135250791-Mix-Design-ppt

8/11/2019 135250791-Mix-Design-ppt

1/75

BUILDING TECHNOLOGY AND MANAGEMENT

CONCRETE MIX DESIGN

8/11/2019 135250791-Mix-Design-ppt

2/75

INTRODUCTION

Concrete is obtained by mixing cement, fine aggregate, coarse

aggregate, water and admixtures in required proportions. The

mixture when placed in forms and allowed to cure becomes

hard like stone.

The hardening is caused by chemical action between water and

the cement due to which concrete grows stronger with age.

It is the most widely-used man-made construction material in

the world.

2CONCRETE MIX DESIGN

8/11/2019 135250791-Mix-Design-ppt

3/75

CONCRETE MAKING MATERIALS

Cement

Aggregates

Water

Admixtures


8/11/2019 135250791-Mix-Design-ppt

4/75

CEMENT

Cement and water forms the active component of concrete, while

the inactive group comprises the fine and coarse aggregates.

The cement and water form a paste that hardens and bonds the

aggregates together.

Types of CementAlthough around 18 types of cements are recognized by BIS, more

commonly used ones are:

Ordinary Portland Cement 33, 43, & 53 grade OPC,

Blended Cements (PPC and PSC).

Sulphate Resisting Cement (SRC),

Low Heat Portland Cement (LHPC),

Hydrophobic Portland Cement,

Colored Cement (White Cement).


8/11/2019 135250791-Mix-Design-ppt

5/75

AGGREGATES

They are cheaper than cement and impart greater volume

stability and durability to concrete.

The main purpose is to provide bulk to the concrete.

Some of the aggregates may be chemically active.

CLASSIFICATION Geological originnatural and artificial

Sizefine, coarse and all-in

Shaperounded, irregular, angular, flaky and elongated

Unit weightnormal-weight, heavyweight and lightweight


8/11/2019 135250791-Mix-Design-ppt

6/75

WATER

The most important and least expensive ingredient of concrete.

One part of the water is used in the hydration of cement to formthe binding matrix.

The remaining water affords lubrication and workability to the

concrete.

Water-cement ratio depends on the grade of concrete, its

workability, durability, nature and type of aggregates etc. Potable water is ideal for concreting.

Seawater may be used in PCC.


8/11/2019 135250791-Mix-Design-ppt

7/75

ADMIXTURES

Added to the concrete immediately or during mixing to modify its

properties in the fresh or hardened state.

Types:

Accelerators - speed up the initial set of concrete.

Retardersdelay the setting time of concrete mix.

Plasticizers and Super-plasticizers - water reducers.

Air entraining admixtures

Water proofers

Pigments

Corrosion-inhibiting chemicals

Antifungal admixtures


8/11/2019 135250791-Mix-Design-ppt

8/75

TYPES OF CONCRETE MIXES

1. NOMINAL MIXMixes of fixed proportions, IS:456-2000 permits nominal mixes

for concretes of strength M20 or lower

2. DESIGN MIX

Designed on the basis of requirements of the concrete infresh and hardened states.


8/11/2019 135250791-Mix-Design-ppt

9/75

TRIAL MIXES

Prepared to verify whether the Design Mix would perform as

per the assumptions. If appreciable variation exists, theavailable alternatives are:

1. directly employ the trial mix proportions at the site

2. modify the trial mix proportions on the basis of intuition and

employ the revised proportions at the site3. prepare further trial mixes incorporating changes in the

proportions based on the feedback generated from the

previous mix.


8/11/2019 135250791-Mix-Design-ppt

10/75

CONCRETE MIX DESIGN

DEFINITION

Mix Design is the science of determining the relative

proportions of the ingredients of concrete to achieve the

desired properties in the most economical way.

