Sandblasting is a technique commonly used to add texture to the surface of hardened concrete, such as patios, walls, columns, driveways, and floors. It is often employed to remove paint or other coatings from the surface, as well as to expose aggregates. The level of sandblasting can vary from a light cleaning to a more aggressive operation that involves cutting deep into the surface to reveal the aggregates, which can be exposed up to a depth of around 2 cm. Overall, sandblasting is a versatile and effective method for achieving a range of surface textures on concrete.
Concrete Sandblasting Equipment
The type of equipment needed for blasting can vary depending on the specified cut depth. When only a light removal of the surface is required, any sandblasting tool or equipment can effectively accomplish the task. This can be seen in Figure 1, which shows lightly blasted concrete.
However, if a deeper cut and a specific texture is required, the capacity of the equipment becomes crucial for the success of the sandblasting operation. In such cases, the specifications of the air compressors used for sandblasting need to be carefully considered. Table 1 provides the desired specifications for these air compressors.
For achieving a deep cut, the equipment must be capable of producing a high-pressure stream of abrasive particles that can penetrate the surface. Figure 2 depicts a close-up view of concrete that has been deeply sandblasted, showing the effectiveness of the equipment in achieving the desired texture.
Fig. 2: Deeply sandblasted surface, close up view
Table 1 Preferred air compressor specifications for sandblasting
| Air compressor specifications | |
| Air compressor components | Specified dimension |
| Nozzle capacity | 8.5 m3/min |
| Minimum air pressure at nozzle | 0.62 MPa (0.69MPa is preferred) |
| Minimum nozzle inside diameter | 9.52mm |
| Hose inside diameter | 38.1mm |
Fig. 3: Sandblasting machine components
Fig. 4: Nozzle
Suitable Time for Sandblasting
When it comes to blasting, the timing of the process is closely tied to economic considerations. Specifically, the optimal time to conduct blasting is when it will be most cost-effective. One key factor to consider in this regard is the state of the concrete matrix that is being blasted. As a general rule, it is easier to cut through the concrete matrix in the first 24 to 72 hours after it has been cast. Therefore, conducting blasting during this timeframe is likely to be more efficient and ultimately more cost-effective than waiting until a later time.
Procedure of Sandblasting Concrete
To prevent damages during sandblasting operations, several measures need to be considered for the area in and around the sandblasting site. First, it is important to remove all objects or items that can be easily moved out of the area. For items that cannot be moved, they should be properly covered to protect them from sandblasting particles. This includes covering surfaces, windows, and any exposed areas around the operation site to keep them clean and safe.
If sandblasting is being carried out in a closed area, such as garages, adequate ventilation should be provided to ensure proper airflow and prevent the accumulation of dust particles. This helps to maintain a safe working environment for the workers and prevents inhalation of harmful dust.
Additionally, workers should use appropriate personal protective equipment (PPE) during sandblasting operations. This includes safety goggles to protect the eyes, suits equipped with hoods to cover the head and neck, and respirators to prevent inhalation of dust particles. Using the proper PPE helps to protect the health and safety of the workers during sandblasting operations.
Fig. 5: Required tools used by sandblasting machine operator
Stencils are an essential component in achieving a desired texture during the sandblasting process. Therefore, it is crucial to fix these stencils in place before commencing the sandblasting procedure.
Fig. 6: Stencil for concrete sandblasting
The first step in preparing the sandblaster machine for operation is to ensure that all the valves are closed. This includes any openings or outlets that allow sand or other materials to flow through. Once all the valves are securely closed, the next step is to fill the tank with the appropriate sandblasting media. This can include various materials such as soda, silica or silicon dioxide, steel grit, glass bead, and bristle blasting media, depending on the specific application and desired results. It’s important to use materials that are specifically designed for sandblasting to ensure effective and safe operation of the machine. Once the tank is filled with the chosen media, the sandblaster machine is ready for use.
Fig. 7: Sandblasting material; Silica sand
To begin, ensure that the compressor is turned on and set to a low pressure range of 275 MPa to 0.689 MPa. The nozzle of the sandblaster should be directed at the concrete surface, keeping it at a distance of 20cm to 40cm away from the body of the operator for safety. The sandblasting process should start from the top of the concrete surface and move downwards, maintaining a nozzle distance of 30.5cm from the surface until the desired texture is achieved and the concrete is properly cleaned. An experienced operator can quickly determine the optimal nozzle position to achieve the specified surface finish.
For difficult areas, short bursts of sand should be used, while sweeping motions can be employed for other parts of the concrete. After completing the sandblasting process, the surface should be cleaned with compressed air to remove any debris. All the sand used during the process should be collected in a wheelbarrow and properly disposed of.
Advantages of Sandblasting
Sandblasting is a highly advantageous technique due to its cost-effectiveness, efficiency, and superior results compared to other traditional methods. This process can help individuals and businesses save money while achieving desired outcomes. Additionally, sandblasting can be completed quickly and with minimal effort, making it an efficient choice for a variety of applications. Its ability to produce high-quality results with minimal surface damage is one of the reasons why it is preferred over other conventional methods.