Why must aluminum conductors not be installed in concrete or masonry?

Aluminum conductors must not be installed in concrete or masonry primarily due to the corrosion issues that arise from the alkali content commonly found in these materials. Concrete and masonry have a highly alkaline environment, which can lead to the corrosion of aluminum over time. This corrosion can significantly degrade the performance of the electrical system, compromising conductivity and potentially leading to failure in the lightning protection system.

Concrete is typically mixed with cement, which has a high pH level that can react with aluminum, causing localized corrosion. The corrosion products can also create a barrier that reduces electrical continuity and increases resistance. This makes it critical to avoid direct contact between aluminum conductors and alkaline materials to maintain the integrity and reliability of the lightning protection system.

In contrast, other options do not accurately address the specific technical reasoning related to material compatibility and reliability in lightning protection systems. Therefore, the issue of corrosion due to alkali content is the most significant factor governing the installation practices for aluminum conductors.