Concrete “Popcorn” Spalling: A High-level Explanation

Almost every building construction project has concrete in it. During the placement phase, it’s important to complete specific steps to mitigate future issues – in this case, spalling.   

Concrete is one of the oldest construction materials on earth, having been around, in some form or other, for the past 2,000 years or so.  In its basic sense, concrete is a combination of cement, aggregates, and water.  When combined, they create a material that is great in compression, but not so great in tension.  This is where the reinforcement comes in handy.

Over time, the reinforcement in the concrete may become exposed to moisture due to various reasons – cracks caused by temperature changes, movement, improper installation, improper curing; or by improperly consolidating the concrete after it has been placed in the formwork. These deficiencies can cause a chain reaction of damage within the concrete and to the unprotected steel reinforcement. As an example, water seeps into cracks, freezes and expands to create larger cracks thus making the steel more susceptible to moisture. The example in the photo is one of improper concrete consolidation after the concrete has been placed. This “popcorn” spall so-called as the concrete surrounding the spalled areas can resemble popcorn.  It can also be referred to as “honeycomb”. Once moisture reaches the unprotected steel the steel will start to rust which exacerbates the degradation of the surface, and the surrounding concrete, over time.

Eventually, the rust build-up on the steel reinforcement will exert so much pressure on the surrounding concrete (through a process known as “rust-jacking”) that the concrete will continue to spall and deteriorate.

Concrete spalling is a common problem BCG often deals with. There’s a number of solutions to consider but one thing is for certain, once you see ‘popcorn’ – you need to call Barnes ASAP!