IS Method For Concrete Mix Design

Hello friends today I am sharing about concrete mix design procedure by IS method, IS code for mix design IS 10262(2009) you can also prefer this code.

NEED:- So first start with why we need this procedure , lets think about if you are a site    engineer and you are in a construction site and you have to construct a  work so for this you have given construction detail about what is the strength of pouring concrete for the construction so for this you have to design a required concrete mix , if we make a concrete sample and test it by standard method then its strength can vary from its required strength because we are making concrete in sight not in laboratory  and remember one thing we can't construct a construction work in a single batch of concrete we have to make a number of batch of concrete and the strength of concrete can vary  in these batches and the concrete strength depend upon many factors. So for these reasons or to get a approx required strength we use mix design procedure .


PROCEDURE :- So lets start the procedure of mix design by IS method.


First Step:-
In first step we determine the mean strength or target strength  of concrete (fm) . So for this Indian standard code give a formula shown in fig.

where fck  is characteristic strength of concrete which is given in construction project details and  sigma is standard deviation and its value come from codes and it can be determine by testing number of cube then find their avg. Standard deviation.

So by this procedure we can find out the target or mean strength of concrete.

Second Step:-
In second step we determine the w/c ratio for concrete for this we use standard curve  given by IS code which is shown in fig.

In this graph A,B,C,etc. are the 28 days compressive strength or grade  of cement which is you are using for concrete making and in graph x axis is w/c ratio and y- axis is 28 days compressive strength of concrete or target mean strength of concrete which is come from step first .
For to determine the w/c ratio first choose your cement grade then take this curve and use your target strength which is come from step first then bisect the target strength point to the curve which give a point on x- axis which is our w/c ratio.

Step Third:-

In third step we estimate the water content and sand content for to estimate these we assume some standard value of workability , sand zone and coarse aggregate type  after estimating  these  we can  do adjustment  to our values.
assume value given below in fig.

 for workability IS code use compaction factor every code has own standards British code use slump value .
Now we estimate the water content and sand content by two tables. 1 table for concrete grade up to M35 or 2. table M35.
we use maximum size of aggregate(m.s.a) which we are using in concrete mix to estimate these values.

Where water content is in kg/m^3  and fine sand content is in percentage (%) of total volume.


Then we adjust our estimated value if our concrete ingredient or specification  are different from standard values  by applying some corrections these correction are given in fig.

We correct all values by using this fig.

We can determine the total cement content by this procedure.
we know w/c ratio for cement and we know total water content then
         
Water content ÷ cement content = w/c
By using this formula we can determine the cement content.

After estimating these we determine the total volume of air content for which table is given.

Using this table we can determine the total % of air content.

We also determine the cement content and w/c by durability aspect these values are given in table. for different exposure of RCC.

After finding cement content and w/c ratio from durability aspect
we choose minimum value of w/c which are come from durability and curves.
And choose maximum value of cement content which are  come  from durability and from previous steps.


Fourth Step:-

In fourth or last step we determine the total quantity of coarse and fine aggregate
for this we use some formulas which is given in fig.

Where
V = total volume of concrete
C = total weight cement
Fagg = total quantity of fine aggregate
Sc = specific gravity of cement
Sfagg= specific gravity of fine aggregate
P = total % of fine aggregate
Cagg= total quantity of coarse aggregate
Scagg= specific gravity of coarse aggregate

By using these procedure we can design a concrete mix by IS method.