Cutting Paragraphs and Important Table of IS CODE 456 : 2000 (PART II)

 Contd ......

     Concrete Mix Proportions (clause 8.2.4)

General

The free water-cement ratio is an important factor in governing the durability of concrete and should always be lowest value. Appropriate value for minimum cement content and the maximum free water-cement ratio are given in Table 5 for different exposure conditions. The minimum cement content and maximum water-cement ration apply to 20 mm nominal maximum size aggregate. For other sizes of aggregate they should be changed as given in Table 6.

Table 5

In Short;

FOR P.C.C WORK

	Min. Cement	Max. W/C ratio	Min.  Grade
Mild	220	0.6	-
Moderate	240	0.6	M15
Severe	250	0.5	M20
Very Severe	260	0.45	M20
Extreme	280	0.4	M25

and 

FOR R.C.C WORK

	Min. Cement	Max. W/C ratio	Min.  Grade
Mild	300	0.55	M20
Moderate	300	0.5	M25
Severe	320	0.45	M30
Very Severe	340	0.45	M35
Extreme	360	0.4	M40

So that minimum cement content ;

(from above table)

         => PCC  -      220 kg/m³

         => RCC  -     300 kg/m³

and maximum water-cement ratio; 

(from above table)

        => PCC -      0.6

        => RCC -     0.55

Table 6

Maximum cement content 

• cement content not including fly ash and ground granulated blast furnace slag in excess of 450 kg/m3 should not be used unless special consideration has been given in design to the increased risk of cracking due to drying shrinkage in thin sections or to early thermal cracking and to the increased risk of damage due to alkali silica reactions.

Mix Constituents Like chlorides , sulphates , and alkalies-aggregate reactions etc as per Clause 8.2.5;

Table 7

Concrete in aggressive soils and water;

Compaction, Finishing and Curing of the Concrete;

(MOST IMPORTANT TOPICS)

Concrete in sea-water;

     CONCRETE MIX PROPORTIONING:

1. Design Mix Concrete

table 8 as per new amendment;

2. Nominal Mix Concrete

Table 9 is very important;

Table 9

Contd in Part-III........