I went for a long walk yesterday and it started to rain lightly.
In one neighborhood the gutters had been repaired about 8 years ago. The
old concrete formed puddled immediately, but the newer concrete absorbed the
water as fast as it fell. I figured that the pores on old concrete must
fill up with oils from the road.
Then I got to another neighborhood where the gutters were repaired 2 years
ago. Both the old and new sections repelled the water equally.
What is going on here? Why did the 2 year old and 30 year old concrete
repel water, while the 8 year old concrete absorbs it?

"Wade Lippman" wrote in message
...

I went for a long walk yesterday and it started to rain lightly.
In one neighborhood the gutters had been repaired about 8 years ago. The
old concrete formed puddled immediately, but the newer concrete absorbed
the
water as fast as it fell. I figured that the pores on old concrete must
fill up with oils from the road.
Then I got to another neighborhood where the gutters were repaired 2 years
ago. Both the old and new sections repelled the water equally.
What is going on here? Why did the 2 year old and 30 year old concrete
repel water, while the 8 year old concrete absorbs it?

In your place, I should ask at the local public works
(road maintenance) office. It seems seldom difficult
to find local experts, where they exist, and most are
keen to share their specialized knowledge.

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)

"Wade Lippman" wrote in message
...
I went for a long walk yesterday and it started to rain lightly.
In one neighborhood the gutters had been repaired about 8 years ago. The
old concrete formed puddled immediately, but the newer concrete absorbed
the water as fast as it fell. I figured that the pores on old concrete
must fill up with oils from the road.
Then I got to another neighborhood where the gutters were repaired 2 years
ago. Both the old and new sections repelled the water equally.
What is going on here? Why did the 2 year old and 30 year old concrete
repel water, while the 8 year old concrete absorbs it?

There is a type of concrete that is designed porous to allow water to drain
through it. It is placed on a subgrade with good drainage such as 6" to 8"
gravel. If I remember correctly it is mixed without sand and is not floated
or troweled but placed, vibrated, and rolled. Stormwater is then filtered on
its way to the water table through the concrete and gravel.

Tim