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NCARB PDD Exam - Topic 2 Question 5 Discussion

Actual exam question for NCARB's PDD exam
Question #: 5
Topic #: 2
[All PDD Questions]

Which of the following admixtures is used to greatly increase the slump of concrete?

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Suggested Answer: D

Comprehensive Detailed Explanation with all NCARB ARE 5.0 Project Development and Documentation (PDD) Study Guide Reference:

In concrete technology, admixtures are used to modify properties of fresh or hardened concrete:

Air-entraining agents: Introduce microscopic air bubbles to improve freeze-thaw resistance; they do not increase slump.

Water-reducing agents: Reduce water content while maintaining slump; increase workability but only moderately.

Calcium chloride: An accelerator, speeds up setting time; does not increase slump.

Superplasticizers (also called high-range water reducers): Significantly increase the slump (workability) of concrete without adding extra water, making the mix more flowable and easier to place.

Thus, to greatly increase slump while maintaining water-cement ratio, the superplasticizer is the correct choice.

Supporting Reference:

NCARB ARE 5.0 Review Manual, Materials and Assemblies section

Portland Cement Association publications on admixtures

ACI (American Concrete Institute) guidelines on admixtures


by Laurene at Oct 02, 2025, 01:50 AM

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Herman
2 months ago
Air-entraining agents are for air, not slump!
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Lashandra
2 months ago
Superplasticizer is the way to go!
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Marylyn
2 months ago
Definitely D) Superplasticizer!
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Anisha
3 months ago
I thought it was B) Water-reducing agent?
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Lavina
3 months ago
Wait, are you sure about that? Sounds too good to be true.
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Jestine
3 months ago
I feel like calcium chloride is more about accelerating curing, not really about increasing slump. So, I’d lean towards D as well.
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Jovita
3 months ago
I’m a bit confused. I know air-entraining agents are for freeze-thaw resistance, but I can't recall how they affect slump.
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Mozell
4 months ago
I remember practicing a question about admixtures, and I think water-reducing agents also help with slump, but not as much as superplasticizers.
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Shannon
4 months ago
I think the answer might be D) Superplasticizer, but I'm not entirely sure. We talked about it in class.
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Markus
4 months ago
D) Superplasticizer, for sure. That's the admixture designed to increase the workability and slump of concrete without adding more water. I'm confident that's the right answer here.
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Nguyet
4 months ago
I'm a bit confused on this one. I know the different admixtures have different effects, but I can't quite recall which one is used to boost the slump. I'll have to review my notes before answering.
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Tamekia
4 months ago
Okay, let me walk through this step-by-step. Superplasticizers are high-range water reducers that can dramatically increase the slump of concrete without adding more water. That's the key thing I remember from my concrete materials course. So I'm pretty sure the answer is D.
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Lazaro
5 months ago
Hmm, I'm not totally sure about this one. I know air-entraining agents and water-reducers can affect concrete properties, but I'm not confident which one specifically increases the slump. I'll have to think this through carefully.
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Winifred
5 months ago
I think the answer is D) Superplasticizer. That's the one that's used to increase the slump of concrete, right?
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