING CONCRETE:
Just mix cement, aggregates and water, cast this mix in a mould, open the mould next day. A uniform hard mass will be found, which is known as concrete, any body can make it. The simplecity in making concrete make this material to be look like very simple in its production, yet it as not so simple. Due to ignorance about concrete no other building materials ever mis-used as concrete in the construction. In India concrete is being used in the construction since the last 70 years. Yet 80% of the builders have no proper understanding of this materials. Go to any construction site (except big construction sites) you will find that sand and aggregates are being taken in iron tasla or cane baskets to charge the mixer without the consideration of site aggregates actual grindings, moisture content and bulking of sand. The water is poured in the mixer without any measured quantity. It could be well imagine what sort of concrete structure will be made with the concrete being produced in this crude method.

Most of the contractors, builders, masons etc. still follow 1:2:4 or 1:1.5:3 mixes they are not aware of Design Mixes and Concrete Admixtures. This paper described how Design Mixes can be converted into volume with 1 Bag Cement, 2 Boxes of sand and 4 Boxes of Aggregate. The site practical problem is the dispersion of water and liquid admixtures into the mixer. For this the site should fabricate a plastic circular graduated measuring container of 30 lit capacity with a tap fitted at its bottom. This container is to be fitted on top of the mixer. From this container water and liquid admixtures can conveniently poured direct into the mixer in a measured quantity.
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