Blended cement pastes made of Portland cement and fine sand (known in Egypt as El-Karnak cement) were made using a water-cement ratio of 0.25 by weight. Three pastes containing admixture (water-soluble condensates) were also prepared using a water-cement ratio of 0.25 and condensate (superplasticizer) content of 0.25% by the weight of cement; the superplasticizers used are Na-phenol sulfonate formaldehyde, Na-polystyrene sulfonate, and Na-beta-naphthol sulfonate formaldehyde condensates. All pastes were cured for various time intervals within the range of 0.02-90 days. Compressive strength tests, hydration kinetics, X-ray diffraction analysis, thermal analysis, and surface properties were studied and related as much as possible to the pore structure of the hardened pastes.