Effects of biogenic sulphuric acid on simulated concrete septic tanks (Kenya)

The use of septic tanks has been met with a dire challenge due to continuous corrosion and degradation of septic concrete surfaces. Concrete sewer septic tanks are constructed using conventional ordinary Portland cement (OPC) and Portland pozzolana cement (PPC). However, OPC and PPC-based concrete sewer systems are susceptible to chemical degradation. The need to explore other possibilities and potential construction materials to achieve sustainable sanitation is therefore inevitable. The use of Limestone Calcined Clay Cement (LC3) in the construction of degradation-resistant concrete sewer septic systems has not been well explored in Kenya. LC3 concrete is resistant to the deterioration effects of aggressive media such as acids, chlorides, and sulphates.

This research involved the performance of Limestone Calcined Clay Cement (LC3) as an alternative cement in the construction of concrete sewer structures. The observations indicated that after 28 days of curing, OPC cubes had slightly higher compressive strength than LC3. However, LC3 concrete cubes are expected to have higher compressive strength than the OPC. Sulphuric acid attacks on hydrated cement products cause a decrease in compressive strength. The water absorption profile of LC3 cubes was lower as compared to OPC cubes. LC3 cubes had a high potential of resisting H2SO4 degradation as compared to OPC cubes and is hence a potential binder for sewer systems construction.