CONCRETE MIX DESIGN 10

8/11/2019 135250791-Mix-Design-ppt

11/75

PRINCIPLES OF MIX DESIGN

1 The environment exposure condition for the structure

2 The grade of concrete, their characteristic strengths and

standard deviations

3 The type of cement4 The types and sizes of aggregates and their sources of supply

5 The nominal maximum sizes of aggregates

6 Maximum and minimum cement content in kg/m3

7 Water cement ratio

8 The degree of workability of concrete based on placing

conditions


8/11/2019 135250791-Mix-Design-ppt

12/75

9 Air content inclusive of entrained air

10 The maximum/minimum density of concrete

11 The maximum/minimum temperature of fresh concrete

12 Type of water available for mixing and curing

13 The source of water and the impurities present in it.


8/11/2019 135250791-Mix-Design-ppt

13/75


IS 456:2000

8/11/2019 135250791-Mix-Design-ppt

14/75


IS 456:2000

8/11/2019 135250791-Mix-Design-ppt

15/75


IS 456:2000

8/11/2019 135250791-Mix-Design-ppt

16/75

FACTORS DEFINING THE CHOICE OF MIX

PROPORTIONS

1. Compressive Strength

2. Workability

3. Durability

4. Type, size and grading of aggregates

5. Aggregate-cement ratio


8/11/2019 135250791-Mix-Design-ppt

17/75

COMPRESSIVE STRENGTH

Abrams Law

log F = log A1x log B1

where F is the compressive strength

A1, B1 are constants and

x is the w/c ratio by weight


8/11/2019 135250791-Mix-Design-ppt

18/75

WORKABILITY

that property of freshly mixed concrete which determines the

ease and homogeneity with which it can be mixed, placed,

consolidated and finished.

DURABILITY

the resistance to weathering action due to environmental

conditions such as changes in temperature and humidity,

chemical attack, abrasion, frost and fire.


8/11/2019 135250791-Mix-Design-ppt

19/75

REQUIREMENTS AND TESTS OF MATERIALS REQUIRED

FOR MIX DESIGN

ASSIGNMENT # 1 TO BE SUBMITTED BY 07-02-2011

Roll #s 01-21Cement

Roll #s 22-42Aggregates

Roll #s 43-63Water and Admixtures


8/11/2019 135250791-Mix-Design-ppt

20/75

METHODS OF CONCRETE MIX DESIGN

1. American Concrete Institute Committee 211 method2. Bureau of Indian Standards Recommended method IS 10262-82

3. Road note No. 4 (Grading Curve) method

4. Department Of Environment (DOE - British) method

5. Trial and Adjustment Method6. Fineness modulus method

7. Maximum density method

8. Indian Road Congress, IRC 44 method


8/11/2019 135250791-Mix-Design-ppt

21/75

American Concrete Institute Method of Mix Design

(a) Data to be collected :

(i ) Fineness m odu lus of selected F.A.

(i i ) Unit weight of dry rodd ed coarse agg regate.

(i i i ) Sp. gravi ty o f co arse and fine aggregates in SSD condit ion

(iv ) Ab so rpt ion character ist ics of bo th coarse and fine

aggregates.

(v ) Specif ic g ravi ty of cement.

(b) From the minimum strength specified, estimate the average

design strength by using standard deviation.

(c) Find the water/cement ratio from the strength and durability

points of view. Adopt the lower value.


8/11/2019 135250791-Mix-Design-ppt

22/75

(d) Decide the maximum size of aggregate to be used. Generally

for RCC work 20 mm and pre-stressed concrete 10 mm size are

used.

(e) Decide workability in terms of slump for the given job.

(f ) The total water in kg/m3of concrete is determined,

corresponding to the selected slump and selected maximumsize of aggregate.

(g ) Cement content is computed by dividing the total water

content by the water/cement ratio.

(h) Select the bulk volume of dry rodded coarse aggregate per unit

volume of concrete, for the particular maximum size of coarse

aggregate and fineness modulus of fine aggregate.


8/11/2019 135250791-Mix-Design-ppt

23/75

( j ) The weight of C.A. per cubic meter of concrete is calculated by

multiplying the bulk volume with bulk density.

(k ) The solid volume of coarse aggregate in one cubic meter ofconcrete is calculated by knowing the specific gravity of C.A.

(l ) Similarly the solid volume of cement, water and volume of air is

calculated in one cubic meter of concrete.

(m) The solid volume of FA is computed by subtracting from the

total volume of concrete the solid volume of cement, CA, water

and entrapped air.

(n) Weight of fine aggregate is calculated by multiplying the solid

volume of fine aggregate by specific gravity of F.A.


