Self-healing efficiency of cement-based materials has so far been evaluated mostly through the healing of surface cracks, without adequately capturing the dominant effects of environmental exposure ...or accurately quantifying the volume of cracks healed. In addition, the effects of diverse additions such as silica-based materials, swelling agents, and carbonating minerals on self-healing performance under different environmental exposure, remain largely unexplored. In this study, multiple test methods were used to investigate self-healing of cracks in cement mortar incorporating metakaolin, bentonite, and calcium carbonate microfiller in different environmental exposure. Change in crack width was monitored using optical microscopy. Backscattered electron microscopy coupled with energy disperse X-ray analysis was used to identify healing compounds. Mercury intrusion porosimetry and water absorption were employed to assess porosity. X-ray computed micro-tomography (X-ray μCT) with 3-dimensional image processing was used to segment and quantify cracks before and after healing. After one year of exposure, no significant self-healing occurred in all specimens exposed to cyclic T and RH. Conversely, all specimens submerged in water exhibited variable levels of self-healing, which depended on the type of mineral added. The healing efficiency was 32.26%, 27.27%, 25.6%, and 24.1% for specimens incorporating limestone microfiller, portland cement alone, bentonite, and metakaolin, respectively. The formation of calcium carbonate was found to be the main contributor to self-healing of surface cracks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The depositional and diagenetic processes involved in the formation of carbonates in the evaporitic environment of the Messinian Salinity Crisis are investigated in Southern Italy (Sicily and ...Calabria). Strong differences are observed between the studied sections that reflect specific depositional and diagenetic evolution in the interconnected sub-basins resulting from the syn-sedimentary tectonic fragmentation of the Central Sicilian and Calabrian domains. These carbonates formed diachronously in restricted perched sub-basins between the Tripoli Formation and the hypersaline settings of the MSC. The Calcare di Base (CdB) that can be interbedded with gypsum layers occurs rhythmically at the transition between the upper part of the Tripoli Formation and the massive gypsum, and at places synchronously with the deposition of the Lower Gypsum unit. It deposited initially as primary peloidal and microbial limestones, but their original structure and mineral composition were modified by the superimposition of early to late diagenetic processes. The first diagenetic step was the development of interstitially grown gypsum and halite crystals from trapped saturated brines that locally led to the formation of salt beds. The Sulphur Limestone (SL) resulted from the activity of sulphate reducing bacteria that occurred locally in the deeper parts of the various basins where anoxic bottom waters favoured microbial processes fuelled by biogenic methane and crude oil, and caused the carbonate replacement of gypsum and the formation of native sulphur. The migration of hydrocarbon and H2S-rich fluids caused the epigenetic dissemination of sulphur and a late diagenetic carbonate replacement of the gypsum. Later influxes of continental fresh waters were responsible for the dissolution of the halite crystals and their replacement by sparry calcite. The vugs, formed during both the gypsum/calcite conversion and the halite dissolution, either remained empty or were filled with calcite, celestine, fibrous silica, anhydrite, secondary gypsum, and native sulphur. The initial accumulation of fine-grained carbonate and gypsum sediments was strongly destabilised by volumetric changes resulting from mineral replacements and fluidisation processes. Their superimposition explains the vuggy and boxwork-like textures, in situ brecciation and lateral displacement, which are responsible for the chaotic organisation without necessarily involving basin-scale re-sedimentation in the form of debris flows.
•The Messinian Salinity Crisis has been investigated in Southern Italy.•The Calcare di Base (CdB) can be interbedded with gypsum layers.•The CdB occurs at the transition between the upper part of the Tripoli and gypsum.•The CdB and SL grade upward and pass laterally to the massive gypsum.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
In this investigation, a comprehensive assessment was conducted on the cooperative effects of Super Absorbent Polymers (SAP), limestone powder, and white cement within the realm of fair-faced ...concrete. We discerned that while white cement augments the color vibrancy of the concrete, its accelerated hydration rate potentially induced early-stage cracks and compromised performance. To mitigate these challenges, SAP was incorporated to regulate early hydration, and limestone powder was introduced as a fortifying agent to bolster the mechanical robustness of the concrete. Our findings highlighted not only the capability of SAP to enhance concrete workability and longevity but also the pivotal role of limestone powder in amplifying its mechanical attributes. Microscopic evaluations, undertaken via Scanning Electron Microscopy (SEM), unveiled the potential of both SAP and limestone powder in refining the microstructure of the concrete, thereby elevating its performance metrics. Synthesizing the research outcomes, we pinpointed an optimal amalgamation of SAP, limestone powder, and white cement in fair-faced concrete, offering a valuable reference for prospective architectural applications.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
AbstractThe cumulative damage to rock and soil mass caused by blasting in tunnel, highway, hydropower, and other projects is very complex, but the process of damage evolution is still unclear. This ...study took Zhujiapo mining area limestone as the research object and analyzed the change in its strength and mechanical parameters with periodic blasting loads. Combined with damage mechanics theory and microcrack propagation zone theory, a micromechanics constitutive model considering cumulative damage evolution was developed. The results show that (1) periodic blasting loads have a continuous cumulative effect on microcrystalline limestone, the peak strength and elastic modulus of which decrease exponentially with increasing blasting cycles; (2) periodic blasting loads cause crystal fractures, microcrack initiation, and propagation; and (3) the micromechanics damage constitutive model considering confining pressure and periodic blasting loads well describes the micromechanics behavior of microcrystalline limestone in the Zhujiapo mining area. The research results provide a theoretical reference to the study of rock damage mechanical properties under periodic blasting loads.
