Discoloured Concrete Paths: Causes and Solutions
There's a reason why so many homes have paths made of concrete tiles. It's relatively inexpensive, aesthetically pleasing, and extremely durable. While concrete tiles can discolour as the years go by, this is generally a very minor lightening due to exposure to the sun and other elements. When one or more concrete tiles begin to darken, this is a sign that all might not be well, and a straightforward replacement is only ever going to be a temporary fix.
More Than Meets the Eye
While concrete might seem to be a solid, immovable object once it has dried, there is more to concrete than meets the eye. It's porous, and as such contains multiple tiny pores that are capable of drawing in moisture. Like a sponge, a concrete tile can only take in a finite amount of moisture before it reaches its capacity. Ideally it should not be taking in that much moisture at all, and a darkened concrete tile is one that has been slowly and steadily soaking up moisture over the years. As its structural integrity becomes compromised, the tile might even begin to crack.
Straightforward Replacement Might Not Be the Answer
Be wary of contractors who just opt to replace the tiles. While the discolouration will be gone (since the tiles are new), this is a band aid solution. Certainly the tiles will need to be removed, but during this process a qualified professional will need to examine what lies beneath the tile. They might in fact be sitting in mud, and this can be a sign that moisture is accumulating somewhere it shouldn't be.
There can be a number of reasons why there is an excessive amount of moisture under the concrete tiles. A leaking pipe could be a culprit, and this will of course require immediate professional repair. It might also be the case that it's a simple case of the path being in the catchment area for drainage on your property, and any moisture on your lawn and outside areas naturally moves to where the concrete path has been laid. While this is difficult to fix, the problem can be rectified by replacing the sections in question with specialist water resistant concrete tiles. These are made of high density concrete with fine particle cement. They are infinitely less porous than standard concrete, and while the moisture will remain, it's not going to affect the concrete tiles.
So while discoloured concrete tiles on your pathways can be a cause for alarm, it's not as though the problem can't be solved.