scholarly journals The Potential to Replace Cement with Nano-Calcium Carbonate and Natural Pozzolans in Cemented Mine Backfill

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Mohammed Hefni ◽  
Maaz A. Ali
Keyword(s):  
Calcium Carbonate ◽  
Unconfined Compressive Strength ◽  
Mercury Intrusion Porosimetry ◽  
Silica Sand ◽  
Strength Development ◽  
Microstructural Properties ◽  
Mine Backfill ◽  
Mercury Intrusion ◽  
Natural Pozzolans ◽  
Gold Tailings

The effectiveness of mine backfilling depends on the properties of its constituents. The high cost of cement, which is commonly used as a binder in mine backfill, has led researchers to seek alternatives to partially replace it with other binders. This study investigated the potential to use nano-calcium carbonate (NCC) and natural pozzolans (zeolite and pumice) along with Portland cement (PC) in mine backfill. Two types of experimental samples were prepared: (1) gold tailings and silica sand to investigate the effect of NCC and (2) nickel tailings to investigate the effect of natural pozzolans. The unconfined compressive strength (UCS) was measured for samples cured for up to 56 days. Moreover, selected samples were subject to mercury intrusion porosimetry to investigate microstructural properties. Results show that addition of NCC did not improve the UCS of backfill prepared with gold tailings and cured for 28 days, whereas a dosage of 1% NCC in backfill samples prepared with silica sand improved UCS by 20%, suggesting that the gold tailings negatively affected strength development. Natural pozzolans, in particular, 20% zeolite, had 24% higher UCS after 56 days of curing compared to samples prepared with PC and thus have the potential to partially replace cement in mine backfill.

scholarly journals The potential use of pumice in mine backfill

2020 ◽  
Vol 1 ◽  
Author(s):  
Mohammed A. Hefni
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Mining Industry ◽  
Strength Development ◽  
Natural Pozzolan ◽  
Mine Backfill ◽  
Natural Pozzolans ◽  
Cemented Backfill ◽  
Compressive Strength Development ◽  
Potential Use

Abstract The use of natural pozzolans in concrete applications is gaining more attention because of the associated environmental, economic, and technical benefits. In this study, reference cemented mine backfill samples were prepared using Portland cement, and experimental samples were prepared by partially replacing Portland cement with 10 or 20 wt.% fly ash as a byproduct (artificial) pozzolan or pumice as a natural pozzolan. Samples were cured for 7, 14, and 28 days to investigate uniaxial compressive strength development. Backfill samples containing 10 wt.% pumice had almost a similar compressive strength as reference samples. There is strong potential for pumice to be used in cemented backfill to minimize costs, improve backfill properties, and promote the sustainability of the mining industry.

scholarly journals Strength and Solidification Mechanism of Silt Solidified by Polyurethane

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Fengyuan Li ◽  
Chaojie Wang ◽  
Yangyang Xia ◽  
Yanjie Hao ◽  
Peng Zhao ◽  
...  
Keyword(s):  
Unconfined Compressive Strength ◽  
Immersion Time ◽  
Mercury Intrusion Porosimetry ◽  
Polymer Content ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mercury Intrusion ◽  
Grouting Material ◽  
Permeable Polymer ◽  
Solidification Mechanism

To determine the mechanism and strength characteristics of solidification of silt by a permeable polyurethane grouting material, the effects of polymer content, soil moisture, and immersion time on the unconfined compressive strength (UCS) of the silt have been studied. The results showed that the permeable polymer grouting material can significantly improve the performance of silt: (1) A higher amount of polymer produced a greater strength in the solidified soil. (2) The strength of the solidified soil increased as the immersion time was increased. (3) Moisture in the soil was not conducive to improving the strength of the solidified soil. The X-ray diffraction (XRD) and energy-dispersive spectroscopy (EDS) have proven that polyurethane does not react with the silt, but they could improve the strength of the silt through physical action. Mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM) were performed to find that polymers can reduce soil porosity, and the addition of polyurethane improved the strength of the silt mainly through adhesion, wrapping, filling, and bridging.

Microstructural and Microanalytical Study on Cementitious Materials Subjected to the Cyclic Sulfate Environment

2014 ◽  
Vol 898 ◽  
pp. 371-374
Author(s):  
Xiao Lu Yuan
Keyword(s):  
Electron Microscope ◽  
Mercury Intrusion Porosimetry ◽  
Cementitious Materials ◽  
Sulfate Attack ◽  
Microstructural Properties ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mercury Intrusion ◽  
Lower Porosity ◽  
Scanning Electron

Microstructural properties have been studied in cementitious materials, which were subjected to cyclic sulfate exposure, through x-ray diffraction (XRD), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and mercury intrusion porosimetry (MIP). Results indicate that portlandite in OPC concrete and OPC-FA concrete is mainly converted to gypsum. Portlandite in OPC-GBFS concrete is mainly converted to gypsum and ettringite. Concrete subjected to the cyclic sulfate attack has a lower porosity and the higher amount of macro-pores than that before exposure. Concretes incorporating FA or GBFS had lower porosity and higher amount of micro-pores than OPC concrete.

