What is cement mortar primarily used for in pipes?

Cement mortar is primarily used in pipes to protect the inside of the pipe from corrosion. This protective barrier is crucial because it helps to prevent the degradation of the pipe material over time due to exposure to water and various chemicals that may be present in the fluid being transported. The use of cement mortar creates a smoother surface that not only assists in water quality by minimizing leaching from the pipe itself but also extends the life of the pipe system by offering resistance to corrosion and abrasion.

The other options don't accurately describe the primary function of cement mortar in the context of piping systems. While enhancing flow capacity, providing thermal insulation, and reducing weight are important factors in pipe design and material selection, they are not the core purposes served by cement mortar specifically. Instead, the emphasis is on corrosion protection, which is vital to maintaining the integrity and functionality of water systems over the long term.