There are increasing interests in using natural pozzolans as partial replacements for ordinary Portland cement (OPC) in concrete due to the benefit to the environment, low-carbon footprint, and durability improvement potentials. In the present research, open-air-burnt non-grinded rice husk ash (RHA) samples from Ganawuri-Plateau State, Nigeria, were used as a partial replacement for OPC in concrete. A water-permeable form (controlled permeability formwork – CPF) was utilized to counter the adverse effects of high-water demand. The combined effects of CPF and RHA on the cover-zone microstructure/porosity were analysed by the mercury intrusion porosimetry (MIP) test. Water sorptivity and sulphuric acid resistance properties were measured by Surface Water Absorption Test (SWAT) and accelerated sulphuric acid resistance test, respectively, to study the suitability of the concrete mixtures for sewerage concrete structures. Compared to Portland cement concrete, the RHA with CPF samples had relatively low permeability and low water sorptivity while the RHA without CPF samples showed the highest resistance to sulphuric acid attack, exhibiting no weight loss, no gypsum formation at the surface with the least surface discolouration.