Project on Concrete Mix Design for various grades of Concrete

Ans1. AIM-: Calculation of Concrete Mix design for M-35 grade concrete with fly-ash.

Procedure-:

Step-1 Calculation of Targeted Compressive Strength(ft).

ft = fck + 1.65*S ( where fck is the compressive strength of concrete, which is 35 N/mm2 for M-35)

( Value of S= 5 for M-35).

ft= 35 + 1.65*5 = 43.25 N/mm2.

Step-2 Calculation of water/cement ratio.

There are three methods for calculating w/c ratio. These are-:

Method 1. From the 28 day compressive strength of cement graph.

The value of the w/c for 43.25 N/mm2 came out to be 0.36.

Method 2. From the 28 day v/s 7 day compressive strength test.

The value from this came out to be 0.41.

Method 3. From the environmental conditions of mild, moderate, severe.

Assuming the conditions to be severe, we get w/c to be 0.45 for M-35.

We will take the value of w/c to be minimum of the above three values, w/c = 0.36.

Step-3 Calculation of quantity of cement and water in the mix.

Assuming the maximum size of coarse aggregate to be 20mm and 50mm to be the slump value of the

slump test, we get-:

Maximum water content = 186 liters.

w/c =0.36.

As we would be using Plasiticizers, the amount of water to be used would only be 70% of original requirement, so water content = 0.70*186 = 130kg.

cement quantity = 130/0.36 = 361kg.

Step-4 Calculation of quantity of fly ash to be used.

If fly ash is to be used its quantity is 20%-30% of the quantity of cement, therefore we will assume it

to be 30% in this particular case.

weight of fly ash used = 0.30*361 =108 kg.

Total cement used = 361-108 = 253 kg.

Total cementitous material = cement + fly ash.

Step- 5 Calculation of percentage volume of coarse and fine aggregate.

Volume of coarse aggregate with respect to graph for zone 1 is 0.60 (value at w/c =0.50).

By interpolating the volume of coarse aggregate for w/c =0.36 will become 0.628.

Now to make this concrete pumpable, we will take 90% of the value of coarse aggregate, this will

make the value = 090*0.625 = 0.57

% of fine aggregate = 0.43.

Step- 6 Calculation of mass of admixture used.

Mass of admixture used = 2% of the weight of cement.

= 0.02*361= 7.22kg.

Step- 7 Calculation of volume of different components of concrete for 1m3 volume.

Volume of cement = 253/3.15*0.001 =0.0803 m3.

Volume of fly ash = 108/2.2*0.001 = 0.0491m3.

Volume of Admixture= 7.22/1.145*0.001= 0.0063m3.

Volume of water = 130/1000*0.001= 0.0001m3.

Total Volume of the above 4 ingredients =0.1359m3.

Volume of aggregates = 1-0.1359 =0.8641m3.

Step- 8 Calculation of mass of coarse and fine aggregate.

Mass of fine aggregate= 0.8641*0.43*2.75*1000 = 1021.798 kg= 1022kg.

Mass of coarse aggregate= 0.8641*0.57*2.75*1000= 1354.477kg.

concrete mix = 253:1022:1354.

= 1:4.04:5.35 (for fly ash concrete).

=1:2.83:3.75( for non fly ash concrete).

Ans 2. AIM-: Calculation of concrete mix design for M-50 grade of concrete without fly ash.

Step 1-: Calculation of Targeted compressive strength

ft = fck +1.65S ( where S =5 for M-50)

ft = 50+1.65*5 =58.25 N/mm2.

Step 2-: Calculation of w/c ratio.

w/c by method 1 =0.38.

w/c by method 2= 0.42.

w/c by method 3 =0.45.

We will take w/c ratio to be 0.38.

Step 3-: Maximum water content for 20 mm aggregate and slump value 50mm =186 litres.

By using plasticizers water content will reduce to 0.70*186 = 130litres.

cement content = 342 kg. This acceptable value as it is above min. value of cement.

Step 4-: % Volume of aggregate.

Volume of coarse aggregate for zone 1 and w/c = .50 is 0.60.

Volume % of coarse aggregate for w/c= 0.38 = 0.624.

Actual volume of coarse aggregate= 0.9*0.624 =0.561

Volume of fine aggregate= 0.44

Step 5-: Volume of different components of concrete.

Volume of cement= 342/3.15 *.001=0.109m3.

Mass of admixture= .02*342 =6.84 kg.

Volume of admixture= 6.84/1.145 *.001=0.00598=.006m3.

Volume of water =130/1000*.001= .0001m3

Total Volume of above materials = .1151 m3.

volume of aggregates = 0.8849m3.

Step 6-: Mass of aggregates.

Mass of coarse aggregate= 1362.7kg. (0.8849*0.56*2.75*1000).

Mass of fine aggregate= 1070.7kg. (0.8849*0.44*2.75*1000).

Design of concrete mix for M-50= 342:1071:1363

= 1:3.13:3.985.