8/11/2019 135250791-Mix-Design-ppt

24/75

ACI METHOD: DESIGN EXAMPLE

1 Design a concrete mix for the construction of an elevated water

tank. The specified design strength of concrete (characteristic

strength) is 30 MPa at 28 days measured on standard cylinders.

Standard deviation can be taken as 4 MPa. The specific gravity

of FA and C.A. are 2.65 and 2.7 respectively. The dry rodded

bulk density of C.A. is 1600 kg/m3, and fineness modulus of FA

is 2.80. Ordinary Portland cement (Type I) will be used. A slump

of 50 mm is necessary. C.A. is found to be absorptive to the

extent of 1% and free surface moisture in sand is found to be 2

per cent. Assume any other essential data.


8/11/2019 135250791-Mix-Design-ppt

25/75

1 Mean Cylinder Compressive Strength

Assuming 5 per cent of results are allowed to fall below

specified design strength,

The mean strength,

fm= fmin+ ks

= 30 + 1.64 x 4

= 36.5 MPa

2 Water/cement ratio

Strength criteria

Durability criteria


8/11/2019 135250791-Mix-Design-ppt

26/75


Strength Criteria

8/11/2019 135250791-Mix-Design-ppt

27/75


Durability Criteria

8/11/2019 135250791-Mix-Design-ppt

28/75


3 Mixing Water Content

Slump = 50 mmMaximum size of aggregate = 20 mm

Concrete is non air-entrained

8/11/2019 135250791-Mix-Design-ppt

29/75


8/11/2019 135250791-Mix-Design-ppt

30/75


The mixing water content is 185 kg/m3of concrete

The approximate entrapped air content is 2%.

The required cement content =185/0.47= 394 kg/m3

8/11/2019 135250791-Mix-Design-ppt

31/75


4 Bulk Volume of C.A.

Maximum size of C.A = 20mm

Fineness Modulus of F.A. = 2.80

Find the dry rodded bulk volume of C.A.

8/11/2019 135250791-Mix-Design-ppt

32/75


8/11/2019 135250791-Mix-Design-ppt

33/75


The dry rodded bulk volume of C.A. = 0.62 per unit volume of

concrete

The weight of C.A. = 0.62 x 1600

= 992 kg/m3

8/11/2019 135250791-Mix-Design-ppt

34/75


5 The first estimate of density of fresh concrete = 2355 kg/m3

8/11/2019 135250791-Mix-Design-ppt

35/75


The weight of all the known ingredients of

concrete

Weight of water = 185 kg/m3

Weight of cement = 394 kg/m3

Weight of C.A. = 992 kg/m3

Weight of F.A. = 2355(185 + 394 + 992)

= 784 kg/m3

6 Weight of FA

Alt ti l th i ht f F A b d t i d b th

8/11/2019 135250791-Mix-Design-ppt

36/75


Alternatively, the weight of F.A. can be determined by the more

accurate absolute volume method

Absolute Volume = weight/(1000) m3

8/11/2019 135250791-Mix-Design-ppt

37/75


Total absolute volume = 697 x 103cm3

Absolute volume of F.A. = (1000697) x 103

= 303 x 103

Weight of FA = 303 x 2.65

= 803 kg/m3

8/11/2019 135250791-Mix-Design-ppt

38/75


7 Estimated quantities of materials per cubic meter of

concrete are:

Cement = 394 kg

F.A = 803 kg

C.A = 992 kg

Water = 185 kg

8/11/2019 135250791-Mix-Design-ppt

39/75


8 Proportions

C : F.A : C.A : water

394 : 803 : 992 : 185

1 : 2.04 : 2.52 : 0.47

Weight of materials for one bag mix

in kg = 50 : 102 : 126 : 23.5

8/11/2019 135250791-Mix-Design-ppt

40/75


9 The above quantities is on the basis that both F.A

and C.A are in saturated and surface dry condition

(SSD conditions).

