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Posted in Concrete Engineering, Mix Design, Research Papers |  Email This Post |

By
Kaushal Kishore
Materials Engineer, Roorkee

A mix of M-80 Grade suitable for pumped concrete is to be designed with the following materials and detail.

1. OPC 53 Grade, 7-day strength 52.5 N/mm2, Spgr 3.15

2. Silica Fume Specific Gravity 2.20

3. Standard deviation for the mix 5.0 N/mm2

4. Grading and properties of river sand and 12.5 mm crushed aggregate are given in Table-1

5. Superplasticizer based on modified Polycarboxylate, specific gravity 1.06, liquid pH 6.0. With the given set of materials, it was found that at a dosages of 2.5 % bwc it gives a reduction of 30% of water for the required slump of 100 mm after one hour at the average day site temperature of 37 degree C.

6. As per grading of aggregates given in the Table-1, it is found that, if sand and aggregate are combined in the ratio of 45% and 55% they will give most suitable combined grading for pumped concrete.

7. Air in the mix assumed 1.5%.

DESIGN CALCULATIONS

1. M-80 Grade of concrete design for a mean target strength of:
80 + 1.65 x 5 = 88.3 N/mm2 at 28 day age

2. With the given set of materials from various trials it was found that with OPC 450 Kg/m3, Silica Fume 45 Kg/m3 and W/C+SF ratio of 0.283 gives 28-day average cube compressive strength of 90.4 N/mm2.

3. Calculated density of the mix, worked out from reference 1.

4. Aggregates = 2440 – 140 – 450 – 45 = 1805 kg/m3

5. Sand = 1805 x 0.45 = 810 kg/m3 (say)

6. 12.5 mm Aggregate = 1805 x 0.55 = 995 kg/m3 (say)

Thus for M-80 Grade of concrete, quantity of materials per cu.m of concrete on the basis of saturated and surface dry aggregates.

 Water 140 kg/m3 OPC 53 Grade 450 kg/m3 Silica fume 45 kg/m3 River sand 810 kg/m3 12.5 mm crushed aggregate 995 kg/m3 Superplasticizer 11.250 kg/m3 W/(C+SF) Ratio 0.283 Slump mm 102 7-day cube strength N/mm2 67.3 28-day cube strength N/mm2 89.5

Table-1 Properties of Aggregates

 I.S. Sieve size Percentage passing by mass River sand 45% 12.5 mm Crushed Agg 55% Combined aggregates grading of the mix 20 mm 100 100 100 12.5 mm 100 95 x 10 mm 100 60 78 4.75 mm 95 5 46 2.36 mm 87 0 39 1.18 mm 72 – 32 600 Micron 40 – 18 300 Micron 22 – 10 150,Micron 5 – 2 Specific gravity 2.65 2.65 – Water absorption % 0.8 0.5 – Organic impurities % Nil – – Coal & lignite % Nil Nil – Clay lumps % Nil Nil – Materials finer than 75 micron I.S. Sieve % 0.2 Nil – Flakiness index – 7.3 – Crushing value % – 10.5 –

REFERENCES
Kishore Kaushal  Mix design with water reduces, The Indian Concrete Journal, August 2011, Vol. 85, pp. 44-51.

We at engineeringcivil.com are thankful to Er. Kaushal Kishore for submitting the paper on M-80 Grade Pumpable Concrete. This will be of great help to the ones who are looking for information regarding the pumpable concrete.

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