No abstract

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.

Two types of Portland Cement Clinker "PCC" were used in this study: high fineness grinded and low fineness grinded , and after grinding of PCC, hydrated lime was used in 5%,10% and 15%; by weight, as a replacement of the blend cement with a constant 3% addition of gypsum by the blend weight. The importance of this study is to show the influences of different fineness on the physical properties of the blended cement, and to find the probability of using hydrated lime (that could be a by-product) in cement and declare its effects on the blend, so the solid waste "lime" and air pollutant of cement factories will reduce. In this research, the low fineness blend exhibited about 87% from compressive strength of high fineness blend at 28 days age. The results show that the using of hydrated lime up to 10%; by weight, as a replacement of cement will give good compressive strength and workability, and will reduce moderately the setting time, but the use of hydrated lime by more than 10% will reduce the compressive strength and increase the unsoundness of the blend (from 3mm expansion at 10% hydrated lime to 29mm expansion at 15% hydrated lime).