FA has surface moisture of 2%

Total free surface moisture in FA = (2/100 x 803)

= 16.06 kg/m3

Weight of F.A in field condition = 803 + 16.06 = 819.06 kg/m3

8/11/2019 135250791-Mix-Design-ppt

41/75


Quantity of water absorbed by C.A. = (1/100 x 992) = 9.92 kg/m3

Weight of C.A in field condition = 9929.92

= 982 kg/m3

C.A absorbs 1% water

Water contributed by F.A = 16.06 kg

Water absorbed by C.A. = 9.92 kg

Extra water contributed by aggs. = 16.069.92 = 6.14 kg

Total water content = 185.006.14

= 179 kg/m3

Change in Water Content

8/11/2019 135250791-Mix-Design-ppt

42/75


Cement = 394 kg/m3

F.A. = 819 kg/m3

C.A. = 982 kg/m3

Water = 179 kg/m3

Field density of fresh concrete = 2374

kg/m3

Quantities of materials to be used in field, corrected for

free surface moisture in F.A and absorption characteristic

of C.A

8/11/2019 135250791-Mix-Design-ppt

43/75

2. A mix with a mean 28-day compressive strength of 35 MPa and

a slump of 50 mm is required, using OPC. The maximum size

of well shaped, angular aggregate is 20mm, its bulk density is

1600 kg/m3and its specific gravity is 2.64. The available fine

aggregate has a fineness modulus of 2.60 and a specific

gravity of 2.58. No air-entrainment is required.


Water/Cement ratio

As durability criteria is not

mentioned, consider strength alone

8/11/2019 135250791-Mix-Design-ppt

44/75


Strength Criteria

8/11/2019 135250791-Mix-Design-ppt

45/75

Water/cement ratio =0.48


Slump = 50 mmMax size of aggregate = 20 mm

Determine water content

8/11/2019 135250791-Mix-Design-ppt

46/75


8/11/2019 135250791-Mix-Design-ppt

47/75


8/11/2019 135250791-Mix-Design-ppt

48/75

Composition of concrete (kg/m3)

Water = 185

Cement = 386

CA = 1020

FA = 738

Density of Concrete = 2329 (kg/m3)


ROAD NOTE No 4 METHOD OF MIX DESIGN

8/11/2019 135250791-Mix-Design-ppt

49/75

ROAD NOTE No. 4 METHOD OF MIX DESIGN

Proposed by the Road Research Laboratory, UK (1950)

Procedure:

1. The average compressive strength of the mix to be designed is

obtained by applying control factors to the minimum

compressive strength

2. Water/cement ratio is read from compressive strength v/s w/c

ratio graph

3. Proportion of combined aggregates to cement is determined

from tables, for maximum size 40 mm and 20 mm

4. If the aggregate available differs from the standard gradings,

combine FA and CA so as to produce one of the standard

gradingsCONCRETE MIX DESIGN 49

8/11/2019 135250791-Mix-Design-ppt

50/75

5. The proportion of cement, water, FA and CA is determined

from knowing the water/cement ratio and the

aggregate/cement ratio.

6. Calculate the quantities of ingredients required to produce 1

m3of concrete, by the absolute volume method, using the

specific gravities of cement and aggregates.


8/11/2019 135250791-Mix-Design-ppt

51/75

DRAWBACKS OF ROAD NOTE NO. 4 METHOD

1. Cannot be used directly for the design of air - entrained

concrete

2. No recommendations for durability or strength, regarding the

water/cement ratio

3. The design tables refer to mixes in which the FA and CA are of

the same shape

4. In selecting aggregate/cement ratio, only 3 shapes of

aggregates and 4 gradings are recommended.


8/11/2019 135250791-Mix-Design-ppt

52/75

DOE METHOD OF MIX DESIGN

Can be used for concrete containing fly ash.

PROCEDURE

1. Target mean strength is calculated

2. Select water/cement ratio, from the type of cement and CA.

Compare this with the ratio from durability conditions.

3. Decide the water content for required workability4. Compare the cement content with the minimum cement content

value and adopt the higher value

5. Find out the total aggregate content

6. Determine the proportion of FA using the appropriate FA% v/s

CA size graph, and find the weight of CA and FA

7. Work out a trial mix.


8/11/2019 135250791-Mix-Design-ppt

53/75

BIS RECOMMENDED MIX DESIGN METHOD

The BIS recommended mix design procedure is covered in IS

10262-82.

