Mercury Intrusion Porosimetry Measurements Research Articles

Investigation on coal floatability and pore characteristics using acidification method

This paper investigated the relationship between coal floatability and pore characteristics from the perspective of froth flotation. Three types of coal samples with different ash contents were pretreated with HCl and acetic acid solutions to alter the pore features. The X-ray diffraction (XRD), Fourier transform infrared spectrometer (FTIR), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) measurements were conducted to specify the reactions that happened in acidification. The batch flotation and contact angle measurements were conducted to evaluate the floatability of the coal samples. The liquid nitrogen adsorption and mercury intrusion porosimetry (MIP) measurements were applied to measure the pore characteristics of the coal. The acidification treatment partially dissolved mineral components and organic functional groups on the coal surface but did not change the types of the major functional groups. The sedimentation of liberated fine minerals on coal pores caused the decrease in pore volume. The BET specific surface area of the three coal samples after acidification was found to have consistent negative relations with the flotation recovery and combustible recovery rate. This indicated the adverse impact of porosity in coal flotation. The floatability of coal is mainly influenced by the pores at the size fraction of 1–20 μm by pore volume. The nano-scale size pore and fine mineral inside the micron pore increased the water-wettability and resulted in the low floatability of coal.

Toward clima-resilient ultra-high performance concrete (UHPC): A survey on high-strength mortars engineered with extra-low dosage graphene-based materials (GBMs)

Latest advances showed that ultra-high performance concrete (UHPC) holds the potential to meet the criteria of future civil infrastructures. Several nanofillers (NFs) proved to enhance the performance of UHPC in terms of economic and environmental sustainability and even assigning novel features. Presently, this promising approach is still in its early stage. In this perspective, mortars based on Portland cement CEM I 52.5 N were engineered with extra-low dosage (0.01% by weight of cement) graphene nanoplatelets (GNPs) or nanographite (nG). An acrylic superplasticizer for high-strength concrete was used as additive. Fresh properties of the cementitious admixtures were characterized by viscosity measurements, flow table and bleeding tests. Prismatic specimens were hardened in water at room temperature for 28 days. Microstructure was observed by Scanning Electron Microscopy, the pore structure and specific surface area (SSA) investigated by Mercury Intrusion Porosimetry (MIP) and nitrogen adsorption-desorption measurements, thermal behavior studied by thermogravimetry, and mechanical strength evaluated by compression and bending tests. Electrical resistivity was determined by Electrochemical Impedance Spectroscopy (EIS). Both 2D-NFs induced a slight lubricant effect that did not significantly affect neither workability nor bleeding. GNPs do not appreciably impact on the mechanical properties of the hardened nano-engineered materials, a decay of bending strength was observed only for nG-loaded samples. The positive impact of the extra-low dosage GNPs on the hardened mortars was clearly detected by MIP and EIS in terms of reduced porosity (−31%), improved bulk density (+5.7%), pore refining (median and average pore diameter −35% and −9%, respectively), increased resistivity (+97%) and lowered predicted intrinsic permeability (−52%). In the same experimental condition, nG-engineered mortars suffered from uneven dispersion that led to increased porosity and pore coarsening.

Field study of the dielectric constant of concrete: A parameter less sensitive to environmental variations than electrical resistivity

In this work, a field study was conducted to evaluate the curing effectiveness of concrete slabs cured by air and compound. Two non-destructive testing methods including ground penetrating radar (GPR) and electrical resistivity measurement were used. The dielectric constant value developments of air and compound cured concrete slabs were determined by GPR measurement. The compressive strength development was tested by concrete cylinders. The hydration degrees of air and compound cured slabs were determined by Ca(OH)2 (CH) content through thermogravimetric analysis (TGA) by a modified calculation method. The microstructure development of air and compound cured concrete slabs were characterized by mercury intrusion porosimetry measurement (MIP). It has found that the dielectric constant value of compound cured concrete slab was always higher than air cured concrete slab. The second reflected pulse peak amplitude of GPR waveform was less influenced by weather conditions, making it a reliable indicator of the dielectric constant value. On the other hand, the dielectric constant value determined by the first reflected pulse peak amplitude was greatly influenced by the weather conditions. The dielectric constant value determined by the two-way travel time method exhibited strong correlations with compressive strength, CH content and porosity. However, the electrical resistivity development of air and compound cured concrete slabs were not consistent with compressive strength, CH content and microstructure development. Our findings suggested that the GPR measurement can be practically used to evaluate the curing effectiveness of concrete and can be a good indicator of “hydration potential” from a development perspective.

