CONCRETE MIX DESIGN BY IS

CODE METHOD USING SUPER PLASTICIZER

INTRODUCTION Cement Concrete Mix Design

means, determination of the proportion of the concrete ingredients i.e. Cement, Water, Fine Aggregate, Coarse Aggregate which would produce concrete possessing specified properties such as workability, strength and durability with maximum overall economy.

IS CODE METHODThis Method is based on two basic assumptions

Compressive Strength of Concrete is governed by its Water-Cement RatioWorkability of Concrete is governed by its Water Content

DESIGN REQUIREMENTS Grade of concrete Type of cement Type and size of aggregate Maximum/minimum cement content Maximum free water-cement ratio by

weight Degree of workability of concrete Type of mixing and curing water Type of admixture used

FACTORS AFFECTING THE CHOICE OF MIX PROPORTIONS

Compressive strength Workability  Durability Maximum nominal size of aggregate Grading and type of aggregate Quality Control

PROCEDURE FOR MIX DESIGN(1) Target mean strength of concrete:- The target mean strength for specified

characteristics cube strength is Fck = fck+ 1.65s

Fck = 20+1.65x4

Fck = 26.6 Mpa

f ck = characteristics compressive strength of 28 days.

S = standard deviation. t = a statistical value depending on expected

proportion of low results= 1.65 as per IS 456:2000

STANDARD DEVIATION (S)Grade of concrete Assumed Standard

Deviation N/mm2

M 10

M 15

M 20

M 25

M 30

M 35

M 40

M 45

3.5

4.00

5.00

(2) SELECTION OF WATER CEMENT RATIO:-

From figure the water cement ratio required for the target mean strength of 26.6Mpa is 0.50. This is lower than the maximum value of 0.55 prescribed for “Mild” exposure (refer table below) adopt W/C ratio of 0.50.

Sl. Exposure Plain concrete Reinforced

concreteNo.

Minimum

cement

contents

kg/m3

Maximum free W/C ratio

Minimum

grade of

concrete

Minimum

cement

contents

kg/m3

Maximum free W/C ratio

1. Mild 220 0.60 - 300 0.55 M 20

2. Moderate

240 0.60 M 15 300 0.50 M 25

3. Severe 250 0.50 M 20 320 0.45 M 30

4. Very severe

260 0.45 M 20 340 0.45 M 35

5. Extreme

280 0.40 M 25 360 0.40 M 20

(3) SELECTION OF WATER AND SAND CONTENT:-

From table(1) below,for 20mm maximum size aggregate ,Sand conforming to grading zone II.

Water content per cubic meter of concrete =186kg and

Sand content as percentage of total agg. By absolute volume

=35% For change in value in W/c

ratio, compacting factor, for sand belonging to Zone III, following adjustment is required:-

Change in condition % adjustment required

Water content sand in

aggregate

For decrease in water cement Ratio by(0.60-0.50) that is 0.1 0 -2.0

For increase in compacting factor(0.90-0.80), that is 0.10 +3 0

For sand conforming to Zone IIIOf table 4, IS: 383-1970 0 -1.5 Total +3 -3.5

Table 1:- Approximate sand and water content per cubic meter of concrete

W/C =0.60, Workability =0.80 C.F.

(Slump 30mm approximately)

(Application for concrete up to grade M35)

Maximum Size Water content including Sand as percent ofOf aggregate surface water per cubic Total aggregate(mm) Metre of concrete (kg) by absolute volume

10 200 4020 186 3540 165 30

Table 2:- Adjustment of value of Water content and sand percentage for other conditions

Therefore required sand content as percentage of total aggregate by absolute volume

= 35 - 3.5 =31.5%

Required Water content = 186 + 5.58 =191.6 l/m3

(4)Determination of sand content:-

Water-Cement ratio = 0.50

Water =191.6 litersCement = 191.9/0.50

= 383 kG/m3 This cement content is adequate for “MILD”

exposure conditions.

