Type of rocks used in mixing concrete
Posted by Shae from Clovis, CA, US on November 26, 2006
HI I am a 7th grader working on a science fair project regarding the strength of concrete if I add a mixture like a fiber or latex paint and I was wondering if it matters what type of rock, size of rock or wether the rock is crushed. I am making 6″ x 12″ cylinders. I would appreciate any information that you can give me.
You are making very large cylinders that will allow you to use larger, stronger aggregate. Choose the largest crushed stones allowable for a 6" diameter test cylinder--which would be 2"-2ΒΌ" stones that are jagged. Don't use more than 60% of the total weight of the aggregates--in this size.
Next, use a blend of smaller crushed gravel from 5/8" down to sand that is at least 60% sand fines. We call this a graded blend of crushed stone and fines.
To this add the amount of cement required for teh strength you are wanting to make--10%, 20% or 30% of the weight of the aggregates.
Go to concrete.org and click on mix designs to read about the all important water/cement ratio. This ratio will allow you to glue crushed aggregates together weakly or strongly.