Chloride-induced corrosion propagation of alkali-activated slag mortar with pulverized fuel ash and metakaolin replacements

Alkali-activated materials have great potential in reducing CO2 emissions in cement production industry. This study aims to investigate the corrosion propagation performance of alkali-activated slag mortars with various pulverized fuel ash (PFA) and metakaolin (MK) replacements subject to chloride-induced corrosion. The corrosion propagation performances including corrosion potential, corrosion rate and mortar electrical resistivity under wetting and drying cycles in seawater are studied. Scanning electron microscope (SEM), mercury intrusion porosimetry (MIP) and pH value measurement were conducted to analyze the effects of PFA and MK replacements on the relationship between reaction degree, pore structure, pH value and corrosion propagation performances. The results show that the MK replacement can enhance the corrosion propagation resistance of slag-based alkali-activated mortars under high activator concentration while the PFA replacement reduces the resistance to metallic corrosion of alkali-activated mortars. Mechanisms controlling the corrosion propagation are discussed.

Evaluation of reproducible cryogel preparation based on automated image analysis using deep learning.

Cryogels represent a class of porous sponge-like materials possessing unique properties including high-fidelity reproduction of tissue structure and maximized permeability. Their architecture is mainly based on an interconnected network of macropores that provides sufficient stability while allowing the movement of substances through the material. In most cryogel applications, the pore size is very important, especially when the material is used as a 3D scaffold for tissue culture, applied as a filter, or utilized as a membrane. In this study, poly(dimethylacrylamide-co-2-hydroxyethyl methacrylate) cryogels have been prepared by two preparation methods to investigate the reproducibility of homogeneous pore structures and pore sizes. Automated image analysis algorithms were developed to rapidly evaluate cryogel pore sizes based on scanning electron microscopy (SEM) images. The quantification approach contained a unique combination of classical and deep learning-based algorithms. To validate the accuracy of the two models, we compared the results obtained from automated SEM image analysis with those from manual pore size determinations and mercury intrusion porosimetry (MIP) measurements. Effect sizes were calculated to compare the results from manual and automated pore size measurements for the cryogel reproducibility series. 81% of the values obtained revealed only trivial differences, which strongly suggests that automated image analysis can reliably substitute the manual evaluation of cryogel pore sizes. The use of an adapted reactor setup yielded cryogels with heterogeneous morphologies in the absence of recognizable pore structures. With the conventional cryogel preparation using plastic syringes, the obtained cryogels represented highly reproducible morphologies and pore sizes in the range between 17 and 22 μm. Calculated effect sizes within the cryogel replicate series revealed only trivial differences between the obtained pore sizes in 83.5% or 99.4% of the data (classical approach and deep learning-based approach, respectively).

Mechanical strength and porosity changes of bituminous coal induced by supercritical CO2 interactions: Influence of saturation pressure

Sequestration of CO2 in the geological formations has great potential to reduce greenhouse gas emissions, and the induced mechanical stability of coal reservoirs is deeply concerned with the long-term safety of CO2 geological storage. After injection, it is likely that CO2 is stored in the form of supercritical state in coal reservoirs. To date, our current knowledge is still lacking in the underlying interaction mechanisms between coal and supercritical CO2 (ScCO2) fluids under the influence of saturation pressure. In this work, ScCO2 saturation was performed on bituminous coal at the pressures from 7.5 to 25 MPa for saturation time up to 10 days. Mercury intrusion porosimetry (MIP), X-ray diffraction (XRD) and uniaxial compression measurements were conducted to evaluate the mechanical strength and microstructure changes of bituminous coal. The results indicate that coal pore structures are greatly changed by ScCO2 interactions, including the increase of pore volume (84.8–173.2%) and surface area (42.1–85.8%). The larger hysteresis effect is found in saturated specimens, illustrating that ScCO2 interactions enhance the pore roughness of coal. The carbonates in coal are sensitive to ScCO2 fluids, which are extensively dissolved during interactions. ScCO2 saturation pressure has significant impact on the mechanical properties of coal. Rapid reduction of mechanical strength (up to 35.6%) was identified when the pressure was increased from 7.5 to 15 MPa. Subsequently, limited further reduction (<9%) occurred as the saturation pressure is further increased up to 25 MPa. Mineral dissolution and porosity changes account for the mechanical degradation, which weakens the cementation degree and interaction force of coal matrix.

