Concrete mix contains 5 liters of superplasticizer (specific gravity 1.2). Superplasticizer has 65% water by mass. Mass of active solids in the superplasticizer is__________
- A3.9 kg
- B1.75 kg
- C3.25 kg
- D2.1 kgCorrect
Solution
Concept
Calculation of active solid content in liquid chemical admixtures based on specific gravity and water content percentage.
Formula
Total Mass = Volume × Specific Gravity × Density of Water Active Solids Mass = Total Mass × (1 - Percentage of Water)
Explanation
First, find the total mass of the superplasticizer by multiplying its volume by its density (mass = volume × specific gravity × density of water). Since the superplasticizer contains 65% water by mass, the mass of active solids is the remaining percentage, which is 100% - 65% = 35% of the total mass.
Shortcut
Mass of active solids = Total Volume × Specific Gravity × (1 - water fraction).
Common mistake
Multiplying volume directly by percentage without converting to mass using specific gravity.
Correct answer: D) 2.1 kg