An Investigation into the Potential Use of Calcium Carbonate Nanoparticles in Mine Backfill

2018 ◽  
Vol 916 ◽  
pp. 184-189
Author(s):  
Mohammed A. Hefni ◽  
Ferri P. Hassani ◽  
Mehrdad F. Kermani
Keyword(s):  
Calcium Carbonate ◽  
Phase I ◽  
Phase Ii ◽  
Particle Dispersion ◽  
Silica Sand ◽  
Binding Agent ◽  
Dispersion Phase ◽  
Mine Backfill ◽  
Before And After ◽  
Potential Use

This study is part of large and ongoing investigation into the potential use of calcium carbonate nanoparticles (NCaCO3) to improve the mechanical and physical properties of mine backfill. The investigation was conducted in two phases. In phase I, gold tailings were used to prepare backfill sample using Portland cement (PC) as the binding agent under various NCaCO3 and superplasticizer (SP) dosages. In phase II, fine silica sand was used to minimize the reactive nature of tailings, which can adversely affect uniaxial compressive strength (UCS). Samples in this phase were prepared under various NCaCO3 dosages using slag:PC weight ratios of 80:20 as the binding agent. Select samples from phase II were subjected to Mercury Intrusion Porosimetry (MIP) to compare microstructural properties before and after addition of NCaCO3. Phase I results showed that the UCS of samples containing NCaCO3 was low, even when SP was used to improve particle dispersion. Phase II samples exhibited up to 9.5% higher UCS after 28 days of curing at a NCaCO3 dosage of 6% by weight of binder. MIP results showed that samples containing NCaCO3 were less porous than the corresponding controlled silica sand backfill samples, which in turn influenced the UCS results.

scholarly journals Loading of Porous Functionalized Calcium Carbonate Microparticles: Distribution Analysis with Focused Ion Beam Electron Microscopy and Mercury Porosimetry

Pharmaceutics ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 32 ◽  
Author(s):  
Maryam Farzan ◽  
Roger Roth ◽  
Gabriela Québatte ◽  
Joachim Schoelkopf ◽  
Jörg Huwyler ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Calcium Carbonate ◽  
Focused Ion Beam ◽  
Mercury Intrusion Porosimetry ◽  
Ion Beam ◽  
Drug Carriers ◽  
Beam Scanning ◽  
Mercury Intrusion ◽  
Scanning Electron

Accurate analysis of intraparticle distribution of substances within porous drug carriers is important to optimize loading and subsequent processing. Mercury intrusion porosimetry, a common technique used for characterization of porous materials, assumes cylindrical pore geometry, which may lead to misinterpretation. Therefore, imaging techniques such as focused ion beam scanning electron microscopy (FIB-SEM) help to better interpret these results. The purpose of this study was to investigate the differences between mercury intrusion and scanning electron microscopy and to identify the limitations of each method. Porous microparticles, functionalized calcium carbonate, were loaded with bovine serum albumin and dipalmitoylphosphatidylcholine (DPPC) by solvent evaporation and results of the pore size distribution obtained by both methods were compared. The internal structure of the novel pharmaceutical excipient, functionalized calcium carbonate, was revealed for the first time. Our results demonstrated that image analysis provides a closer representation of the material distribution since it was possible to discriminate between blocked and filled pores. The physical nature of the loaded substances is critical for the deposition within the pores of functionalized calcium carbonate. We conclude, that a combination of mercury intrusion porosimetry and focused ion beam scanning electron microscopy allows for a reliable analysis of sub-micron porous structures of particulate drug carriers.

scholarly journals Effect of Hydrogen Nanobubbles on the Mechanical Strength and Watertightness of Cement Mixtures

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1823
Author(s):  
Won-Kyung Kim ◽  
Young-Ho Kim ◽  
Gigwon Hong ◽  
Jong-Min Kim ◽  
Jung-Geun Han ◽  
...  
Keyword(s):  
Mercury Intrusion Porosimetry ◽  
Cement Mortar ◽  
Stable State ◽  
Pozzolanic Reaction ◽  
Hydration Reaction ◽  
High Concentration ◽  
Mercury Intrusion ◽  
Electron Microscope Analysis ◽  
Mixing Water ◽  
Cement Mixtures

This study analyzed the effects of applying highly concentrated hydrogen nanobubble water (HNBW) on the workability, durability, watertightness, and microstructure of cement mixtures. The number of hydrogen nanobubbles was concentrated twofold to a more stable state using osmosis. The compressive strength of the cement mortar for each curing day was improved by about 3.7–15.79%, compared to the specimen that used general water, when two concentrations of HNBW were used as the mixing water. The results of mercury intrusion porosimetry and a scanning electron microscope analysis of the cement paste showed that the pore volume of the specimen decreased by about 4.38–10.26%, thereby improving the watertightness when high-concentration HNBW was used. The improvement in strength and watertightness is a result of the reduction of the microbubbles’ particle size, and the increase in the zeta potential and surface tension, which activated the hydration reaction of the cement and accelerated the pozzolanic reaction.

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