mix design for pumped concrete with ppc, opc, opc flyash

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Mix Design for Pumped Concrete with PPC, OPC,OPC+Flyash

A simple method of concrete mix design for pumpable concrete based on an

estimated weight of the concrete per unit volume is presented in the

article. The Tables and Figures included are worked out by the author from

a wide range of materials available in the country. The method is suitable

for normal weight concrete and with admixtures.

Kaushal Kishore, Materials Engineer, Roorkee, Uttaranchal

Pumped Concrete

Pumped concrete may be defined as concrete that is conveyed under pressure through either rigid

pipe or flexible hose and discharged directly into the desired location. Pumping may be used for

most all concrete construction, but is especially useful where space or access for construction

equipment is limited.

Pumping equipment consists of pumps which are of three types:

Piston type concrete pumpa.

Pneumatic type concrete pumpb.

Squeeze pressure type concrete pumpc.

Other accessories are rigid pipelines, flexible hose and couplings etc.

A pumpable concrete, like conventional concrete mixes, requires good quality control, i.e. properly

graded uniform aggregates, materials uniformly and consistently batched and mixed thoroughly.

Depending on the equipment, pumping rates may vary from 8 to 130 m3 of concrete per hour.

Effective pumping range varies from 90 to 400 meters horizontally, or 30 to 100 meters vertically.

Cases have been documented in which concrete has successfully been pumped horizontally upto

1400 meters and 430 meters vertically upward. New record values continued to be reported.

Pumping

For the successful pumping of concrete through a pipeline, it is essential that the pressure in the

pipeline is transmitted through the concrete via the water in the mix and not via the aggregate; in

effect, this ensures the pipeline is lubricated. If pressure is applied via the aggregate, it is highly

likely that the aggregate particles will compact together and against the inside surface of the pipe to

form a blockage; the force required to move concrete under these conditions is several hundred

times that required for a lubricated mix.

If, however, pressure is to be applied via the water, then it is important that the water is not blown

through the solid constituents of the mix; experience shows that water is relatively easily pushed

through particles larger than about 600 microns in diameter and is substantially held by particles

smaller than this.

In the same way, the mixture of cement, water and very fine aggregate particles should not be

blown through the voids in the coarse aggregate. This can be achieved by ensuring that the

aggregate grading does not have a complete absence of material in two consecutive sieve sizes

for example, between 10 mm and 2.36 mm. In effect any size of particle must act as a filter to

prevent excessive movement of the next smaller size of materia l.

Basic Considerations

Cement Content

Concretes without admixtures and of high cement content, (over about 460 kg/m3) are liable to

prove difficult to pump, because of high friction between the concrete and the pipeline. Cement

contents below 270 to 320 kg/m3 depending upon the proportion of the aggregate may also prove

difficult to pump because of segregation within the pipe line.

Workability

The workability of pumped concrete in general has an average slump of between 50 mm and 100

mm. A concrete of less than 50 mm slump is impractical for pumping, and slump above 125 mm

should be avoided. In mixtures with high slump, the aggregate will segregate from the mortar and

paste and may cause blocking in the pump lines.

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The mixing water requirements vary for different maximum sizes and type of aggregates. The

approximate quantity of water for a slump of 85 mm and 100 mm is given in Table 1. In high

strength concrete due to lower water/cement ratio and high cement content, workability is reduced

with the given quantity of water per cu.m. of concrete. In such cases, water reducing admixtures

are useful. In the addition to this type of admixtures at normal dosage levels, to obtain a higher

workability for a given concrete mix, there is no necessity to make any alteration to the mix design

from that produced for the concrete of the initial lower slump. There is generally no loss of cohesion

or excess bleeding even when the hydroxycarboxylic acid baset materials are used.

If this class of product is used to decrease the water/cement ratio, again no change in mix design

will be required, although small alterations in plastic and hardened density will be apparent and

should be used in any yield calculations.

A loss of slump during pumping is normal and should be taken into consideration when proportioningthe concrete mixes. A slump loss of 25 mm per 300 meters of conduit length is not unusual, the

amount depending upon ambient temperature, length of line, pressure used to move the concrete,

moisture content of aggregates at the time of mixing, truck-haulage distance, whether mix is kept

agitated during haulage etc. The loss is greater for hose than for pipe, and is sometimes as high as

20 mm per 30 meter.

