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pozzolanic Activity of Old Volcanic Tuffs of Mako Area (Senegal-Oriental, West African Craton): An Economic and Environmental Interest

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International Journal of Geosciences 2019年第3期10卷 225-237页

作者： Matar Ndiaye Mahamadane Diène Mouhamadou Bassir Diop Papa Malick Ngom I. S. T. BP: 5396 F Sciences et Techniques Université Cheikh Anta Diop de Dakar Dakar Sénégal Département de géologie Faculté des Sciences et Techniques Université Cheikh Anta Diop de Dakar Dakar Sénégal

The volcanic tuffs of Senegal-Oriental in Mako area are produced during a calc-alkaline volcanism which occurs in this region and which is dated from about 2.3 - 1.95 Ga. Despite their altered appearance, the X-Ray diffractions show mineral paragenesis: Quartz-Kaolinite-Illite and an important amorphous phase. On the Ternary Keil-Rankin diagram for the CaO-SiO2-Al2O3 the volcanic tuffs of Mako area are situated between pozzolan and the fly ash. The difference between silica and lime is greater than 34% in these volcanic tuffs. In this study, they have been mixed with Portland cement to obtain pozzolanic cements respectively with 20%, 30%, 35% and 40% of addition of volcanic tuffs. The pozzolanic reactivity is highlighted by the compressive strength increase until 90 days of conservation in water. It supposes that the vitreous phase of the volcanic tuffs reacts with the free CaO (CaOf) of Portland cement to produce new hydrated minerals. This study has a positive economic and environmental impact. Because the time of grinding of pozzolanic cements is reduced. Also, the addition of volcanic tuffs reduces the production of clinker, then the CO2 emission.

关键词： Old Volcanic Tuffs Calc-Alkaline X-Ray Diffractions Amorphous pozzolanic Cements Compressive Strength Economic Environmental

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

An investigation into the properties of ternary and binary cement pastes containing glass powder

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Frontiers of Structural and Civil Engineering 2019年第3期13卷 741-750页

作者： Marcelo Frota BAZHUNI Mahsa KAMALI Ali GHAHREMANINEZHAD Department of Civil Architectural and Environmental EngineeringUniversity of MiamiCoral GablesFL 33146USA

The properties of binary and ternary cement pastes containing glass powder (GP) were *** at early age was evaluated using semi-adiabatic calorimetry and at late ages using non-evaporable water content and thermogravimetric *** transport characteristic was assessed by measuring electrical *** binary paste with slag showed the highest hydration activity compared to the binary pastes with GP and fly ash (FA).The results indicated that the pozzolanic behavior of the binary paste with GP was less than that of the binary pastes with slag or FA at late *** increase in the electrical resistivity and compressive strength of the binary paste with GP compared to other modified pastes at late ages was *** was shown that GP tends to increase the drying shrinkage of the *** pastes containing GP did not exhibit synergistic enhancements compared to the respective binary pastes.

关键词： cement paste glass powder pozzolanic reaction supplementary cementitious material

Carbon steel slag as cementitious material for self-consolidating concrete

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2010年第7期11卷 488-494页

作者： Yu-Chu PENG Chao-Lung HWANG Graduate Institute of Construction Engineering National Taiwan University of Science and Technology Taipei Department of Leisure Management Taiwan Hospitality and Tourism College Taipei

This study deals with the recycling of carbon steel slag (CSS) to produce self-consolidating concrete (SCC). Since the chemical composition of CSS is similar to that of Portland cement or blast furnace slag (BFS), it is expected to behave similarly. In the current study, the pozzolanic activity index of CSS is examined. Furthermore, the use of CSS as a pozzolanic material to partially replace Portland cement in the production of SCC is tested. We designed concrete mixtures with different water-tocementitious material ratios (w/cm) keeping water and superplasticizer (SP) contents constant. Results showed that the design and performance of all the concrete mixtures used in this investigation were comparable to those of SCC and high performance concrete (HPC). However, compared to ordinary plain concrete (OPC), the additional CSS content increases the setting time. In the CSS mixtures set for 90 d, compressive strengths of 86%, 134% and 121% were attained as compared to the control concrete; the corresponding w/cm ratios were 0.28, 0.32 and 0.40, respectively. Verifying the soundness of the SCC for meeting the criteria for HPC, the ultrasonic pulse velocity (UPV) of CSS was found to be comparable to that of ordinary concrete. In conclusion, the recycling of CSS can be advantageously employed in the production of SCC.

关键词： Carbon steel slag (CSS) Self-consolidating concrete (SCC) pozzolanic Recycling

Effect of Nano Silica on Hydration and Microstructure Characteristics of Cement High Volume Fly Ash System Under Steam Curing

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Journal of Wuhan University of Technology(Materials Science) 2019年第3期34卷 604-613页

作者：马保国梅军鹏 TAN Hongbo LI Hainan LIU Xiaohai JIANG Wenbin ZHANG Ting State Key Laboratory of Silicate Materials for Architectures Wuhan University of TechnologyWuhan430070China Department of Construction Cost Wuhan University of TextileWuhan430200China

The influences of nano silica (NS) on the hydration and microstructure development of steam cured cement high volume fly ash (40 wt%, CHVFA) system were investigated. The compressive strength of mortars was tested with different NS dosage from 0 to 4%. Results show that the compressive strength is dramatically improved with the increase of NS content up to 3%, and decreases with further increase of NS content (e g, at 4%). Then X?ray diffraction (XRD), differential scanning calorimetry-thermogravimetry (DSCTG), scanning electron microscope (SEM), energy disperse spectroscopy (EDS), mercury intrusion porosimeter (MIP) and nuclear magnetic resonance (NMR) were used to analyze the mechanism. The results reveal that the addition of NS accelerates the hydration of cement and fly ash, decreases the porosity and the content of calcium hydroxide (CH) and increases the polymerization degree of C-S-H thus enhancing the compressive strength of mortars. The interfacial transition zone (ITZ) of CHVFA mortars is also significantly improved by the addition ofNS, embodying in the decrease of Ca/Si ratio and CH enrichment of ITZ.

