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Characterization of Pyroclastic Deposit from Three Different Areas within Foumbot Region (West-Cameroon): Comparative Studies of Their Effects as Pozzolanic Materials in Mortars and Cement Manufacture

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Journal of Geoscience and Environment Protection 2019年第11期7卷 195-209页

作者： Mahomed Aziz Mounjouohou Amidou Moundi Benjamin Ntieche Daouda Dawai Frédéric Michel Department of Earth Sciences University of Maroua Maroua Cameroon Department of Earth Sciences University of Yaoundé I Yaounde Cameroon Higher Teacher Training College Geology laboratory University of Yaoundé I Yaounde Cameroon Department of Architecture Geology Environment and Construction University of Liege Liege Belgium

pyroclastics which are known natural pozzolanic materials due to amorphous contents, are present in several areas of the Mbepit Massif in West Cameroon. In this work natural pozzolan from three zones namely Pouoloum, Njimbouot and Nkouonja were characterized. A comparative study was then developed to attest the effect of these pyroclastics as partial substitution in portland cement. The mixtures were made at different pozzolanic proportions (00%, 10%, 15%, 25% and 35%) of substitution of the cement. The compressive and flexibility strength was carried out at 7, 28 and 90 days on mortar specimens (4 × 4 × 16 cm3). The results revealed apozzolanicactivity index of 81.99 %, 83.47% and 74.54% respectively for rock sample from Pouoloum (PCB), sample from Njimbouot (PCC) and sample from Nkouonja (PCN). After 90 days, for a substitution rate of 25% compressive strength are respectively 55.69 MPa, 60.4 MPa, 53.34 MPa for PCB, PCC and PCN. According to the American Society for Testing and Materials (ASTM) C618 classification, the pyroclastics are in accordance with all the criteria to be classified as pozzolan. Independent of the substitution rate, the mechanical performance increases with age in PCB, PCC and PCN. However PCC is most reactive than PCB and PCN. This may be due to the amorphous reactive content in this material and can be linked to the eruptive dynamisms which were more explosive in some areas than in others. The amorphous content is 32.01%, 36.99%, 24.84% for PCB, PCC and PCN respectively. These results also prove that Natural Pozzolan is interesting in the manufacture of composite cement CEM II, CEM IV in accordance with EN197-1 or can be added in mortar for buildings and sustainable environmental management.

关键词： pyroclastics Pozzolanic Activity Compressive Strength Composite Cement Natural Pozzolan Mbepit Massif

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Possible Correlation of Oligocene Climate Changes with Afro-Arabian Silicic Pyroclastic Eruptions

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地学前缘 2009年第S1期16卷 278-278页

作者： Dereje Ayalew Department of Earth Sciences Addis Ababa University

The Oligocene Afro-Arabian flood volcanic province contains significant silicic pyroclastic rocks (>60000 km^3 constituting up to 20%of the volcanic stratigraphy).Rhyolitic tephras,synchronous with the Afro-Arabian silicic pyroclastic rocks,are found in Indian Ocean ODP holes *** are geoche-mically akin to the Afro-Arabian silicic pyroclastic *** suggests that the tephras originated from Afro-Arabian silicic eruptions and represents more distal fallout of this *** temporal coin-

关键词： Afro-Arabian climate India Oligocene silicic pyroclastics

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