Aggregates

The maximum size of crushed aggregate is limited to one-third of the smallest inside diameter of

the hose or pipe based on simple geometry of cubical shape aggregates. For uncrushed (rounded)

aggregates, the maximum size should be limited to 40% of the pipe or hose diameter.

The shape of the coarse aggregate, whether crushed or uncrushed has an influence on the mix

proportions, although both shapes can be pumped satisfactorily. The crushed pieces have a larger

surface area per unit volume as compared to uncrushed pieces and thus require relatively more

mortar to coat the surface. Coarse aggregate of a very bad particle shape should be avoided.

Difficulties with pump have often been experienced whentoo large a proportion of coarse aggregate is used in an

attempt to achieve economy by reducing the amount of

cement; such mixes are also more difficult and costly to

finish. The grading of coarse aggregate should be as per

IS : 383-1970. If they are nominal single sized then 10

mm and 20 mm shall be combined in the ratio of 1:2 to

get a 20 mm graded coarse aggregate. In the same way,

10 mm, 20 mm and 40 mm aggregates shall be combined in the ratio of 1:1.5:3 to get a 40 mm

graded coarse aggregate.

Fine aggregate of Zone II as per IS: 383-1970 is generally suitable for pumped concrete provided

15 to 30% sand should pass the 300 micron sieve and 5 to 10 percent should pass the 150 micron

sieve. Fine aggregate of grading as given in Table 2 is best for pumped concrete. The proportion of

fine aggregate (sand) to be taken in the mix design is given in Table 3. However, the lowest

practical sand content should be established by actual trial mixes and performance runs.

In practice, it is difficult to get fine and coarse aggregates of a particular grading. In the absence of

fine aggregate of required grading they should be blended with selected sands to produce desiredgrading, and then combined with coarse aggregates to get a typed grading as per Table 4.

Uncrushed Aggregate (River Gravel)

It has become a custom that almost in all the construction sites crushed aggregates are being used.

To save environmental pollution as far as possible in ordinary construction works uncrushed

aggregates (River Gravel) including river sand should be used.

Production of crushed aggregates from crushers poses air and noise pollution problems.

Crusher & Air Pollution Problem

When the rocks and river bed boulders are crushed, dry surfaces are exposed and air borne dust

can be created. An inventory of sources of dust emissions usually begins with the first crusher and

continues with the conveyor transfer points to and including the succeeding crushers. Here the

aggregate is more finely grounded, and dust emission become greater. As the process continues,

dust emission are again prevalent from sources at conveyor transfer points and the final screens.

In the modern screening and washing plant in the production of uncrushed (gravel/shingle)

aggregate from the river bed they are not crushed, thus no dust is formed. Further aggregates are

washed to remove silt and clay like materials. Therefore, uncrushed (gravel/shingle) aggregates

produces in these plant arrive at site in a moist condition, hence do not present a dust problem.

Whereas the crushed aggregate leave crushing plant very dry and create considerable dust when

handled. To prevent dust in handling it is not possible to wet each load of crushed aggregate

thoroughly before it is dumped from the delivery truck. Attempts to spray the crushed aggregate as

it is being dumped have had very limited effectiveness.

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During crushing of aggregate particles less than 100 micron remains suspended in the air. The

suspension of a particle in the air follows a certain trajectory depending on its size, density, shape

and other physical properties. In air turbulence the dry crusher dust has long trajectories or

suspension time and settling distance to the ground. If a crushing plant is not properly designed and

operate without any efficient prevention system this fugitive dust may generate air pollution.

Air quality due to pollution should be monitored monthly.

The ambient air quality standards as recommended byCentral Pollution Control Board (CPCB) India are given in

the following table.

Note:

SPm : Suspended particle matters

SO2 : Sulpher dioxide

CO : Carbon Mono oxide

NOx : Nitrogen Oxide

1.

The concentrations for the above pollutants shall be 95% of the time within the limits

prescribed.

2.

Category C sensitive areas are: Hill Stations, Tourist Resorts, Sanctuaries, National Part,

National Manuments etc.

3.

The air quality levels should be determined by sampling and brought down within specified

ambient air quality standards through use of various mitigation measures, modern pollution

free equipment and advance construction technology, such as giving preference in usinguncrushed (gravel/shingle) natural aggregate in the general civil engineering construction

work in place of crushed aggregate obtained from crusher.

