Question

Q1) Design a concrete mix by using ACI Method of Mix Design having 28-day characteristic mean strength of 27 MPa for a deck of a residential building at Nebraska. Dry weather and gradually warming temperatures may be expected throughout the working week. Fresh concrete composed of a slump of 90 mm and maximum aggregate size of 25 mm. Determine the amount of water reducing admixture to be used for 0.24 % and 0.65 %. Deck is a flat surface capable of supporting weight, similar to a floor, but typically constructed outdoors, often elevated from the ground, and usually connected to a building. Decks that need piers or footings must have them installed below the frost line. This will keep the piers from heaving up out of the ground from the strength of the freeze. Reinforcing steel will help keep the piers from cracking. The freeze or frost line is the depth to which the soil freezes or has been known to freeze at some point in the past. It is absolutely critical that the foundations of buildings extend below this point in a soil profile. Except for a few arid locations, soils typically contain water and this water expands approximately nine percent in volume when it freezes. The frost line depth is not consistent around the nation because there

is such a dramatic difference in climate from state to state. Deck is composed of 2.5 cm reinforcement and there is no need for piers. The material properties are as follows:

For Coarse aggregate: SSD bulk specific gravity: 2.75, absorption capacity = 1.5 %, total moisture: 2.5 %, Dry-rodded unit weight: 1514 kg/m³.

For Fine aggregate: SSD bulk specific gravity: 2.65, absorption capacity = 1.0 %, surface moisture: 3 %, F.M: 2.6.

Cement: Type V, Sp.Gravity: 3.23

Probability constant: 1.22 and standard deviation: 2 MPa

Answer 1

Mix design using ACI method with given specifications is shown below.