Sunday, February 26, 2006

Freeze/Thaw

One aspect that really has jumped out at me here in Montreal is the freeze/thaw cycles. Although it stays below freezing more consistantly, there are three places that I see more of it than I remember back in Chicago.

First is rooftops. The above picture is of a rooftop near where I work. You can see that the bricks leftover from a chimney repair have completely disintegrated into a conical pile of brick rubble. My guess is that the bricks have only been there for about a decade or two. Rooftops see quite a bit of the freeze/thaw because they are in unblocked sunlight all day. Plus there is usually some warmth escaping from below to melt the snow. Over the course of the past couple winters, I have been able to see the rooftops alternate between snow covered and clear throughout the season. Whereas the ground has constantly been covered with snow all winter long.

Second is the roads. They see the freeze/thaw often because unless the roads are dry, salt needs to be laid down after a night of freezing temps. It could be a small snowfall or the morning after some thawing, but it is often that roads need to be salted. Then there is the problem of ice lensing where water either coming down from the salted road or up from the unfrozen earth hits a cold layer. The water freezes and expands usually destroying the road surface above. The roads take one heck of a beating and I'll elaborate on the potholes soon.

Lastly is the sidewalks or concrete in general. I'll also elaborate soon on other abuses the sidewalks endure. But the sidewalks also see their share of salt. It is primarily those on the sunny side of the street that get hit hardest with the freeze/thaw. I am surprised each time and how often I see disintegrating concrete. It is not the strength of the concrete because I know they use the same strength as back home. The way it crumbles apart suggests that it must be the freeze/thaw. And it is not simply age because structures built in Chicago at the same time as the Turcotte interchange don't show as much superficial wear.

I'll have those posts on potholes and sidewalks in the upcoming weeks.