Spalling is the deterioration of a concrete surface over time, with crack lines forming first, then chunks of concrete falling out as the problem advances. It is caused by moisture penetrating the layer of concrete covering the reinforcing steel in the beam, column, or foundation pier. Eventually the steel begins to rust inside the beam and, because rust is slow but very powerful expansive process, cracks appear at the surface over the reinforcing steel. It‘s a progressive deterioration, because the open crack allows more moisture to accelerate the corrosion--formally known as ferrous oxide scale--which opens the crack further. 

    Spalling in concrete beams starts as long horizontal cracks.

    As it progresses further, chunks of concrete start to fall out. The fix is simple but labor-intensive: each crack line has to be jack-hammered open to expose the surfaces of the steel reinforcing bars. The rust is then cleaned away with a chemical solution like Ospho®, shown below, and stiff brush, coated with an anti-corrosion solution, and then a special concrete/mortar mixture is packed into the damaged area and smoothed out along the surface. 

   Simply patching the cracks without repairing the steel, like in the photo below, is a temporary fix and the cracks will reopen.

    Spalling can also occur at concrete columns, slabs, curbs, chimney caps, and window sills, as shown below.    

    A similar type of spalling can occur in brick mortar lines when steel reinforcing ladders are used in the wall, like in the photo below. To read more about it, go to our blog post What would cause long horizontal lines of brick mortar to fall out?

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Here’s links to a collection of some of our blog posts about CONCRETE AND CONCRETE BLOCK:

• What causes raised white lines of residue on a block wall that are crusty and crumbling? 

• Do stucco walls mean a house is concrete block?

• What causes stair-step cracks in a block or brick wall?

• Why is the concrete window sill cracking?

• What causes a horizontal crack in a block or brick wall? 

• What are the pros and cons of concrete block versus wood frame construction?

 • What does CBS mean in house construction?

• There's cracks running along the home's concrete tie beam. What's wrong? 

• What would cause long horizontal lines of brick mortar to fall out?

• How do I recognize structural problems in a retaining wall? 

• Should I be suspicious about a concrete block house covered with siding? 

• What is fiber reinforced concrete?  

• What is "Ocala" block?

• How can I tell if cracks in the garage floor are a problem or not? 

• How do I recognize serious structural problems in a house?

• Why did so many concrete block homes collapse in Mexico Beach during Hurricane Michael? 

• How can I tell if the concrete block walls of my house have vertical steel and concrete reinforcement?

• How can I tell if the exterior walls of a house are concrete block (CBS) or wood or brick?

• What is concrete spalling? 

• What is a "slab on grade" house?  

• What causes a vertical crack in an exterior concrete block or brick wall? 

• Why is there a "WARNING! POST-TENSION SLAB" sticker in my house?

• How can I identify a home as ICF (Insulated Concrete Form) construction?

• How can I tell if cracks in the wall or floor are getting worse or staying the same?

• Why do concrete blocks have holes in them? 

• What are those powdery white areas on my concrete block wall? 

• Is efflorescence a serious problem? 

   Visit our CONCRETE AND CONCRETE BLOCK page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.