关键词： nano silica cement high volume fly ash hydration pozzolanic reaction pore structure interfacial transition zone

Hydration of Portland Cement in the Presence of Highly Reactive Metakaolin

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Materials Sciences and Applications 2015年第5期6卷 391-400页

作者： Alexey Brykov Svetlana Krasnobaeva Maxim Mokeev Faculty of Chemistry of Substances and Materials St. Petersburg State Institute of Technology St. Petersburg Russia Institute of Macromolecular Compounds Russian Academy of Sciences St. Petersburg Russia

The degree of conversion of highly reactive metakaolin in Portland cement metakaolin paste at different ages as well as the influence of metakaolin on the degree of hydration of Portland cement and composition of C-S-H is investigated by?27Al- and 29Si-MAS NMR spectroscopy. At the age of 7 days, in the paste with 10% of metakaolin, the additive is completely consumed. In the 30% substituted cement paste, the content of metakaolin remains quite high (about 40% of the initial amount) even after 3 months of hydration. At the age of 1 - 3 months, the degree of Portland cement hydration in the presence of metakaolin is of 15% - 20% less than without it, probably, due to deficit of water or spatial restrictions. After 7 days of hydration, about half of C-S-H consists of material derived from metakaolin. Metakaolin mainly contributes to Q2 and Q2 (1Al) species, whereas PC does to Q1. After 1 day of hydration, an amount of ettringite in cement paste with high dosage of metakaolin is higher than in pure PC paste.

关键词： Metakaolin Portland Cement Hydration MAS NMR pozzolanic Reaction

Effect of Clay Fines on the Behavior of Self-Compacting Concrete

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Engineering（科研） 2013年第2期5卷 213-218页

作者： Zine Eddine Abib Haifa Gaher-Abib Fattoum Kharchi 不详

The technology of concrete has significantly increased in recent years through the use of super plasticizer and availability of mineral additions. One of the most recent materials used as an additive, replacing a portion of cement in concrete, is fine clay fired at a temperature of 800℃ to 900℃. This research is based on trials that complied with artificial pozzolan (waste crushed brick), and their effect on the rheological and mechanical behavior of mortar. The addition of 5% of a waste crushed brick has helped not only to improve the strength (tensile and compression), but also to foster a better rheological behavior in terms of fluidity and stability, with a low heat of hydration compared to control. However, tests of optimizing the content of self-compacting concrete (SCC) in coarse aggregates, sand and binder, led us to confirm that the combined mass of more optimal (better workability and stability) is that based on low in volumetric percentage of sand/paste with a granular skeleton richest gravel low dimensions (2/3 of G 3/8 and 1/3 of G 8/15).

关键词： Waste Crushed Brick pozzolanic Activity Heat of Hydration Workability Strength Self Compacting Concrete

Using Microwave Heating to Completely Recycle Concrete

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Journal of Environmental Protection 2014年第7期5卷 583-596页

作者： Heesup Choi Myungkwan Lim Hyeonggil Choi Ryoma Kitagaki Takafumi Noguchi Department of Architecture The University of Tokyo Tokyo Japan Department of Civil Engineering Kitami Institute of Technology Hokkaido Japan

The aim of this study was to develop a technique for the complete recycling of concrete based on microwave heating of surface modification coarse aggregate (SMCA) with only inorganic materials such as cement and pozzolanic materials (silica fume, fly ash). The mechanical properties of SMCA, which was produced using original coarse aggregate (OCA) and inorganic admixtures, as well as its separation from the cement matrix and recovery performance were quantitatively assessed. The experimental results showed that micro structural reinforcement of the interfacial transition zone, which is a weak part of concrete, by coating the surface of the OCA with cement and admixtures such as pozzolanic materials can help suppress the occurrence of micro-cracks and improve the mechanical performance of the OCA. Microwave heating was observed to cause micro-cracking and hydrate decomposition. Increasing the void volume and weakening the hydrated cement paste led to the effective recovery of recycled coarse aggregate.

关键词： Recycling Surface Modification Interfacial Transition Zone pozzolanic Reaction Microwave Recovery

Reactivity of Fine Quartz in Presence of Silica Fume and Slag

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Engineering（科研） 2011年第6期3卷 569-576页

作者： Karima Arroudj Abdelfetah Zenati Mohamed Nadjib Oudjit Abderrahim Bali Arezki Tagnit-Hamou 不详

Dune sand is a very abundant material in south of Algeria. Its high silica content gives a partial pozzolanic reactivity due to its crystalline state. This paper investigates the evolution of cement hydration based on a binary addition particularly the reactivity of dune sand finely ground in the presence of an amorphous addition: silica fume or blast furnace slag. Thus, four combinations of binary additions by substitution have been chosen. The X-ray diffraction analyses performed on cement pastes containing additions have shown the importance of the mineralogy and silica content of additions on their pozzolanic reactivity. Dune sand becomes reactive at long term, especially when associated up to 10% of amorphous addition (blast furnace slag or silica fume). It results an increasing in mechanical strength of Ultra High Performance Concrete (UHPC) and an improvement of the microstructure.

关键词： Dune Sand Blast Furnace Slag Silica Fume C-S-H pozzolanic Reactivity XRD Ultra High Performance Concrete