4.

Pumping

Before the pumping of concrete is started, the conduit should be primed by pumping a batch of

mortar through the line to lubricate it. A rule of thumb is to pump 25 litres of mortar for each 15

meter length of 100 mm diameter hose, using smaller amounts for smaller sizes of hose or pipe.

Dump concrete into the pump-loading chamber, pump at slow speed until concrete comes out at the

end of the discharge hose, and then speed up to normal pumping speed. Once pumping has started,

it should not be interrupted (if at all possible) as concrete standing idle in the line is liable to cause a

plug. Of greater importance is to always ensure some concrete in the pump receiving hopper at all

times during operation, which makes necessary the careful dispatching and spacing of ready-mix

truck.

Testing for Pumpability: There is no recognized laboratory apparatus or precise piece of

equipment available to test the pumpability of a mix in the laboratory. The pumpability of the mix

therefore, should be checked at site under field conditions.

Field Practices: The pump should be as near the placing area as practicable and the entire

surrounding area must have adequate bearing strength to support the concrete delivery trucks, thus

assuring a continuous supply of concrete. Lines from the pump to the placing area should be laid out

with a minimum of bends. For large placing areas, alternate lines should be installed for rapid

connection when required.

When pumping downward 15 m or more, it is desirable to provide an air release valve at the middle

of the top bend to prevent vacuum or air buildup. When pumping upward, it is desirable to have a

valve near the pump to prevent the reverse flow of concrete during the fitting of clean up

equipment, or when working on the pump.

Illustration example on Concrete Mix Design.


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Test Data for Materials

The grading of fine aggregate, 10 & 20 mm aggregates are as given in Table. 5. Fine

aggregate is of zone-I of IS:383-1970. 10 and 20 mm crushed aggregate grading are single

sized as per IS: 383-1970.

1.

Properties of aggregates2.

Target strength for all A, B and C mixes

fck = fck + 1.65 x S40 + 1.65 x 5

= 48.3 n/mm2 at 28 days age

3.

For Mix A and B free W/C ratio with crushed aggregate and given strength for target strength

of 48.3 n/mm2 at 28 days from Fig. 1 Curve D found to be 0.40. This is lower than specified

maximum W/C ration value of 0.45

Note: In absence of cement strength, but cement conforming to IS Codes, assume from Fig.

1 and Fig. 2.

Curve A and B for OPC 33 Grade

Curve C and D for OPC 43 GradeCurve E and F for OPC 53 Grade

Take curves C and D for PPC, as PPC is being manufactured in minimum of 43 Grade of

strength.

4.

Other data: The Mixes are to be designed on the basis of saturated and surface dry

aggregates. At the time of concreting, moisture content of site aggregates are to be

determined. If it carries surface moisture this is to be deducted from the mixing water and if

it is dry add in mixing water the quantity of water required for absorption. The weight of

5.


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aggregates are also adjusted accordingly.

Design of Mix-a with PPC

Free W/C ratio for the target strength of 48.3 n/mm2 from Fig. 1 curve D found to be 0.4a.

Free water for 100 mm slump from Table 1 for 20 mm maximum size of aggregate.

From trials, it is found that Retarder Superplasticizer at a dosages of 18 gm/kg of cement

water may be reduced 25% without loss of workabilityThen water = 200 (200 x 0.25) = 150 kg/m3

b.

PPC = 150/0.4 = 375 kg/m3c.

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 = Wight of fresh concrete kg/m3

Ga = Weighted average specific gravity of combined fine and coarse aggregate bulk, SSD

Gc = 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 entrapped air 1% for 40 mm maximum size of aggregate,

1.5% for 20 mm maximum size of aggregate and 2.5% for 10mm maximum size of

aggregate. There are always entrapped air in concrete. Therefore, ignoring entrapped air

value as NIL will lead the calculation of higher value of density.

Wm = Mixing water required in kg/m3

Cm = Cement required, kg/m

3

Note:- The exact density may be obtained by filling and fully compacting constant volume

suitable metal container from the trial batches of calculated design 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 2.75 (100 1.5) + 375(1- 2.75/3.00) 150 (2.75 -1)

Density = 2477 kg/m3

d.

aggregates = 2477 375 150 = 1952 kg/m 3e.

