Question

1) What is the additional water content to be added to the mix, if the slump...

1) What is the additional water content to be added to the mix, if the slump has to be maintained at 3 in. when the fresh concrete temperature changes from 60 oF to 80 oF?

2) Suppose the additional water content in question 3 was added to the mix to maintain the required slump of 3 in. while maintaining the same cement content.  What is the water-cement ratio of the mix at 80 oF?

Homework Answers

Answer #1

Ans 1) According to ASTM C94 , a 10o F rise in temperature of concrete require an additional gallon of water to maintain a same slump that the concrete had at lower temperature . Here rise in temperature is ,

T = 80 - 60

   T = 20 F

Water required to be added = (2 x 1) gallon

Water required = 2 gallon

Ans 2) Let the water cement ratio at temperature 60o F = 0.50

Let initial mass of concrete = 100 lb

Mass of cement = 0.50 x 100

Mass of cement = 50 lb

Mass of water = 25 lb

Mass of water at 80oF = 25 + 2

= 27 lb

Water cement ratio at 80oF = 27 / 50

= 0.54

  

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