Nadia is the expert construction foreperson and is fielding all sorts of questions while the colonists set up Underhill. During one exchange, some other colonists are having trouble getting concrete to set:
A call from the Chernobyl crew interrupted her bulldozing. "Nadia, how do we get concrete this thick to set in the cold?"
"Heat it more."
I am notoriously bad at understanding emotion in stories, so I can't really tell what is implied here. Is the "Oh!" meant as a "That's a great idea" or a "Oh, we should have thought of that"? Is Nadia frustrated with them or just casually mentioning it (sort of like "turn left here" when you are giving directions to a driver, instead of "NO! Turn left here!")?