Fine aggregate = From Table 3 for zone-I Fine aggregate and 20 mm maximum size of

aggregate, W/C ratio = 0.4 found to be 44 53%. For consideration of grading of Table 4 let

it be 45% Fine aggregate = 1952 x 0.45 = 878 kg/m3 Coarse aggregate = 1952 878 =

1074 kg/m3

10 and 20 mm aggregate are single sized as per IS: 383-1970. Let they be combined in the

ratio of 1:2

10 mm aggregate = 358 kg/m3

20 mm aggregate = 716 kg/m3

With the consideration of grading of Table 5 let Fine aggregate, 10 and 20 mm aggregate

combine in the ratio of 45%, 19% and 36% and check with the required grading of Table. 5.

Thus,

Fine aggregate = 878 kg/m3

10 mm = 1952 x 0.19 = 371 kg/m 3

20 mm = 1952 x 0.36 = 703 kg/m 3

f.

Thus for M-40 Grade of concrete quantity of materials per cu.m. of concrete on the basis of

saturated and surface dry aggregates:

Water = 150 kg/m3

PPC = 375 kg/m3

Fine Aggregate (sand) = 878 kg/m3

10 mm Aggregate = 371 kg/m3


Retarder Super Plasticizer = 6.75 kg/m3

g.


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Mix-B with OPC

Water = 200 (200 x 0.25) = 150 kg/m3a.

OPC = 150/0.4 = 375 kg/m3b.

Density:

10 x 2.75 (100 1.5) + 375 (1 2.75/3.15) 150 (2.75 1)

= 2495 kg/m3

c.

Total Aggregates = 2495 150 375 = 1970 kg/m3

Fine Aggregate = 1970 x 0.45 = 887 kg/m3

10 mm Aggregate = 1970 x 0.19 = 374 kg/m3

20 mm Aggregate = 1970 x 0.36 = 709 kg/m3

d.

Thus for M-40 Grade of concrete with OPC per cu.m of concrete on the basis of saturated and

surface dry aggregates.

Water = 150 kg/m3

OPC = 375 kg/m3

Fine Aggregate (sand) = 887 kg/m3



Retarder Super Plasticizer = 5.625 kg/m3

e.

Mix. C with OPC + Flyash

With the given set of materials increase in cementitious

materials = 13%

Total cementitious materials = 375 x 1.13 = 424 kg

Note:-

Specific gravity of Retarder Superplasticizer = 1.151.

Addition of Flyash reduces 5% of water demand.2.

Note:-

For exact W/C ratio the water in admixture should also be taken into account.1.

The W/C ratio of PPC and OPC is taken the same assuming that the strength properties of

both are the same. If it is found that the PPC is giving the low strength then W/C ratio of PPC

have to be reduced, which will increase the cement content. For getting early strength and in

cold climate the W/C ratio of PPC shall also be required to be reduced.

2.

PPC reduces 5% water demand. If this is found by trial then take reduce water for

calculation.

3.

Conclusion

Pumped concrete may be used for most/all concrete construction, but is especially useful where

space or access for construction equipment is limited.

Although the ingredients of mixes placed by pump are the same as those placed by other methods,

quality control, batching, mix ing, equipment and the services of personnel with knowledge and

experience are essential for successful pumped concrete.

The properties of the fine normal weight aggregates (sand) play a more prominent role in theproportioning of pumpable mixes than do those of the coarse aggregates. Sands having a fineness

modulus between 2.4 and 3.0 are generally satisfactory provided that the percentage passing the

300 and 150 micron sieves meet the previously stated requirements. Zone-II sand as per IS:

383-1970 meets these requirements, and is suitable for pumped concrete.

For pumped concrete, there should be no compromise in quality. A high level of quality control for

assurance of uniformity must be maintained.


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T ER MS & C OND IT IO NS P RIVAC Y PO LIC Y C ANCE LLAT IO N/R EFU ND P OLIC Y DISCL AIM ER

A simple method of concrete mix design with normal weight aggregates and with admixtures for

pumped concrete is described in the article. The author has worked out the Tables and Figures for

materials available in the country by numerous trials. Therefore, the proportions worked out with

the help of these Tables and Figures will have quite near approach to the mix design problems in the

field.

Note:- When coarse and fine aggregate of different types are used, the free-water content is

estimated by the expression,

Where, Wf = Free-water content appropriate to type of fine aggregate.and, Wc= Free-water content appropriate to type of coarse aggregate.

