Properties of blended cement using metakaolin and hydrated lime

Thermal activation of Ga'ara kaolin is used to produce a good quality metakaolin. Portland cement clinker is ground and blended with 3% gypsum. In this study, two types of mixes are made: the first using 10% hydrated lime and different percentages of metakaolin as replacement by weight of the blended cement; in the second type, only metakaolin is used, without hydrated lime, in mixes as a replacement by weight of the blended cement. The aim of this study is to make a new type of environmentally friendly, blended cement with good fresh and hardened properties. Energy savings can be achieved by using materials produced as industrial by-products (metakaolin, hydrated lime). The compressive strength is 42·1 MPa for the mix with 12% metakaolin and 0% hydrated lime, and 38·8 MPa for 12% metakaolin with 10% hydrated lime, as compared to the reference mix value of 37·9 MPa at age 90 d. Blended cement can be made with 86% Portland cement fineness, adding 22% metakaolin + hydrated lime as a replacement by weight of the blend, to give almost the same compressive strength as the reference mix, with excellent soundness properties. This could reduce the annual production of cement, as well as the associated emission of gaseous pollutants from factories during the cement production process.