Mineral-impregnated carbon-fiber (MCF) composites made with differently sized fly-ash geopolymers for durable light weight and high temperature applications

For a wide application of carbon-fiber reinforcement in large-scaled, lightweight construction, mineral-impregnated carbon-fiber (MCF) composites provide a promising alternative to rebar or reinforcement made of non-metallic fibers and polymer matrix. The penetration ability of the aluminosilicate particles is a key factor for a stable, reproducible impregnation and the maximal reinforcing efficiency of continuous fiber geopolymer composites.The work at hand focuses on the influence of the particle sizes of geopolymer precursors on the processing quality, microstructural development and final composite performance regarding the flexural, tensile and pullout behavior. Three differently sized fly ash (FA) sources were used to impregnate a carbon fiber heavy tow before curing at 75 °C. FA particles in the same size range as the filament diameter proved to be the most efficient, enhancing both mechanical properties of MCF and its bond to concrete matrix, well beyond the effects induced by other, coarser precursors. The results of the microscopic investigation, μCT, thermal gravimetric analyzes and mercury intrusion porosimetry measurements show that the use of this particle fraction resulted in the best fiber-matrix distribution over the cross-section, densest microstructure and highest fiber volume fraction in the impregnated yarn. Furthermore, the geopolymerization kinetics of all FAs at ambient temperature and at 75 °C were determined by isothermal calorimeter, showing an increase in the reaction rate with elevated curing temperature and higher particle finesse.

Multiple Gas Seepage Mechanisms and Production Development Research for Shale Gas Reservoirs from Experimental Techniques and Theoretical Models.

Shale gas seepage theory provides a scientific basis for dynamically analyzing the physical gas flow processes involved in shale gas extraction and for estimating shale gas production. Conventional experimental techniques and theoretical methods applied in seepage research are unable to accurately illustrate shale gas mass transfer processes at the micro- and nanoscale. In view of these scientific issues, the knowledge of seepage mechanisms and production development design was improved from the perspective of experimental techniques and theoretical models in the paper. First, multiple techniques (e.g., focused ion beam scanning electron microscopy and a combination of mercury intrusion porosimetry and adsorption measurement techniques) were integrated to characterize the micro- and nanopore distribution in shales. Then, molecular dynamics simulations were carried out to analyze the microscale distribution of gas molecules in nanopores. In addition, an upscaled gas flow model for the shale matrix was developed based on molecular dynamics simulations. Finally, the coupled flow and productivity models were set up according to a long-term production physical simulation to identify the production patterns for adsorbed and free gas. The research results show that micropores (diameter: <2 nm) and mesopores (diameter: 2-50 nm) account for more than 70% of all the pores in shales and that they are the primary space hosting adsorbed gas. Molecular simulations reveal that microscopic adsorption layers in organic matter nanopores can be as thick as 0.7 nm and that desorption and diffusion are the main mechanisms behind the migration of gas molecules. An apparent permeability model that comprehensively accounts for adsorption, diffusion, and seepage was developed to address the deficiency of Darcy's law in characterizing gas flowability in shale reservoirs. The productivity model results for a certain gas well show that the production in the first three years accounts for more than 50% of its estimated ultimate recovery and that adsorbed gas contributes more to the annual production than free gas in the eighth year. These research results provide theoretical and technical support for improving the theoretical understanding of shale gas seepage and optimizing shale gas extraction techniques in China.

