In this article, We're going to create Concrete Mix Design by DOE Method with a concrete mix design example for a better explanation for making this concrete mix design calculation easy to understand so read the whole article & download concrete mix design doe method pdf
Concrete Mix Design by DOE Method
The DOE method was first introduced (published) in 1975 and then revised in 1988.
While Grading Curve Method was specifically developed for concrete pavements, the DOE method applies to concrete for most purposes, including roads.
Since the DOE method presently is the standard British method of concrete mix design, the procedure involved in this method is described instead of the outdated Road Note No 4 method.
Step 1: Required Data to be Collected
- Fineness modulus of selected F.A.
- Unit weight of dry rodded coarse aggregate.
- Sp. gravity of coarse and fine aggregates in SSD condition
- Absorption characteristics of both coarse and fine aggregates.
- Specific gravity of cement.
Let me take a concrete mix design example for data to make it easy to understand
- Grade Designation = M 30
- For which we have to design concrete mix to achieve this particular strength of concrete for construction work of the project
- Type of cement = O.P.C- 43 grade
- More than 17 different types of cement available for special construction work and every condition demand different material to more suitable, economical and durable structure.
- Fine Aggregate = Zone-II
- Sp. Gravity Cement = 3.15
- Fine Aggregate = 2.61
- Coarse Aggregate (20mm) = 2.65
- Coarse Aggregate (10mm) = 2.66
Step 2: Target Mean Strength
Find the target mean strength from the specified characteristic strength (Grade Designation)
Target mean strength = specified characteristic strength + (Standard deviation x risk factor)
Where risk factor is on the assumption that 5 percent of results are allowed to fall less than the specified characteristic strength.
𝑓𝑚=30+(1.65 𝑥 5.0)
𝑓𝑚=38.25 𝑀𝑃𝑎
Step 3: Water/cement ratio
Calculate the water/cement ratio. This is done in a rather round about method, using Table 11.11
Referring to Table 11.11, for OPC, uncrushed aggregate, for W/C ratio of 0.5, 28 days compressive strength is 49 MPa.
In above Fig. find an intersection point for 42 MPa and 0.5 W/C ratio. Draw a dotted line curve parallel to the neighbouring curve. From this curve read off the W/C ratio for a target mean strength of 39 MPa.
The Water/cement ratio is = 0.58
Check this W/C ratio from durability consideration from Table 9.20. The maximum W/C ratio permitted is 0.50. Adopt lower of the two Therefore adopt a W/C ratio of 0.50
Step 4: Calculation of Water Content
- Next decide the water content for the slump of 75 mm (assumed) 20 mm uncrushed aggregate from Table 11.12.
- In the case of CA & FA are different
- Water demand for natural fine aggregate = 195 lit
- Water demand for crushed coarse 20mm max size aggregate = 225 lit
𝑊𝑎𝑡𝑒𝑟 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 = [(2/3)×W𝑓]+[(1/3)×W𝑐𝑎]
𝑊𝑎𝑡𝑒𝑟 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 = [2/3×195]+[1/3×225]
𝑊𝑎𝑡𝑒𝑟 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 = 205.0 𝑘𝑔𝑚^{3}
Table 11.12: Approximate Free Water Contents Required to Give Various Levels of Workability According to the 1988 British method
Step 5: Calculating Cement Content
Mixing water content is 205 kg/m^{3} of concrete.
𝐶𝑒𝑚𝑒𝑛𝑡 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 = 205/0.50
𝐶𝑒𝑚𝑒𝑛𝑡 𝐶𝑜𝑛𝑡𝑒𝑛𝑡=410.0 𝑘𝑔𝑚^{3}
Which is more than 350 kg (As per Table No. 9.2 of BS 8110: Part I: 1985) Hence o.k.
Step 6: Calculating Weight of Total Aggregate
- This requires an estimate of the wet density of the fully compacted concrete. This can be found out in Fig. 11.4 for approximate water content and specific gravity of aggregate.
- Next, find out the density of fresh concrete from Fig. 11.4 for the water content of 205 kg/m^{3}, 20 mm uncrushed aggregate of sp.gr. 2.65
The wet density = 2375.0 kgm^{3}
Total Weight of aggregate is find out
Weight of Total Aggregate = The wet density - (Weight of Cement + Weight of Free Water)
Weight of Total Aggregate = 2375 - (410 + 205)
Weight of Total Aggregate = 1760 kg/m^{3}
Step 7: Calculating Weight of Fine Aggregate
Then, the proportion of fine aggregate is determined in the total aggregate using below Fig. Fig. (a) is for 10 mm size, (b) is for 20 mm size and Fig. (c) is for 40 mm size coarse aggregate.
The parameters involved are the maximum size of coarse aggregate, the level of workability, the water/cement ratio, and the percentage of fine spassing 600 μ seive.
For 20 mm aggregate size, W/C ratio of 0.50, Slump of 75 mm, for 50% fines passing through 600 μ sieve, the percentage of
% 𝐹𝑖𝑛𝑒 𝐴𝑔𝑔𝑟𝑒𝑔𝑎𝑡𝑒 = 41 %
Weight of F.A. = 1760 × (41/100)
Weight of F.A. = 721.6 kg/m^{3}
and
Weight of C.A. = 1760 × (59/100)
Weight of C.A. = 1038.4 kg/m^{3}
Step 8: Combination of Different Coarse Aggregate Fractions
Course aggregate can be further divided into different fractions depending on the shape of aggregate. As general guidance the figures given in Table 11.14 can be used.
Step 9: Proportions for Concrete Mix Design
Ingredients |
Quantity |
Ratio |
1 Bag Cement |
Cement |
410 |
1 |
50 |
Fine
Aggregate |
721.6 |
1.76 |
88 |
Coarse
Aggregate |
1038.4 |
2.54 |
127.0 |
Water |
205 |
0.50 |
25 |
Chemical |
NM |
NM |
NM |
Step 10: Adjustment for Field Condition
The proportions are required to be adjusted for the field conditions. Fine Aggregate has surface moisture of 2 %
Weight of F.A. = 721.6 + (2/100) 721.6
Weight of F.A. = 736.03 kg/m^{3}
Course Aggregate absorbs 1% water
Weight of C.A. = 1038.4 - (1/100) 1038.4
Weight of C.A. = 1028 kg/m^{3}
Step 11: Final Design Proportions
Ingredients |
Quantity kg/m^{3} |
Ratio |
1 Bag Cement |
Cement |
410 |
1 |
50 |
Fine
Aggregate |
728 |
1.80 |
90.0 |
Coarse
Aggregate |
1029.1 |
2.51 |
125.5 |
Water |
205 |
0.50 |
25.0 |
Chemical |
NM |
NM |
NM |
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