Regarding asbestos-cement (AC) sewers, which statements accurately describe their characteristics and limitations in wastewater conveyance?

Introduction / Context:
Material selection for sewers must consider weight, structural capacity, and corrosion resistance. Asbestos-cement (AC) piping has been used historically, but it has notable constraints in modern wastewater environments.

Given Data / Assumptions:

• Sewer environment can produce hydrogen sulphide, which oxidizes to sulphuric acid on moist surfaces.
• Structural loads may include soil cover, traffic, and trench conditions.

Concept / Approach:
AC pipes are relatively lightweight, easing handling. However, their compressive and ring strengths are limited compared with reinforced concrete or ductile iron. In aggressive sewer atmospheres, biogenic sulphuric acid attacks cementitious matrices, leading to material degradation, softening, or loss of section over time.

Step-by-Step Solution:
Assess weight → AC is lighter than many alternatives, aiding installation.Assess structural capacity → limited ability to withstand high compressive and external loads.Assess corrosion resistance → susceptible to sulphuric acid in crown corrosion scenarios.

Verification / Alternative check:
Case histories document corrosion at the pipe crown where H₂S oxidizes to H₂SO₄; standards often recommend protective linings or alternative materials in high-sulphide systems.

Why Other Options Are Wrong:

• Each individual statement (a–c) is accurate; hence (d) is correct.
• “None of the above” contradicts well-established material behavior.

Common Pitfalls:
Ignoring crown corrosion risk; assuming light weight implies adequate strength under deep burial or traffic loads without proper bedding and design checks.

Final Answer:
All of the above.