Which material should not be used for pumping grout?

The use of aluminum pipes for pumping grout is not recommended due to several reasons, primarily related to chemical compatibility and structural integrity. Grout, particularly when it contains cementitious materials, can be quite abrasive. Over time, this abrasiveness can wear down softer materials like aluminum, leading to failure or leaks in the piping system.

In addition, grout mixtures can have a somewhat high pH level due to the cement content, which can cause corrosion in aluminum pipes. This not only compromises the integrity of the pipes but also poses risks to the quality of the grout being pumped. Steel, PVC, and plastic pipes are more suitable for this application because they are more resilient and resistant to the effects of the grout being pumped through them. Steel pipes, for example, are robust and can handle the pressure created during pumping, while both PVC and plastic pipes offer good corrosion resistance and do not react negatively with the grout.

Therefore, the correct choice highlights a fundamental consideration in construction and materials science: selecting appropriate materials based on their physical and chemical properties for specific applications is critical to ensure long-term performance and safety in building projects.