But it is an important plot point to the beginning chapter of a four part story I’m writing.
Scenario: our poor hero has been ruthlessly drugged in a bar and awakens in chains in the bottom of a dilapidated Olympic sized pool. Evil drug dealer with organized crime connections arranges for shady contracting buddy(-ies?) to drive over from nearby construction site with cement trucks to bury him alive.
I need to know:
Which dries faster, concrete or cement? Whichever dries faster is the one I’ll actually use in the story.
About how many cement trucks would I need to fill the bottom of the pool, say, five feet deep in the deep end??
About how long would it be before three or four evil drug dealers could safely walk on the surface of the pool and satisfy themselves the deathtrap is escape-proof?
Hope you don’t have someone chained at the bottom of your pool right now (and I am not a expert in pools nor cement).
1 concrete is cement w/ some additive like stones so dryign time shoudl be the same.
2 Don’t know, but it seems easy enough to calculate.
3 The guy would die when air is cut off, and then baked as the cement hardens. They may be able to walk on it the next day.
PS not the way you layed it out.
Concrete is just cement mixed with an aggregate; I’d WAG that the aggregates don’t affect the curing rate and that they both set at the same rate.
An Olympic pool is 25 meters wide. I can’t find any info on how such pools are layed out (the FINA regulations only give minimum depths). Let’s fudge and assume the “deep end” is the rear 1/4 of the 50m long pool. So we need to fill 25 m x 12.5 m x 5 feet, or about 622 cubic yards. Typically a cement truck holds 7-10 yards, so you’d be looking at 63-89 truck loads of Redi-Mix.
Er, they could probably safely walk on the surface of the pool immediately after the concrete is poured. The stuff is so dense they wouldn’t sink.
So what happens is: As they begin to fill the pool, he has jimmied the locks but feigns unconsciousness. As the pool fills to say 2 or 3 feet deep he sinks a little, out of sight, takes off his shirt and lets it float on the surface so it looks like he’s still there. He makes his way to the stream of concrete pouring into the pool and clandestinely makes his way into the mixer. Where he waits…
Second, definately use concrete which contains aggregate (small rocks) as it will cure harder, and quicker. Yes quicker. Increase the volume of aggregate and you reduce the volume of cement, thereby reducing the cure time.
Third, walking hardness will vary depending on the temp and humidity, how loose the concrete was mixed (ammount of water added) and size of the pour, but to walk on without leaving footprints, a good 6-8 hours. If you don’t care about prints, maybe as soon as 2-3 would keep you from sinking to the ankles
Have you considered having the evil drug dealers just shoot the guy in the head? Maybe the bullet could go in-and-out without destroying anything too vital and he lives? Give him some cognitive defects in the rest of the novel to make it more realistic.
Okay. For the sake of plausibility I’m changing it from an Olympic-sized pool to a residential-sized pool in a dilapidated community center. I have the crooked contractor bring over several truckloads of filler dirt that’s been removed from the construction site and THEN filling everything in with concrete. I think I can get away with … five trucks? I’ll call them “supermixers.”
I’ll have the thugs say “dry” and the professional contractors say “cure.”
Don’t believe everything you read above about the differences between cement and concrete.
Cement, or more specifically Portland cement, is a dry grey powder that when mixed with water and sand and, if wanted, other larger aggregates such as stones, makes concrete, or more exactly, Portland cement concrete. The use of the terms “cement”, to refer to the solidified mixture, and “cement mixer” and “cement truck” are misnomers.
After about 24 hours, they could walk around on it without leaving footprints and after about 30 days, it will have cured almost completely.
If your hero can convince the perps to add a truckload of sugar to sweeten the pot then the concrete will never harden. Of course, he would need a straw or hose to breathe through, if he can wiggle to the surface before the weight of the material crushes him.
I’d be kinda shocked if he could breath through a straw or hose if he was under more then a few inches of concrete. Any deeper and you have a LOT of pressure on your chest…
My typical 16’x32’ residential pool holds 18,000 gallons of water, but you would likely only need a third of this to really cover the fellow up. Since the bottom of the pool slopes from 3’ at one end to 8’ at the other end, most of the water is within a few feet of the surface. In other words, when you are filling the empty pool, the first four feet fill very quickly since you are only filling the deep part.
I just had my pool liner replaced and filled the pool up with the garden hose: it took two and a half days, but the deep end had already filled by the end of the first day.
Could our nearly dead hero possibly shimmy out through some kind of vent/filter system for the pool? He’d have to be like Frank Sinatra skinny, though.
Remember, bad guys don’t stick around for very long, so they could do the pouring of the mix and get scared off (or, even better in my book) get a phone call to go off and see some strippers. Bad guys have needs, too.
Thirdly, Cement Trucks have about a 45+ minute window to get their load to where it needs to be ( overmixed or starts curing, I can’t remember) If they don’t stop every so often to spray water in there it gets thick. That is how it was explained to me by my husband who knows these kinds of things. So with this kinda info, you could have a lazy, slow driver who doesn’t do it right and eveyrthing is crap to begin with, leaving Our Hero, to breath through a filter system until he hears ( though the pipes to the filter that they are standing on) everyone leave and the truck drive off and he ‘swims’ to the top.
They sell a kind of concrete mix that you don’t mix with water first. You pour it in dry, and then pour water over it. It’s useful for setting posts into the ground. You dig the hole, put the post in, fill the gaps with the mix, and then spray water in. It’s nowhere near as good as regular concrete mix for most types of jobs, but for Joe Homeowner putting up a fence, it’s just the ticket.
I mention this because I think it would be awfully funny to have the thugs buying bag after bag of this stuff from the Home Depot. And then tearing open all the bags, dumping them in, arguing over how much water to use, and then having to get rid of all the empty bags.
What kind of pool is this that no one would be suspicious of it being full of concrete? You know…
“Hey, Hero-dude has disappeared.”
“Check mob connections.”
“Howdy, mobmen, I see you’ve got a pool full of concrete back there.”
“Making a skate park.”
“Ah, I see. Carry on.”
Is it somewhere several cement trucks wouldn’t be noticed?
Sorry. Haven’t read a good book in a while. I need a good deus ex machina to perk me up again.