Sulfur-based denitrification process has attracted increasing attentions because it does not rely on the external addition of organics and avoids the risk of COD exceeding the limit. Traditionally, ...limestone is commonly employed to maintain a neutral condition (SLAD process), but it may reduce the efficiency as the occupied zone by limestone cannot directly contribute to the denitrification. In this study, we propose a novel sulfur-based denitrification process by coupling with iron(II) carbonate ore (SICAD system). The ore was demonstrated to play roles as the buffer agent and additional electron donor. Moreover, the acid produced through sulfur driven denitrification was found to promote the Fe(II) leaching from the ore and likely extend the reaction zone from the surface to the liquid. As a result, more biomass was accumulated in the SICAD system compared with the controls (sulfur, iron(II) carbonate ore and SLAD systems). Owing to these synergistic effects of sulfur and iron(II) carbonate on denitrification, SICAD system showed much higher denitrification rate (up to 720.35 g·N/m3·d) and less accumulation of intermediates (NO2 – and N2O) than the controls. Additionally, sulfate production in SICAD system was reduced. These findings offer great potential of SICAD system for practical use as a highly efficient postdenitrification process.
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IJS, KILJ, NUK, PNG, UL, UM
For the first time, depositional models of Lower Miocene carbonate systems from New Caledonia (Southwest Pacific) are proposed, on the basis of a sedimentological and paleoenvironmental study of both ...cores and outcrops. In the Népoui area, two distinct stages of carbonate ramp development (Aquitanian Lower Népoui and Burdigalian Upper Népoui carbonate systems), separated by a phase of siliciclastic deltaic deposition, are evidenced. The post-obduction marine transgression of the Western New Caledonian margin occurred at approximately 24Ma and is characterized by the development of an aggrading foraminiferal–coralline algal–scleractinian ramp system (“Chapeau Chinois Limestone”) during the early Aquitanian (24–23Ma). A retrogradational event is evidenced at approximately 23Ma followed by the development of a shallowing upward carbonate unit (Operculina “Green Sands” and Xuudhen Limestone) during the late Aquitanian. This unit is topped by a major erosional unconformity overlain by conglomeratic deposits (“Pindaï conglomerates”), and interpreted to record a significant uplift at around 21–19Ma. During the Burdigalian, a marine transgression occurred at around 19Ma, followed by the development of a low-angle carbonate ramp or open platform (“Népü Limestone”) up to the late Burdigalian (19–17Ma). In both Aquitanian and Burdigalian carbonate ramps, extensive sea-grass meadows are shown to have colonized the proximal ramp environments within the euphotic zone. In the Aquitanian carbonate ramp (Lower Népoui Formation), carbonate production within sea-grass meadows is dominated by large benthic foraminifera, together with red algae and sparse scleractinians. Mesophotic environments are characterized by large and flat lepidocyclinids, rhodoliths and platy corals whereas in deeper oligophotic settings significant carbonate producers consist mainly of large and flat benthic foraminifera. In the Burdigalian carbonate ramp (Upper Népoui Formation), porcellaneous foraminifera thriving in sea-grass meadows together with red algae and scattered coral colonies characterize the carbonate production in the euphotic zone. Antecedent topography is regarded as a major factor controlling the extension of carbonate systems at regional and local scale. The thickness and development pattern of Lower Miocene deposits from Népoui are dominantly controlled by tectonic subsidence. Finally, extensive sea-grass development promoted the dominance of foralgal carbonate production within the euphotic zone.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In Western Slovakia, especially in the Bratislava region and Trnava region, Leitha limestone of the Badenian (Langhian – early Serravalian) age from St. Margarethen in Austria was widely used for ...architectural articles and sculptures (200 realizations), alternatively a similar limestone from Fertőrákos in Hungary. 380 tombstones were identified only in Bratislava cemeteries. From the second half of the 17th century to the first half of the 20th century, the limestones were one of the most used in Slovakia due to their light dressing and relatively homogeneous appearance. The strongly porous coarse-grained to medium-grained the Leitha limestone has the appearance of sandstone and is composed of a predominance of red algae nodules over foraminifers, sea urchin, moss and shell fragments. The rhodoliths, pectenoids and oysters are scattered in the Leitha limestones up to a few cm size, which distinguish the limestone type from other the Leitha limestones and similar Sarmatian limestones. The limestone is dominated by rhodolithes in the St. Margarethen quarry and by bivalves and macroscopic quartz in Fertőrákos quarry. Porous limestones are exposed to weathering outdoors, leading to mass loss, flaking, sulphate efflorescence, black crusts from microscopic organisms and the colonization by lichens and mosses. The peak of limestone use for public buildings and sculptures was the years 1745 to 1780 (reign of Maria Theresa), and about 1880 to 1915, when there was relative prosperity and machine production began. The tombstones made of the Leitha limestones shifts to a peak between 1905 and 1925. In the 20th century, the Leitha limestones gave way to a competition from Czech decorative stones.
