pervious concrete void ratio equation ???

[boffintech]

Have a pervious concrete pavement job and the specs require that the void ratio be determined. Not sure of my formula. What do you think?

core length = 5 7/8"
core dia. = 3.74
A = wt in air = 2128g
B = SSD wt. = 2177.2g
C = wt in water = 1250.1g
BSG = A/(B-C) = 2.295
job mix formula density = 117.21
% compaction = 143.2 lbs/ft3
% air voids = 2.2%

The 2.2% air voids doesn't seem reasonable and my compaction is way over.

 

[Ron]

What you have shown as your % compaction is the unit weight as determined by your BSG. I think you have a problem with the bulk specific gravity determination and your % air voids is way off. I'll check it when I get a chance.

 

[CarlB]

Measuring the weight in water gives the weight of water displaced, thus volume displaced.

Water displaced 2177.2 - 1250.1=927.1g
Vol displaced = 927.1g x 1cc/g=927.1 cc

Assume regular cylinder,
Vol = Pi x r^2 x h=64.59 in^3
=1057.6 cc
Vol voids=1057.6 - 927.1=130.5 cc
%voids=130.5/1057.6=12.3%