Concrete Mix Design

By Abhishek Khandelwal

Introduction

• 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.

Types of Concrete Mixes1. Nominal Mixes – • These mixes are of fixed cement-aggregate ratio. • These offer simplicity and under normal circumstances.• Have a margin of strength above that specified.

2. Standard Mixes – • The minimum compressive strength has been included by IS-

456:2000 in many specifications. These mixes are termed standard mixes.

• E.g.: M10, M15, M20, etc.

3. Designed Mixes -• In these mixes the performance of the concrete is specified by the

designer but the mix proportions are determined by the producer of concrete, except that the minimum cement content can be laid down.

Methods of Concrete Mix Design

• American Concrete Institute Method (ACI Method)

• Road Note Number 4 Method• DOE Method• Indian Standard Method (IS Method)

Indian Standard Recommended Method Of Concrete Mix Design

(IS 10262 - 2009)

Data Required:• Grade of Concrete• Slump required in mm• Degree of Site Control• Type of Exposure• Grade of Cement

Workability (Clause 7.1, IS:456-2000)

Degree of Site Control(Table 8, IS:456-2000)

Type of Exposure (Table 3, IS:456-2000)

Concrete Mix Design steps

IS - 10262 : 2009

Step1 Target Mean Strength

• Target mean strength

ft = fck+ k x s

ft = 30+1.65 x 5

ft = 38.25 N/

ft = target mean compressive strength at 28 days

fck = Characteristic compressive strength of concrete at 28 days,

k = usually 1.65 as per IS:456-2000

s = standard deviation.

Step2 Selection of water/cement ratio• Using graph

= 0.38

Step2 Selection of water/cement ratioBut from table – 5, IS-456:2000

Step2 Selection of water/cement ratio

Considering moderate exposure,

Max w/c = 0.5

Hence w/c = 0.38

w/c = 0.38

Step3 Selection Of Water Content.

• From table – 2, IS-10262:2009

(For 20mm nominal max. size of aggregate & 25 to 50mm slump)

Max WC = 186 kg/m3

# Correction for slump in water content (according to clause 4.2, IS:10262)

Slump = 100 mm

Correct WC for 100 mm slump = 186 + 6%

= 197.16 kg

197 kg of water per m3 of concrete

Step4 Calculation Of Cement Content

W/C = 0.38

C = = 518.42 kg/m3

Min CC = 300 kg/m3 concrete

(From table: 5, IS:456)

Hence, C = 518.42 kg/m3

518.42 kg of Cement per m3 of Concrete

Step 5: Selection of Proposition of Volume of Coarse Aggregate

From table 3,(IS-10262:2009) for zone IIIrd of F.A.

Maximum size of aggregate = 20 mm.

Vol. of CA per unit vol. of total aggregate = 0.64

# For 0.1 decrease in w/c & increase in CA by 0.02

Applying correction of 0.024

Vol. of CA = 0.64 + 0.024

=0.664m3

Total aggregate = 1

CA = 0.664m3

FA = 0.336m3

Step6 Mix Calculation Results:

Mass of Cement

Water F.A. C.A.

518.42 197 586.36 1161.76

1 0.38 1.13 2.24

Ratio Obtained

1 : 1.13 : 2.24

Thanks For

Hearing