Paleontological survey in the remote Yukon-Charley Rivers National Preserve in Alaska led to the discovery of lobed Zoophycos from the lower Tahkandit Limestone (informally named Sandstone unit), an ...interval characterized by grayish-green glauconitic sandstone and conglomerate of coastal origin. The studied Zoophycos consists of a lobate skirt-like spreite bounded by a marginal tube. Smaller tongue-shaped lobes branch off from larger parent lobes that share the same tongue-like shape. Sedimentological features, together with body fossils and associated trace fossils (Planolites, Chondrites), indicate a shoreface habitat for the Zoophycos producer. This shallow-marine environmental setting is in contrast with the deeper bathymetries in which lobed Zoophycos are recovered in post-Palaeozoic times. The producer of the lobed Zoophycos of the Yukon River is interpreted as a deposit-feeder that used sensory-driven, directed search for locating heterogeneously distributed trophic resources. The Zoophycos producer filled its burrow with Coprolus-like fecal pellets, possibly complementing deposit feeding with microbial gardening and/or food caching. Data presented here provide useful insight into the morphological evolution and bathymetric distribution of Zoophycos, suggesting two ‘Golden Ages’ for lobed Zoophycos: (1) Carboniferous–Permian and (2) Cretaceous–Neogene. This stratigraphic distribution supports the important ecological role of major terrestrialization events, that are, the Palaeozoic expansion of land plants and the Mesozoic expansion of angiosperms. The consequent increased input of nutrients to coastal areas was an important contributor to declining trends in porewater oxygen concentrations. This phenomenon favored adaptive traits to exploit nutrient-rich but oxygen-poor niches, among which the U-shaped marginal tube of lobed Zoophycos was an efficient adaptation to bring oxygenated water into low-oxygen substrates.
•New ichnological information is added to a poorly understood Permian rock unit along the Yukon River in eastern Alaska.•This report illustrates the important role of terrestralization events in driving the Zoophycos morphology.•In contrast to previous work, this study shows larger spirals of Zoophycos preserved in more inshore environments.•This is one of the oldest known trace morphologies of Zoophycos with such a complex vertical structure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
•H3PO4 can be used as an acid-base activator for MK to produce insulation material.•LS can be used as a foaming agent for MK-based geopolymer activated with H3PO4.•Thermal conductivity, density, ...mechanical strength decreased with increasing LS dosage.•Total porosity increased with increasing LS dosage.
The current article aims to elaborate an insulating material synthesized from metakaolin, limestone powder and phosphoric acid. For that purpose, metakaolin was activated with phosphoric acid to produce geopolymer paste. Afterward, metakaolin was partially replaced with limestone powder at ratios fluctuated from 1% to 5% with a step of 1%, by weight. After curing, the bulk density, total porosity, compressive strength and splitting tensile strength were measured at ages of 7, 28 and 91 days. The thermal conductivity was determined for the various mixtures after 28 days of curing. The results were analyzed by using sophisticated tools such as X-ray diffraction, thermogravimetric/its derivative, scanning electron microscopy and energy dispersive analytical X-ray. The results showed a good thermal insulation of all mixtures with an accepted compressive strength. The thermal insulation increased with increasing limestone powder content accompanying with higher total porosity and lower compressive strength.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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