Quantitative Investigation on Natural Gas Flooding Characteristics in Tight Oil Cores after Fracturing Based on Nuclear Magnetic Resonance Technique

SummaryTight reservoirs are mainly developed by injecting various gases after fracturing. However, the formed fractures are complex, and different fracture conditions have an important impact on the gas injection effect. In addition, natural gas is considered to be suitable for the development of tight reservoirs in China because of the abundant gas source and no corrosion. For this paper, the natural gas injection experiments were studied by combining mercury intrusion porosimetry (MIP) measurements and nuclear magnetic resonance (NMR) measurements. The method can be used to study the distribution characteristics of core pore structure and the recovery characteristics of oil in different pore spaces.In this work, the tight cores of the Changqing Oil Field were selected for fracturing for the natural gas flooding experiments. At first, the distribution characteristics of the core pore structure were studied based on the MIP and NMR measurements. The conversion relationship between the core pore throat radius and the relaxation time (T2) was decided. The NMR T2 distribution was transformed into the distribution of oil in pore space with different throat radii. Then, the gasflooding experiments were conducted to study the oil recovery law of tight cores with different fracture conditions. Finally, the recovery characteristics of oil in different pore spaces were analyzed based on the NMR results of cores.The results show that the pore throat radius of the core is mainly distributed in the range of 0.001 to 10 μm. The oil is mainly stored in the pore space whose pore throat radius ranges from 0.01 to 1 μm. The natural gas also mainly drives the saturated oil in the pore space with a pore throat radius of 0.01 to 1 μm. The increase in fracture area improves the distribution of oil in the larger pore space. In the process of natural gasflooding, with the increase of gas injection, the oil began to be recovered, and then gas was observed at the end of the core. With the continuous injection of natural gas, the rate of recovering oil gradually slowed down, and finally gas breakthrough occurred. The displacement oil process of the nonfractured core was uniform and slow. However, the oil and gas rapidly flowed along the fracture when the natural gas displaced the oil in the fractured core. The oil in the matrix was poorly recovered. Gasflooding mainly recovered the saturated oil in the matrix of nonfractured cores and the saturated oil in the fracture of fractured cores. As the fracture length increased, the oil recovery became lower and the gas breakthrough occurred earlier. The higher fracture density increased the fracture area, which also increased the oil recovery and caused a more intense gas breakthrough.In this paper, the displacement law of tight oil cores by injecting natural gas and the recovery characteristics of oil in different space pores were illuminated. The results can provide theoretical guidance for the formulation of the natural gas injection development plan in tight reservoirs.

Phase and porosity changes in a calcium aluminate cement and alumina system under hydrothermal conditions

When refractory castables are dried, hydrothermal conditions may result inside the bodies if the H2O cannot escape from the material. Under such high-pressure conditions, problems such as explosive spalling can arise. As different curing temperatures during the hydration of calcium aluminate cement (CAC)-bound castables lead to the formation of different hydrate phases, different microstructures can develop in the hardened material. This study presents the changes in porosity and in the mineralogical composition of a refractory castable model system under hydrothermal conditions depending on the curing temperature (5, 23 and 40 °C).Quantitative X-ray diffraction (QXRD) measurements show that different hydrate phases are formed during curing, while C3AH6 and boehmite are formed in the same quantities after hydrothermal treatment in an autoclave at ∼11 bar/180 °C. Although the mineralogical composition after autoclaving is not different, the three samples differ in their microstructure. Mercury intrusion porosimetry measurements reveal that although the total porosity after autoclaving is the same, the 40 °C samples have a higher proportion of large pores. SEM images also show that the appearance of C3AH6 in the 40 °C autoclaved samples varies, which originates from the starting phase composition and microstructure after curing.

Carbonation Behavior of Engineered Cementitious Composites under Coupled Sustained Flexural Load and Accelerated Carbonation.

