In the present study physicochemical characterization of slate sample was carried out which was collected from slate mine in Lasbela District, Baluchistan. Slate was evaluated for its effectiveness as partial replacement of ordinary Portland cement (OPC) in the production of Portland Pozzolana cement (PPC). The grain size analysis of crushed slate sample using ball mill revealed that maximum fraction retained on 44 μm was about 72.8 %. Sum of the major oxides (SiO2 + Al2O3 + Fe2O3) is about 90.09 % that meet the requirement as per ASTM C 618 (minimum 70.0 %). Other oxides including SO3 (<0.05), CaO (4.04), MgO (1.66), K2O (0.10), Na2O (0.16), TiO2 (0.35), MnO (<0.02) and Cl (0.12) also meet the international standard of ASTM C 618 for PPC. OPC without and with using slate sample in a ratio of 5 % and 10 % with clinker was tested to measure compressive strength, physical tests and setting time. The results showed that after 5 % and 10 % replacement, insignificant effect was observed on the physical properties, setting time and compressive strength in 2-, 7- and 28-days curing. Hence, slate can be used as natural pozzolan for manufacturing PPC. It is cost effective for the production of cement as well as to sustain the resources of limestone for long time and reducing emission of CO2 in the environment. It can also be used in the sulfate rich environment, coastal areas especially for the construction of dams and bridges.
Cílem článku je upozornit na nejistoty provázející výzkum paleolitu v Čechách, a zejména publikace z posledních let. Pro kulturní i absolutní zařazení velkých souborů předmětů, získaných výzkumy prakticky pod ornicí, scházejí nesporné morfologické, stratigrafické a jiné přírodovědné argumenty. Data vzešlá z těchto výzkumů autor porovnává s výsledky z precizně zkoumaných evropských lokalit. Současně shrnuje aktuální stav bádání o starém paleolitu v Evropě a do jeho kontextu řadí nejstarší doklady přítomnosti člověka z Čech a Moravy. and The aim of the article is to point out the uncertainty accompanying studies of the Palaeolithic period in Bohemia, particularly in recent publications. Indisputable morphological, stratigraphic and other natural science arguments are lacking for cultural and absolute classification of larger assemblages of finds obtained by terrain excavation. The author of the article compares the data resulting from these excavations with meticulously investigated European sites. At the same time, the author also summarises the current state of research into Early Palaeolithic Europe and classifies the oldest evidence of man in Bohemia and Moravia into its context.