What Are Different Grades of Concrete And Its Uses|Grade Of Concrete And Their Uses - Concrete Mix Ratio

Different Grades of Concrete and their Uses | 

    Concrete is a mixture of cement sand aggregate and water which hardens with time when we change the proportion of these components the strength of concrete changes accordingly.     

    Just take the case of building in building various structural elements are there like footing, columns, beams, slabs, etc. depending on type and height of the building, the strength of concrete required for constructing these elements change. So it is necessary to choose the correct grade of concrete for construction. Structure grade of concrete is nothing but a strength of concrete of that particular mix that is a mixture of cement sand aggregate and water in 28 days. Grade of concrete is denoted by M and M stands for a mix.

 For example for my grade the mix proportions one is two fives to 10 where one is the ratio of cement five is the ratio of sand and pain is the ratio of coarse aggregate. Based on the volume or weight of materials at least three concrete cubes of 150 by 150 by 150 mm are cast for each mix at 27 degree Celsius and they were tested in a laboratory for 28 days. It's mean strength is calculated at 28 days and that is the strength of concrete for that particular mix now the question is why 28 days, why not 20 or 40 this table shows the compressive strength of concrete. 

Strength of Concrete in Percentage Perdays

     Here you can see concrete I choose 40 percent strength in three days 90 percent in 14 days and 99 percent strength in 28 days so it is clear that concrete gains strength rapidly in initial days after casting that is 90 percent in only 14 days and after that concrete gains only 9 percent strength in the next 14 days so rate of gain of strength decreases since concrete against 99 percent strength in 28 days. So it's almost close to its final strength and that's why we use this strength.

     At the base for our design and evaluation now coming back to grades of concrete this table shows the proportion of cement and aggregate and water in different grades of concrete.

    For my grade the mix proportion is 1 is 2 pins and the quantity of water required shall be 60 liters in the same way you can see the mixed proportions of other grades of concrete up to m25. In a nominal mix can be made which shall be used for small-scale construction where concrete consumption is not high. 

    But for M 30 and above grades design mix should be used here you can see as the strength of concrete increases the cement content is constant in proportion but sand aggregate and water content is reducing. So if you add more water to the concrete the strength of concrete decreases and vice versa one more thing I have observed in most of the cases the concrete grade of foundation and columns will be more than slabs and beams. But note that this is not the general rule that's why I said in most of the cases the reason: 

        1- is foundations and columns are compression members whereas beams and slabs are tensile members.

        2-the reason number two is the load shall be transferred from slabs to beams, beams to columns and columns to foundations and the third reason is it's economical to reduce the grade of concrete for slabs and beams.

    I hope you have understood the different grades of concrete and their uses.