In line with IS 456-2000, the first revision IS 10262-2009 was

published, to accommodate some of the following changes:

Increase in strength of cement

Express workability in terms of slump, rather than the

compacting factor

Extend the W/C ratio v/s compressive strength graph


Modifications in IS 10262-2009

8/11/2019 135250791-Mix-Design-ppt

54/75


Modifications in IS 10262 2009

8/11/2019 135250791-Mix-Design-ppt

55/75

MIX DESIGN BASED ON IS RECOMMENDATIONS

Based on IS 10262:1982

Procedure:


1. Target mean strength for mix design:

fck*= fck+ tS

where fck= characteristic compressive strength at 28 days

S = standard deviation

t = a statistical value depending on the risk factor.

8/11/2019 135250791-Mix-Design-ppt

56/75


8/11/2019 135250791-Mix-Design-ppt

57/75


8/11/2019 135250791-Mix-Design-ppt

58/75

2. Selection of Water/Cement ratio


8/11/2019 135250791-Mix-Design-ppt

59/75

8/11/2019 135250791-Mix-Design-ppt

60/75

4. Selection of Water Content and Fine to Total Aggregate ratio


8/11/2019 135250791-Mix-Design-ppt

61/75


8/11/2019 135250791-Mix-Design-ppt

62/75

5. Calculation of Cement Content:

cement by mass = Water content/Water cement ratio

To be checked against the minimum cement content for the requirement

of durability and the greater of the two values to be adopted.


8/11/2019 135250791-Mix-Design-ppt

63/75

6. Calculation of aggregate content:


7 A t l titi i d f i

8/11/2019 135250791-Mix-Design-ppt

64/75

7. Actual quantities required for mix

Adjust the mix for deviations from assumed conditions


8. Check the calculated mix proportions

8/11/2019 135250791-Mix-Design-ppt

65/75

DESIGN EXAMPLE: BIS RECOMMENDED METHOD

Grade M20

(a ) Design stipulations

(i ) Characteristic compressive strength

required in the field at 28 days - 20 MPa

(ii ) Maximum size of aggregate - 20 mm (angular)

(iii ) Degree of workability - 0.90 compacting factor

(iv ) Degree of quality control - Good

(v ) Type of Exposure - Mild

8/11/2019 135250791-Mix-Design-ppt

66/75

(b) Test data for Materials

(i ) Specific gravity of cement - 3.15

(ii ) Compressive strength of cement at 7 days - Satisfies the

requirement of IS: 2691989

(iii ) 1. Specific gravity of coarse aggregates - 2.60

2. Specific gravity of fine aggregates - 2.60

(iv ) Water absorption:1. Coarse aggregate - 0.50%

2. Fine aggregate - 1.0%

(v ) Free (surface) moisture:

1. Coarse aggregate - Nil2. Fine aggregate - 2.0%

8/11/2019 135250791-Mix-Design-ppt

67/75

Design Procedure

1. Target mean strength of concrete

fck*= fck+ tS


fck= 20, t = 1.64 , S = 4

fck*= 26.6 MPa

8/11/2019 135250791-Mix-Design-ppt

68/75

2. Selection of Water/Cement Ratio


Durability Criteria: Mild Exposure Conditions

8/11/2019 135250791-Mix-Design-ppt

69/75


8/11/2019 135250791-Mix-Design-ppt

70/75

W/C ratio from strength considerations = 0.50

W/C ratio from durability considerations = 0.55

Adopt the lower value


8/11/2019 135250791-Mix-Design-ppt

71/75

3. Selection of water and sand content


8/11/2019 135250791-Mix-Design-ppt

72/75

Adjustments in Water and Sand Contents


8/11/2019 135250791-Mix-Design-ppt

73/75

4. Determination of cement content

Water-cement ratio = 0.50

water = 191.6 kg/m3


Cement = 191.6/0.50 = 383 kg/m3

Is this satisfactory for mild exposure condition?

8/11/2019 135250791-Mix-Design-ppt

74/75

5. Determination of coarse and fine aggregate contents

Specified max. size of aggregate = 20 mm

Corresponding entrapped air = 2%


fa = 546 kg/m3,

Ca= 1188 kg/m3

Fi l Mi P ti

8/11/2019 135250791-Mix-Design-ppt

75/75

Final Mix Proportions

Water Cement FA CA

191.6 383 546 1188

0.50 1 1.425 3.10

Date post:	02-Jun-2018
Category:	Documents
Upload:	ashok-rajanavar
View:	218 times
Download:	0 times

135250791-Mix-Design-ppt

Documents