Plants don't really break through concrete: The concrete breaks around the plant.
Plant roots will grow anywhere there is water. The edges of a concrete slab are particularly attractive as all the runoff water from the slab's surface collects there. The roots will continue to grow into any gaps beneath the concrete, exerting enough force to lift it.
Imagine lifting a piece of paper from its center: the unsupported ends will fold down. It can do this because paper is flexible. The same happens when the root lifts the concrete, but because concrete is brittle the pressure will eventually cause the concrete to shatter, creating a crack.
Something similar happens with masonry pipes, although the result is far more catastrophic. A pipe is essentially two arches, and when an arch develops a crack it loses its structural integrity. Without this strength, the pipe collapses under the weight of the ground above it.
Posted 4446 day ago