Engineered cementitious composites (ECCs) belong to a broad class of fibre-reinforced concrete. They incorporate synthetic polyvinyl alcohol (PVA) fibres, cement, fly ash and fine aggregates, and are designed to have a tensile strain capacity typically beyond 3%. This paper presents an investigation on the carbonation behaviour of engineered cementitious composites (ECCs) under coupled sustained flexural load and accelerated carbonation. The carbonation depth under a sustained stress level of 0, 0.075, 0.15, 0.3 and 0.6 relative to flexural strength was measured after 7, 14 and 28 days of accelerated carbonation. Thermogravimetric analysis, mercury intrusion porosimetry and microhardness measurements were carried out to show the coupled influence of sustained flexural load and accelerated carbonation on the changes of the mineral phases, porosity, pore size distribution and microhardness along the carbonation profile. A modified carbonation depth model that can be used to consider the coupled effect of flexural tensile stress and carbonation time was proposed. The results show that an exponential relationship can be observed between stress influence coefficient and flexural tensile stress level in the carbonation depth model of ECC, which is different when using plain concrete. Areas with a higher carbonation degree have greater microhardness, even under a large sustained load level, as the carbonation process refines the pore structure and the fibre bridges the crack effectively.

Influence of metakaolin on the hydration and microstructure evolution of cement paste during the early stage

The incorporation of metakaolin into cementitious materials could improve the compressive strength and durability of cement paste, which are correlated well with the hydration behavior of cement-metakaolin blended mixture. The aim of this work is to reveal the coupled effects between the cement hydration and the pozzolanic reaction of metakaolin during the early stage, the methodologies including fluidity, setting time, compressive strength were employed to measure the properties of cement paste, while another methodologies, such as conductivity, Mercury Intrusion Porosimetry (MIP), Thermogravimetric (TG), X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) were adopted to investigate the hydration behavior and microstructure characterization. The results indicated that the fluidity of fresh cement paste decreased sharply with the increase of metakaolin, and the addition of superplasticizer could improve the fluidity of fresh cement paste effectively. The setting times of fresh cement paste were delayed slightly with the incorporation of metakaolin. The conductivity of cement suspension dropped gradually with the increase of metakaolin during the early stage, meaning the hindrance to the ion dissolution from cement-metakaolin blended mixture. The compressive strength increased slightly with the addition of metakaolin at 1 d, while it increased remarkably at 3 d. The results of MIP presented that the pore structure was refined with the increase of metakaolin at 3 d. The TG results showed that the incorporation of metakaolin promoted the formation of hydration products at 3 d. The XRD results presented that calcium hydroxide (CH) decreased with the addition of metakaolin, which may be consumed by the pozzolanic reaction of metakaolin. SEM observation confirmed that the microstructure of cement paste became much denser with the increase of metakaolin, which was in good agreement with the results of compressive strength and MIP measurement.

Effect of preparation parameters on properties of metakaolin-based geopolymer activated by silica fume- sodium hydroxide alkaline blend

In this study, metakaolin was activated using an alkali activator containing silica fume and sodium hydroxide to obtain a metakaolin-based geopolymer. Silica fume was used to partially substitute metakaolin (0 to 25 wt% of metakaolin). Enough reactive silica was introduced using silica fume, which was added to sodium hydroxide solution before being mixed with metakaolin. The Na2O/Al2O3 molar ratio was adjusted in the range of 0.8 to 1.2 by varying the sodium hydroxide concentration, and the geopolymer paste specimens were cured at three different temperatures, i.e., 60, 70, and 80 °C. The specimens were analyzed by X-ray diffraction, Fourier transforms infrared spectroscopy, scanning electron microscopy, mercury intrusion porosimetry, energy dispersion spectroscopy, and compressive strength measurement techniques. The results revealed that geopolymer-zeolite composites were produced in the presence of less than 10 wt% silica fume and Na2O/Al2O3 molar ratios higher than 1. When the SF content was raised above 10%, a significant increase in the formation of the geopolymer phase developed, resulting in increased compressive strength. Mercury intrusion porosimetry measurements show the geopolymer composite with 10 wt% silica fume and a Na2O/Al2O3 molar ratio of 1. It contained large zeolite crystals embedded in its macroporous geopolymer matrix and had a pore size of 400 nm. Maximum compressive strength of 33 MPa was achieved at 15 wt% silica fume, Na2O/Al2O3 molar ratio of 1, and curing temperature of 70 °C.

