Question

Q2)What would be the maximum aggregate size used for the given mixture properties by using ACI Method of Mix Design. 28-day specified concrete strength is 3bMpa, standard deviation is choosen as 3.aMpa and it is required that no more than 1 test result in 200 will fall below the specified strength.

Project Title:Detoration of wood column of a commercial building

Project summary:Wood deterioration at the lower level of a heavy timber column, which supports five floor levels, was remedied by removing a section of column and the construction of a new concrete pier and footing.

For Coarse Aggregate (Uncrushed):SSD Bulk Specific Gravity: 2.60, Absorption Capacity: 1.8 %, Total Moisture: 2.3 % and Dry Rodded Unit Weight: 1430 kg/m³.

For Fine Aggregate (Crushed):SSD Bulk Specific Gravity: 2.70, Total Moisture: 3.c% and Free Moisture: 1.d%. FM= 2.65, Zone II.

Cement:Portland Composite Cement, Specific Gravity: 3.01. For 0.2am³cement is calculated as 12bkg.

with a=7   

b=4

c=4

d=4

e=1

Answer 1

● Maximum aggregate size is affected by PCC parameters as amount of cement content, workability of concrete and strength of concrete and aggregate properties.

●According to ACI recommendations that maximum aggregate size be least of the 1/3 of the slab depth and 3/4 of the minimum clear space between reinforcing bars (Note:- If the it is PCC this criteria will not applicable) and 1/5 th of the minimum spacing between the side of form work.

● Aggregate larger than these dimensions will make difficulty and result of this is honeycombed structure or large air pockets.

In general conditions pavement PCC maximum aggregate sizes are on the order of 25 mm (1 inch) to 37.5 mm.

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thank you.