Question 38

[addiaz2714087]

Wouldnt the inclusion of rubber make B RIC? and the passage says that concrete is stronger than RIC.
So the answer that makes more sense would be C... C is regular concrete and has the least amount of water among the concrete mixes. Also the question is asking about concrete specifically, not RIC, so I dont see how B is right.

[dnpgr16513]

Hi,

I agree with the student above me. Also in the passage, it stated that the aggregate composition also had to be decreased. Isn't 50% too high for the aggregate content?

I know you guys are busy, but so are we. I kindly ask you if you can respond back in a timely manner with these questions.

Thank you!

[jeanne7524]

Hi there!

First, you have to understand what the question is really asking: "...which of the following mixtures would make the strongest concrete?" It only requires determining which among the choices would have the best mixture to make the strongest concrete - whether it's RIC or "regular" concrete. These are what the passage provides:
(1) "The less water in concrete the stronger it is. Hydration, the chemical reaction that takes place as soon as water is poured in with the cement is what holds the concrete together."
(2) "By replacing a proportion of ordinary concrete's course aggregate, or stone, with rubber, it is possible to create a concrete with more desirable properties." In this case, the desirable property is that it adds durability to concrete.
(3) "In order to incorporate rubber the amount of course aggregate must be decreased."
(4) "The inclusion of rubber in concrete produces a lighter weight material with increased toughness."

Based on the information given in 3 and 4, increasing the ratio of rubber in reverse to that of aggregates would make the concrete stronger and more durable. However, information 1 is even more crucial: even if we decrease the aggregates' proportion and increase the rubber, the resulting mixture would still NOT HOLD to make strong concrete if a high ratio of water is present.

More importantly, the question asks which among the choices would make the strongest mixture of concrete, NOT the most ideal - regardless if it's RIC or not. In Option B, the small amount of water in the mixture would work together with the inclusion of rubber, despite its small proportion, in strengthening the concrete in terms of toughness and durability.

Hope this clarifies.