(5) Determination of coarse and fine aggregate contents:

From table 3 ,for the specified maximum size of aggregate of 20mm , the amount of entrapped air in the wet concrete is 2 %. Taking this in to account and applying the given equation:-

Where,

V = Absolute volume of concrete, which is equal to

Gross volume (m3) minus the volume of

Entrapped air,

W = mass of water (kg)/m3 of concrete, C = mass of cement (kg)/m3 of

concrete Sc = Specific gravity of cement

P = Ratio of FA to total aggregate by absolute volume

fa, Ca = Total masses of FA and CA (kg)/m3 of concrete Respectively and

Sfa, Sca = Specific gravities of saturated, surface dry FA & CA

Table 3:- Approximate Entrapped air content

Maximum size of Entrapped air, as percentage of Aggregate(mm) Volume of concrete

10 3.020 2.040 1.0

fa =546kg/m3

Ca =

Ca = 1188kg/m3

The mix proportion the becomes=

Water Cement Fine aggregate

Coarse aggregate

191.6 383 546 1188

0.50 1 1.425 3.10

MIX DESIGN USING SUPER PLASTICIZER Super Plasticizer used is:-

Sikament 170

High Performance Plasticizer

DESCRIPTION:- Sikament 170 is a purpose designed

material which is a chemical combination of Modified Lignosulphonates.

Sikament 170 allows the manufacture of economic high quality concrete without undesirable side effects.

Sikament 170 is a ready to use liquid for producing a more uniformly cohesive quality concrete to meet the specifications and needs of Architects, Consulting Engineers and Contractors.

TECHNICAL DATA:- Form: Liquid Colour: Brown Relative Density @ 20°C: 1.210

Dry Material Content %: 46.0 pH Value: 7.5 Water Soluble Chloride Content %: <0.1

Chloride free Alkali Content %: <0.60 (as Na2O equivalent)

USES:- Ready mix concrete Precast concrete Pumped concrete Lightweight concrete

ADVANTAGES:-

Improved workability/reduces w/c ratio

Flexible high performance plasticiser

High resistance to segregation/reduces bleeding

Improved surface finish

Reduces shrinkage cracking potential

Higher initial and ultimate compressive strengths

Higher durability concrete

METHOD OF USE:- For maximum dispersion Sikament 170 should be

added with the mixing water, on no account should it be added to the dry cement. Where concrete is being mixed by ready mixed trucks, Sikament 170 can be added at the batching plant but the trucks must rotate their drums until a uniform mix is achieved. To produce flowing concrete a well proportioned pump mix should be used.

DOSAGE:- The dosage rate of Sikament 170 is best found after initial site trials, which will take into consideration

the best performance/dosage rate. As a guide an addition rate of between 0.3–0.5% by weight of cement is recommended (ie 0.15–0.25 litres per 50 Kg).

RESULTS (1) Results of standard mix:-

Cubes Dial gauge reading(KN)

Surface area of cube

Strength of cube in days 7 14 28

1. 350 15cmx15cm 15.55

2. 360 15cmx15cm 16.00

3. 390 15cmx15cm 17.33

Hence,

Average strength of concrete in 7 days is= 16.30 N/mm2

Average strength of concrete in 14 days is=

N/mm2

Average strength of concrete in 28 days is=

N/mm2

(2) Results of mix after adding super Plasticizer:-

Cubes Dial gauge reading(KN)

Surface area of cube

Strength of cube in days 7 14 28

1. 400 15cmx15cm 17.77

2. 380 15cmx15cm 16.90

3. 380 15cmx15cm 16.90

Hence,

Average strength of concrete in 7 days is=

17.19 N/mm2

Average strength of concrete in 14 days is=

N/mm2

Average strength of concrete in 28 days is=

N/mm2

CONCLUSION We have concluded that the result obtained from

the standard mix is less when compared to the mix design with super plasticizer. The 7 day strength of standard mix was 16.30 N/mm2, where as the 7 day strength of mix after adding super plasticizer was 17.20 N/mm2.

We have also seen that the workability of standard mix was less than the workability of the mix with super plasticizer. The slump value of standard mix was found to be 20mm, where as the slump value of the mix with super plasticizer was 25mm which is more than the standard mix.

THANK YOU Presented by :- Mahesh Sahu Md. Hasil Khan Devendra Yadav Saddam Husain Khan Tumeshwar Sahu