Spalling means that the concrete is breaking apart, which can make surfaces look bad and become weaker. By knowing how to spot and fix spalling and taking steps to prevent it, you can maintain the safety and appearance of your concrete structures and surfaces. In today’s Brick & Bolt blog, you are going to understand the basics of spalling, including what it is, what causes concrete spalling, how to recognize the signs, the effects it can have on structures, and much more.
What Is Spalling?
Spalling is the term used when the concrete breaks into little pieces or flakes off the surface. Can you imagine having a smooth, solid surface and chipping away parts of it, leaving unsmooth patches and holes? That is exactly how spalling happens. This problem occurs in many concrete forms on buildings, bridges, sidewalks, and even driveways. If spalling occurs, the surface will not only look bad but also weaken over some time.
Concrete Spalling: What is it?
Concrete spalling is characterized by the flaking or chipping off of surface layers of concrete. This can make concrete appear uneven and jagged. In its more advanced stages, you will notice actual spots with missing concrete, possibly exposing stone or aggregate. Such surface damage poses safety risks and compromises the durability of the concrete.
Causes of Concrete Spalling
Several reasons may lead to concrete spalling: Here’s a closer look at some common reasons:
| Cause | Explanation |
| Corrosion of Reinforcement | Concrete reinforcement mainly contains steel bars to provide additional support. As the steel bars corrode, they increase in volume, hence bursting the concrete in which they are contained and resulting in the detachment from the concrete. |
| Freeze-Thaw Cycles | Water can penetrate concrete, and upon freezing, it expands. The expansion of ice forms cracks in concrete. Once ice thaws, the cracks increase in size, which leads to spalling. |
| Fire Exposure | Heat from a fire will convert the water contained within the concrete into steam. Steam generates pressure, and this pressure can lead to the cracking and spalling of concrete. |
| Poor Concrete Mix | A poorly proportioned concrete mix, whether excessive or insufficient in ingredients, can reduce strength and make it more susceptible to spalling. |
| Chemical Exposure | Chemicals such as salt or acid can have a chemical reaction with the concrete; it break down the cement matrix of the concrete, making it brittle and crack. |
| Carbonation | The carbon dioxide in the atmosphere reacts with the concrete, which becomes weak. This is an untreated phenomenon famously referred to as carbonation, which can eventually cause spalling. |
Signs of Concrete Spalling
It’s important to notice the signs of spalling early to fix it before it gets worse. Here are some signs to watch out for:
| Sign | Description |
| Flaking or Chipping | Small concrete pieces will start to come out of the surface, opening up gappy areas and some uneven patches. |
| Cracking | There will be visible lines or cracks on the surface. Those cracks may extend and develop more spalling if not repaired. |
| Exposed Aggregate | The inner stones or gravel of the concrete are exposed as the outermost layer of the concrete flakes away. |
| Discolouration | In the concrete, there is a change of colour whereby it appears with whitish hues in some parts as if the colouration has become pale or washed off, which may be indicative of further damage inside. |
| Pitting or Pockmarks | Small holes or indentations around the surface can make the concrete appear damaged and rough. |
Effects of Concrete Spalling
Spalling can have several negative effects on concrete surfaces:
| Effect | Description |
| Weakened Structure | Spalling could weaken the strength of the concrete to the extent that it would lose the capacity to support weight and resist stress applied to it. |
| Increases Moisture Problems | Further saturation of the affected areas can increase degradation and can lead to water damage. |
| Reduces Strength | As the concrete deteriorates, its ability to hold up against forces and pressure decreases, making it less reliable. |
| Exposes Reinforcement | When the outer layer of concrete is gone, the steel bars inside can become exposed and rust, further weakening the structure. |
| Aesthetic Issues | The surface can become uneven and unattractive, affecting the appearance of the structure or pavement. |
How can I Repair Concrete Spalling?
Repairing spalling depends on how serious the damage is. Here are some ways to fix it:
| Repair Method | Description |
| Surface Patching | Minor damages require the area to be cleaned and subsequently filled with a special patching material that is made up of concrete. This method is good for minor, small cracks and surface flaking. |
| Full-Depth Repair | For more serious damage, the failure concrete should be removed and replaced by new concrete. It involves removing the defective concrete and then replacing it with a new one. |
Steps for Surface Patching
Clean the Area: Remove any of the affected concrete and dirt by wiping with a wire brush or by using a pressure washer.
Prepare the Surface: Before coating with the patching material, the area should be wet so that it is better to stick onto the surface. You may have to use a grinder or perhaps a chisel.
Apply Patching Material: Again, for the spalled area, you can use a concrete patch repair mix, which can be bought from the local hardware store. Follow the instructions well if you want the best results from your work.
Smooth the Surface: Finish off the repair by levelling the patch with the surrounding concrete using a trowel or even a putty knife to minimise its visibility.
Cure the Repair: Let the patch dry and set it according to the instructions. Keeping the patch moist while it dries can help it set properly.
Steps for Full-Depth Repair
Remove Damaged Concrete: If possible, take off the deteriorated concrete and move it up to sound concrete and ensure that all the loose concrete is pulled out during the process.
Prepare the Surface: Roughen the surface on portions where new concrete is to be poured. These have the capability of making newly formed concrete have a very good bond with previously formed concrete.
Add Reinforcement: If needed, place new steel bars or mesh inside the prepared area to add strength.
Fill with New Concrete: Pour new concrete into the prepared space, and level it using a trowel so that it is at the same level as the existing surface of the structure.
Finish and Cure: Let the newly placed concrete harden and cure well. This may involve the process of covering the concrete with moist fabric and keeping it applied for several days.
How can I Prevent Spalling?
Preventing spalling is easier than fixing it later. Here are some steps to help keep your concrete in good shape:
| Prevention Method | Description |
| Use Proper Concrete Mix | Make sure the mix of concrete has the proper proportions of cement, sand, and water. This provides you with an assurance that the resulting concrete is strong and less likely to spill. |
| Cure the Concrete Well | Maintain wet conditions during the setting and hardening phase. This may be done by covering it with wet burlap or polyethylene sheeting. |
| Avoid Excess Water | Watering too much water in the mix will weaken the concrete obtained and could even cause it to spill. Only the minimum quantity of water required must be applied. |
| Protect from Chemicals | Use special coatings or sealers to protect concrete from harmful chemicals that can cause damage. |
| Regular Maintenance | Routine inspection of the surface of concrete and minor defects should be done on time before they develop into hitches. Otherwise, various defects in concrete, including spalling, can be prevented by periodic maintenance. |
Conclusion
Although concrete spalling can be a major issue, understanding what it is and how to solve it can help you maintain your concrete surfaces. When you know its causes, observe the symptoms, and undertake repair and preventive measures, your concrete will always look good and serve you best.