Prepared metakaolin produced by calcination of a kaolin sample at 750˚C after soaking for 5 hrs was tested as an active pozzolan for locally produced cement. Blended pastes of partially replaced ordinary Portland cement with different metakaolin amounts 5%, 10% and 15% were prepared, then they were hydrated with water for various time intervals of 1, 3, 7, 14 and 28 days. At each time interval, the hydrated paste specimens were tested for compressive strength, hydration kinetics and followed up using differential scanning calorimetry, X-ray diffractometry analyses and scanning electron microscopy techniques. Results showed that the blended pastes OPC-MK10 recorded the highest compressive strength values at all the hydration times reaching 33. 10, 86.40, 101.20, 112, and 122 MPa with increasing the age of hydration as compared with the neat samples which recorded 31.70, 65.20, 72.6, 82 and 101.30 MPa respectively. Meanwhile, the OPC-MK10 blend showed a decrease in the free CaO content reaching 4.07%, 4.27%, 4.23%, 4.19%, and 4.11% CaO with increasing age of hydration compared with the neat samples which recorded 4.27%, 5.15%, 5.42%, 5.61%, and 5.96% CaO respectively. The DSC thermograms results for the hardened neat and OPC-Mk10 pastes at the 14 and 28 hydration days showed the formation of hydrated materials mainly calcium silicate hydrates, calcium sulphoaluminate hydrates and calcium aluminates hydrates. The X-ray diffractometry analyses of both hardened neat and OPC-MK10 showed that, the intensity of calcium hydroxide peaks of OPC-MK10 was lower than in case of neat OPC, while the peak of the hydration products of calcium silicate hydrates and calcium aluminates silicate hydrates of OPC-MK10 samples were of higher intensity than in case of neat OPC. Scanning electron microscopy micrographs indicated the formation of denser microstructure for the hardened OPC-MK10 paste as compared to neat OPC pastes after the 28 days age of hydration.

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In recent years the demand for limestone as a building material, a base layer in roads construction and a raw material in cement manufacture in Egypt has markedly increased. It becomes therefore a national need not only to satisfy the requirements of this material but also, to orient these rocks to the optimum uses "techno-economic". The optimum utility of any limestone deposit determined according to the physical and mechanical properties, which is used rating and weight to determine the quality index for each deposit site. The quality index depends on physical properties such as porosity, density and water absorption and mechanical properties such as compressive strength, tensile strength and coefficient of dynamic fragmentation. Rating of uses as building material, in road construction, and in cement manufacture are considered. All of these parameters are determined for three different locations for limestone quarries around Cairo (El Katameya-Ain El Sokhna road, 15 th of May city, and Ber Gendary in Helwan), and four locations for dolomite quarries (Ataqa Cairo-Suez Road, El Saf, Wadi Garawi, and Wadi El Gebbu). The final result indicated that, all studied locations are suitable for using as building materials except El Saf site.

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The role of alumina waste as a reactive pozzolan for the local Portland cement has been thoroughly investigated. The results showed that the initial and final setting times of the hardened blended pastes were reduced significantly by increasing the amount of the added alumina. In addition, the compressive strength and the hydraulic property measures of the hardened blends showed progressive improvement reaching approximately 42% and 23% after the early ages of hydration (1 and 3 days), respectively. According to such conditions, these cement blends could be applied in many concrete applications, such as high speed construction, rapid repair, frost prevention, tunneling, shoring, gas and oil well cementing, that require concrete to have rapid setting and strength development abilities.The improvement of the physico-mechanical characteristics and the hydration kinetics of the hardened blended pastes with the recycled alumina were explained after the microstructure study included the examinations of hydration product morphology and type, the thermal gravimetric (TG), the differential scanning calometry (DSC) and the differential thermo-gravimetric (DTG) thermographs analyses. The scanning electron microscope (SEM) was used to examine the microstructure and morphology of hydration products.