Posted: 4/25/2013 2:24:26 PM EDT
Ok, it's been almost 10 years since I had this type of math in construction class in HS, so I have forgot it all Anyways I need to pour a small slab of concrete here at the house for a small charcoal pit I'm building. The dimensions of the slab are 36"x26"x4" thick. I'm going to buy this Sakrete from Lowes So, concrete math experts, how many bags do I need???
EDIT: forgive me for posting something that requires thought in GD
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Ok, it's been almost 10 years since I had this type of math in construction class in HS, so I have forgot it all Anyways I need to pour a small slab of concrete here at the house for a small charcoal pit I'm building. The dimensions of the slab are 36"x26"x4" thick. I'm going to buy this Sakrete from Lowes So, concrete math experts, how many bags do I need???
EDIT: forgive me for posting something that requires thought in GD 3.14159 Posted Via AR15.Com Mobile |
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Ok, it's been almost 10 years since I had this type of math in construction class in HS, so I have forgot it all Anyways I need to pour a small slab of concrete here at the house for a small charcoal pit I'm building. The dimensions of the slab are 36"x26"x4" thick. I'm going to buy this Sakrete from Lowes So, concrete math experts, how many bags do I need???
EDIT: forgive me for posting something that requires thought in GD 3.14159 Posted Via AR15.Com Mobile smart ass
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Ok, it's been almost 10 years since I had this type of math in construction class in HS, so I have forgot it all Anyways I need to pour a small slab of concrete here at the house for a small charcoal pit I'm building. The dimensions of the slab are 36"x26"x4" thick. I'm going to buy this Sakrete from Lowes So, concrete math experts, how many bags do I need???
EDIT: forgive me for posting something that requires thought in GD OP, I just poured a concrete slab not too far off from your dimensions Roughly, I had 27" x 45" x 4" and I ended up just a tad short using 280 lbs worth of quikrete premixed. (3x 80# bag + 1x 40# bag) So based on that, you should be fine with a little left over if you get about that much. (Figure five bags if you can only get 60#'ers) Eta - just noticed you chose to use high strength formulation. That takes quite a bit more as less water is mixed in. As said above BUY EXTRA. You can always bring it back, but if you come up short during the mix you'll be in big trouble. E. |
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10 bags ETA to show work: You're covering 6.5 square feet at 4" thick According to the specs, each bag covers 1.4 square feet at 2" thick So 6.5/1.4 X 2(double the thickness) = 9.29 bags 9.286 bags.... 26*36=936 sq.in = 6.5sq.ft bags cover 1.4 sq ft at 2" thick,, you have 4" thickness, so 6.5*2=13 sq.ft needed 13sq.ft / 1.4 (sq.ft/bag) ~9.2857 10 ought to do it, based on your websites info ETA> beat |
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Ok, it's been almost 10 years since I had this type of math in construction class in HS, so I have forgot it all Anyways I need to pour a small slab of concrete here at the house for a small charcoal pit I'm building. The dimensions of the slab are 36"x26"x4" thick. I'm going to buy this Sakrete from Lowes So, concrete math experts, how many bags do I need???
EDIT: forgive me for posting something that requires thought in GD 8 bags, and you will have 2/3 of one bag left over. |
| i have come to love this site: http://www.engineeringtoolbox.com/ |
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I see no information on the site about how many pounds of concrete fills a given volume. Without that, we can't help. Under specifications it says covers 1.4 square feet a 60lb. bag, or 4 square feet per 80lb bag  Square feet is not a volumetric measure. It is a surface measure. The posters above are making an assumption that it is implied the manufacturer means 1.4 sq. ft. at the minimum 2" thickness required. But that is not necessarily a fact. Lowes website is not publishing the full specifications for that formulation. I suggest the OP go to sakrete's website for the data sheet for that product, or go to the store and look at the printed package in person for the actual fill volume. E. |
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It took me less than 30 seconds to find the data sheet for this product on their website.
