you know those black dots that stick out
2007-02-22 12:49:51 · 6 answers · asked by Ernando 4 in Education & Reference ➔ Other - Education
no those like black spots that form after a while, i think there bacteria or something but what are they really and what are they called
2007-02-22 12:58:11 · update #1
it is not tar trust me, tar is used on rooftops not sidewalks and plus these are little spots like dots about 2 inches wide
2007-02-22 13:04:11 · update #2
I think it's an algae. I found out that:
Algae (singular alga) encompass several groups of relatively simple living aquatic organisms that capture light energy through photosynthesis, using it to convert inorganic substances into organic matter.
So I conclude that those black things on the sidewalks are algae because when it rains, the water stays on the little holes on the sidewalks and algae forms because (what it says above (capture light energy through photosynthesis, using it to convert inorganic substances into organic matter, called algae)).
=]
2007-02-22 12:59:41 · answer #1 · answered by Ycie 2 · 0⤊ 0⤋
They are felt dividers that absorb the expansion and contraction of the concret due to cold or heat. Keeps it from cracking
2007-02-22 20:53:04 · answer #2 · answered by lori l 1 · 1⤊ 0⤋
Uh....my sidewalks don't have any black dots that stick out.
2007-02-22 20:52:08 · answer #3 · answered by Anonymous · 0⤊ 0⤋
If it isn't one of the things listed already, it could be the stones they use in the concrete to strengthen it, also known as aggregate.
2007-02-22 20:55:32 · answer #4 · answered by knownothing 4 · 0⤊ 0⤋
I don't know what are you talking about but Can YOU be a little bit CLEARER.
2007-02-22 20:54:30 · answer #5 · answered by Right here Right now 1 · 0⤊ 0⤋
are you talking about tar?
2007-02-22 20:52:21 · answer #6 · answered by Kimbola 2 · 0⤊ 0⤋