Potential of calcined brick clay as a partial substitution in blended cement mortars

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 600oC and 700oC and blended with Portland cement at weight percentages of 10, 20 and 30. From the Frattini test, clay calcined at 700oC showed a better pozzolanic reactivity than that calcined at 600oC . Blended cements containing 700oCcalcined clay recorded lower water demand and setting times as compared to 600oC calcined clay. There was a reduction in compressive strengthat all replacement levels, both at early and later ages. Mortar containing 700oC calcined clay recorded higher compressive strength than the clay
calcined at 600oC .