data sheet According to that, an 80# bag fills .60 cu ft of volume. Base your bag count needs on that and you should be fine. |
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http://www.sakrete.com/products/detail.cfm/prod_alias/High-Strength-Concrete-Mix Per their datasheet, 0.45 cu-ft per 60lb bag. 3ft x 2.17ft x 1/3 ft = 2.17 cu ft. 2.17 cu ft/0.45 cu ft = 4.8 bags, so 5 bags. |
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I see no information on the site about how many pounds of concrete fills a given volume. Without that, we can't help. Under specifications it says covers 1.4 square feet a 60lb. bag, or 4 square feet per 80lb bag Square feet is not a volumetric measure. It is a surface measure. The posters above are making an assumption that it is implied the manufacturer means 1.4 sq. ft. at the minimum 2" thickness required. But that is not necessarily a fact. Lowes website is not publishing the full specifications for that formulation. I suggest the OP go to sakrete's website for the data sheet for that product, or go to the store and look at the printed package in person for the actual fill volume. E. The spec sheet for the product gives the 2 inch thickness, but why they can't put it next to the area is a mystery. Probably written by a moran. |
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Ok, it's been almost 10 years since I had this type of math in construction class in HS, so I have forgot it all Anyways I need to pour a small slab of concrete here at the house for a small charcoal pit I'm building. The dimensions of the slab are 36"x26"x4" thick. I'm going to buy this Sakrete from Lowes So, concrete math experts, how many bags do I need???
EDIT: forgive me for posting something that requires thought in GD 3.14159 Posted Via AR15.Com Mobile smart ass You're paying attention, that's good!!! Not going to bother with a real answer - I see that's already done, just wanted to give you an "attaboy"! 
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Ok, I see the sakrete thing on their site, will go figure it up again, thanks to you guys above!
I got the hole all dug, sod removed, and the dirt (garden is right next to it, so I got rid of the dirt easy ) Built up a form out of scrap 1x's I had saved. I'll level it all up, and stake it tomorrow, and i already checked it for square, and it's about a 1/4" out, so I'm not really too worried about that. Like I said above, I know my carpentry, I just forgot how to figure concrete
I have some old concrete blocks that are crumbling around back, I'm going to smash up and put in the bottom of the hole for a good base, that and a sheet of plastic so all the water in the concrete doesn't soak away from the slab while it dries. |
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Ok, I see the sakrete thing on their site, will go figure it up again, thanks to you guys above! I got the hole all dug, sod removed, and the dirt (garden is right next to it, so I got rid of the dirt easy ) Built up a form out of scrap 1x's I had saved. I'll level it all up, and stake it tomorrow, and i already checked it for square, and it's about a 1/4" out, so I'm not really too worried about that. Like I said above, I know my carpentry, I just forgot how to figure concrete
http://i67.photobucket.com/albums/h313/joe7170/100_1528_zps716b5bc8.jpg I have some old concrete blocks that are crumbling around back, I'm going to smash up and put in the bottom of the hole for a good base, that and a sheet of plastic so all the water in the concrete doesn't soak away from the slab while it dries. Dont put plastic under the concrete, just lightly wet the dirt before you pour it. Its just a tiny slab so it doesnt even matter but when placing concrete you want the water to evenly bleed through the bottom and top. With plastic all the bleed water will come to the surface and weaken it. If you are overly concerned about this tiny pad that is below grade and going to be covered and unseen.....add a 45lb bag of portland cement to your total mix to give it more strength. Those pre mix concrete bags have hardly any cement in them, thats why they are only 3 bucks each |
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Ok, it's been almost 10 years since I had this type of math in construction class in HS, so I have forgot it all Anyways I need to pour a small slab of concrete here at the house for a small charcoal pit I'm building. The dimensions of the slab are 36"x26"x4" thick. I'm going to buy this Sakrete from Lowes So, concrete math experts, how many bags do I need???
