Potentials of calcined clay as a pozzolan

Abstract

Calcined clay (CC) is a promising pozzolan recently attracting research attention globally. Various investigations have shown the desirable attributes of the material as a Supplementary Cementitious Material (SCM) in cement concrete systems. This paper captures the compressive strengths impact of calcined clay-Portland cement (CC-PC) as binders in both concrete and soil systems. Grade 20 concrete cubes were prepared and tested; adopting five CC-PC binder blends obtained by replacing PC with CC at 0(control), 5, 10, 15, and 20%; designated as PC100, PC95, PC90, PC85, and PC80, respectively. Similarly, four CC-PC binder blends PC100(control), PC75, PC50, and PC25 were adopted to stabilise samples of A-2-6 lateritic soils at increasing content of 0, 2.5, 5, 7.5, 10% of the soil’s weight. Results show that compressive strengths of the concrete samples increase with cement replacement. PC80 impacts the highest strengths with 7, 28 and 56-day strength activity indices (SAIs) of 174.7, 126.0 and 144.9%, respectively. In soil stabilisation, unconfined compressive strength (UCS) of the soil was found to increase with binder contents (2.5% to 10%) for the four binder designations. Compared to control (PC100), the PC75, and PC50 binders were better stabilisers with 7 and 28-day SAIs ranging between 105 and 275%, respectively. From the results, for applications across concrete and soil stabilisation works, CC has been shown to be a potential supplementary material for mitigating carbon emission without compromising on strength enhancement.