The availability of some supplementary cementitious materials, especially fly ash, is of imminent concern in Europe due to the projected closure of several coal-fired power generation plants. Pure kaolinitic clays, which arguably have the potential to replace fly ash, are also scarce and expensive due to their use in other industrial applications. This paper examines the potential utilisation of low-grade kaolinitic clays for construction purposes. The clay sample was heat-treated at a temperature of 800 °C and evenly blended with Portland cement in substitutions of 10–30% by weight. The physical, chemical, mineralogical and mechanical characteristics of the blended calcined clay cement were determined. The Frattini test proved the pozzolanic potential of the calcined impure clay, as a plot of its CaO and OH− was found below the lime solubility curve. The 28 days compressive strengths trailed the reference cement by 5.1%, 12.3% and 21.7%, respectively, at all replacement levels. The optimum replacement level between the three blends was found to be 20 wt.%.

Pervious concrete has been reported as a viable solution to reduce stormwater run-off, the heat-island effect, road noise, and pavement flooding. Previous researchers have focused on analysing the structural properties and functionality of pervious concrete. However, relatively few studies have been conducted into the addition of supplementary cementitious materials (SCMs), such as calcined clay, in pervious concrete and its effect on long-term durability. This paper has studied the effect of calcined clay pozzolan as a partial substitute for Portland cement in pervious concrete, together with the influence of coarse aggregate size. A water–binder ratio of 0.4 and aggregate–binder ratio of 4.0, as well as a superplasticiser content of 0.95%, were maintained for all mixes. Two sizes of coarse aggregates were used for this study: 9.5 mm and 20 mm. CEM-I cement was partly substituted with calcined clay in dosages of 0 to 30% in replacement intervals of 5%. The mechanical tests conducted included the split tensile test, compressive strength test, and flexural strength test. Durability measurements such as the rapid chloride permeability test (RCPT), thermal conductivity and sulphate resistance tests were also carried out. The mechanical properties of the pervious concrete followed a similar trend. The results showed that at 20% replacement with calcined clay, the compressive strength increased by 12.7% and 16% for 9.5 mm and 20 mm aggregates, respectively. The flexural strength improved by 13.5% and 11.5%, whereas the splitting tensile strength increased by 35.4% and 35.7%, respectively, as compared to the reference concrete. Beyond 20% replacement, the tested strengths declined. The optimum calcined clay replacement was found to be 20% by weight. Generally, pervious concrete prepared with 9.5 mm obtained improved mechanical and durability properties, as compared to those of 20 mm aggregates.