Influence of serpentinite aggregate on the microstructure and durability of radiation shielding concrete

Concrete mix design for radiation shielding is mainly based on selection of aggregate materials of specified elemental composition. Serpentinite aggregate could be a desirable component of concrete for mixed-radiation attenuation and for high temperatures, however its durability performance needs further attention. The objective of the study is to reveal the influence of serpentinite aggregate on the microstructure and transport properties of baryte-serpentinite concrete. Mix design was developed for low-heat Portland cement and slag cement by using a combination of serpentinite aggregate and baryte aggregate. The compressive strength, chloride migration coefficient, carbonation resistance were experimentally investigated. The durability tests were compared with open porosity, mercury intrusion porosimetry measurement and examination of thin section of concrete by optical microscope. The results revealed increased porosity of contact zone of serpentinite aggregate with cement matrix. Open and capillary porosity of concrete was found to increase with increase of serpentinite aggregate content. Consequently, an increase of the chloride migration coefficient up to 2.5 times, the rate of carbonation up to 4 times were observed.

Porosity of a Fast-Setting Mortar with Crystallization Admixture and Effect of a SA-PA Modification.

Air permeability measurements according to the Hagen–Poiseuille equation, Scanning Electron Microscopy (SEM) and mercury intrusion porosimetry (MIP) tests were conducted on samples of cementitious mortar at different curing times to study the correlation between the increased crystallization and their microstructure. The mortar samples were prepared with a commercial fast-setting premix containing calcium silicates and quartz. The average permeability coefficient (K) was 2.96 × 10−15 m2 after 3 days and decreased to 3.07 × 10−17 m2 after about one month. The continuous C-S-H nucleation in the capillary pores of the cement mortar changes their shape and improves the mortar’s impermeability. The SEM images showed the development of crystals that refine the pore size distribution of the cement paste, with more of the smallest pores, and fewer of the largest, as demonstrated by the MIP measurements. Adding a superabsorbent polyacrylate (SA-PA) in the amount of 0.5% wt of dry powder, without adding any extra water, makes a mortar less fluid but not faster-setting. Twenty-four hours after mixing and casting, it is still plastic and, with time, the pore size distribution differs from that of standard mortar. Over time in air, permeability remains high, but in water it could be low due to swelling of SA-PA residues.

Tartaric acid effects on hydration development and physico-mechanical properties of blended calcium sulphoaluminate cements

The fast setting of calcium sulphoaluminate (CSA) cement-based systems is typically controlled using set-retarding admixtures, despite the notable efficiency of tartaric acid (TA) in adjusting CSA-based mixtures setting times, its use has only been marginally investigated, with an almost exclusive focus on the early age properties of TA manufactured mortars. This paper aims at evaluating the effect of the addition of tartaric-acid retarder on the hydration mechanism and physical properties of CSA-based mixtures from 4 h to 84 days. Macro- and microstructural properties were investigated using X-ray diffraction and differential thermal-thermogravimetric analyses, mercury intrusion porosimetry measurements, mechanical tests and analyses at fresh and hardened state. The experimental results reveal that the use of TA delays the formation of ettringite, modifies the porosity of hardened mixtures and strongly reduces strength in the short term. Nevertheless, the addition of TA slightly influences the properties at longer periods.

Boosting the faradaic efficiency for carbon dioxide to monoxide on a phthalocyanine cobalt based gas diffusion electrode to higher than 99% via microstructure regulation of catalyst layer

Various electrocatalysts have been developed to efficiently catalyze the CO2 electrochemical reduction reactions (CO2-ERRs). However, the electrode on which the CO2-ERRs occur is more crucial from a practical viewpoint. Herein, we have investigated the phthalocyanine cobalt (CoPc) based gas diffusion electrodes (GDEs) for CO2 to carbon monoxide (CO) conversion. CoPc based GDEs achieved CO partial current densities of up to 110 mA cm−2, and faradaic efficiency for CO (FECO) clearly above 99%. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), mercury intrusion porosimetry (MIP) and contact angle measurement reveal the important role of perfluorinated sulfonic acid (PFSA) binder and the carbon black (CB) in the catalyst layer (CL) of the CoPc based GDE, whose presence and distribution constitute likely the basic networks for mass transfer and electrons conduction, the origins of the favorable CO2-to-CO current density and selectivity. This work provides vital insight into practical consideration in designing efficient reaction regions for CoPc based GDEs with an optimal structure, that must optimize mass transport as well as electron conduction.

