I’m writing a scene in which my protagonist is bound and gagged in the bottom of an empty old swimming pool. To kill the guy, the bad guys in question pour a bunch of cement off a cement truck over him, enough to fill the entire pool, then they sit around telling murder stories while they watch the cement dry.
Three questions.
#1: Would they need more than one cement truck to do the job?
#2: After filling the pool, approximately how long does it take for the cement to dry completely?
#3: Suppose you were a cop and got wind of this. What procedures would you need to go about getting the body exhumed, and what kinds of equipment might it take, and how long would it take? (Assume the cement has set)
#4: I don’t swim. What are some sizes of swimming pools besides “Olympic-size” that you might find in an athletic club like the YMCA?
Thanks! When writing bullsh**t I know nothing about, the secret’s in the details.
First, let me say that that’s a nice, mean idea. I like it a lot.
Second, your pool cannot be full. You’ve all that concerete yet to dump, and mixer trucks are already pre-mixed, so water actually interferes with the setting of the concrete. May I suggest a mostly-drained pool? That way you might get away with turning a twelve-foot deep end into a nine-foot deep end (and scrap the high-dive for insurance reasons).
Re-finish the bottom of the pool, and your unfortunate victim is sitting around the fire with Jimmy Hoffa. Jackhammers are the only way to find him once it sets, and the passage of time might leave only a cavity and bones (and other interesting things), not unlike the victims of Pompeii. That would take a lot of time, though.
Setting concrete can still be walked through, if it is of the right consistency–another possible saving grace for your protagonist. There is no logical reason for my being alive and ambulatory after playing in the setting foundations of a mansion as a kid, but I did. Concrete burns a little, and can get quite hot. Civil Engineers work long hours figuring out how much you can pour at a time without overheating and cracking.
Before I forget, a similar death was recounted in Dashiell Hammett’s The Thin Man.
Spoiler:
The killer buried the victim in a basement and resurfaced the floor. To throw off any potential discoverers, like Nick, the killer threw the clothing of a very thin man onto the obese victim, knowing that forensics of the time would not be able to determine the physiology of the victim from bones alone. Clever indeed, but not clever enough.
Concrete does not dry. Cement chemically reacts with the water. Concrete will set, even at the bottom of a pool, although not as smoothly. On a hot summer day, construction workers usually have to keep adding water to the top of concrete so that there is enough water for the chemical reaction to take place.
Folks, it’s an empty pool. As in waterless, bone dry. And very deep. So how much would it take to fill such a pool full of concrete, assuming its empty, and how long would it take for the concrete to dry?
Could you dump it all in at once or would you have to do it in stages?
Yeah. I finally realized I meant concrete, not cement. My bad.
In the US, concrete is sold by the cubic yard. Your average, run-of-the-mill concrete truck (the kind with the big revolving mixing cylinder on the back) holds about 8 yd[sup]3[/sup].
My parents had a pool in the back yard when I was growing up. It was about 16’x32’ and a average depth of say 5’. That gives you a volume of 2560 ft[sup]3[/sup] or about 95 yd[sup]3[/sup]. So figure that it would take about 12 truckloads to fill the thing to the top.
Drying time would be on the order of a few days to be solid enough to walk on, and weeks or months until its at full strength.
If all this is accurate, this throws off my plot somewhat —
Shiva: In the first draft of my story, the victim in my story weighs, like, 300 pounds and is also weighted down at the bottom of the pool, so his floating to the top is not a likely problem.
Minkman: I love people who reason with math. Your “12 trucks” scenario is slightly more problematic; I suppose can fudge suspension of disbelief and add two more, for a total of three trucks. Or have a MUCH bigger mixing trucks involved (assuming they exist) that can mix, say, 12 sq. yds. Maybe suggest it’s a smaller-than-average pool, or have it filled only halfway.
Biggest hurtle: the several days needed to dry. In the context of the story, I’d need it dry in 12-24 hours MAX. Is there any way to speed up the drying process? Don’t worry about things that might cause cracks or the concrete to not set evenly. The baddies involved are burying the guy to make a point, not to make a foundation.
But in the end scene of this current draft, two of the baddies do walk around the top of the pool until they’re satisfied it’s solid enough to leave. Question: assuming optimal conditions, when is the soonest that can happen?
Have you thought about using a smaller pool, like a spa? I suppose it’s less dramatic, but a 12’ diameter by 3’ deep could probably filled by one or two trucks. Drying time may still be a while.
As a side note, most 300 lb humans have a disproportionate amount of fat, making them more likely to float. Tying him down there works, of course.
The type of concrete we’ve been talking about so far is “ready-mix” concrete. The trucks that it gets delivered in range in capacity from 6 - 12 yd[sup]3[/sup]. With about 8 yd[sup]3[/sup] being about the average size. As I mentioned above, the “cure” time for this stuff is measured in days. One manufacturer of flooring recomends that you wait 60 days after pouring a concrete slab before installing thier flooring over it. Typically you are pouring a slap that only several inches thick. Since you want to pour a several foot thick pool full, I would think that the time to cure would be longer. It’s hard to find references for the actual time since no one typically constructs things like that. There are accelerants that can be added to the concrete to speed the set time, but we’re talking the diference in waiting a week to start building the rest of the structure on the slab to only waiting 3 days (with accelerants).
There are “rapid-set” concretes on the market, that can cure in a matter of hours. One claims that in one hour, it will have a compressive strength of 2000lbs, definately enough to walk on. The problem for you however, is that the kind of mixing trucks we’re talking about don’t deliver rapid-set concrete. Imagine a traffic jam ruining your brand new $100,000+ truck because the concrete cured before you could get to the site.
Here’s a suggestion: Have the bad guys bury the victim in a spa by dumping several (8-10) bags of rapid-set in the spa water. Perhaps you could work the spa into the story before the deed so it has some symbolic value.
