How to calculate the amount of materials needed to fill a specific volume with concrete?

[alexmax]

Hello all..

I'm doing a small project at my house with GFRC, with a mix of 1:1 cement to sand by weight, and I was wondering how can I calculate how much do I need for the mix to get the materials ready?
I calculated the volume that needs to be filled and it's about 4 cubic feet.

Thanks in advance

 

[Ron]

alexmax....first, you don't need a 1:1 mix. 1 part cement to 3 parts aggregate is ok. If you use only sand and no coarse aggregate, along with the cement content you are using, you will get a lot of shrinkage and cracking. Since you only have 4 cubic feet to deal with, buy a few bags of premixed concrete mix (Sakrete or similar). It has proper proportions and will yield a reasonable strength of concrete without extraordinary shrinkage if you follow the directions. Each bag is about 1/3 of a cubic foot, so you'll need about 12 bags or so. At about 5 bucks a bag.....$60.

 

[alexmax]

Thank you Ron for your reply
Unfortunately premixed concrete is not available in my area, Also, I wanted a smooth surface therefor I wanted to eliminate aggregate and go with glass fiber reinforced concrete.

 

[LehighLarry]

Hi Alex,

The key to true GFRC is to sure to use alkali resistant glass fiber and a polymer formulated for the application. Both Ball (Smooth-on)and Nippon Electric Glass produce products under the name Forton and Polyplex respectively. Goon info on the products and process are on their websites. As far as volume goes the industry standard is to use the Absolute Volume method employing the specific gravity (SG) of the products to convert weight to volume. The SG of white portland cment (or gray) is 3.15, Water is 1.0 and most sands run around 2.7. The specific gravity will get you to the volume of the mix. Form there you can do a simple volume calculation. Figure at least 20% waste.

There is a good article on this by Dennis Clute,

http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs143_024034.pdf

Larry from Lehigh White Cement Company