The paper talks about the elaboration of geopolymer with two types of kaolinite clays containing muscovite. The kaolinite materials were first calcined at different temperatures, and mixed with an activator solution, ...The paper talks about the elaboration of geopolymer with two types of kaolinite clays containing muscovite. The kaolinite materials were first calcined at different temperatures, and mixed with an activator solution, called liquid precursor, at a different solid/liquid mass ratio depending on their normal consistency to produce geopolymer binders. Results show that the geopolymer products obtained from the different clays have good physichomechanical properties: their open porosity and their water absorption rate decrease while their compressive strength and their apparent density increase with the increase in calcination temperature of the clays. The density of GABD binders varies between 2.92 and 2.47 g/cm<sup>3</sup> and that of GARD binders between 1.86 and 2.16 g/cm<sup>3</sup>. Specimens in the GABD series have the best mechanical performance, ranging from 14.43 to 31.37 MPa, while those in the GARD series oscillate between 6.18 and 11.56 MPa. These properties make kaolinite materials from this region suitable for use as construction materials for adequate waterproof structures.展开更多
This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma...This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma–mass spectrometry and isotope ratio mass spectrometry was used to investigate trace and rareearth element geochemistry and hydrogen and oxygen isotopic compositions. These data were then used to infer the sediments' provenance and paleoclimatic conditions during their deposition. The sediments contained low concentrations of most trace elements, with the exceptions of Zr(651–1352 ppm), Ba(56–157 ppm), V(38–90 ppm),and Sr(15.1–59.6 ppm). Average values of Co and Ni were1.5 and 0.7 ppm, respectively. Trace and rare earth element values were lower than corresponding values for upper continental crust and Post-Archean Australian Shale, with the exception of Zr. The samples showed only slight light rare-earth enrichment and nearly flat heavy rare-earth depletion patterns, with negative Eu and Tm anomalies,typical of felsic sources. Geochemical parameters such as La/Sc, Th/Sc, and Th/Co ratios support that the kaolinitic sediments were derived from a felsic rock source, likely deposited in an oxic environment.^(18 )O values ranged from+ 15.4 to + 21.2% for the investigated samples, consistent with a residual material derived from chemicalweathering of felsic rock and redeposited in a sedimentary basin(typical values of + 19 to + 21.2%). While in the basin, the sediments experienced extended interactions with meteoric water enriched in d D and d16 O. However,the variation in d D and d16 O values for the investigated samples is attributed to the high temperature of formation(54–91 °C). The d D and d^(18 )O values suggest that the sediments, although obtained from different localities within the Lower Benue Trough, formed under similar hot,tropical climatic conditions.展开更多
Akure area in southwestern Nigeria falls within the basement complex underlain by migmatite,quartzite granite and charnockite.Geochemical features of these crystalline rocks and their overlying in-situ weathering prof...Akure area in southwestern Nigeria falls within the basement complex underlain by migmatite,quartzite granite and charnockite.Geochemical features of these crystalline rocks and their overlying in-situ weathering profiles are investigated and reported.Analytical result from ICP-MS facility at the University of Malaya reveals average SiO_(2) content in quartzite(91.1%),granite(73.8%),migmatite(67.4%)and charnockite(58.6%)categorize the rocks as siliceous.SiO_(2) contents in the weathering profiles above these rocks are 61.9%,60.2%,52.2%and 54.6%respectively.Alumina contents in the weathering profiles overlying quartzite(23.8%),granite(19.9%),migmatite(26.3%)and charnockite(24.3%)are substantially higher than the precursor rocks.In the same order,average alkali(Na_(2)O+K_(2)O)contents in the profiles are 3.38%,3.42%,3.48%and 2.68%.Chemical features of the profiles reflect that there exists some correlation between the chemistry of crystalline basement and their in-situ weathering profiles.The residual soils contain low plastic clays with kaolinitic characteristics and compare well with other clays reported from other parts of Nigeria basement complex.展开更多
文摘The paper talks about the elaboration of geopolymer with two types of kaolinite clays containing muscovite. The kaolinite materials were first calcined at different temperatures, and mixed with an activator solution, called liquid precursor, at a different solid/liquid mass ratio depending on their normal consistency to produce geopolymer binders. Results show that the geopolymer products obtained from the different clays have good physichomechanical properties: their open porosity and their water absorption rate decrease while their compressive strength and their apparent density increase with the increase in calcination temperature of the clays. The density of GABD binders varies between 2.92 and 2.47 g/cm<sup>3</sup> and that of GARD binders between 1.86 and 2.16 g/cm<sup>3</sup>. Specimens in the GABD series have the best mechanical performance, ranging from 14.43 to 31.37 MPa, while those in the GARD series oscillate between 6.18 and 11.56 MPa. These properties make kaolinite materials from this region suitable for use as construction materials for adequate waterproof structures.
文摘This study evaluated the Cretaceous(Campanian–Maastrichtian) kaolinitic sediments of the Ajali/Mamu and Enugu/Nkporo Formations from the Lower Benue Trough of Nigeria. A combined method of inductively coupled plasma–mass spectrometry and isotope ratio mass spectrometry was used to investigate trace and rareearth element geochemistry and hydrogen and oxygen isotopic compositions. These data were then used to infer the sediments' provenance and paleoclimatic conditions during their deposition. The sediments contained low concentrations of most trace elements, with the exceptions of Zr(651–1352 ppm), Ba(56–157 ppm), V(38–90 ppm),and Sr(15.1–59.6 ppm). Average values of Co and Ni were1.5 and 0.7 ppm, respectively. Trace and rare earth element values were lower than corresponding values for upper continental crust and Post-Archean Australian Shale, with the exception of Zr. The samples showed only slight light rare-earth enrichment and nearly flat heavy rare-earth depletion patterns, with negative Eu and Tm anomalies,typical of felsic sources. Geochemical parameters such as La/Sc, Th/Sc, and Th/Co ratios support that the kaolinitic sediments were derived from a felsic rock source, likely deposited in an oxic environment.^(18 )O values ranged from+ 15.4 to + 21.2% for the investigated samples, consistent with a residual material derived from chemicalweathering of felsic rock and redeposited in a sedimentary basin(typical values of + 19 to + 21.2%). While in the basin, the sediments experienced extended interactions with meteoric water enriched in d D and d16 O. However,the variation in d D and d16 O values for the investigated samples is attributed to the high temperature of formation(54–91 °C). The d D and d^(18 )O values suggest that the sediments, although obtained from different localities within the Lower Benue Trough, formed under similar hot,tropical climatic conditions.
文摘Akure area in southwestern Nigeria falls within the basement complex underlain by migmatite,quartzite granite and charnockite.Geochemical features of these crystalline rocks and their overlying in-situ weathering profiles are investigated and reported.Analytical result from ICP-MS facility at the University of Malaya reveals average SiO_(2) content in quartzite(91.1%),granite(73.8%),migmatite(67.4%)and charnockite(58.6%)categorize the rocks as siliceous.SiO_(2) contents in the weathering profiles above these rocks are 61.9%,60.2%,52.2%and 54.6%respectively.Alumina contents in the weathering profiles overlying quartzite(23.8%),granite(19.9%),migmatite(26.3%)and charnockite(24.3%)are substantially higher than the precursor rocks.In the same order,average alkali(Na_(2)O+K_(2)O)contents in the profiles are 3.38%,3.42%,3.48%and 2.68%.Chemical features of the profiles reflect that there exists some correlation between the chemistry of crystalline basement and their in-situ weathering profiles.The residual soils contain low plastic clays with kaolinitic characteristics and compare well with other clays reported from other parts of Nigeria basement complex.