Fresh and hardened properties of self-compacting concrete containing recycled fine clay brick aggregates

Clay brick is one of the major components of demolition waste, which is generally landfilled. Effective and new uses of recycled clay brick may provide sustainability benefits in terms of landfill reduction. Therefore, this research aims at applying Recycled fine clay brick aggregates (RFCBA) with sizes from 0.075 mm–4.75 mm to prepare Self-compacting concrete (SCC). The effects of RFCBA on fresh and hardened properties of SCC were investigated. Saturated surface dry RFCBA was used to replace Natural fine aggregate (NFA) with the percentage of 25%, 50%, 75% and 100%, respectively, in making the SCC mixes. Although experimental results showed that the flowability, passing ability, and segregation resistance of SCC containing RFCBA (RFCBA-SCC) decreased with the increasing RFCBA content, these properties still satisfy the criteria of SCC. The compressive strength, splitting strength, flexural strength, and elastic modulus of the RFCBA-SCC mixes decreased with an increase of RFCBA content. Due to their porous nature, recycled fine clay brick aggregates may also be a source of additional water for internal curing. The internal curing effect was confirmed by the mercury intrusion porosimetry, X-ray diffraction, and thermogravimetric analysis measurements. Moreover, a significant autogenous shrinkage reduction of SCC is achieved by using the RFCBA due to the release of additional water pre-stored in the RFCBA. Therefore, it can be concluded that the addition of RFCBA to SCC mixtures can provide additional practical benefits in the hardened state.

Measuring Gas Transport and Sorption in Large Intact Geologic Specimens via the Piezometric Method

Uptake of noble gases into heterogeneous geologic core samples was measured using a piezometric methodology. In addition to measuring accessible porosity—as with gas pycnometry—by monitoring the rate of pressure decay, this method can also be used to estimate the gas effective diffusivity in the sample. In contrast to previous applications of this method, where milligram quantities of fractured grains are characterized, here approximately kilogram core samples were left intact when tested. In doing so, a more representative sample of the heterogeneous field geology is provided. Additionally, alteration of the pore structure and connectivity during sample preparation is avoided. To scale the piezometric method from milligrams to kilograms, the system was designed to operate at medium vacuum (1 to 100 Pa) to restrict transport in pores less than approximately 60 µm to large Knudsen numbers. To test the system performance, two samples of interest were selected: a rhyolitic welded tuff from Blue Canyon Dome at the Energetic Materials Research and Testing Center and a zeolitized non-welded rhyolitic tuff from the Nevada National Security Site. Three noble gases were utilized in this test series; Argon and xenon as they are of direct interest to nuclear monitoring efforts and helium as it is a weakly adsorbing reference standard. Additionally, mercury intrusion porosimetry measurements were made on subsamples of the core to compare the observed porosity by the two methods and to discuss gas transport rates in the context of the measured pore distribution.

Thermal stability, pore structure and moisture adsorption property of phosphate acid-activated metakaolin geopolymer

Phosphate acid-activated metakaolin geopolymer (PMG) was successfully prepared using a two-step curing method and the thermal stability, pore structure and moisture adsorption property of the obtained PMG were studied by techniques of thermogravimetry (TG), mercury intrusion porosimetry (MIP) and dynamic vapor sorption meter (DVS). TG result shows that thermal decomposition of the PMG majorly occurs in the range of 220−550 ℃, much higher than that of the common binder of C-S-H, due to the removal of the chemically bonded water and the water content of the PMG is around 16%. MIP measurement indicates that the porosity of the PMG is 13.6% and the most probable pore size is about 100 nm. DVS results shows that the water adsorption amount of PMG powder is about 0.132 ml/g, which is in good agreement with the total porosity measured by MIP test.