Note:- The above combined obtained grading is for PPC and OPC mixes. For OPC + Flyash Mix fine

aggregate is about 43%, 10 mm 20% and 20 mm is 37%. This is also within the permissible limits

of recommended grading for pumped concrete.

References:

IS : 383-1970 Specifications for coarse and fine aggregates from natural sources for concrete

(second revision) BIS, New Delhi

IS: 456-2000 Code of practice for plain and reinforced concrete (fourth revision), BIS, New

Delhi

IS: 9103-1999 Specification for admixtures for concrete (first revision) BIS, New Delhi

IS: 8112-1989 Specifications for 43 Grade ordinary portland cement (first revision) BIS, New

Delhi

IS: 2386 (Part-III) 1963 method of test for aggregate for concrete. Specific gravity, density,voids, absorption and bulking, BIS, New Delhi

IS: 3812 (Part-I) 2003 Specification for pulverized fuel ash: Part-I for use as pozzolana in

cement, cement mortar and concrete (second revision) BIS, New Delhi

IS: 1489-Part-I 1991 Specifications for portland pozzolana cement (Part-I) Flyash based.

(Third revision), BIS, New Delhi

Kishore Kaushal, Design of Concrete Mixes with High-Strength Ordinary Portland Cement.

The Indian Concrete Journal, April, 1978, PP. 103-104

Kishore Kaushal, Concrete Mix Design. A manual published for Structural Engineering

Studies, Civil Engineering Department, University of Roorkee, 1986.

Kishore Kaushal, Concrete Mix Design Based on Flexural Strength for Air-Entrained

Concrete, Proceeding of 13th Conference on our World in Concrete and Structures, 25-26,

August, 1988, Singapore.

Kishore Kaushal, Concrete Mix Design, Indian Concrete Institute Bulletin September, 1988,

pp. 27-40 and ICI Bulletin December, 1988, pp. 21-31.

Kishore Kaushal, Method of Concrete Mix Design Based on Flexural Strength, Proceeding ofthe International Conference on Road and Road Transport Problems ICORT, 12-15 December,

1988, New Delhi, pp. 296-305.

Kishore Kaushal, Mix Design Based on Flexural Strength of Air-Entrained Concrete. The

Indian Concrete Journal, February, 1989, pp. 93-97.

Kishore Kaushal, Concrete Mix Design, VIII All India Builders Convention 29-31, January,

1989, Hyderabad, organized by Builders Association of India, Proceeding Volume pp.

213-260.

Kishore Kaushal, Concrete Mix Design Containing Chemical Admixtures, Journal of the

National Building Organization, April, 1990, pp. 1-12.

Kishore Kaushal, Concrete Mix Design for Road Bridges, INDIAN HIGHWAYS, Vol. 19, No.

11, November, 1991, pp. 31-37

Kishore Kaushal, A Concrete Design, Indian Architect and Builder, August, 1991, pp. 54-56

Kishore Kaushal, Mix Design for Pumped Concrete, Journal of Central Board of Irrigation

and Power, Vol. 49, No.2, April, 1992, pp. 81-92

Kishore Kaushal, Concrete Mix Design with Fly Ash, Indian Construction, January, 1995, pp.16-17

Kishore Kaushal, High-Strength Concrete, Civil Engineering and Construction Review,

March, 1995, pp. 57-61.

Kishore Kaushal, High-Strength Concrete, Bulletin of Indian Concrete Institute No. 51,

April-June, 1995, pp. 29-31

Kishore Kaushal, Mix Design of Polymer-Modified Mortars and Concrete, New Building

Materials & Construction, January, 1996, pp. 19-23.

Kishore Kaushal, Concrete Mix Design Simplified, Indian Concrete Institute Bulletin No. 56,

July-September, 1996, pp. 25-30.

Kishore Kaushal, Concrete Mix Design, A Manual Published by M/S Roffe Construction

Chemicals Pvt. Ltd., Mumbai, pp. 1-36

Kishore Kaushal, Concrete Mix Design with Fly Ash & Superplasticizer, ICI Bulletin No. 59,

April-June 1997, pp. 29-30

Kishore Kaushal. Mix Design for Pumped Concrete, CE & CR October, 2006, pp. 44-50.

NBMCW September 2010

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