CHICAGO (CBS) — Pavement has been buckling in the summer heat along South Lake Shore Drive.

CBS 2’s Ed Curran looked into what is causing the problem.

The problem with South Lake Shore Drive is the same thing that makes it so durable.

It’s the concrete.

While it lasts for about 50 years, the surface expands when heated, so needs room to grow.

If it can’t expand freely, it buckles.

The surface of South Lake Shore Drive is filled with expansion joints that contain a compressible sealant to keep water and debris out. Some are filled with rubber but most contain a soft putty-like material.

Those joints are spaced about 15 feet apart, filled with a soft pliable material.

Over time, it becomes brittle and it doesn’t give like it’s supposed to.

When that happens, something else has to give, and that is what causes the street to buckle.

Lake Shore Drive near Oakwood Boulevard popped on Monday, the concrete buckling between the joints.

Crews patched it and are working at night this week to make permanent repairs and to make sure expansion joints stay squishy.