Potential of Calcined Brick Clay as a Partial Substitution in Blended Cement Mortars

Abstract

Calcined kaolinitic clays, among other supplementary cementitious materials, have been acknowledged as having a good potential to reduce the CO2 emissions associated with cement and concrete production. However, little attention has been given to impure kaolinitic clays which are usually used in the manufacture of burnt bricks and other products. This paper has studied the potential use of less pure kaolinitic clay, which is normally used in brick production, as a pozzolan in blended cement mortar. X-ray diffraction studies revealed the presence of kaolinite, illite and quartz in the clay. The clay was calcined at 600 o C and 700 o C and blended with Portland cement at weight percentages of 10, 20 and 30. From the Frattini test, clay calcined at 700 o C showed a better pozzolanic reactivity than that calcined at 600 o C . Blended cements containing 700 o C calcined clay recorded lower water demand and setting times as compared to 600 o C calcined clay. There was a reduction in compressive strength at all replacement levels, both at early and later ages. Mortar containing 700 o C calcined clay recorded higher compressive strength than the clay calcined at 600 o C .

Influence of Calcined Clay Pozzolan and Aggregate Size on the Mechanical and Durability Properties of Pervious Concrete

“…A reduction in cement content impacts the pozzolanic reaction, leading to a shortage of the formation of C-S-H [47,48]. Therefore, raising the calcined clay content beyond 20% overburdens the concrete with excess unreacted SiO 2 and Al 2 O 3 , which do not contribute to strength development [49,50].…”