EDIT: forgive me for posting something that requires thought in GD Ask a carpenter. |
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Ok, I see the sakrete thing on their site, will go figure it up again, thanks to you guys above! I got the hole all dug, sod removed, and the dirt (garden is right next to it, so I got rid of the dirt easy ) Built up a form out of scrap 1x's I had saved. I'll level it all up, and stake it tomorrow, and i already checked it for square, and it's about a 1/4" out, so I'm not really too worried about that. Like I said above, I know my carpentry, I just forgot how to figure concrete
http://i67.photobucket.com/albums/h313/joe7170/100_1528_zps716b5bc8.jpg I have some old concrete blocks that are crumbling around back, I'm going to smash up and put in the bottom of the hole for a good base, that and a sheet of plastic so all the water in the concrete doesn't soak away from the slab while it dries. Dont put plastic under the concrete, just lightly wet the dirt before you pour it. Its just a tiny slab so it doesnt even matter but when placing concrete you want the water to evenly bleed through the bottom and top. With plastic all the bleed water will come to the surface and weaken it. If you are overly concerned about this tiny pad that is below grade and going to be covered and unseen.....add a 60lb bag of portland cement to your total mix to give it more strength. Those pre mix concrete bags have hardly any cement in them, thats why they are only 3 bucks each Got you on the plastic, I'll leave that out. I'll just fill the bottom in with those busted up blocks, and wet them. It's not really too far under grade, it just looks like it, as the ground is uneven, on the side of a hill. The blocks will be sitting on top, so really, it'll be even to just slightly below grade. |
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http://www.sakrete.com/products/detail.cfm/prod_alias/High-Strength-Concrete-Mix Per their datasheet, 0.45 cu-ft per 60lb bag. 3ft x 2.17ft x 1/3 ft = 2.17 cu ft. 2.17 cu ft/0.45 cu ft = 4.8 bags, so 5 bags. Yep, or I can buy the 80lb bags, and buy 4, and have plenty of extra 
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Ok, I see the sakrete thing on their site, will go figure it up again, thanks to you guys above! I got the hole all dug, sod removed, and the dirt (garden is right next to it, so I got rid of the dirt easy ) Built up a form out of scrap 1x's I had saved. I'll level it all up, and stake it tomorrow, and i already checked it for square, and it's about a 1/4" out, so I'm not really too worried about that. Like I said above, I know my carpentry, I just forgot how to figure concrete
http://i67.photobucket.com/albums/h313/joe7170/100_1528_zps716b5bc8.jpg I have some old concrete blocks that are crumbling around back, I'm going to smash up and put in the bottom of the hole for a good base, that and a sheet of plastic so all the water in the concrete doesn't soak away from the slab while it dries. Why are you putting a fire pit right next to that old, dry piece of wood that appears to make a border with some other area? Won't you be tripping on it if it doesn't burn away first? |
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Ok, I see the sakrete thing on their site, will go figure it up again, thanks to you guys above! I got the hole all dug, sod removed, and the dirt (garden is right next to it, so I got rid of the dirt easy ) Built up a form out of scrap 1x's I had saved. I'll level it all up, and stake it tomorrow, and i already checked it for square, and it's about a 1/4" out, so I'm not really too worried about that. Like I said above, I know my carpentry, I just forgot how to figure concrete
http://i67.photobucket.com/albums/h313/joe7170/100_1528_zps716b5bc8.jpg I have some old concrete blocks that are crumbling around back, I'm going to smash up and put in the bottom of the hole for a good base, that and a sheet of plastic so all the water in the concrete doesn't soak away from the slab while it dries. Why are you putting a fire pit right next to that old, dry piece of wood that appears to make a border with some other area? Won't you be tripping on it if it doesn't burn away first? It's a charcoal pit, not gonna be a big fire in there, plus there will be 8" of solid concrete block betweent he charcoal and the border for my raised bed garden I've thought it out trust me
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Play it safe order a yard from your local concrete company 3 yd minimum here. So what should he make with the other 2.91 cu yds? (rounded to .09 cu yds after adding 10%) Quoted:
Add stakes to the outside of your form so it will stay 'square' or it will DE-form when filled with concrete........ I would go ahead and hog-trough it and stake some turnbuckles to each side, too. 
On a more serious note the blocks you plan to use will probably not stand up to any serious heat. |
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On a more serious note the blocks you plan to use will probably not stand up to any serious heat. The concrete wouldn't, either, unless it was a high temp mix. I don't think cinder blocks will go without cracking. Maybe an inside border of steel plate gapped 1" inside the blocks would save the cinder blocks, as well as allow for a way to get fresh air into the bottom of the fire so it doesn't go out easily. I'm guessing an all steel surround would be undesirable due to rust, burn hazard, and aesthetics. Maybe go with a fired clay surround? Looks good and will stand up to heat. |